A Study on the Effect of Carbonation on Properties of Concrete

Abstract

Premature deterioration in concrete is the manifestation of durability issue observed in newlinethe recent times. This is mainly due to the exposure of concrete to aggressive newlineenvironments and poor surface porosity of the concrete to resist the ingress of weathering newlineagents. Carbonation of concrete is one such durability issue where atmospheric carbon newlinedioxide dissolves with pore solution in concrete to form calcium carbonate upon reaction with calcium phases in concrete. This reduces the pH of the reinforced concrete and leads to corrosion of steel reinforcement. Though the concept of blended cements has been introduced in the recent years, there is no dearth of cases where the use of mineral admixtures as partial replacement of cement resulted in lesser durability mixture. Hence, newlineit is important to fully understand the influence of mineral admixtures on carbonation resistance. The present work deals with the influence of water binder ratio on the mechanical properties and durability of carbonated concrete. To achieve the carbonation conditions, the concrete specimens were exposed to a carbon dioxide concentration of 5%, thereby accelerating the process of carbonation in controlled conditions which otherwise would newlinetake decades under natural environmental exposure conditions. Mineral admixtures such newlineas fly ash and blast furnace slag were used to at their optimum dosages (30 and 40% newlinerepsectively) as cement replacement by weight, to study the influence they have in newlineresisting carbonation. Similar tests were conducted on concrete mixtures made with newlineordinary Portland cement to check the effect of water curing duration as a potential newlineleverage to resist carbonation. Cement mortar mixtures were also used to authenticate the newlinereliability of field carbonation test phenolphthalein acid base indicator in locating the accurate depth of carbonation. On these mixtures, microscopic tests such as Scanning Electron Microscopy (SEM), X-Ray powder Diffraction (XRD) and Thermo gravimetric Analysis (TGA) were conducted to locate the accurate