NRMCA Files Report on ASTM Meeting of Concrete, Cement Committees
The following is a summary of activity at the ASTM meeting in June 2018 of Committees C09 on Concrete and C01 on Cement attended by NRMCA staff in San Diego.
C09.20 Concrete Aggregates - ASTM C33, specification for aggregates, was revised to remove the appendix that provided guidance on alkali aggregate reactions. The committee will consider removing the figure that outlines areas of severe exposure (cold weather) in the U.S. due to misuse. ASTM C33 will refer to ASTM C1778 for guidance on AAR. The implication may be that aggregate suppliers will have to test aggregates for ASR as required in ASTM C1778. Revisions are in the works for ASTM C88 on soundness of aggregates, C566 on measuring moisture content of aggregate samples, C70 on surface moisture content of fine aggregate by volumetric method and C136 on sieve analysis to permit drying an aggregate sample by vacuuming. It was noted that the standard color scale for organic impurities was not available and will require revisions to C40. Some minor revisions are being made 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 and to remove a limit for total organic carbon.
C09.24 Supplementary Cementitious Materials - A change to the classification of fly ash was approved in ASTM C618: Class F will be those that contain <18% CaO; while those containing higher amounts will be Class C. This classification will be consistent with guidance in the practice for AAR, ASTM C1778. The sum of oxides will still have limits of a minimum 50% but will not be the basis for fly ash class. Proposed specifications for ground glass pozzolan and colloidal silica were also discussed; these will be revised for a new ballot. A new performance specification for SCMs is also being developed. A task group was established to develop a separate specification for natural pozzolans (currently covered in ASTM C618). A group will also work on establishing the same requirements between ASTM and AASHTO for fly ash. The strength activity index used to qualify fly ash has been a concern for some time because it cannot distinguish between inert fillers and fly ash. A variation of strength activity index that will evaluate strength due to water reduction and chemical reactivity will be proposed as an appendix in ASTM C311. Other measures of pozzolanic activity are being considered; these include bound water; calcium hydroxide consumption; heat of hydration based on calorimetry and a lime based strength reactivity index test. A workshop on Sunday included presentations of various alternatives, including those being developed in Europe.
C09.40 Ready Mixed Concrete - 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. Negative voters did not support removing the numerical time limit as it is useful to establish a limit. The proposal will be revised based on comments and will likely state the historical limit in a non-mandatory note. Other work in progress is to require a retest when tests fail slump and air content; to include a reference to the specification for mineral fillers, C1797 in C94; address scheduling and other items in the ordering section; revise the delivery ticket section for clarity and to include reporting information on returned concrete reuse; and revise technician certification requirements by referencing C1077.
C09.50 Risk Management for Alkali Aggregate Reactions (AAR) - Subcommittee C09.26 that manages the AAR test methods has been absorbed into this subcommittee. All AAR tests and ASTM C1778 will be under the purview of Subcommittee C09.50. The subcommittee will ballot to withdraw the older mortar bar test for ASR, C227 because its results lack reliability to field performance. The subcommittee has four task groups (TG): 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. Additional guidance will be provided on aggregate testing frequency. ASTM C1778 will be revised to include considerations for the use of ground glass and natural pozzolans containing high alkalis and use of blended cement and blended supplementary cementitious materials. Researchers will be asked to present to the subcommittee on the mini concrete prism test, the autoclave test and testing aggregates for iron sulfides.
C09.60 Fresh Concrete Tests - A proposed revision to C172 on sampling concrete to permit obtaining a concrete sample in one portion (as opposed to two or more as a composite) for testing concrete did not pass and the item will be revised and re-balloted. A new method on measuring the electrical resistance of fresh concrete continues to evolve through the balloting process. The subcommittee will consider reinstating C1362, measuring workability using the K-slump tester. The subcommittee received a presentation on the super air meter (SAM) that is an AASHTO provisional standard. Establishing this as an ASTM standard will be considered. The SAM number obtained from this method evaluates whether a good air void system is present in fresh concrete.
C09.61 Strength - A revision was approved to C31 to ensure that specimens were placed in initial curing within 15 minutes of being cast. Other revisions are in the works on improving the requirements related to initial curing in the field and transportation to the laboratory and to prohibit the use of cardboard molds for standard cured specimens used for acceptance testing. The subcommittee continues to work on several revisions to C39 on testing specimens for compressive strength on details of testing and to include a reference to the sampled load on the strength test report. 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. A ballot will propose a new precision statement for the standard. The inter-laboratory study (ILS) included strength levels of concrete from 8,000 to 18,000 psi. NRMCA's laboratory participated in the ILS.
C09.61 Performance of CM and Admixture Combinations - The subcommittee discussed comments from ballots for two new standards. The first one involves developing a guide for performing mini mixtures for material compatibility and quality control and the second one is a test method for foam index test for evaluating fly ash for air entrainment.
C09.66 Fluid Penetration - Some revisions were approved to ASTM C1202, the rapid chloride permeability test, including clarifying vacuum level for saturating test specimens. A proposal to withdraw the method to determine permeable voids in concrete, ASTM C642, was not successful as there were users of this method. The method will be updated. Precision data based on a 2003 inter-lab study indicates that the chloride ponding test, ASTM C1543, has a high variability; the subcommittee will ballot to withdraw this standard. It exists as an AASHTO standard. Precision and bias statements based on previous ILS have been developed C1585 (sorptivity), C1556 (diffusion) and 1760 (electrical conductivity). A ballot to revise ASTM C1760 test to include a precision statement and to address retesting specimens will be issued. The subcommittee addressed ballot results on a proposed bulk resistivity test and it continues to work on the surface resistivity test method. Degree of saturation of the specimens and pre-conditioning specimens prior to measuring resistivity is a significant factor impacting the results. The subcommittee discussed the development of a new guide to calculate the formation factor of concrete, which provides a property characterizing permeability of concrete. The results of the electrical tests are used to determine the formation factor.
ASTM C09.67 Resistance to Environment - An appendix to ASTM C666 test will be added to suggest including petrographic evaluation of tested specimens to evaluate whether deterioration to specimens is caused by non-durable aggregate as opposed to the lack of a good air void system.
C09.98 Evaluation of Laboratories - A revision is being proposed to C1077 to permit licensed professionals other than engineers to have supervisory responsibilities of testing agencies. Another item is better defining certification requirements for technicians. The idea of only requiring independent certification programs was discussed. Many organizations, including some state highway agencies, only use in-house certification programs.
C01.10 Hydraulic Cement - Revisions in progress involved replacing heat of hydration limits determined by C186 with limits based on isothermal calorimetry, C1702 in the specifications for portland cement (C150) and blended cements (C595). An approved revision to C150 will remove the definition of low-alkali (0.60%) for portland cements while requiring that alkali content be reported on the mill test report. Other revisions include reporting of chlorides and removing the Wagner method of measuring fineness of cement. Revisions to C595 on blended cement include removing testing pozzolans for alkali silica reactivity and deleting a requirement to test shrinkage with low heat (LH) cements. Many of the revisions to cement standards are coordinated to ensure consistency between ASTM and AASHTO specifications for hydraulic cement.