Cement paste characteristics and porous concrete properties

In this paper, cement paste characteristics and porous concrete properties are studied. The results indicate that cement paste characteristics are dependent on the water to cement ratio (W/C), admixture and mixing time. Cement paste with high viscosity and high flow suitable for making porous concrete is obtained with the use of low W/C of 0.20-0.25, an incorporation of 1% superplasticizer, and sufficient mixing. Porous concretes having suitable void ratios are produced with appropriate paste content and flow, and sufficient compaction. Good porous concretes with void ratio of 15-25% and strength of 22-39 MPa are produced using paste with flow of 150-230 mm and top surface vibration of 10 s with vibrating energy of 90 kN m/m(2). For low void ratio, high strength porous concrete of 39 MPa is obtained using paste with low flow. For high void ratio, porous concrete of 22 MPa is obtained using paste with high flow. Furthermore, the results indicate that the strength of porous concrete could be estimated from strength equation of porous brittle material. (C) 2007 Elsevier Ltd. All rights reserved.