This site is dedicated to topics of interest to our members, their employees, and other interested parties. We encourage our readers to submit any questions or points of view that may be of interest to others. Answers have been prepared and submitted by CCTIA members and are the opinion of the author. The answers do not represent an official position of CCTIA. For comments or questions, please contact us.
10.062 Mortar Testing by Cylinders or Cubes
|Q||When testing for compressive strength of mortar, the 2007 California Building Code (CBC) specifies “average compressive strength at 28 days” as noted in Table 2103A.8(2). Is this strength tested and computed by cylinders or cubes?
— Special Inspector in Sacramento, California
|A||5/10 – Response prepared by David Chippero, Special Inspection Division Manager at Testing Engineers, Inc.
Mortar testing is normally required for schools and hospitals, hence your reference to table 2103A.8(2) in 2007 CBC. In the title block of the reference table under Average Compressive Strength there is a small b notation, referring to the note at the bottom, which reads “b. Average of three 2-inch cubes of laboratory-prepared mortar, in accordance with ASTM C270.:” So, the specified strength is based on 2-inch cubes prepared in the laboratory.
Section 2105A.5 specifies “Test specimens for mortar shall be made as set forth in ASTM C1586”. As we were informed in FAQ 10.043, C1586 refers us to C780 Annexes A.7, which describes specimens made as cylinders or cubes.
A further clarification is found in “Reinforced Concrete Masonry Construction Inspector’s Handbook” Fourth Edition, which indicates “The 2-inch cube is typically used for laboratory prepared mortar while the 2-inch x 4-nch cylindrical specimen is used for field cast mortar.” To obtain an equivalence of a 2″x4″ cylinder field test specimen to a 2″ cube specimen, divide the compression test result of the cylinder specimen by 0.85. The factor of 0.85 is the normal correction h/d found in ASTM C780 5.2.6 Note 3.
When testing for compressive strength of mortar in the field you could use either 2-inch cube molds or 2-inch x 4-inch cylindrical molds. The typical standard of practice that most testing laboratories follow is to test field mortar by preparing specimens in a 2-inch x 4-inch cylindrical mold and if required showing a correction factor when the specimens are tested depending on which specimen, cubes or cylinders, was specified for the project.
10.057 Water/Cement Ratio vs Strength
|Q||Many published articles relate how changing the water-cement ratio has a large effect on concrete strength. Is there a simple explanation for this effect?
— Technician in San Leandro, California
|A||2/09 – Response prepared by Terry Egland, a principle at Testing Engineers, Inc., and a registered engineer in California.
In general, there exists a fundamental inverse relationship between porosity and strength of solids. This strength-porosity relationship is applicable to a wide range of materials, such as iron, stainless steel and granite. Think of examining a concrete core, which exhibits voids created by a lack of consolidation. You can imagine, why with a lack of internal structure, the compressive strength would be lower than expected. On a much smaller scale, there is a theoretical volume of water (based on curing conditions) required to hydrate a given volume of cement. Once you have added more than that amount, it creates capillary porosity (i.e. microscopic cavities or voids). The higher the water-cement ratio, the more porous and the weaker the strength. Generally, to maximize strength and durability, the water-cement ratio should be the lowest possible to hydrate the cement while maintaining its workability.
10.054 Specified Strength of Cylinders vs Cores
|Q||On a recent project, the concrete column strengths for one pour fell short of the specified 4,000 psi. Cores were taken in accordance with CBC 2010 Section 1905.6.5 and ACI 318 Section 5.6.5. Due to project schedules and forming techniques, cores were taken vertically from the column tops. Subsequent strength testing indicated acceptable results and the project continued with only this small blip. Afterwards, our client questioned our field testing. They claimed that if the core testing results met the requirements of the Code, the cylinder testing was obviously incorrect and therefore refused to pay for the coring. What is the relationship between the strength indicated by the test cylinders compared with the strength of the concrete in the structure?
— Terry Egland, P.E., San Leandro, California
|A||06/12 – Response prepared by Peter Grossman, a Senior Consultant at Testing Engineers, Inc., and a registered engineer in California.
Test specimens (cylinders) are made, cured and tested under certain standard conditions that are usually appreciably different from the conditions existing in the structure. The value of field-cast test specimens is that they give a measure of the strength potential (they evaluate the materials and mix as supplied by the producer, to ascertain the concrete meets project specifications). Test specimens are not intended to yield an exact strength of the concrete in the structure, and the actual strength of the concrete in the structure can be appreciably different. Besides
variable environmental site conditions and curing, other variables between test specimens and the concrete in the structure include variations of mix components, water content, size and shape of the structure, workmanship, degree of consolidation, possible presence of defects such as rock pockets, restraint, and combinations of loading in the structure. It is because of these unknowns that the Structural Engineer must consider a factor of safety when the structure is designed.
Variations in cylinder strengths are not always reflective of a problem in the structure. For instance, if three sets of specimens are made from one day’s concrete placement and maintained under identical conditions throughout the test duration, there is no assurance they will all fail at the same strength when they are tested at the same age. In fact, each one will almost always break at a different strength. These are normal variations, and should be expected.
Cored specimens are usually obtained days or weeks, even months, after the laboratory testing of cylinders. This additional time must be taken into account when comparing cylinder and core test results. In addition, cored specimens are tested in a dry or moist condition, but rarely in the saturated condition similar to test cylinders. It is well documented that dry specimens have a higher compressive strength than saturated specimens.
We do know that there are variations in the strength of the structure that are not caused by basic variations in the concrete itself. For example when cores are taken from a column, the cores from the upper portion of the column invariably indicate lower strength than the cores from the bottom portion of the column. The reason is that the concrete near the bottom was compacted by static hydraulic head of the concrete being worked above, yet there was no change in mix or materials.
10.052 How is a Bolt Head Formed?
|Q||A colleague of mine suggested that the head of a high-strength bolt was attached to the shaft by welding the two parts. Could you explain the process for the assemblage?
— Structural Engineer in Oakland, California
|A||1/09 – Response prepared by Terry Egland, a principle at Testing Engineers, Inc., and a registered engineer in California.
The head of a bolt is formed by heating the end of a piece of steel round bar and then forging (reshaping) the heated end into a head. The head is not welded on or otherwise attached to the end of the round bar.
For example, the production of a 1″ diameter x 12″ long A325 bolt begins by cutting a 20 ft. length of 1045 steel round bar into 13-11/6 pieces. Since the finished bolt length of 12″ is measured from the end of the bolt to the underside of the head, we must add 1-11/16 to the cut length of the bolt. After cutting the bolt to length, this added material (1-11/16) is heated to approximately 2000 degrees Fahrenheit and forged into whatever head style the specific bolt requires. In the case of an A325 bolt, the head style is a heavy hex structural bolt. After the head is forged, an A325 bolt undergoes a heat-treating process in which the bolts are quenched and tempered to develop the high strength mechanical properties required by the specification. The next step in the the process is to test the bolts to ensure that they meet the strength requirements. After verification, they are threaded with 1-3/4 of 8 pitch Unified National Coarse thread,
Information provided by Portland Bolt & Manufacturing Company
10.050 Low Concrete Strengths on California School Projects
|Q||We have a school project in California where the specified concrete strength is 4000 psi at 28-days. On one specific pour, the following strengths were obtained:
7-day strength = 2780 psi
Do you report the results as meeting the requirements of the DSA approved documents?
— Testing Lab Manager in Northern California
|A||2/09 – Response prepared by David Chippero, the Special Inspection Division Manager at Testing Engineers, Inc.
California Building Code, Title 24, Part 2, Chapter 1905.A.6.3 Strength Test Specimens states: Strength test acceptance criteria shall comply with the provisions of ACI 318, Section 5.6.3. Section 18.104.22.168 notes: Concrete shall be considered satisfactory if both of the following requirements are met:
A) Every arithmetic average of any three consecutive strength tests equals or exceeds f’c.
Using this guideline, the results above would be acceptable if the 28-day cylinders, when averaged with three consecutive strength test results on the project are equal to or greater than 4000 psi. This assumes than no individual test was less than 3500 psi.
The Division of the State Architect holds a different position regarding low strength concrete test results. DSA believes that the LEA approved laboratory should report all failing test results immediately as a non-conformance. It is then up to the design professional and DSA to determine a corrective action plan. If an approved stamped change order is not received from DSA, the failing results should be reported on your laboratory verified report, DSA Form 291. In the 2007 California Administrative Code, Title 24, Park 1, Section 4-335b, Performance of Tests, states: Where a sample has failed to pass the required tests the architect of engineer, subject to the approval of DSA, may permit retest of the sampled material. Section 4-335d, Test Reports, also notes: Reports of test results of materials not found to be in compliance with the requirements of the plans and specifications shall be forwarded immediately to DSA, the architect, the structural engineer, ad the project inspector.
So, although the 56-day strength test met the 28-day f’c requirements, DSA does not consider the results to be valid. The test report must be distributed noting “the results do not meet the requirements of the DSA approved documents“. there are no provisions in the California Building/Administrative Code, Title 24 that allow the use of a 56-day test result in lieu of the required 28-day test result. However, a 56-day test result may be useful to the design professional and DSA in arriving at a corrective action plan.
2007 California Administrative Code, California Code of Regulations, Title 24, Part I
2007 California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2
Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary
10.048 Validity of Mortar Testing
|Q||During a preconstruction meeting, concern was voiced that the mortar testing should be suspended since it would not represent the actual field strength conditions. What circumstances can be stated to explain the concern?
— Project Manager in Southern California
|A||12/08 – Response prepared by Kurtis K. Siggard, Executive Director of the Concrete Masonry Association of California & Nevada (CMACN).
Care must be taken in how we sample, test, and report mortar tests. Mortar, by its nature, retains water for an extended period of time. The water in the mix is necessary to maintain the workability of the mortar and to create the bond between the masonry unit and mortar. There have been significant problems lately with field-testing pre-blended mortars that are proportioned to meet the property requirements of ASTM C270. Many of these pre-blended products have constituents that retain a greater amount of water requiring less retempering of the mortar. Due to the high water/cement ratio of these mortars when sampled soon after mixing, and the molding of samples in watertight containers, sampled strength may be much lower than the strength of the mortar used in construction. ASTM C1586 22.214.171.124 states: Measuring mortar compressive strength of field-sampled mortar has no relevance unless preconstruction testing is performed in the laboratory using similar mixing equipment, mortar materials, and the same specimen geometry. Even when this is done, the field compressive strength data can only be compared to the preconstruction mortar strength data in general, due to other factors, such as weather, temperature of mortar, and the absorption properties of the specific masonry units being used.
ASTM C270 Standard Specification for Mortar for Unit Masonry
ASTM C1586 Standard Guide for Quality Assurance of Mortars
10.047 Prism Testing per 2007 CBC
|Q||My question is in 2007 CBC Chapter 21 Section 2105A.126.96.36.199 states as always a set of 5 prisms shall be built prior to construction to meet the Fm’ before CMU block is placed. But it does not specify age days of testing, nor does the ASTM referenced is the same section, which is ASTM C1314. Should we test all 5 prisms at 28 days? Sometimes a specific job specification may state prism age days to be tested testing but if not stated what is the correct age days of testing field fabricated prisms?
— Steve Marcki, Construction Inspection Manager at Youngdahl Consulting Group, Inc.
|A||1/09 – Response prepared by Kurtis K. Siggard, Executive Director of the Concrete Masonry Association of California & Nevada (CMACN).
For pre-construction prisms we refer to Section 2105A.188.8.131.52 of the 2007 California Building Code which states that “Prior to start of construction, a prism test shall consist of five prisms constructed and tested in accordance with ASTM C 1314.”
We find the age that prisms should be tested in ASTM C1314 Section 7.1, which states “Test prisms at an age of 28 days or at the designated test ages. Test a set of prisms at each age.”
A set of prisms is defined in ASTM C1314 Section 3.1.1 as “a set consists of at least three prisms constructed of the same material and tested at the same age.”
If the project specification indicates a different number of prisms to be tested than indicated in the building code or ASTM, a different age for testing the prisms other than that found in the ASTM, or anything less than three prisms per set, a request for clarification should be forwarded to the design professional.
It is critical that the prisms be transported and handled with care in accordance with ASTM C1314 Section 6.1.
ASTM C1552 should be followed closely to properly cap each prism. Care should be taken to avoid voids between the capping material and prism. Only caps using gypsum cement or sulfur materials are authorized for capping prisms.
ASTM C1314-07 Standard Test Method for Compressive Strength of Masonry Prisms
ASTM C1552-07 Standard Practice for Capping Concrete Masonry Units, Related Units and Masonry Prisms for Compression Testing
10.046 Standardization Records
|Q||Recently, we were in the process of installing a new temperature recorder for our curing room. During this period we experienced a CCRL inspection. They correctly noted a footnote of deficiency: “The accuracy of the temperature recorder for the moist storage facilities was not verified at six month intervals as required by Section 5.2.1 of C511.” Subsequently AMRL is requesting our current standardization records. Could you enlighten us to what is meant by this terminology (verify standardization)?
|A||8/09 – Response prepared by Pete Holter, a Quality Analyst with AASHTO Materials Reference Laboratory.
The standardization record for the recorder is a record that details the comparison made between the recorder and a reference thermometer as described in ASTM C511, and adjusting the recorder if it is outside the allowable tolerance. There are six items of information you’ll want to include on the record:
1. Unique identification of the recorder.
|8/09 – Response prepared by Terry Egland, a principle at Testing Engineers, Inc., and a registered engineer in California.
According to Section 184.108.40.206 of ASTM C511-06, the laboratory is to verify the accuracy of the temperature recorder with that of the reference temperature-measuring device and adjust the temperature recorder if the difference is greater than 1 degree C. This process is considered “standardization”, which is a simplified form of calibration. The process determines the correction to be applied to the result of a measuring device when compared to a reference standard. Standardization does not address all of the elements of uncertainty and does not lead to traceable measurements.
According to AASHTO PP57-06, this process is termed “verification of standardization“, a process that establishes whether the results of a previously standardized measurement device are in control.
10.045 Are Ceramic Back-ups Prequalified?
|Q||Upon partial completion of a project, the project manager rejected one of the WPS’s used. The contractor had used an AWS prequalified TC-U4a-GF joint configuration that by code requires metal backing. But, the contractor used ceramic backing. He removed the ceramic backing, back-gouged and welded the root. Is there any way that this might be considered acceptable?
— Structural Engineer in Oakland, California
|A||10/09 – Response prepared by Dave Palfini, a principle at Testing Engineers, Inc., and an ASNT Level III and AWS Senior CWI.
AWS D1.1 – 2.17 Prohibited Joints and Welds
We aren’t talking about “One-Sided Groove Welds”, so this restriction does not apply.
In an attempt to mitigate this situation, from an administrative point of view, we designate the prequalified joint configuration to be TC-U4b-GF, similar to the TC-U4a-GF joint configuration.
Next, we look at “D1.1 – Fabrication”. We cannot prohibit the contractor from using his own “methods and means” to produce welds, as long as they are within the limitations of the code.
The contractor uses the TC-U4b-GF joint configuration, elects to use the widest “As Fit-Up” root opening allowed, uses ceramic backing, and cites the following:
“AWS D1.1 – 5.10 Backing
Since the weld is to be back-gouged and welded, as an inspector, I would have to allow this, verifying that the groove angle was within the tolerances of the 45° bevel preparation and not the 30° that may be used in the case of the TC-U4a-GF joint configuration.
(After back-gouging, the other side of partially welded joints should resemble a prequalified U- or J-joint configuration at the joint root, and, for administrative purposes, would require an additional WPS.)
10.043 Is Mortar Testing Required?
|Q||Can you clarify the mortar testing requirements according to the 2006 IBC and 2007 CBC? Some people in my area are still using the old UBC Standard 21-16.
— Special Inspector from Southern California
|A||11/08 – Response prepared by William Wahbeh, the responsible engineer at Signet Testing Labortories, Inc. and a registered engineer in California
The UBC Standard 21-16 as referenced in previous CBC’s is no longer applicable in the 2007 CBC. The new code section for structural testing of masonry (1708.1) is adapted from the ACI 530/ASCE 5/TMS 405 reference, which does not require any field mortar testing for quality assurance. The rational of the reference is that mortar is specified based on long standing prescriptive proportioning or property testing performed in a laboratory enviroment that must meet ASTM C270. In either case, material certifications and/or test records should be provided prior to construction to confirm the materials meet the standard and the Special Inspector is responsible for verifying the proper use and proportioning of the material in the field. Per 2007 CBC, Section 2105A.5, essential facilities (schools and hospitals) still require verification testing according to ASTM C1586 for the first three successive days and once every week thereafter for strength requirements only.
11/08 – Response prepared by Jeffry Cannon, the Materials Technical Discipline Leader at Kleinfelder, Inc.
ASTM C1586 specifically states that ASTM C780 should be used to sample and test mortar from project sites (not C270), but goes on to say strength verification of field-sampled mortar should not be performed because strengths of test specimens do not equate to actual strengths of the in-place mortar (Section 5.5).
These conflicts between the CBC and the ASTM stadards that are referenced in the code have not been rectified to date. It is suggested that if field sampled mortar specimens are obtained for strength testing, specimens are fabricated and tested in accordance with C780. Some member firms are adding a statement on their reports of laboratory test results indicating that the strengths of the test specimens may not be indicative of the in-place mortar.
One side note to ASTM C780 is that after initial curing in the field, compression specimens must be cured in moist closets or moist rooms until they are tested. The use of water tanks (curing tanks) is not allowed.
10.041 Clarification ASTM E605 SFRM Density
|Q||A fireproofing contractor contends that when measuring SFRM thickness on a density sample, the minimum maximum of 25%-1/4 inch rule (ASTM Section 220.127.116.11) applies when averaging the 12-thickness measurements. As a laboratory we believe the measurements should be actual not allowables.
— Bob McCormick, Field Service Manager at Raney Geotechnical, Inc.
|A||7/08 – Response prepared by Terry Egland, a principle at Testing Engineers, Inc., and a registered engineer in California. He can be reached at email@example.com.
You are correct, the averaging calculations for thickness measurements as mentioned in ASTM E605 section 18.104.22.168 do not apply when measuring thickness for a density sample. Section 8.1 of E605 specifies how to correctly measure the thickness of SFRM for the purpose of determining the average thickness, and areas of excessive thickness are dealt with in section 22.214.171.124. By limiting the measured thickness to a maximum of ¼′” over the design thickness, uneven application will not significantly skew the average thickness calculation to a “false high” reading.
When measuring density, IBC 2006 refers us to section 8.2 of E605. Section 8.2.3 deals with thickness measurements for determining density, and quizzically refers to section 7.1, which has no practical meaning on thickness measurement. However, this section does note that 12 thickness measurements are to be taken, and no statement is made regarding adjusting the average of the 12 measurements.
From a practical viewpoint, the use of actual measurements for density calculations prevents “false high” density calculations. For a given weight of SFRM, a limited average thickness/lower volume (as determined by section 126.96.36.199) would generate an erroneous higher density than the actual higher thickness/higher volume measurements would. Thickness measurements are concerned with the application of the SFRM, while the density measurements pertain to the product itself.
For SFRM to provide the required level of protection both the minium average thickness and the density requirements must be met. “Understating” the average thickness by disregarding a false high point does not result in an understatement of protection. However, if we use thicknesses as determined by a maximum of the design thickness +1/4” (as used for average thickness determination) and not the actual thickness, we would be overstating the density. This would result in an overstatement of the protection level, which must be avoided.
When this question was asked of Luke Woods of W.R. Grace & Co. – Conn. He stated the following:
“The density test in Section 8.2 states that the thickness of the sample shall be determined by averaging the thickness of 12 measurements. I do not believe the 25% – ¼ inch allowance is applicable to these measurements. Also I would encourage you and your team to use the displacement method for determining density, Section 8.3.”
It’s very appropriate to mention the alternate displacement method for determining the in-place density stated, in ASTM E605 Section 8.3 as a referee method. This method measures the volume of the material without the need for thickness or area measurements. It can be used to retest a sample that may be in question. It reduces some of the measuring and sampling variables that are inherent with other methods.
10.038 Deficient SFRM Density/Increase Thickness
|Q||If the density of the SFRM does not meet the design criteria can an increase of thickness compensate for the deficient density? If the preceding is possible, what responsibility or duties does the Special Inspector or the agency/laboratory have?
|A||5/08 – Response prepared by Terry Egland, a principle at Testing Engineers, Inc., and a registered engineer in California. He can be reached at firstname.lastname@example.org.
When determining the density of SFRM the Special Inspector is referred to ASTM E605 Standard Test Method for Thickness and Density of Sprayed Fire-Resistive Materials (SFRM) Applied to Structural Members. Section 188.8.131.52 states that when the calculated average density of the SFRM is less than that allowed by the respective fire resistance design see Note 4 & 5. And Note 4 states the following: “A thickness to density correction formula is contained in certain fire resistance rating criteria or is available from some SFRM manufacturers. Consult the rating criteria….before citing for deficiency.” In some cases it has been determined that an increase in thickness will compensate for the deficient density, so what duty does the special inspector/agency/laboratory have in such a case? If we go back to the IBC 1704.10.4 the laboratory is to determine the density according to E605. It makes no reference to Note 4 in using a correction formula. 1704.10.4 states, “The density of the sprayed fire-resistant material shall not be less than the density specified in the approved fire-resistant design.” Unless the fire-resistant design mentions a correction formula and the design professional performs this calculation, the as-measured low density is a non-compliance. From the point of view of the special inspector /agency/laboratory it should be reported in a timely manner to the contractor as a discrepancy for correction.
The concept of a correction formula has a valid basis and should not be considered as a loop hole or an easy way out. It is based on the same design concept of the original tested assembly but it is up to the design professional to determine if the increase in thickness compensates for the low density of the SFRM. As special inspectors or agency/laboratory we report our findings, and the interpretation and revisions are at the discretion and approval of others.
It would be appropriate to mention the alternate method for determining the in-place density stated, in ASTM E605 Section 8.3 as a referee method. This method measures the volume of the material without the need for thickness or area measurements. It can be used to retest a sample that may be in question. It reduces some of the measuring and sampling variables that are inherent with other methods.
10.037 How Many Thickness Measurements for SFRM on Fluted Deck?
|Q||When measuring thickness of SFRM on fluted decks IBC 1704.10.3.1 now references ASTM E605, while in the past we have used Technical Manual 12A. While the wording in the manual seemed confusing, an appendix clarified that 12 thickness measurements should be taken. Upon reading E605 it seems to indicate that we should “take four random symmetrical measurements”. With such a significant discrepancy between the two can you explain the right procedure?
|A||5/08 – Response prepared by Terry Egland, a principle at Testing Engineers, Inc., and a registered engineer in California. He can be reached at email@example.com.
The new IBC replaces the Technical Manual 12A, Standard Practice for the Testing and Inspection of Field Applied Sprayed Fire-Resistive Materials with ASTM E605 as a reference standard. However the user should be cautious as to the extent of the reference. The IBC uses E605 for thickness determination but has wording that supersedes E605 on the rate of testing. E605 conducts thickness testing at a Rate of one bay per floor or one bay for each 10,000 sq. ft., whichever provides the greater number of tests. On the other hand, IBC 1704.10.3.1 would have the inspector take the average of “not less than four measurements for each 1000 sq. ft. of sprayed area on each floor or part thereof”. With such a conflict we refer to IBC 102.4 “Where differences occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply”. So, when writing an SOP for performing thickness determination the following could be adopted:
“Layout a 12 inch square every 1000 square ft of sprayed floor area and take four random symmetrical measurements within that square, one each of the following: valley, crest, and sides, and report as an average”.
NOTE: This change has drastically increased the amount of testing on fluted decks.
10.036 Frequency of Testing Thickness for SFRM
|Q||IBV 1704.10.3.1 references ASTM E605 for thickness testing and E605 uses a frequency of testing, “at one bay or 10,000 sq. ft. of floor area”, but 1704.10.3.1 call for four tests on floor decking per 1,000 sq. ft. and 25% of the other proteced elements per floor. Is this a contradiction, and which frequency should be used?
|A||5/08 – Response prepared by Terry Egland, a principal at Testing Engineers, Inc. and a registered engineer in California
The IBC uses E605 for thickness determination but has wording that supersedes E605 on the rate of testing. E605 conducts thickness testing at a rate of one bay per floor or one bay for each 10,000 sq. ft., whichever provides the greater number of tests. On the other hand, IBC 1704.10.3.1 would have the inspector take the average of “not less than four measurements for each 1,000 sq. ft. of sprayed area for floor decking and 25% of the other protected elements per floor. With such a conflict we refer to IBC 102.4 “Where differences occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply.”
A sample Operating Procedure follows:
FLOOR, ROOF AND WALLS
For every 1,000 sq. ft. of SFRM applied, four measurements shall be taken in accordance with ASTM E605 and averaged for determination of the thickness.
10.034 Minimum Bolt – Nut Engagement
|Q||I’m working on a project where the bolts were mis-ordered short. When installed according to the plans and specs, the end of the bolt is flush with the face of the nut. How much of a bolt must project beyond the nut when properly installed?
— Special Inspector in San Francisco
|A||10/12 – Updated response prepared by Terry Egland, a principal at Testing Engineers, Inc. and a registered engineer in California
Though a common rule-of-thumb is “three threads past the nut”, it is just that – a rule-of-thumb, with no basis in fact, In order to arrive at the right answer, we need to follow the reference document chain.
If we start with the 2012 IBC, Section 1705.2.1 states “… Special inspection for structural steel shall be in accordance with quality assurance inspection requirements of AISC 360”, which is a very broad statement. Chapter 35 is a little more specific by designating AISC 360-10 “Specification for Structural Steel Buildings”.
Section N5 (6) uses the provisions of RCSC Specification for Structural Joints Using Gigh Strength Bolts to confirm materials, procedures and workmanship. Thus, we have arrived at the collect specifying document, Specification for Structural Joints Using High Strength Bolts, hereafter referred to as the RCSC 2009.
Section 2.3.2 of the RCSC 2009 states, “The bolt length used shall be such that the end of the bolt extend beyond or is at least flush with the outer face of the nut when properly installed.” So while the old rule-of-thumb won’t hurt, the short bolts will work just fine,
2009 RCSC “Specification for Structural Joints Using High Strength Bolts”
AISC 360-10 Specification for Structural Steel Buildings
10.033 Concrete Shrinkage
|Q||Our project specifications indicate that a specific class of concrete mix shall not exceed a shrinkage limit of 0.040% at 21 days drying. The concrete supplier does not have lab test data to support the performance of the mix, but has some field test results from a recent project. Should we use this information to accept the mix?
— San Francisco Structural Engineer
|A||8/07 – Response prepared by William Wahbeh, a responsible engineer at Signet Testing Laboratories and a registered engineer in California
The typical standard used to reference shrinkage limits for a project is ASTM C157 “Length Change of Hardened Hydraulic-Cement Mortar and Concrete”. This test method is a very sensitive laboratory test based on specific criteria for mixing, sampling, curing and measuring. Some criteria may vary, such as storage, allowing for either water or air, which can have significant influence on the test results. SEAONC developed a modified procedure to C157 in the 1960’s commonly referenced in project specifications that make several changes that include sample size (4x4x11 vs. 3x3x11), initial curing (7 days vs. 28 days wet cure) and air drying (50% RH). It is this modified procedure that most project specification limits are based. As with interpreting and analyzing any test results, it is critical to make sure you are comparing apples to apples.
Although every project would like to limit shrinkage to the least possible amount, it is important that limits be specified only when necessary and if the proper quality control, including laboratory testing, can be established. Local materials or mix proportions may not be able to meet shrinkage requirements without the addition of costly admixtures that can affect other properties of the mix. Lab test values should be used as a basis to determine the acceptability of materials and proportions and should not be used categorically. Furthermore, as with concrete compression testing, the results from shrinkage testing are not necessarily representative of the performance of the mix in-place because of the complexity of the factors that influence shrinkage. Similarly, field cast shrinkage samples are typically found to be greater than lab cast samples. Some specifications allow for 15% to 25% higher tolerances, while the SEAONC “Supplementary Recommendations for Control of Shrinkage in Concrete” gives maximum ranges for differenct classes of concrete at 21 days drying for lab from .036 to .060, while field cast specimens are in the range of .048 to .080.
Given the factors noted above, field-testing data can give some indication of the quality of the shrinkage characteristics, however reliance on this information for material acceptance should be avoided. The bottom line is that, in the absence of a new ASTM for field-testing or modified specifications, there is no substitute for laboratory trial batching to determine the shrinkage limits of a specific mix.
10.032 Adhesion/Cohesion of SFRM (Bond Strength of Fireproofing)
|Q||During a recent project, we found the Sprayed Fire-Resistive Material applied to the steel substrate to sound hollow upon surface tapping. The project specifications call ASTM E-736 Cohesion/Adhesion of Sprayed Fire-Resistive Material Applied to Structural Members as controlling the required bond strength. The old UBC Standard 7-6 and ASTM E-736 do not specify whether to cut to the substrate or not. My question is after setting the cap with epoxy and letting it set for approximately 24 hours, are we to cut around the cap to the substrate or are we to test it in-place without cutting around the cap?
— Steve Marcki, Construction Inspection Manager, Youngdahl Consulting Group, Inc.
|A||9/07 – Response prepared by Terry Egland, a principal at Testing Engineers, Inc. and a registered engineer in California
The intent of ASTM Subcommittee E06.21 when writing E-736 was to outline a standard method to measure the combined bond strength from cohesion and adhesion of SFRM when applied to a structural member. Cutting around the cap down to the substrate will isolate the bond strength to only adhesion and may thereby indicate why your project sounds hollow but would not be a standard method to substantiate an unacceptable application of SFRM.
Since you suspect an improper application, it would be prudent to test the SFRM in the standard method and to also cut around the cap and test just for adhesiveness and report the findings to the design professional.
www.wordnet.princeton.edu/perl/webwn defines cohesion as the intermolecular force that holds together the molecules in a solid or liquid. They further define adhesion as the property of sticking together (as glue or wood) or the joining of surfaces of different composition.
10.031 Requirement for ACI Grade 1 Certification
Is ACI certification required for both concrete and masonry special inspectors?
|A||6/07 – Response prepared by Michelle Craig, the owner of Dynamic Consultants, Inc. and three time past president of CCTIA. She can be reached at firstname.lastname@example.org.
Many years ago, ASTM C94 Standard Specification for Ready-Mix Concrete included a certification requirement for the technician sampling fresh concrete. Specifically, Section 16.2 reads, “Tests of concrete required to determine compliance with this specification shall be made by a certified ACI Concrete Field Testing Technician, Grade I or equivalent. Equivalent personnel certification programs shall include both written and performance examinations as outlined in ACI CP-1.”
For the most part, building officials throughout the State of California interpreted this to mean the ACI certification only. By mutual agreement with the three Greater Bay Area ICC (formerly ICBO) Chapters, CCTIA included the ACI Grade I certification as a requirement in its Guidelines for Issuing Identification Cards for Special Inspectors for both Reinforced Concrete and Pre-Stressed Concrete Technicians. This certification is also required by ICC in order to become fully certified as a Reinforced Concrete Special Inspector and Pre-Stressed Concrete Special Inspector.
Sampling masonry grout is another matter. Note 8 in ASTM C1019 Standard Test Method for Sampling and Testing Grout states, “The field technician sampling, making, and curing specimens for acceptance testing should be certified (American Concrete Institute Field Testing Technician – Grade I, National Concrete Masonry Association Masonry Testing Technician, or equivalent). Equivalent certification programs should include both written and performance examinations.”
As we know from a previous FAQ (reference number 10.002), the language contained in the “Notes” of an ASTM Standard are not considered mandatory. In addition, the language of the note suggests a recommendation as opposed to a requirement with the use of the word “should” as opposed to “shall.”
As the ACI Grade I certification has nothing to do with the proper methods or procedures for fabricating masonry grout samples, it would be inappropriate to require this certification for masonry inspectors. This certification is not a requirement of ICC in order to become fully certified as a Structural Masonry Special Inspector.
Today, most of the testing laboratories have to meet the requirements of Practice C1077 Laboratories Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Laboratory Evaluation (through CCRL) and Standard Specification E329 Agencies Engaged in Construction Inspection and/or Testing. Practice C1077 in Section 6.1.6 states “Concrete field technician shall possess current technician certification.” And continues to say ACI or NICET can satisfy this requirement. Specification E329 in Section 13.1.2 states “The agency shall comply with the most recent edition of Practice C1077 for tests of concrete and aggregates.” Under PERSONNEL in E329 the requirement for inspector or technician is a little vague. Section 6.2.4 states the technician must be able to demonstrate competence for the test which is being conducted either by oral or written examination or both.” So certification is one means of showing competence but this section does not require certification. But with the requirement to meet C1077, certification is required. It’s interesting that Specification C94 also requires the testing laboratory to meet C1077.
10.028 Is an NR311 Ni Electrode E70 Equal to an E80?
|Q||I have a project where we are welding ASTM A913-Grade 65 I-sections to each other. Our specification calls for E80 electrodes for these welds, in conformance with AWS D1.1. The steel erector submitted a WPS for these welds using NR-311 Ni electrodes. The WPS listed these electrodes as E80, thus we approved the WPS. However, the label on the weld wire box out in the field lists this electrode as E70, as does Lincoln Electric’s literature on the electrode. When asked by the special inspector, the steel erector claimed that NR-311 Ni electrode is equal to an E80 even though it is technically listed as E70. They have submitted documentation, with Lincoln Electric letterhead, stating that the electrode is E70 but meets the requirements of E80.
We are trying to determine if the electrode they are using meets the specifications, which specifically call for E80 electrodes. We’re attempting to contact Lincoln Electric directly to get their opinion but we could use some outside advice, especially since the testing agency for the project seems reluctant to suggest anything and is looking to us for direction. Have you ever encountered a similar situation and if so how was it resolved? Please let me know what you would suggest.
— Structural Engineer from Oakland, CA.
|A||2/07 – Response prepared by Doug Williams, a consulting metallurgical and welding engineer with over 35 years of experience in metal working industries
Strictly speaking, “E80” is not explicity defined in any AWS document that I am aware of, although it clearly suggests an 80 ksi minimum UTS electrode. If the specification did not specify a consumable classification, then “matching” requirements for an ASTM A913, Grade 60 or 65 would be the classifications listed in AWS D1.1, Table 3.1, Group III. These do not all start with “E80”, although they are nominally 80 ksi minimum UTS. If the consumable manufacturer states in writing that the particular electrode meets the properties of an E8XTX-X classification, then the Engineer could accept it. I would not expect any inspector or test lab to accept a classification unless it is shown as such on the consumable manufacturer’s literature or it was approved by the Engineer.
2/07 – Response prepared by Dave Palfini, Principal, ASNT Level III, AWS SCWI, Testing Engineers, Inc., San Leandro
AWS A5.29-98 classifies the Lincoln NR-311 Ni electrode a E70T7-K2 indicating that it has a minimum tensile strength to 70,000 psi. To add value to his or her service, the special inspector should have researched the contractor’s claim that this electrode met the requirements of the specifications. The special inspector, or his or her support personnel at the inspection agency’s laboratory, should have gone to the Lincoln Electric Company’s website (www.lincolnelectric.com) and downloaded information for this electrode from the manufacturer’s catalog as well as the electrode’s Certificate of Conformance. Both of these documents indicate that the electrode meets the requirements of the specifications, 80,000 psi minimum tensile strength, as wells as FEMA 353 requirements. These documents then should have been forwarded to the EOR for review, and either approval or rejection.
10.027 NDT of Fillet Welds?
|Q||What NDT inspection criteria is required by code for fillet welds?
— Structural Engineer from Houston, TX.
|A||1/07 – Response prepared by Tim Hart, S.E., an Associate at Dasse Design Inc.; Doug Williams, P.E., a consulting and welding engineer; and Dave Palfini, Divison Manager for Testing Engineers and an ASNT Level III
There are no general requirements for NDT of fillet welds in the 2001 CBC, AWS D1.1, AWS D1.8, or the AISC Specifications. The requirements in CBC Section 1703 apply only to the welds noted, and are the minimum NDT requirements. The Engineer has the option of requiring testing beyond the minimum requirements, including NDT of fillet welds, as part of the Statement of Special Inspections prepared by the responsible design professional. However, such testing is not specifically required by code.
Appendix Q of the 2005 AISC Seismic Provisions for Structural Steel Buildings (AISC 341) now lists specific locations where NDT is required for connections resisting seismic forces. The only connections that could potentially involve fillet welds are welds within the “k-area” of the section and repairs within the plastic hinge region of reduced beam section (RBS) moment frame connections. These provisions have not yet been adopted into the California Building Code.
FEMA-353 recommends the Engineer to develop a Quality Assurance Plan and indicate the appropriate Seismic Weld Demand Category and Seismic Weld Consequence Category for each welded joint on the design drawings. Magnetic particle testing is specified for fillet and PJP welds in all but two categories.
If desired, Magnetic Particle Testing (MT) should be used to test fillet welds. Ultrasonic Testing (UT) should not be specified for fillet welds.
10.024 Is an Overhead Puddle Weld Possible?
|Q||I have specified an overhead puddle weld on a project and the contactor is claiming that they cannot perform this weld. I’m attempting to determine if the contractor is correct. Do you have any thoughts on this?
— Structural Engineer from Oakland, CA.
|A||1/17/07 – Response prepared by Greg Ruf, Managing Engineer for Krazan & Associates’ San Francisco Bay Area Operations
Puddle welds are typically used to join sheet metal to underlying structural steel elements. These welds are generally completed by using high heat settings to allow for burning through of the sheet metal. With the higher heat required for this welding technique, a larger weld puddle is formed than would typically be created with the use of a lower heat (amperage) setting.
The connection strength of the puddle metal is a function of the perimeter area of the weld. With the larger puddle area of a puddle weld versus that of a linear weld or plug weld, and the higher heat of the molten metal, the application of a puddle weld is governed by gravity. The forces of gravity do not allow for the creation of a larger weld puddle as is common for a puddle weld in any position other than the flat position.
1/17/07 – Response prepared by Dave Palfini, Principal, ASNT Level III, AWS SCWI, Testing Engineers, Inc., San Leandro
Arc spot (puddle) welds and arc seam welds are only done in the flat position. See AWS D1.3-98, Table 1.2. It is almost impossible to do them in any other position.
1/17/07 – Response prepared by Doug Williams, Consulting Metallurgical and Welding Engineer
The simple answer is that if the contractor won’t do it, it’s not going to get done – regardless of theory.
See D1.3-98 Table 4.1 for standard joints. #4.4, Arc spot weld-sheet to supporting structural member is only shown for F, i.e., flat welding only. #4.5B is only shown for the horizontal position.
The relevant all-position weld might be #4.5, the arc plug weld.
|10/26/11 – Response prepared by Randy Ortiz, Safety & Technical Services Manager, Contract Erectors, Inc.
Yes, it is possible. However, it will have to be done with an all position welding electrode. The fact that it is possible does not relieve any inspector from following the code for the acceptance of the weld requirements. AWS D1.3 has tolerances that limit out of position puddle welds
10.023 What is Pulsed Arc Wire?
|Q||I’m working on a project where the welding inspector and the fabricator are recommending that for complete penetration welds, the root pass be 3/32 inch stick and the rest of the passes will be pulsed arc wire. Can you tell me something about pulsed arc wire?
— Structural Engineer from Oakland, CA.
|A||1/17/07 – Response prepared by Greg Ruf, Managing Engineer for Krazan & Associates’ San Francisco Bay Area Operations
The two most common types of Gas Metal Arc Welding (GMAW) metal transfer are short-circuit and spray transfer. Both processes use constant voltage and direct current. In the short-circuit process, which uses both a constant voltage and constant current, the filler wire contacts the base metal causing a short-circuit. The short circuit processes sufficient heat to melt the filler wire where the wire is in contact with the base metal.
Spray transfer is a process where the filler metal wire melts above the base metal and is projected across the arc as globules or as fine droplets of molten metal. Spray transfer can be accomplished using conventional constant voltage constant current or pulse current techniques and equipment.
Pulsed arc welding, also known as pulsed spray welding, is a spray-transfer form of GMAW. Pulsed arc welding process is also a constant voltage direct-current process where the current is not held constant but is pulsed. Melting of the filler wire occurs at the higher current associated with the electrical pulse wave, with the droplets of molten filler metal projected across the arc from the wire to the weld puddle. Thus the spray-transfer of the filler metal.
The spray transfer process has the ability to make high-deposition welds on thick carbon steels when using larger diameter filler wire. The current AWS Welding Code D1.1 precludes the use of short-circuiting for welding of structural steel and stipulates that the spray transfer method be used for GMAW.
An advantage of the pulse method of GMAW versus that of conventional spray transfer GMAW, as cited by suppliers of the equipment, is that the average current of pulse arc is equal to and often less than that of conventional spray transfer. The pulse method of welding can result in increased penetration with less heat buildup in the joint. Spray transfer, and in particular the pulsed arc method, is also identified with better root fusion than the short circuit method of GMAW. Another advantage of the pulse method of GMAW is the reduction in spatter over that of the steady current short-circuit method.
10.018 Specified Epoxy or Equal
|Q||On this project the Structural Engineer has specified a brand name epoxy or APPROVED EQUAL but the contractor wants to use a different brand – “the equal”. What constitutes an equivalent epoxy?
|A||2/07 – Response prepared by Lee Mattis, Division Manager for CEL Consulting and a registered engineer in California
Let’s talk about the different types of adhesives first. There are two primary types of adhesives: pure epoxies, which depend on the physical mixing of the two parts (resin and hardener) and vinyl esters and acrylics, which depend on a polymeric chemical reaction between two parts (resin and initiator). There are fast set and standard (slower) set versions of epoxies. The vinyl esters and acrylics typically gain strength quickly and can have load applied accordingly. Acrylics work well at low temperatures. Some products do not have good long term creep performance, which is an issue when constant loads are applied.
The application drives what is specified.
The chemical formulations provide the performance characteristics and they can vary greatly. So it’s not just a matter of load-carrying capacity when looking to determine an “equal” or “equivalent” epoxy. The application drives what is specified. In some cases it may not make any difference which product is used (e.g., a hold down inside a wall). In others it is critical (e.g., a suspended ceiling). Therefore the issue of “or equal” for adhesives is something that only the specifier (project engineer) who knows what is needed for the specific application, can answer.
It should also be noted that when a specification included on Approved (Building Department approved) plans includes an allowance of an “approved equal” or “approved equivalent” the responsible design professional must provide the Approval. Where the plans include a simple allowance of an “equal” or “equivalent” the responsible design professional should be requested to provide their approval for a proposed substitution based on the variable performance characteristics of the numerous epoxies available as discussed above.
10.017 UT Acceptance Criteria – FEMA-353 vs. AWS D1.1
|Q||I need some advice on the UT acceptance criteria for CJP welds. The welding inspector for the project that I’m working on claims that the acceptance criteria specified in AWS D1.1 differs from that specified in FEMA-353, and he is asking us to specify which criteria they should use. Our project uses special moment resisting frames, so the welds at the connections and the column splices are critical elements. The project specifications state the following: “Ultrasonic testing (UT) shall be conducted by the Owner’s Testing Agency for the percentage of joints designated in Table 2-1. UT shall be performed in accordance with AWS D1.1.” FEMA-353 is cited elsewhere in the specifications but not in regards to UT. I looked at AWS D1.1 and cannot determine if or how it differs from FEMA-353. I also reviewed AWS D1.8 and it appears to match FEMA-353 and thus adds to my confusion.
What concerns me about the specification is that I’m sure that the differences between AWS D1.1 and FEMA-353/D1.8 were not taken into account when the provision was written. That’s why I need the clarification. Should we be using D1.8 or D1.1 or both?
— Structural Engineer from Oakland, CA.
|A||7/23/06 – Response prepared by Dave Palfini, Principal, ASNT Level III, and AWS SCWI, Testing Engineers, Inc., San Leandro
AWS D1.1 has two ultrasonic testing procedures and acceptance criteria. The primary one, used for decades and most commonly accepted, is contained in Section 6, Part F.
Annex K, referenced in FEMA-353, UT Examination of Welds by Alternate Techniques, is relatively new. Since FEMA-353 was not specified for ultrasonic testing in the project documents, AWS D1.1, Section 6, Part F would be the procedure to be used. Some reasons for this are as follows:
AISC 341s1-05 and AWS D1.8-06 specify AWS D1.1, Section 6, Part F unless alternative procedures are approved by the engineer.
7/23/06 – Response prepared by Doug Williams, Consulting Metallurgical and Welding Engineer
If given the choice, I prefer the D1.1 criteria, primarily because there are precious few UT technicians that can accurately and reliably size flaws in 3 dimensions. As the welding inspector suggests in his original request, the FEMA-353 criteria may not be as conservative as D1.1, particularly considering the lower probability of detection and accuracy of sizing for technicians whose experience is predominantly with the D1.1, Sec. 6, Parts C & F criteria and methods.
10.016 Some Rust on Rebar is Acceptable
|Q||There is some question on our project whether rust on the reinforcing steel is acceptable. I’ve been told that rust was not a reason for rejection. Do you know of some authoritative document that takes account of cleanliness of the bar?
|A||1/17/07 – Response prepared by Terry Egland, Principal, Registered Engineer, Testing Engineers, Inc., San Leandro
According to the Concrete Reinforcing Steel Institute (CRSI) in a similar FAQ, they state “Rust actually improves bond because it increases the roughness of the surface. However – and this is the exception – if there is so much rust that the weight of the bar is reduced or the height of the deformation is reduced, then the rust is considered harmful.”
Check out the following references:
As noted in documents issued by ASTM, ACI, CRSI, and Caltrans, some rusting of the reinforcing steel is acceptable and advantageous. The difficulty in addressing this issue is the subjectivity of a visual evaluation as suggested by CRSI (“A light surface coating…”) and Caltrans (“…free of …excessive mill scale and scabby rust and other coatings of any character…’). Common sense and fabrication tolerances should be used. Where there is readily visible pitting or scale associated with rust (not mill scale) and where the engineer or inspector have cause for concern that the deformations and/or cross sectional area of the bar have been reduced, the degree of rusting may need to be determined by laboratory testing. As always, the project specifications, where more stringent than the published standards, shall prevail over all else.
10.015 Floor Flatness & Levelness
|Q||What is the difference between the new floor flatness numbers FF and FL and the old straightedge specifications of 1/8″ in 10 ft.?
|A||2/07 – Response prepared by Cliff Craig, Vice President of Technical Operations for Dynamic Consultants, Inc. and a registered engineer in California.
The FF and FL numbers represent a statistical calculation of the flatness and levelness of a concrete slab as determined with slope measuring equipment. Testing is performed in accordance with ASTM E1155 Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers. The higher the F-number the better the characteristic of the floor.
The straightedge method specifies that the gap observed under a free-standing or leveled 10 ft. long straightedge shall not exceed 1/8″. The problem with this method is that there is no standard method for taking measurements (i.e., number of tests, location, direction) or quantitative procedure for establishing compliance of a test surface.
The following excerpts from ACI help clarify some of the industry guidelines:
ACI 302 Guide for Concrete Floor and Slab Construction
Section 184.108.40.206 – The older method of using a 10-ft. straightedge can also be used to measure floor flatness, but it is much less satisfactory that the F-number system. There is no nationally accepted method for taking measurement or for establishing compliance of a test surface using the tolerance approach. This can often lead to litigation.
ACI 117 Standard Specifications for Tolerances for Concrete Construction and Materials
Section 4.5.7 – Floor finish tolerance as measured by placing a freestanding (unleveled) 10 ft. straightedge anywhere on the slab and allowing it to rest upon two high spots within 72 hr after slab concrete placement. The gap at any point between the strightedge and the floor (and between the high spots) shall not exceed:
The 1/8 inch in 10 ft specification has been a common specification. However, it is seldom measured and rarely enforced due to its unscientific and non-repeatable method. It is approximately equivalent to an FF of 50, which is a very flat floor, not normally required for typical concrete slab surfaces. Most convenventional slabs have flatness readings (FF) between 20 and 30.
The F number system is the preferred method of specifying and verifying compliance of floor finish tolerances and should be used in lieu of the archaic 1/8″ in 10 ft.
10.014 Do Metal Fasteners in Contact With Wood Preservative Require Corrosion Protection?
|Q||Do foundation hold-down bolts, anchor bolts, plate washers, straps, nails, etc., attaching pressure preservative treated wood, have to be hot-dipped zinc coated galvanized, stainless steel, silicon bronze, or copper?
— From the October 2001 Inspection Division Quarterly Newsletter,
|A||2/09 – Response prepared by Terry Egland, a principle at Testing Engineers, Inc., and a registered engineer in California.
The International Residential Code (R319.3) and the International Building Code (2304.9.5) have similar requirements for fasteners used with treated wood. The IRC states, “Fasteners for pressure-preservative and fire-retardant-treated wood shall be of hot-dipped zinc coated galvanized steel, stainless steel, silicon bronze or copper. The coating weights for zinc-coated fasteners shall be in accordance with ASTM A153. Exceptions: 1) One-half inch (12.7 mm) diameter or greater steel bolts. 2) Fasteners other than nails and timber rivets shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55, minimum.”
The codes do not discriminate between types of preservatives and do not take into account exposure conditions, nor do they contain provisions for other hardware such as connectors or flashing.
The potential for corrosion of hardware in contact with treated wood occurs when metals in the preservative (such as copper) are different from the metals in the hardware (the iron in steel, or aluminum). In a wet environment these dissimilar metals create a small electrical current that triggers a chemical reaction resulting in galvanic corrosion.
In damp or wet exposure, hardware in contact with pressure-treated wood must be corrosion resistant. Hardware includes fasteners (e.g. nails, screws, and bolts) and all connectors (e.g. joist hangars, straps, hinges, post anchors, and truss plates).
Regardless of exposure condition, fasteners and connectors should be specified in compliance with the hardware manufacturer’s recommendations and the building codes for their intended use.
A conclusion from the above would indicate that shear wall nailing to a pressure-treated sill plate requires galvanized nails.
10.010 What Variations Can Be Developed From A WPS?
|Q||Does a PQR for a butt joint qualify a WPS for a T or corner joint with the same weld size?
Also, does a PQR for a groove weld qualify a WPS for a fillet weld of the same size?
|A||6/16/06 – Response prepared by Dan Watanabe, Metallurgical Laboratory Mansger, Testing Engineers, Inc., San Leandro
Yes, WPS qualification of a complete joint penetration (CJP) groove weld (butt joint) qualifies tee and corner (CJP and PJP) joints within the limits of the qualified WPS. It also qualifies fillet welds within the limits of AWS D1.1 Table 4.1 and 4.2 Note 4. Most fillet welds are afforded pre-qualified status per AWS D1.1 Section 3.9.
6/16/06 – Response prepared by Dave Palfini, Principal, ASNT Level III, and AWS SCWI, Testing Engineers, Inc., San Leandro
When responding to frequently asked questions, the apparent code answer is not always what the inquirer may be seeking. When reviewing and approving welding procedure specifications, the Engineer has the authority to “relax” code requirements or enforce more stringent requirements. In this case, it is possible that the project team was looking for a more comprehensive analysis due to a critical connection required by their design. Following is an interpretation of the code with that thought in mind.
1. For a complete joint penetration (CJP) groove weld, at first glance, yes. AWS D1.1-06, Section 220.127.116.11 Corner or T-Joints states “Test specimens for groove welds in corner or T-joints shall be butt joints having the same groove configuration as the corner or T-joint to be used on construction….”
However, AWS D1.1-06, Table 4.3, Note 2. states “If a PJP bevel- or J-groove weld is to be used for T-joints or double-bevel- or double-J-groove weld is to be used for corner joints, the butt joint shall have a temporary restrictive plate in the plane of the square face to simulate a T-joint configuration.”
Welding Procedure Specifications (WPSs) requiring qualification by test, resulting in Performance Qualification Test Records (PQR), are typically done to qualify an unproven joint configuration, base metal, weld metal combination. The ability of a/any welder to accomplish a sound weld during construction using this type of WPS is very important
It is recommended that WPSs that are not pre-qualified for T-joints and/or corner joints with J-grooves or double-bevel groove or double-J-groove, whether CJP or PJP, be qualified using a temporary restrictive plate, prior to approval by the Engineer.
2. Yes. AWS D1.1-06, Table 4.2, Note 4. states “CJP groove weld qualification on any thickness or diameter shall qualify any size fillet or PJP groove weld for any thickness.”
10.009 Curing Room Recording Thermometer
|Q||In ASTM C511-04, it talks about calibration of the recording thermometer, then continues to discuss how to perform verification of the recording thermometer. If the recording thermometer is calibrated every six months, what logic says we have to perform verification? This seems redundant. Can you give us a little insight of this logic?
Excerpt from Section 5.1, ASTM C511, Standard Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic Cements and Concrete:
“The recording thermometer shall be calibrated at least every six months or whenever there is a question of accuracy.
Perform the verification of the recording thermometer by comparing the temperature reading of the recording thermometer with the temperature reading of a reference thermometer during the normal operation of the moist cabinet or moist room.
The thermometer used as the reference thermometer must be accurate and readable to 0.5°C.”
|A||10/12/05 – Response prepared by Terry Egland, Principal, Testing Engineers, Inc., San Leandro
I posed this question to the ASTM staff member in charge of C511, who asked Mr. Ray Kolos of CCRL to respond. Mr. Kolos stated that the intent of the standard is that verification of the recording thermometer will be conducted every six months using a reference thermometer. Section 5.1 uses the term “calibrated” even though verification is intended. Mr. Kolos will ask the chairman of the ASTM Committee C1.95, Mr. Dave Norris, to consider modification to correct the error.
10.008 Substitution of Specified Anchor Bolts
|Q||The contractor has substituted ASTM A307 Grade C anchor bolts where ASTM A36 anchor bolts are specified. Is this acceptable?
|A||2/23/06 – Response prepared by Dave Palfini, Principal, Testing Engineers, Inc.
A quick look at the “Scope” of ASTM A307 Standard Specification for Carbon Steel Bolts and Studs, 60,000 psi Tensile Strength, indicates that Grade Cs are non-headed anchor bolts, either bent or straight, and having properties conforming to Specification A36. This seems to answer our question in a very straightforward manner
If we look at the Standard Specification ASTM A36 for Carbon Steel the mechanical properties listed in Table 3 for bars are as follows:
and Section 3.1of A36 states “When components of a steel structure are identified with this ASTM designation but the product form is not listed in the scope of this specification, the material shall conform to one of the standards listed in Table 1 unless otherwise specified by the purchaser.”
So, in Table 1 of A36, for anchor bolts, we find the designated specification of ASTM F1554 Standard Specification of Anchor Bolts, Steel, 36, 55, and 105-ksi Yield Strength with the following Note:
The mechanical property requirements for ASTM F1554 Grade 36 anchor bolts are identical to A36 and A307 Grade C.
Conclusion: ASTM A307 designates F1554 as the controlling specification and the mechanical properties of A307 Grade C are identical to that specified for F1554 Grade 36.
Discussion: ASTM F1554 Standard Specification of Anchor Bolts, Steel, 36, 55, and 105-ksi Yield Strength was introduced in 1999. It marked the first time that hooked, headed and threaded and nutted rods in multiple grades were fully addressed in one specification. F1554 grades 36, 55, and 105 are essentially the anchor-rod equivalent of the generic rod specification ASTM A36, A572 Grade 55, and A193 Grade B7, respectively. The benefits of F1554 are clear: there is no other specification that brings all requirements for anchor-rods together into one place – mechanical, chemical, threading, manufacturing, and dimensional. Compared to older “material-only” specifications like A36, F1554 eliminates confusion about what product is required.
10.007 Concrete Strength Tester
|Q||My laboratory has ACI Concrete Laboratory Testing Technicians – Grade 1. Recently, we were informed by ACI that we should be using ACI Concrete Strength Testing Technicians to break concrete. This does not seem correct since the tests for the strength tester are also in the Grade 1. Please advise?
|A||8/25/05 – Response prepared by Jeffry Cannon, Laboratory Manager, Kleinfelder, Inc., Sacramento
The ACI Concrete Laboratory Testing Technician – Grade 1 certification includes capping and testing concrete cylinder specimens for compressive strength, but does not include flexural strength testing. Certification for this test may be obtained by the Concrete Strength Testing Technician or Concrete Laboratory Testing Technician – Grade 2 certifications. If certification for performing only compression tests is required, the Concrete Laboratory Testing Technician – Grade 1 certification should be sufficient.
10.006 7-Day Concrete Strength Reports
|Q||Is it required that my laboratory report 7-day break results to the client? The customer often calls back worried that the project requirements are not met.
|A||8/25/05 – Response prepared by Jeffry Cannon, Laboratory Manager, Kleinfelder, Inc., Sacramento
There is no requirement in the UBC or ASTM standards that requires reporting concrete test results. Project specifications typically address the required 28-day compressive strength, with some specifications also including a 7-day compressive strength. On projects where the concrete compressive strength is specified at an age of 28 days, a 7-day compressive strength test may provide an indication of the 28-day strength. Many laboratories consider concrete with a 7-day strength of less than 65% of the 28-day strength to be suspect (see FAQ 10.004). Most laboratories consider it good business to notify their clients of 7-day compressive strength results that are less than 65% of the 28-day strength, and to include the 7-day strength when reporting the 28-day results.
10.005 Shotcrete Core Diameter
|Q||What is the diameter for a shotcrete core tested in compression?
|A||11/22/05 – Response prepared by Jeffry Cannon, Laboratory Manager, Kleinfelder, Inc., Sacramento
UBC Section 1924.10 states that shotcrete with maximum nominal aggregate larger than 3/8-inch shall be tested using 3-inch diameter cores or 3-inch cubes. Shotcrete with maximum nominal aggregate of 3/8-inch or smaller shall be tested using 2-inch diameter cores or 2-inch cubes.
ASTM C1140 requires shotcrete be tested as drilled cores or sawed cubes, and references C42 and C513, respectively, for obtaining the specimens. Cores shall be at least 3.70-inches in diameter for load bearing structural shotcrete. Cores for non-load bearing shotcrete, or when it is impossible to obtain cores with length-diameter ratios greater than or equal to 1, are not prohibited. Cubes shall be 2-inches to 4-inches in size, with no size requirement based on aggregate size.
8. CORES FOR COMPRESSIVE STRENGTH
8.1 Diameter – The diameter of core specifications for the determination of compressive strength in load bearing structural members shall be at least 3.0 in. [75 mm] (see Note 4).
Core diameters less than 3.0 in. [75 mm] shall be permitted as directed by the specifier of the tests.
Note 4 – The compressive strengths of 2-in. [50-mm] diameter cores are known to be somewhat lower and more variable than those of 3-in. [75-mm] diameter cores. In addition, smaller diameter cores appear to be more sensitive to the effect of the length-diameter ratio.
This new standard will bring us better into alignment with IBC, UBC and CBC
10.004 7-Day Concrete Strength is a Percentage of What?
|Q||Our testing laboratory routinely supplies our customers with 7-day concrete break results. At what percentage of the specified strength should we state there might be a problem with the final result?
|A||07/28/05 – Response prepared by Jeffry Cannon, Laboratory Manager, Kleinfelder, Inc., Sacramento, CA
|Different concrete mixtures will gain strength at different rates, so there is no universally applicable rule about what a 7-day strength versus 28-day strength ratio will be. This is also true because of the numerous types and brands of cement, and the hundreds of different admixtures routinely used in concrete today. But as a general rule of thumb for normal-weight concrete that does not contain unusual ingredients, 7-day strengths that are less than 65% of the required 28-day strength should warrant close attention.
NOTE: If the concrete mix contains fly ash, especially large amounts of fly ash, strength gain will be slower than mixes that do not contain fly ash.
10.003 Free Falling Concrete
|Q||Where in the UBC does it state the maximum drop height of concrete? The closest code sections I can find in 1905.10 that just states to deposit the concrete as close as possible to final position.
|A||11/?/05 – Response prepared by Greg Ruf, Managing Engineer – San Francisco Bay Area Operations, Krazan & Associates
The short answer to your question is that there is no UBC limitation on the maximum drop height of concrete during placement. Although factually there is no UBC requirement to limit concrete drop height, there are implied practical limits. The Code refers to the issue of concrete segregation during conveying and depositing of concrete. In referencing UBC Section 1905.10 you correctly cited the Code but left out an important element of the Code provision. Section 1905.10 states “Concrete shall be deposited as nearly as practical in its final position to avoid segregation [emphasis added] due to rehandling or flowing.” Section 1905.9.2 states “Conveying equipment shall be capable of providing a supply of concrete at site of placement without separation of ingredients…”. These two provisions show intent to maintain concrete quality to the point of final deposit by preventing or avoiding separation of materials. Experience has shown that free falling of concrete through close spaces with obstructions, such as reinforcing steel and embeds, can cause segregation of concrete. Based on this experience and the absence of specific limits on free-fall drop heights in the UBC, a specific provision was added to Title 24 of the California Building Code. CBC Section 1905A.10.9 states “In depositing concrete in columns, walls or thin sections of considerable height, concrete shall be placed in a manner that will prevent segregation… unless otherwise approved by the enforcement agency, the unconfined vertical drop of concrete… to the placement surface shall not be greater than 6 feet (1829 mm).” The American Concrete Institute also addresses placement of concrete in several publications, including ACI 304R-00. ACI 304R-00 states that “… if forms are sufficiently open and clear so that concrete is not disturbed in a vertical fall into place, direct discharge without the use of hoppers, trunks, or chutes is favorable.” In summary, though not specifically limited, drop height has been shown to have practical limits based on the conditions where the concrete is being placed. The drop height should be limited to that where concrete quality can be maintained and segregation is prevented.
The reader may wish to closely examine position paper #17 from American Society of Concrete Contractors, which does note than “Concrete placing operations are often planned to allow for the free fall of concrete. This planning must also consider any segregation that might occur when the concrete free falls into place.” The paper may be viewed at www.ccagc.org/tech_info.php or purchased online at www.ascconline.org.
10.002 Notes & Footnotes in ASTM Standards – Mandatory or Not?
|Q||We’ve just had a laboratory evaluation and one of the test methods examined was ASTM C39. As a footnote to our evaluation they noted that the compression testing machine had bearing blocks that were slightly softer than the 55 HRC mentioned in NOTE 4 of C39. How do we handle this in the future without the cost of hardness testing?
|A||3/24/05 – Response prepared by Terry Egland, Principle, Testing Engineers, Inc.
Rather than address the subject of hardness and what might be a reasonable tolerance, let’s discuss the point of authority that the evaluator is quoting. According to an ASTM document “Form and Style for ASTM Standards” Section A27.1 “Notes in the text shall NOT include mandaroty requirements. Notes are intended to set explanatory material apart from the text itself, either for emphasis or for offering informative suggestions not properly part of the standard.” Therefore, I would suggest that the Subcommittee C09.61 on “Testing Concrete for Strength” feels that a comment on hardness is appropriate but cuts short of mandatory language. The subcommitee has recommended a hardness number of 55 HRC. A slight difference from the recommended would not be a violation of the intent of C39 but a reasonable tolerance is not given.
The same document mentioned above also discusses Footnotes in Section A26.1. “Footnotes referenced in the text are intended ONLY for reference and shall never include any informaton or instructions necessary for the proper application of the method. Table footnotes area a part of the table.” Therefore, again, we see that no mandatory language should be outside of the main text of the document.
10.001 Establishing Concrete Strengths with Core Tests @ 85%
|Q||I’m investigating an older concrete building and would like to use ACI 318 Section 5.6.5 to confirm the existing concrete strengths. Can you outline a procedure for specifying the work and explain the rule of 85%?
|A||3/24/05 – Response prepared by Terry Egland, Principle, Testing Engineers, Inc.
|A nondestructive test method, such as probe penetration, impact hammer or ultrasonic pulse velocity may be useful in surveying structural members for areas of lower strength concrete. From this preliminary view point use ASTM C823-00 “Standard Practice for Examination and Sampling of Hardened Concrete in Construction” to formulate specific areas of investigation. The selected areas then can be specified for investigation for concrete strength according to ASTM C42-04 “Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete”. Section 3.2 states “Generally, test specimens are obtained when doubt exists about the in-place concrete quality” and “use of this method is to provide strength information on older structures.”
|According to International Building Code (IBC) Section 1905.6.5.2, three cores will be taken for each strength test. And Section 1905.6.5.4 states, “the average of three cores is equal to at least 85% of f’c“.
The rule of 85% can be best explained by ASTM C42-04 Section 3.5: “There is no universal relationship between the compressive strength of a core and the corresponding compressive strength of standard-cured molded cylinders. The relationship is affected by many factors such as the strength level of the concrete, the in-place temperature and moisture history, and the strength gain characteristics of the concrete. Historically, it has been assumed that core strengths are generally 85% of the corresponding standard-cured cylinder strengths, but this is not applicable to all situations.”
The commentary of ACI 318 Section R5.6.5 also states “Core tests having an average of 85% of the specified strengths are realistic. To expect core tests to be equal to f’c is not realistic, since differences in the size of specimens, conditions of obtaining samples, and procedures for curing, do not permit equal values to be obtained.”
NOTE: According to ACI 214.4R-03 “Guide for Obtaining Cores & Interpreting Compressive Strength Results” the preceding method is NOT an option when evaluating for structural capacity.
For further information ASTM references Neville, A., “Core Tests: Easy to Perform, Not Easy to Interpret”, Concrete International, Vol.23 No. 11 November 2001, pp. 59-68.