NRMCA Attends ASTM Meeting in Toronto, Files Updates on Key Issues

Earlier this month, NRMCA Engineering Staff attended the ASTM meeting of Committees C09 on Concrete and C01 on Cement in Toronto and filed the following update:

C09.20 Concrete Aggregates - Revisions on drying aggregate and consolidation methods were approved to ASTM C29, bulk density of aggregates, that will result in revised standard C29-17a. Minor revisions were approved to C142 on clay lumps and friable particles and C87 on effect of organic impurities. A proposed revision to delete the appendix to C33 that provides guidance on alkali aggregate reaction and refer to practice ASTM C1778 was not successful; this will be revised and re-balloted. Discussion related to the implied requirements to test aggregates for ASR with the reference to C1778. Minor revisions to the new specification on mineral fillers, ASTM C1797 are moving forward for consideration by the main committee. One concern is the use of carbonate-based mineral fillers in concrete that will be exposed to sulfates in service.

C09.24 Supplementary Cementitious Materials - The subcommittee approved a revision to classify fly ash based on the calcium oxide content (as opposed to the current sum of oxides) and this will be on the main committee ballot. A proposed revision to use fly ash on a volume replacement for the strength activity index was not successful. The subcommittee is proposing to use a standard reference cement (like is available for slag from CCRL) for the strength activity index test. An effort to develop a separate specification for natural pozzolan was not successful. The subcommittee felt that natural pozzolans should continue to be covered in ASTM C618. Specifications are being developed for colloidal silica and finely ground recycled glass powder. The subcommittee is considering three different tests to evaluate pozzolanic activity based on bound water; calcium hydroxide consumption; and heat of hydration based on calorimetry. Ongoing work by a RILEM committee in Europe will be considered. The subcommittee will ballot the lime-based strength activity index test (CSA A3004-E1, Annex A) and hydraulic activity test (ASTM C1073). It was noted that a Natural Pozzolan Association has been formed. It was reported that 600,000 tons of natural pozzolans was used in concrete last year, primarily in western U.S.

C09.26 Chemical Reactions - Revisions are in progress for ASTM C1293 to permit the use of blended supplementary cementitious materials and to clarify the alkali content of mixtures when using blended cements. This subcommittee will be merged with subcommittee C09.50 to address all standards related to alkali aggregate reactions.

C09.40 Ready Mixed Concrete - ASTM C94-17 included some substantive revisions from the previous meeting. At this meeting, a revision was approved to C94 to permit the use of returned fresh concrete by referencing recently-approved standard C1798 with the restrictions and reporting requirements stated therein. The purchaser will need to be notified regarding reuse of returned fresh concrete. The subcommittee also considered a proposal to eliminate the numerical delivery limitation of 90 minutes. The response to the ballot generated considerable discussion for consideration. Voters provided several philosophical and technical reasons to support and oppose this change. Several new items for inclusion in C94 were also discussed and will be proposed in future ballot items. 

C09.50 Risk Management for Alkali Aggregate Reactions (AAR) - The committee has four task groups 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; 4. Improve the process of classifying risk of ASR to different types of structures.

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. The subcommittee is collecting data on the mortar bar (C1260) and concrete prism (C1293) results on the same aggregate.

C09.60 Fresh Concrete Tests - Revisions to C138 (density of fresh concrete) references C1758 for filling and consolidation of self-consolidating concrete. A revision to C231 includes a precision statement resulting from a recently performed inter-laboratory study (air content by pressure method). The single operator and multilaboratory variation of the results increases as the air content increases. The subcommittee continues to develop a new standard on measuring the electrical resistance of fresh concrete.

C09.61 Strength - Revisions approved to ASTM C39 include a simplified formula for calculating compressive strength, stating tolerances for test age, and clarifying the process of centering the specimen in the testing machine. A task group is working on better defining the initial curing requirements in the field for standard curing in ASTM C31. A new standard was approved for fabricating and testing specimens of ultra-high performance concrete. This standard establishes procedural differences to C31 and C39 for this type of concrete. There were several revisions in process for ASTM C78 on testing beams for flexural strength. A new precision statement has been proposed to cover 6-in and 4-in wide beam specimens. 

C09.66 Fluid Penetration - Precision and bias statements are being developed for many test methods, including ASTM C1202 (RCPT), C1543, C1585, C1556 and 1760. There was discussion on balloting to withdraw ASTM C1543 and C642. The subcommittee continues to work on two test methods to measure the resistivity of hardened concrete – a surface resistivity method and a bulk resistivity method. Degree of saturation of the specimens is a major factor in the measured resistivity results.

C01.10 Hydraulic Cement - A revision was approved to revise C595 and C1157 to remove a drying shrinkage limit for blended cement with the low heat of hydration (LH) special property. Revisions were approved to ASTM C150 (portland cement) and C595 (blended cement). Other revisions to the cement standards are being developed through a joint ASTM AASHTO harmonization task group. These include reporting chlorides, requirements for alkali aggregate reactions, establishing similar strength requirement for all special property blended cements and reporting alkali content of constituents of blended cements.

New Subcommittee C01.14 - Was established to develop standards for non-hydraulic cements. These could include carbonate or magnesium phosphate based products or activated fly ash cementitious materials used without portland cement (often referred to as geopolymers). The subcommittee plans to develop specifications and test methods pertinent to these products.

Workshop - Nick Carino and NRMCA's Colin Lobo presented a workshop on determining ingredient variability of concrete and writing specification limits based on testing variability. The applicable standards are ASTM C1451 and D6607, respectively.