What is it about?

This test method is intended to detect the alkali silica reactivity of an aggregate (28-45 days) or assess the effectiveness of mitigation measures of SCMs (75-90 days) in terms of measuring length change of a cylindrical concrete specimen immersed in a soak solution with a chemistry equal to the pore solution of the tested concrete specimen at 60ºC (140ºF). ACCT is able to test concrete specimens at varying alkali loadings (i.e., alkali loading = 4.5 lb/yd3 as well as higher and lower than 4.5 lb/yd3). This test has been accepted as an AASHTO provisional standard and scheduled to be published in April 2021.

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Why is it important?

This test (ACCT) is intended to provide results similar to the concrete prism test (CPT, ASTM C1293) or modified concrete prism test (MCPT, T 380). This test is performed differently than the CPT or MCPT method. The test conditions such as using LVDT to measure length change in a closed system, soak solution = pore solution, use of as-received aggregate, alkali level close to field level of alkalinity (no alkali boosting) increase the reliability of this test. As ACCT doesn’t suffer from alkali leaching and ensures negligible alkali penetration from soak solution into the concrete specimen, the effect of cement alkalis as well as soluble alkali contributions from SCMs on ASR expansion can be detected by the ACCT method.

Perspectives

This test method also has the ability to test job concrete mix. The authors have developed a performance based approach based on proper consideration on pore solution alkalinity and aggregate threshold alkalinity and the ACCT method. This approach was found to be very effective to determine the effectiveness of any kind of fly ashes (Off spec ashes, harvested ashes) and other non-conventional SCMs (ground glass, natural pozzolans, calcined clays etc.). As fly ash crisis is already in effect, this approach can be used to test whatever locally available and make long lasting durable concrete.

ANOL MUKHOPADHYAY
Texas A&M University System

Read the Original

This page is a summary of: Accelerated Concrete-Cylinder Test for Alkali–Silica Reaction, Journal of Testing and Evaluation, January 2015, ASTM International, DOI: 10.1520/jte20140334.
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