Synergistic effect of RHA and FCW in alkali-aggregate reaction mitigation

Abstract

Pozzolans rich in silica, such as Rice Husk Ash (RHA), contribute to compressive strength gain but at the same time might increase alkali-aggregate reaction (AAR) in mortar mixtures. Pozzolans that have aluminates, such as Fired Clay Brick Waste (FCW), can be efficient to mitigate AAR but tend to lead to a slower compressive strength development. The association of different types of pozzolans, however, may result in a synergistic effect, compensating individual deficiencies. This paper presents a study of mixtures containing RHA, FCW and these two materials combined, aiming to obtain benefits in the mechanical behavior and in the durability regarding AAR. A substitution rate of 20% Portland cement by pozzolanic material was used. Through accelerated AAR tests and compressive strength measurements, it was found that while RHA is considered harmful to AAR - even when using an innocuous aggregate - FCW presents benefits, also avoiding this deleterious effect when combined with RHA. The same occurs in the compressive strength development, where RHA compensates a small loss of compressive strength associated with the use of FWC alone.

Uma revisão sobre a utilização de cinza de casca de arroz na construção civil

“…Estudos desenvolvidos por Guillante, et al (2019), avaliaram o efeito sinérgico da CCA e do resíduo de cerâmica vermelha (RCV) na mitigação da reação álcali agregado. As composições foram submetidas aos ensaios de resistência à compressão e ensaio acelerado de reação álcali agregado (RAA).…”

“…Resultados semelhantes foram observados por Nehdi, Duquette e Damatty (2003), Park, Kwon e Wang, 2016, Calheiro, et al (2016, VIgneshwari, Arunachalam e Angayarkanni 2018, Sharma e Sharma, 2018, Guillante, et al (2019, Cecconello, et al (2019), Hu, He e Zhang (2020). Hu, He e Zhang (2020) avaliaram as CCAs em diferentes tempos de combustão.…”

The Effect of a Pozzolanic by-Product Containing Glass Powder and Metakaolin on the Properties and Aar Resistance of Mortar Incorporatring Crushed Glass

“…A lower Cl concentration in the pore solution was found in cement pastes containing 10 % and 20 % of metakaolin. Metakaolin incorporated in concrete mixes reduces the expansion of concrete in sodium hydroxide solutions as well as the expansion caused by an alkali aggregate reaction [22][23][24]. Metakaolin was also found to be an alternative pozzolanic addition and an effective replacement of silica fume in high performance concrete [25].…”