Resistance of Concrete Containing Rice Husk Ash to Carbonation.

Abstract

Cement is one of the most valuable materials used in the construction industry to construct structurally sound infrastructure. Though, in many developing countries such as Uganda, cement is expensive due to the scarcity of local resources and limited industrial capability to produce enough cement locally to meet the demand for this material. As a result, cement has to be imported. Among the leading causes of structural failure in Uganda is corrosion of steel in concrete. This is caused mainly through carbonation therefore for more durable structures the materials used must be able to effectively resist carbonation in concrete. Rice husk ash is one of the most active research areas that incorporates a number of disciplines including civil engineering and construction materials. Rice husk ash is an agricultural waste product which is produced in large quantities globally every year and due to the difficulty involved in its disposal it is becoming an environmental hazard. Rice husk ash-a material naturally high in silica, can be used as a supplementary cementitious material and can replace a portion of ordinary Portland cement in concrete without compromising the durability and strength of the concrete. This study investigates the effect of rice husk ash in 5,10, 15, 20 and 25% replacements of Ordinary Portland cement by mass on the resistance to carbonation of concrete with optimization of the ash by controlled burning. The rice husks were collected from one source in Uganda and burnt to ash. The ash was then assessed for its suitability for use in construction via testing the depth of carbonation of 100mm by 200mm concrete cylinders and determining its chemical composition using x-ray diffraction techniques. A 10% replacement of rice husk ash was deemed appropriate for use in small-scale structural applications.