CARBONATION OF MORTAR CONTAINING A MINERAL ADMIXTURE

Abstract

In this study, the effects of curing period, curing condition, water to cement ratio and the use of mineral admixtures as partial replacement of ordinary portland cement on the rate of carbonation and the pore structure have been investigated. The mineral admixtures used in this study are ground granulated blast furnace slag and pulverised fuel ash having different fineness at different replacement percentages. All carbonation tests were carried out under accelerated conditions. For the same mix proportion or materials used, a good relationship has been observed between the total pore volume of pores having radius larger than a specific value and the carbonation coefficient of mortar specimens cured in water. Moreover, irrespective of the curing period, curing condition or water to cement ratio, a denser microstructure of mortar is found to lower the rate of carbonation. For mortar specimens containing a mineral admixture, it is observed that the cement content is the dominant factor influencing the rate of carbonation. The interrelation between pore structure, carbonation rate and compressive strength has also been investigated. It is observed that the relationship between the carbonation rate and the corresponding pore volume or compressive strength of mortar specimens is dependent on the mix proportion or materials used but a good linear relationship is observed between the pore volume and the compressive strength and this seems to be independent of the mix proportion or materials used.