Design and development of low cost lightweight concrete composites with mixture of fly ash and concrete sludge aggregate

Abstract

In this research, fly ash and concrete sludge aggregates (CSA) as partial replacement have introduced into lightweight foam concrete where these materials play an important role to enhance the properties of concrete. Fly ashes are finely residue from the combustion powdered coal for generating electric purpose. On the other hand, recycle aggregates play a main key role in reducing the need for landfill waste disposal and converse natural aggregates to protect environment. Mainly, the effect of CSA can be determined by substituted 10%, 30%, and 50% as partial replacement of coarse aggregates with the fix amount of 15% fly ash and 50% of foam in the mixing ratio 1:1:2 of concrete. Then, the suitable of amount fly ash can be added into concrete is 15%, 20%, 25% and 30% as partial replacement of cement with the fixed amount of 30% CSA and 50% of foam. Based on the result obtained, the lightweight foam concretes achieved density from 1798 kg/m3 to 2305 kg/m3. Besides that, water absorption of the lightweight foam concretes varies from 6.508% to 14.013%. Next, the samples achieved vary in compression strength at 28 days from 9.584 MPa to 32.229 MPa. In conclusion, the optimum content of fly ash and CSA can be used in this research are 25% and 30% as partial replacement of cement and coarse aggregates to achieve the highest compression strength compared to other mixing ratio. This sample achieved bulk density 1844 kg/m3 which can be categorized as lightweight concrete and with the highest compression strength of 16.970 MPa.