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.

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In this paper, a study was conducted on the parameters affecting the sorption of water, chloride ingress and permeability of water into lightweight aggregate concrete. The parameters being studied are the effects of the water-to-cement (w/c) ratio, aggregate type, initial moisture content of the lightweight aggregate, size of the lightweight aggregate, density of the lightweight aggregate, cement paste volume and volume of the lightweight aggregate. Experimental programmes were designed to look into the effects of these parameters on the penetration of water and free chloride ions into lightweight aggregate concrete by water sorption under capillary action in unsaturated concrete, chloride diffusion under a constant concentration gradient, and water permeability under a constant pressure gradient. From this research, it was found that variations in the w/c ratio, cement paste volume, as well as size, density and volume of the lightweight aggregate, have reasonable effects on penetrability properties of lightweight aggregate concrete. The effect of initial moisture content in the lightweight aggregate on properties of lightweight aggregate concrete is not obvious from this research.

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