ASTM Developing Aggregate, Methacrylate, SAC Concrete Standards
August 24, 2009 // Published as a news service by IHS
ASTM International Committee C09 on Concrete and Concrete Aggregates is developing four proposed standards that cover aggregate resistivity, lightweight aggregates, methacrylate bonding systems and semi-adiabatic calorimetry.
Aggregate Resistivity
Reinforcement embedded in embankment walls during construction is affected by the environment's resistance to corrosion, according to ASTM.
A proposed new test method will measure how resistant the aggregate used for such reinforcement will be.
ASTM WK24621 - Test Method for Measurement of Aggregate Resistivity Using the Two-Electrode Soil Box Method is being developed by Subcommittee C09.20 on Normal Weight Aggregates.
John Yzenas, a member of Committee C09, said that in addition to Subcommittee C09.20, Subcommittee G01.10 on Corrosion in Soils - part of ASTM International Committee G01 on Corrosion of Metals - is also involved in the development of ASTM WK24621.
"G01.10's original work resolved many questions that previous test methods had left unanswered such as adequate description of 100% saturation, ability to test various size materials and testing materials in 'as-received' condition," Yzenas said. "This proposed test method is a variation of G01.10's work, dealing specifically with aggregate."
Yzenas notes that, upon its approval, ASTM WK24621 will be useful to designers, specifiers and testing companies because current corrosion test methods are based on soils and may not adequately characterize aggregates.
Lightweight Aggregates
ASTM WK23421 - Specification for Lightweight Aggregates for Internal Curing Applications is being developed by Subcommittee C09.21 on Lightweight Aggregates and Concrete because lightweight aggregates are used differently during the internal curing process than when they are used for other purposes.
"Instead of using lightweight aggregates to reduce the density of the concrete, the pre-wetted or preconditioned lightweight aggregates are used in relatively small quantities in high performance normal weight concrete to provide internal moisture reservoirs throughout the cross-section of the concrete," said Jeffrey Speck, chair of C09.21.
Speck said ASTM WK23421 will be used by design engineers who are designing structures built of concrete with a very low water/cementitious materials ratio and by concrete producers supplying the concrete for such structures.
Highway engineers will also find the proposed standard useful since lightweight aggregates used for internal curing are proving to be effective in reducing concrete pavement cracking, said Speck.
Methacrylate Bonding Systems
Methacrylate is used to strengthen and fortify finely cracked concrete and to minimize the ingress of contaminants such as chlorides and deicing salts that could further degrade concrete.
Once approved, ASTM WK24405 - Specification for Reactive Methacrylate Bonding Systems for Concrete, will provide guidance on relevant properties for these bonding systems and how to evaluate such properties to enable users to determine acceptable material performance.
ASTM WK24405 is being developed by Subcommittee C09.25 on Organic Materials for Bonding.
According to Quentin Hibben, member of the subcommittee, the proposed standard will be used by specifiers, engineers and material producers for bridge maintenance, parking deck and airport tarmac projects. Transportation departments could also potentially use the standard for projects.
Hibben notes that the subcommittee is seeking input for relevant properties and acceptable values for low viscosity methacrylate-based resin systems, as well as assistance in reproducibility testing.
Semi-Adiabatic Calorimetry
Thermal measurements of hydrating cementitious mixtures, referred to as "semi-adiabatic calorimetry (SAC)," can be used to evaluate behavior of concrete mixtures and concrete-making materials, as well as for troubleshooting certain types of abnormal concrete performance.
According to ASTM, interest in using SAC for these purposes grew in recent years along with increased availability of both generic hardware that can be used for SAC and manufactured systems designed specifically for the process.
ASTM WK23967 - Practice for Measuring Hydration Kinetics of Hydraulic Cementitious Mixtures Using Semi-Adiabatic Calorimetry will help guide users in planning and implementing productive SAC testing programs for concrete mixture evaluation.
ASTM WK23967 is being developed by Subcommittee C09.48 on Performance of Cementitious Materials and Admixture Combinations.
Tim Cost, chair of the task group that is developing the practice, pointed out that when ASTM WK23967 is approved, it will provide standard protocols for conducting tests that will produce meaningful and repeatable results and will help users avoid methods and test conditions that have been shown to produce confusing or misleading data.
The proposed standard will be used by ready-mixed concrete producers, suppliers of concrete-making materials, contractors, testing firms, researchers and academia.
Doug Hooton, chair of Subcommittee C09.48, said that this new practice will help both suppliers of materials and concrete producers to pinpoint the source of fresh concrete problems in complex concrete mixtures and can be used to help prevent future problems as materials properties, mixture proportions and placing temperatures change.
Source: ASTM International.