Properties of Cement Mortar containing GGBS and Subjected to Carbon Dioxide Curing

Abstract

The aim of this study was to evaluate the effect of carbon dioxide curing and normal water curing on mortar specimen incorporating GGBS as partial replacement of cement. An effort has been made to generate a mortar mix with optimum replacement of GGBS. The focus of the study was to compare the strength development on mortar specimen incorporating different percentage of GGBS, cured with CO2 and water. The other properties such as water absorption, apparent weight, porosity, SEM and XRD are also examined on the mortar specimen. The level of replacement of cement with GGBS was varied from 10% to 50%. In all, six mixes, including the control mix, was studied. For each mix twelve 70X70X70 mm cubes and six 100mm diameter and 150mm height cylindrical mortar specimens were casted incorporated with varying percentage of GGBS as partial replacement of cement. These specimens were de-molded after 22 hours. After de-molding half of the samples were water cured and remaining samples were kept for carbon di-oxide curing. For carbon di-oxide curing, the curing chamber with specimens was closed, vacuumed to a pressure of around 600 mm of Hg and maintained for 2 min before CO2 was injected to remove all the gases from the chamber and then a constant pressure of 10psi was maintained for a period of 6 hours. The pressure inside the curing chamber was monitored by a pressure gauge attached on the curing chamber. It was found that the short term CO2 curing promoted early strength development, which is almost equal to that of water curing at 28-day. Durability performance of the carbon-dioxide cured mortar samples was compared with normally water cured. The CO2 cured mortar specimens were exhibited more resistance to water absorption and chloride permeability. The micro-structural analysis i.e. SEM and XRD of the mortar samples were also observed during the study. It was concluded that slower strength development due to GGBS can be compensated by small duration of CO2 curing of the specimen.