Non-Autoclaved Aerated Concrete Porosity and Factors Affecting it

Abstract

The total volume of cellular porosity, which comprises pores, interpore partitions, and air-entrained pores, depends on the spatial packing of pores, size distribution, maximum and average size, their shape, and the thickness of interpore partitions. Interpore partitions contain gel and capillary pores, which have a significant impact on the total porosity, thus affecting the operating properties of aerated concrete. This paper presents the calculations of gel, capillary, air, and total porosity in non-autoclaved aerated concrete of average-density grades D100...D1200 for different cement hydration degrees (0.6; 0.8, and 1) and water-cement ratios (0.5; 0.6, and 0.7); calculations use the author-developed methodology. Cement consumption depends on the average-density grade as well as on cement hydration degree. Reducing the latter from 1 to 0.6 in D500 concrete raises cement consumption by 7.4 %; other grades have similar patterns. This is why aerated concrete should be conditioned to maximize the utilization of the binder by enabling its complete hydration. The amount of water in the mixture is what determines the cement consumption and the water-cement ratio, whereby the density of cement dough will not depend on the average-density grade provided that the hydration degree and the WC ratio are constant. The finding is that the ability of cement to form its own pore structure is crucial to D500 and D400 aerated concrete if the mixture has high initial water content.