Moderate strength lightweight concrete from organic aquagel mixtures

The present study describes a new approach for making lightweight concrete that uses aquagels in the concrete formulation. Aquagels are semi-rigid gels that contain mostly water and a small amount of solids that act as the gelling agent. Aquagels were made using wheat starch, algin, agar and high amylose corn starch (HACS). Concrete samples were made using each of the four aquagels and perlite. The plastic, cured and oven-dried densities of concrete samples decreased with increasing concentrations of aquagel or perlite. Thermal conductivity (k) was strongly correlated with density. The k values decreased more than three times the rate of the decline in density. Oven-dried density of the samples ranged from approximately 0.91 g/cm3 for samples containing the highest concentration of aquagel to 1.95 g/cm3 for control samples. The compressive strength of the samples decreased from 55 MPa for the control to approximately 10 MPa for samples containing the highest concentration of aquagel. Samples made from wheat starch and algin aquagels had a lower compressive strength than the other samples even at concentrations as low as 0.19 parts aquagel to one part cement. The density of wheat starch aquagel-based concrete remained uniform and unaffected by hydrostatic pressures created at depths of up to 3 m. Of the aquagel materials tested, wheat starch is the lowest in cost and the most widely available.