An Experimental Study on Mitigating Alkali Silica Reaction by Using Fly Ash (FA) in Combination with Silica Fume and Expanded Perlite Powder (EPP)
ASR suppression by FA, SF, EPP, FA in combination with SF and EPP were evaluated by both mortar bar and concrete prism test. Mortar bars were made based on JIS A 1146, meanwhile concrete prism bars were casted in accordance with Rilem AAR-3. Both specimens were stored in 40°C 100% R.H. controlled room. Mortar and concrete mixtures used reactive aggregate in pessimum proportion. The results indicated that FA in combination with SF and EPP showed smaller expansion compared to FA. The best of concrete mixtures in reducing expansion is combination of FA with SF (FA15SF10).
Effectiveness of mineral admixtures in reducing ASR expansion
Abstract This paper investigates the effectiveness of eight mineral admixtures in reducing the alkali silica(te) reactivity of cement mortar. The admixtures include one class F fly ash, a condensed silica fume, a ground fiberglass, three glass containing waste materials, and two inert fillers (carbon and calcium carbonate). Mortar bar expansion, the change in evaporable water content, the evidence of reaction and the composition of reaction products were studied. It was found that shale is the only reactive component of the sand and the effectiveness of admixtures in reducing alkali-silica reaction depends largely on the chemical composition of the admixtures. Ground fiberglass is very effective in controlling the alkali silica reaction, while inert fillers have only a “dilution effect”. It is thought that admixtures reduce ASR expansion by two reactions: (1) pozzolanic reaction that reduces the permeability of concrete and entraps some fraction of the alkali ions; (2) alkali silica reaction that consumes most of the available alkali ions and thereby prevents the reaction between alkalis and aggregate.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.