NRMCA Staff Attends ASTM Meeting, Files Updates on Key Committee Action
Earlier this month, NRMCA staff attended a meeting in Orlando, FL, of ASTM Internation Committees C09 on Concrete and C01 on Cement. The following is the report of key committee action:
C09.20 Concrete Aggregates - Revisions were approved for ASTM C29, bulk density of aggregates, and C40 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. The subcommittee is considering revisions to the new specification on mineral fillers to accommodate other types of materials.
C09.24 Supplementary Cementitious Materials - The mission of the subcommittee is being revised to so that it can develop standards for other types of supplementary cementitious materials. Specifications are being developed for colloidal silica, finely ground recycled glass powder and natural pozzolans. The subcommittee is considering alternative methods to evaluate pozzolanic activity of supplementary cementitious materials based on bound water, lime pozzolanic reactivity test or calorimetry. Ongoing work by a RILEM committee in Europe will be considered. A revision to C618 will remove a reference to the ASR optional test (ASTM C441) and develop an appendix that discusses ASTM C1778. A revision will establish more definitive procedures for the loss on ignition (LOI) test. The subcommittee continues to discuss classification of fly ash based on calcium oxide content.
C09.26 Chemical Reactions - A ballot has been developed to remove guidance in the appendices of the ASR test methods and refer to ASTM C1778. Revisions are in the works for ASTM C1293 to permit the use of blended SCMs and to clarify the alkali content of mixtures when using blended cements. The subcommittee was updated about the CSA efforts in developing test methods for pyrrhotite based on sulfide content, oxygen consumption and mortar bar expansion. This mineral in aggregates has been identified as the cause of concrete deterioration in Connecticut.
C09.40 Ready Mixed Concrete - Some substantive revisions were approved to ASTM C94:
• A revision to slump tolerances will indicate that water addition at the jobsite should not be restricted when a maximum slump is specified.
• A revision will permit adjustment to achieve required slump with water reducing admixture in transit or at the jobsite
• A revision clarifies batching accuracy of aggregate.
• A revised Annex provides detailed procedures for mixing uniformity evaluation of mixers.
Revisions in the process include:
• Requiring a retest on a separate sample when tests fail requirements for slump and air content;
• Section related to technician certification;
• Including a reference to C1797 that will permit the use of mineral fillers
• Addressing the use of returned concrete in C94 by providing a reference to ASTM C1798; and
• Addressing the use of electronic tickets.
Researchers from the CIM Program at the New Jersey Institute of Technology presented a study on extended delivery time and impact on concrete properties in hot and cold weather. The research results will be used to address and possibly eliminate the 90-minute limit for delivery of concrete in C94.
C09.50 Risk Management for Alkali Aggregate Reactions (AAR) - The committee discussed ways to improve the flow chart in C1778 that provides guidance on developing mixtures that can mitigate ASR. Task groups are active on risk level classification of structures and criteria for performance-based prevention levels.
C09.60 Fresh Concrete Tests - Minor revisions were approved to ASTM C138 regarding verifying vibrators and to C231, air content by the pressure method. A precision statement for air content by C231 is being finalized. The subcommittee is working on revisions to slump, C143, sampling, C172, and temperature, C1064. A new method to measure the resistivity of fresh concrete has been balloted a few times and this effort is continuing. The method is being proposed to check on setting time, checking w/cm when previously calibrated and for other indicator properties of fresh concrete.
C09.61 Strength - Revisions approved to ASTM C39 include expressing the calculation of compressive strength using a formula, establishing tolerances for test age and defining 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. The subcommittee is finalizing a standard to measure the compressive strength of ultra high performance concrete to include provisions where the current standards cannot accommodate such testing. A presentation was delivered on an inter laboratory study to develop the precision statement for flexural strength of beams – this includes 4 x 4 in and 6 x 6 in cross section beams.
C09.66 Fluid Penetration - Precision and bias statements being developed for many test methods, including ASTM C1202 (RCPT). The subcommittee continues to work on a test method to measure the resistivity of hardened concrete.
C09.69 Miscellaneous Tests - Tests that measure chloride content – water soluble (C1218) and acid soluble (C1152) will consider expanding the scope of these tests to include testing aggregates.
C01.10 Hydraulic cement - Revisions were approved to ASTM C150 (portland cement) and C595 (blended cement). These revisions were consecutively approved in the equivalent AASHTO standards. The significant revision in ASTM C595 is to permit Type IL portland-cements for use in concrete that will be exposed to sulfates in soil or water, when qualified for sulfate resistance. The subcommittee discussed reporting requirements for blended cements on alkalis to cover information needed for ASR and on reporting on chlorides as needed to establish chloride content of concrete relative to chloride limits.
Workshop - Nick Carino and Colin Lobo presented a workshop on planning an inter-laboratory study and developing a precision statement. The applicable standards are ASTM C802 and C670, respectively.