Effect of nano-CaCO3 on hydration of cement containing supplementary cementitious materials

The efficacy of the addition of nano-CaCO3 in accelerating the hydration of ordinary Portland cement (OPC) delayed by the presence of high volumes of supplementary cementitious materials including fly ash and slag was investigated. The conduction calorimetry indicated that the early hydration of OPC was significantly accelerated by the addition of the nano-CaCO3 and the higher the amount of CaCO3 addition, the greater was the accelerating effect. The thermogravimetric analysis results showed that the amounts of added CaCO3 became slightly lower as the hydration took place; however any new reaction products were not detected by the X-ray diffractometry analysis. The engineering properties including microhardness and modulus of elasticity, in the early stage of the hydration were remarkably improved by the addition of nano-CaCO3. It was suggested that the seeding effect of the nano-CaCO3 particles and the nucleation of C-S-H caused the enhanced strength development.On examine ici l?efficacit\ue9 de l?ajout de nano-CaCO3 au ciment Portland ordinaire (CPO) en termes d?acc\ue9l\ue9ration de son hydratation, laquelle est retard\ue9e par la pr\ue9sence de volumes \ue9lev\ue9s de mat\ue9riaux cimentaires d?appoint comprenant des cendres volantes et du laitier de haut fourneau. La calorim\ue9trie \ue0 conduction nous a indiqu\ue9 que l?hydratation pr\ue9coce du CPO \ue9tait consid\ue9rablement acc\ue9l\ue9r\ue9e par l?ajout du nano-CaCO3 et que l?effet d?acc\ue9l\ue9ration \ue9tait d?autant plus marqu\ue9 que la quantit\ue9 de CaCO3 ajout\ue9e \ue9tait grande. Les r\ue9sultats de l?analyse thermogravim\ue9trique ont r\ue9v\ue9l\ue9 que les quantit\ue9s de CaCO3 ajout\ue9es diminuaient l\ue9g\ue8rement lorsque intervenait l?hydratation; cependant, aucun nouveau produit de r\ue9action ne fut d\ue9tect\ue9 par l?analyse par diffraction des rayons X. Les propri\ue9t\ue9s m\ue9caniques au stade initial de l?hydratation, dont la microduret\ue9 et le module d?\ue9lasticit\ue9, ont \ue9t\ue9 remarquablement am\ue9lior\ue9es par l?ajout de nano-CaCO3. Il a \ue9t\ue9 avanc\ue9 que le d\ue9veloppement rehauss\ue9 de la r\ue9sistance du mat\ue9riau \ue9tait attribuable \ue0 l?effet d?ensemencement des particules de nano-CaCO3 ainsi qu?\ue0 la nucl\ue9ation des hydrates de silicate de calcium (C-S-H).Peer reviewed: YesNRC publication: Ye