複合則を適用したポーラスコンクリートの静弾性係数推定式の提案

 Porous concretes have been used as various construction materials. However, the mechanical properties of the porous concretes are lower than that of the ordinary concrete because of its porous structure. The several techniques to improve the mechanical properties have been developed by many researchers for applying the porous concretes as structural members. The static modulus of elasticity is an important factor for such applications of the porous concretes.<br> On the other hand, the authors have been proposed the mix design system of the porous concretes, and the estimating methods for compressive strength, flexural strength and flexural toughness of the porous concretes by applying the law of mixture. This paper deals with a method for estimating the static modulus of elasticity of porous concretes based on Hashin-Hansen's equation as the law of mixture for two-phase composite material.<br> The porous concretes using cement mortars as a binder are prepared with the water cement ratios of 22.5, 25.0 and 30.0%, and the percentage of target voids of 10, 15, 20, 25, 30%. Porous concrete specimens are subjected to total voids test and the compression test including the static modulus of elasticity.<br> The test results show that the correlation between the compressive strength, the static modulus of elasticity and the total voids of the porous concretes are recognized. Regardless of the water-cement ratio, the static modulus of elasticity of the porous concrete is decreased with an increase in the total voids. The estimated values of the static modulus of elasticity of the porous concrete calculated by the Hashin-Hansen's equation is considerably higher than the experimental values because the equation is not include the factor of the total voids introducing the reduction of the static modulus of elasticity.<br> Therefore, the percentage of the total voids is an important factor to estimate the static modulus of elasticity of the porous concretes by applying the law of mixture. Namely, the porous concrete is the three-phase composite material consisted of the phases of matrix, aggregate and voids. To establish the correction coefficient of the voids, the experimental values of the static modulus of elasticity of the porous concretes are divided by the values calculated from the Hashin-Hansen's equation as the static modulus of elasticity of the voids-less porous concrete. The correction coefficient of the voids can be estimated by the function of the total voids. The equation multiplying Hashin-Hansen's equation by the correction coefficient of the voids is proposed to estimating the static modulus of elasticity of the porous concretes.<br> The applicability of the proposed equation in this paper will be discussed in more detail because the equation is obtained by using the estimated value for the static modulus of elasticity of the coarse aggregate.