Earlier this month, NRMCA Engineering Staff traveled to Seattle to attend the ASTM meeting of Committees C09 on Concrete, C01 on Cement, and E05 on Fire. The following is a summary of action with ready mixed concrete implications.
C09.20 Aggregates - Some of the aggregate test methods will be reviewed for revisions as they approach a time limit on the last version. Revisions to the specification for mineral fillers, ASTM C1797, to remove a requirement to measure total organic carbon will be balloted. The subcommittee continues to work on simplifying the deleterious material limit for coarse aggregates and to possibly remove the map representing weather regions in the U.S.
C09.23 Chemical Admixtures - The subcommittee is working on specifications for anti-washout, shrinkage reducing and ASR control admixtures in various stages of development. The subcommittee discussed developing a method to measure chlorides in admixtures that can be referenced in the specifications. Because of anticipated limited availability of ASTM C150, Type I or II cements, the subcommittee will consider permitting the qualification of admixtures in ASTM C494 and C260 using ASTM C595 Type IL (Portland limestone cement) as an alternate. A category for mid-range water reducing admixtures will not be added in ASTM C494.
C09.24 Supplementary Cementitious Materials - The subcommittee will try to achieve consensus over a limit for the ASTM C1897 SCM reactivity test that will differentiate inert materials from reactive materials. A ballot to remove a requirement to measure soundness using the autoclave expansion test in ASTM C618 was approved. The subcommittee is developing specifications for colloidal silica and for a generic SCM. The ballot to remove limits for loss on ignition (LOI) for fly ash but to require that it be reported did not pass. A draft specification for natural pozzolans is being developed to possibly address these products separately from ASTM C618. The subcommittee ballot on the inclusion of harvested fly ash in ASTM C618 passed and will move to the main committee.
C09.40 Ready Mixed Concrete - Revisions approved to ASTM C94, specification for ready mixed concrete, include: use of blended supplementary cementitious materials conforming to ASTM C1697 is permitted; also permitted are ground calcium carbonate and aggregate mineral filler conforming to ASTM C1797 – these materials are not considered to be cementitious materials but should be weighed on the same scale as cementitious material; clarification to testing requirements and consistent indication of sampling at discharge from the transportation unit. A minor revision was approved to the specification for mixing water, ASTM C1602. Other revisions in progress include revisions to address including limits to discharge and hold back water that sets a limit for jobsite addition on the delivery ticket; clarification to the strength overdesign guidance in the Appendix and to consistently use the word manufacturer for the concrete producer in the specification. A revision to the testing of mixing water from non-potable sources, ASTM C1603, is in progress.
C09.50 Risk Management for Alkali Aggregate Reactions (AAR) - The subcommittee will ballot a revision to the ASR concrete prism test, ASTM C1293, to make it a dual unit standard. The subcommittee decided that more data was needed before permitting the use of Type IL cements in the ASR test methods, ASTM C1260 and ASTM C1567. These test methods also need an updated precision statement. The NRMCA Research Laboratory agreed to participate in the testing. The subcommittee was advised that there was no need to develop an equivalent of AASHTO T 380, the miniature concrete prism test, which has shown better correlation to exposure blocks than the ASTM C1293.
C09.60 Fresh Concrete Tests - A revision was approved to the air content by pressure method test, C231, to address filling the measure with self-consolidating concrete.
C09.61 Strength - A proposal to require measuring density of fresh concrete when casting cylinders in ASTM C31 received several negatives and will not be revisited. Several other revisions to ASTM C31 are being addressed through balloting. Revisions to ASTM C469 (modulus of elasticity) added a precision statement based on a recently completed inter-laboratory study. Other revisions to the practice for making and curing strength specimens, ASTM C31, to address size required based on aggregate size and to include new terminology, are in progress. A precision statement for 4 x 8 in cylinders made in the field has been developed from about 10,000 tests from various sources and will be proposed as a revision to ASTM C39.
C09.66 Fluid Penetration - The subcommittee discussed several changes to ASTM C642, test method to determine density and voids in hardened concrete. The subcommittee approved revisions to ASTM C1556, test to measure the apparent diffusion coefficient of concrete, involving discarding 2 inches from the cast surface of the specimen. This is needed as the method measures the diffusion of the bulk concrete and can be skewed by the cured and finished surface. Results from the ASTM inter laboratory study on surface resistivity (AASHTO T 358), bulk resistivity (ASTM C1876), rapid chloride permeability (ASTM C1202) and bulk diffusion (ASTM C1556) were presented and discussed.
NRMCA lab participated in the ILS program and helped develop the guidelines and interpret the data. NRMCA lab’s original observation of unstable readings when measuring bulk resistivity for specimens immersed in simulated pore solution was confirmed by other labs. Rinsing the specimens in water before the measurement marginally increased the measured resistivity, but considerably reduced the variation related to the stability of the measurement. Conditioning specimens in lime water indicated similar measured variability to specimens conditioned in simulated pore solution. Some labs cured specimens in the moist room and pooling these data with limewater cured specimens likely increased the variability of the results. The precision of the RCP test (ASTM C1202) was considerably better than that published in the current standards and was seen to improve after applying corrections for measured specimen diameter and thickness.
ASTM C09.67 Resistance to Environment - The subcommittee ballot on ASTM C666 received multiple negatives. This standard will be reballoted after making the three tests optional. Possible changes to ASTM C672 were discussed.
C01.10 Hydraulic Cement - Limestone interground in Portland and blended cement currently needs to be from quarried rock. A presentation was received by the subcommittee indicating that cement properties were similar when using calcium carbonate from alternative sources. The subcommittee will consider permitting calcium carbonate additions other than limestone in a future revision. The cement specifications, C150 and C595, are being revised to remove low heat of hydration options, while permitting the purchaser to request information on this as measured by isothermal calorimetry, ASTM C1702.
Committee C09/C01 Symposium - Several presentations were delivered by researchers and practitioners at a 7-hour Symposium on Reactivity Tests for Cement-Based Materials. Presenters discussed new tests to evaluate emerging supplementary cementitious materials, evaluation of reclaimed ash from coal burning, natural pozzolans, innovative materials, and other aspects to address supply issues with fly ash and other SCMs. Papers will be published for most of the presentations and will be available soon in the ASTM Journal: Advances in Civil Engineering Materials.
E05.11 Fire Resistance - NRMCA proposed a new work item relating to revision of ASTM E119 Standard Test Methods for Fire Tests of Building Construction and Materials. The proposed revision seeks to provide clarifications to ASTM E119 Table X3.1 Guide for Determination of Restrained and Unrestrained Conditions of Construction. The clarifications are proposed for concrete framing based on language and terminology used in current engineering and construction practice and are intended to avoid over conservative estimations for fire resistance of concrete structural elements.
E05.14 External Fire Exposures - The Subcommittee on External Fire Exposures is reviewing considerations for a new method for determining fire propagation of exterior wall assemblies focusing on flame impingement. Parameters under review by a panel of test laboratories include the ignition sources, observation periods, presence of a soffit for the test window opening and pass/fail criteria among others. Input from the laboratories and their test phases will inform the draft of a potential new test standard.
The subcommittee will also be balloting a revised version of the proposed Standard Test Method for Determining Flammability of Exterior Wall Assemblies for Mass Timber Multi-Story Structures. Data was presented with the intent of demonstrating higher heat fluxes implying a more severe fire exposure for the proposed new test method in comparison with the fire exposure conditions of NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components. The subcommittee ballot is anticipated before the end of the year.
E05.23 Combustibility - ASTM E0136 is a standard test method referenced in the International Building Code (IBC) and International Wildland Urban Interface Code (IWUIC). The test method is used to determine combustibility of materials using a vertical tube furnace. A recent ballot clarifying that no thermocouples may exceed the temperature failure criterion in order to pass the test. The membership voted to support the clarifications and resolve negative votes opposing this clarification. The decision maintains the integrity of noncombustible materials.
For more information, contact Colin Lobo at clobo@nrmca.org, Karthik Obla at kobla@nrmca.org or Shamim Rashid-Summar at ssumar@nrmca.org.
National Ready Mixed Concrete Association