STARCH MODIFIED CONCRETES EXPOSED TO AGGRESSIVE ACIDIC ENVIRONMENT

The deterioration processes are linked with transport mechanism of various fluids: gas, ionic diffusion, water absorption and permeation. Dense and durable concretes are required for concrete structures to be able to adequately resist aggressive sulphate environment. The effects of starch extracted from cassava and maize on concretes with starch introduced as admixtures in various concentrations (0%, 0.5%, 1%, 1.5% by weight of cement) were produced. The concrete samples were subjected to an aggressive environment by placing them in 10% sulphuric acid solution for accelerated assessment of the suitability or otherwise of this organic admixture in such an environment. Compressive strength tests were carried out on the cubes at 7, 28, 56, and 90 days, respectively. In order to assess the depth of penetration of the sulphuric acid solution into the concrete cubes, a set of concrete cubes was cast and cured for 7, 28, 56, and 90 days, respectively, in the same acidic (10% sulphuric () 4 2SO H ) solution. Another set of concrete cubes was cast and cured for the same number of days for a wet and dry curing regime in the same solution. The outcome showed that maize starch (MS) concrete of 1% and cassava starch (CA) concrete of 1% gave greater compressive strength, and the 1% maize starch concretes provide better resistance to sulphate attack. For the concretes cured by wet and dry method, CA 1% concretes gave the optimum result both in increased compressive strength and enhanced durability.