Cement paste characteristics and porous concrete properties P. Chindaprasirt a, * , S. Hatanaka b , T. Chareerat a , N. Mishima b , Y. Yuasa c a Department of Civil Engineering, Khon Kaen University, 123 Friendship Hwy., Muang District, Khon Kaen 40002, Thailand b Department of Architecture, Faculty of Engineering, Mie University, Japan c Industrial Research Division, Mie Prefecture Science and Technology Promotion Center, Japan Received 18 November 2006; received in revised form 6 December 2006; accepted 19 December 2006 Available online 5 February 2007 Abstract In this paper, cement paste characteristics and porous concrete properties are studied. The results indicate that cement paste character- istics 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 sur- face 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. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Cement paste; Porous concrete; Compressive strength; Void ratio; Compaction 1. Introduction Porous or pervious concrete is concrete with continuous voids which are intentionally incorporated into concrete. It belongs to a completely different category from conven- tional concrete and hence its physical characteristics differ greatly from those of normal concrete. Porous concrete can be used in numerous applications such as permeable concrete for pavement, base course, concrete bed for vege- tation or living organism, noise absorbing concrete, ther- mal insulated concrete and other civil engineering and architectural applications. Porous concrete pavement has been used for over 30 years in England and the US [1]. The interest and research in porous concrete has been generated worldwide especially in the US and Japan [2]. Although fundamental information including the influence of the void ratio, W/C, cement paste characteristic, volume ratio of coarse aggregate, size of coarse aggregate and strength of porous concrete have been studied [1–7], the optimum condition to produce good por- ous concrete has not been established. The mix design, method of mixing and compaction to produce porous con- crete with potentially highest strength and durability at designed void ratio are still needed. This is mainly due to the fact that porous concrete is a special concrete with differ- ent mix design and compaction allowing continuous voids to be formed with relatively good compressive strength. In order to obtain the required continuous void and suf- ficient strength, the most important condition is to keep the continuity of cement paste with coarse aggregate embedded such that continuous void is maintained [8]. This is achiev- able with the use of cement paste with relatively low W/C and sufficiently high workability. At low W/C, an improve- ment in the texture and property of paste is obtained with sufficient mixing time and proper mixing. The knowledge on rheology of cement paste is, there- fore, a basic requirement for preparing good cement paste 0950-0618/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2006.12.007 * Corresponding author. Tel.: +66 4320 2355; fax: +66 4320 2355x12. E-mail address: prinya@kku.ac.th (P. Chindaprasirt). www.elsevier.com/locate/conbuildmat Construction and Building Materials 22 (2008) 894–901 Construction and Building MATERIALS