Effect of w/c ratio on air-void system of foamed concrete and their influence on mechanical properties

Abstract

A study was undertaken to investigate the effect of water to cementitious material (w/c) ratio (ranging from 0 . 22 to 0 . 60) on the air-void system (air content ranging from about 10 to 70%) of foamed concrete, and their effects on the mechanical properties of foamed concrete without sand. The cementitious material used in this study was blended cement with 50% ordinary Portland cement (OPC) and 50% ground granulated blastfurnace slag (ggbs) by weight.The linear traverse method was used to characterise the air-void system, referring to air content, average air-void size, air-void frequency and spacing factor. The results show that although the same quality of foam was introduced, the air-void size and frequency, and hence spacing factor, of the foamed concrete varied with different w/c ratios and air contents, which in turn affected the mechanical properties of the concrete. For the different w/c ratios and air contents adopted, it was found that an air-void system with a spacing factor of about 0 . 05 mm, air-void size of 0 . 15 mm and air content of 40% was optimal in terms of achieving a high strength to weight ratio. The compressive strength of foamed concrete seems to be influenced by the spacing factor, w/c ratio and air content in relation to density. The results also indicated that the inclusion of air-voids in foamed concrete had a greater effect on compressive strength than the modulus of elasticity and it increases with increase of w/c ratio. The results of a numerical analysis concurred with the experimental observations.

Investigations on the Relationship Between Porosity and Strength of Admixtures Modified High Performance Self-Compacting Concrete

“…The strength of cement mortar or paste is more heavily influenced by the volume and number of large size pores and mean pore diameter than by smaller pores (Robler, Odler 1885;Kearsley, Wainwright 2002). The research (Wee et al 2011) results proved that the compressive strength of foamed concrete seems to be influenced by the spacing factor, w/c ratio and air content in relation to density. The results also indicated that the inclusion of air-voids in foamed concrete had a greater effect on compressive strength than the modulus of elasticity and it increases with increase of w/c ratio.…”

Effect of sodium sulfate and sodium nitrite on air-void system in air-entrained concrete

“…A slump of 80-100 mm was achieved with a superplasticiser (UNF-5) dosage of 0·5% by mass of cement. Specimens were cast in plastic beam moulds of dimensions 100 mm  100 mm  400 mm and were cured for 28 d. Previous concretes studied (Li et al, 2015;Liu et al, 2015b;Wee et al, 2011) were tested in accordance with ASTM C231 (ASTM, 2004) for fresh air content and ASTM C457 (ASTM, 2012) for air-void system parameters. In this work, the samples were cut into 10 mm wide slices and polished with successively finer abrasives until they were suitable for testing in accordance with ASTM C457 (ASTM, 2012).…”

Properties of Foam Concrete Prepared From Magnesium Oxychloride Cement

“…Yang and Lee studied the effect of the w/b on the performance of foam concrete. As the w/b increases, the number of fine pores decreases, and the number of large pores increases, which results in the high porosity of the foamed concrete, resulting in a low strength [12][13]. According to the research, foam concrete has excellent thermal insulation performance.…”