Alkali-Silica Reaction Mechanisms and Detection: An Advanced Understanding, TechBrief

15543062014PDFTech ReportFHWA-HRT-14-078DTFH61-08-R-00010Alkali silica reactionsReactive aggregatesNitratesDeicers (Equipment)Neutron activation analysisThermodynamic modelLithium nitratePassive acoustic emissionX-ray and neutron imagingUnited StatesUnited States. Federal Highway AdministrationUnited States. Federal Highway Administration. Office of Research, Development, and TechnologyPurdue University. School of Civil EngineeringFederal Highway AdministrationThe deterioration caused by alkali-silica reaction (ASR) was first described 70 years ago in the pioneering paper by Stanton and has since been extensively researched. The traditional attempts to mitigate ASR in concrete structures focused on preventing and/or reducing the amount of gel formed by modifying the chemical environment. Limiting the alkali content of concrete, using supplementary cementitious materials, or using chemical admixtures all have been found to be effective and have been extensively used for that purpose. However, the complexity of chemical and mechanical mechanisms of ASR made it difficult to develop reliable quality control test methods and performance prediction models. Therefore, increased understanding of the fundamental mechanisms of ASR may lead to the development of additional (and possibly better) options for ASR control and for reactivity characterization of susceptible aggregates. The main purpose of this research was to investigate the fundamental mechanisms involved in the ASR process and to advance approaches to detect the damage caused by ASR. A more indepth understanding of the mechanisms underlying ASR, combined with the methods to detect ASR damage developed in the course of this study, is expected to help establish more reliable methods of mitigating ASR and increasing the design life of newly constructed concrete structures.75