A Novel Concrete Mix Design Methodology

Abstract

Concrete mix design is the methodology for mixing binder, aggregate and water to achieve required physical, mechanical, and thermal properties. In particular, the physical properties depend on the volume fraction of each element in the concrete recipe. In this study we considered cement mortar, complying with ASTM C105, as the reference concrete with cement as the binder and silica sand as the aggregate. The reference mortar was denser with high thermal conductivity and compressive strength at given rheological properties. A denser concrete presents difficulty in material handling and imposes a safety risk, and high thermal conductivity increases building energy consumption. Therefore, lightweight concrete (LWC) has been developed by replacing silica sand with porous materials. LWC includes cement as the binder, with silica sand and other porous materials as the primary and binary fillers. The mass of the filler materials is determined by their particle density and volume fraction. LWC has low thermal mass, thereby exacerbating the summertime overheating and peak cooling demand of buildings. Therefore, there is a need to design a LWC with high thermal mass by incorporating phase change materials (PCM), which are mainly incorporated as tertiary filler. Here, we propose a novel concrete mix design methodology to incorporate PCM composite as a partial replacement of the porous material without changing binding materials.