Structure and Properties of Alkali-Silica Reaction Gels Treated with Lithium Nitrate

Описание: Presented By: Jianqiang Wei, University of Massachusetts Lowell

Description: Alkali-silica reaction (ASR) is a deleterious reaction between reactive silica in aggregates and the alkaline pore solution of concrete. The reaction forms hygroscopic ASR gels, which can absorb water, swell, and exert pressure on surrounding concrete, causing internal stresses, volume expansion, and cracking of concrete. Mixing lithium admixtures in fresh concrete has been proven as an effective ASR mitigation approach at the concrete level. However, the exact mechanism has not been fully understood. Moreover, the morphology, chemical composition and properties of ASR gels might vary with their age and forming location in concrete. To uncover the role of lithium in mitigating ASR, synthetic ASR gels containing various dosages of lithium nitrate admixture were prepared. Microstructure, composition, and crystallization of ASR gels in the presence of lithium were investigated through microscopy, spectrographic, and X-ray diffraction techniques. Physical and mechanical properties, such as water absorption, swelling and strength development, were also studied through vapor sorption, weight, static volume change and compressive strength tests, respectively. The results indicate that the gelation time of ASR gels was extended significantly. The swelling, stiffness, and strength of ASR gels were also decreased in the presence of lithium.