NRMCA Attends ASTM Meeting in New Orleans, Files Key Updates
Earlier this month, NRMCA Engineering Department Staff traveled to New Orleans to attend the ASTM meeting of Committees C09 on Concrete and C01 on Cement and filed the following report:
C09.20 Concrete Aggregates - The subcommittee continues to work on revisions to ASTM C33, Specification for Aggregates, to remove the guidance on alkali aggregate reactions by providing a reference to ASTM C1778. The primary concern is testing aggregates for alkali aggregate reactivity and the revision will propose that methods and details will be based on the request of the purchaser. A revision is in progress for sieve analysis, C136 to permit drying an aggregate sample by vacuuming. Some minor revisions were approved to the specification on mineral fillers, C1797. Moving forward, the subcommittee will consider options for testing the sulfate resistance of mortars containing carbonate-based mineral fillers. Currently, there is a caution regarding the use of these materials in concrete exposed to sulfates in service. Revisions were approved to the method for measuring soundness of aggregates, ASTM C88.
C09.24 Supplementary Cementitious Materials - The main committee ballot negatives for fly ash classification based on calcium oxide limit were discussed and a tolerance on the limit will be removed while retaining a requirement that the sum of oxides should exceed 50% for all fly ashes. Negatives on a main committee ballot for a proposed specification for ground glass pozzolan were discussed. It was decided to include language in the specification where the supplier will provide adequate data on ASR mitigation. A new specification is being developed for colloidal silica and for alternative SCM based on the ASTM C1709 guide. A variation of strength activity index that will differentiate between the strength gain due to water reduction and chemical reactivity will be balloted as an appendix in ASTM C311. The subcommittee is considering four tests to evaluate pozzolanic activity based on bound water; calcium hydroxide consumption; heat of hydration based on calorimetry; and a lime based strength reactivity index test. The current strength activity index requirement is unable to distinguish between inert fillers and SCMs that provide hydraulic or pozzolanic reactivity to improve strength. Some of the proposed methods will take only 7 days.
C09.26 Chemical Reactions - This subcommittee will be merged with subcommittee C09.50 to address all the standards related to alkali aggregate reactions (AAR) as well risk management for AAR.
C09.40 Ready Mixed Concrete - ASTM C94-17a included some substantive revisions from previous balloting. The primary issue discussed at this meeting was a proposed revision to replace the 90-minute time limit for delivery with a limit set by the producer or purchaser. The subcommittee addressed several negatives and will revise and reissue a revised ballot. Other work in progress is to require a retest when tests fail slump and air content and to include a reference to the specification for mineral fillers, ASTM C1797.
C09.50 Risk Management for Alkali Aggregate Reactions (AAR) - The committee has four task groups (TG) looking at the following: 1. Improve the flowchart for establishing the reactivity of aggregates in C1778; 2. Finding a correlation between ASTM C1293 and ASTM C1260 with existing data and correlating with field performance; 3. Define multiple prevention levels for the performance-based approach similar to the prescriptive approach; and 4. Improve the process of classifying risk of ASR to different types of structures.
Some issues considered: the current flowchart requires petrography to be done even if the aggregate is known to be reactive; establishing a time limit for ASR test results; the reliability of the performance approach in some situations; the considerable variation in mitigation requirements by the prescriptive approach depending on the risk level selected. Typically, the prescriptive approach was more conservative than the performance approach. Other revisions discussed were related to the use of natural pozzolans and ground glass type pozzolanic material. Clarifications will be proposed regarding the use of blended cement and blended supplementary cementitious materials.
C09.60 Fresh Concrete Tests - Minor revisions were approved to the temperature method, C1064, and sampling, C172. A proposed revision, based on data from two studies, will permit obtaining a concrete sample in one portion (as opposed to two or more as a composite) for testing concrete. This revision needs to be approved by the main committee. The subcommittee balloted revisions to a new standard on measuring the electrical resistance of fresh concrete that will continue to evolve with revisions. The subcommittee considered a request to re-establish the K-slump tester, a probe device inserted in fresh concrete, for measuring workability of super-plasticized concrete, but support was lacking.
C09.61 Strength - A revision was approved to ASTM C39 on testing cylinders to include a tolerance of 2% to the specified test age. Several revisions were addressed with some being approved for C78 for testing flexural strength of beams (3rd point loading). A revision will be proposed to ASTM C39 ballot to include a record of the max/min temperatures during initial curing that is required to be reported to the lab in ASTM C31. An inter-laboratory study has been completed for development of a precision statement for measuring the modulus of elasticity and Poisson’s ratio by ASTM C469. The data is being analyzed to establish the precision statement, but it was indicated that the variation of the measured modulus on 6x12 inch specimens was lower. Strength levels of concrete evaluated were from 8000 to 18000 psi. A revision will better define the gage length in this method.
C09.66 Fluid Penetration - Several revisions were approved to ASTM C1202, the rapid chloride permeability test, including an editorial revision to the precision statement. A revision will be proposed to include a correction to the measured value based on the specimen length and to verify the amperage using a standard resistor. A task group has been set up to clarify the language pertaining to the vacuum pressure requirement in ASTM C1202. The subcommittee considered the usefulness of the method to determine permeable voids, ASTM C642, which several users continue to use. Precision data based on a 2003 round robin program showed that the chloride ponding test, ASTM C1543, was highly variable. The subcommittee will allow the method to lapse due to lack of revisions at the end of 2018. The method is available as an AASHTO standard.
Precision and bias statements have been developed for other test methods, including C1585, C1556 and 1760. The subcommittee discussed negatives on the main committee on a new bulk resistivity test. The subcommittee continues to work on the surface resistivity method. Degree of saturation of the specimens is a major factor in the measured resistivity results. The subcommittee discussed the development of a new guide to calculate the formation factor of concrete, which provides a property characterizing permeability. The results of the electrical tests will be used in the calculation of the formation factor.
C09.64 Non Destructive Testing - The subcommittee discussed potential revisions to the testing of cubes in ASTM C1074 (maturity methods) for determining the activation energy.
ASTM C09.67 Resistance to Environment - Revisions are proposed to the test for evaluating scaling, ASTM C672, to make it more consistent with the Canadian (CSA) standard. The main differences are the use of sodium chloride instead of calcium chloride as the ponding solution and conditioning the specimens by immersion in sodium chloride solution for 7 days prior to exposure to freezing and thawing cycles. These revisions reduce the severity of this test and make it more predictable to field performance.
C09.94 Data Analysis - A revision was approved to ASTM C1451 that included a change in title: Standard Practice for Determining the Variability of Concrete-Making Materials from a Single Source. The revision clarifies some details of the standard and the calculations involved.
C01.10 Hydraulic Cement - Revisions in progress to ASTM C150 involved removing references to ASTM C186 for heat of hydration and including reporting requirements based on isothermal calorimetry, C1702, and retaining the heat index value based on composition; reporting of chlorides; removing reference to fineness by Wagner, and to remove the criteria defining low-alkali cement, while requiring that the alkali content be reported. Revisions to C595 on blended cement include some revisions to testing pozzolans for alkali silica reactivity, replacing C186 with C1702, and deleting a requirement to test shrinkage with low heat (LH) cements. Revisions approved include a requirement to report alkali content of natural pozzolans if used in a blended cement and simplifying the strength requirements for different cement types with special properties.
New Subcommittee C01.14 established to develop standards for non-hydraulic cements, discussed options with moving forward. One of the products is a calcium silicate-based cement that develops its hardened properties by carbonation. The model for a specification for these types of cement would be a combination of performance based tests as in ASTM C1157.
C01.27 Cement Strength - A revision was approved to ASTM CC917 that included a change in title: Test Method for Evaluating the Variability of Cement from a Single Source based on Strength. The revision addresses several clarifications on the use of the standard, the calculations involved and the reporting format. The revision makes this a dual unit standard.