MODERATE STRENGTH LIGHTWEIGHT CONCRETE FROM ORGANIC AQUA GEL MIXTURES

The present study describes a new approach for making lightweight conc rete that uses aquagels in the concrete formulation. Aquagels are semi -rigid gels that contain mostly water and a small amount of solids tha t act as the gelling agent. Aquagels were made using wheat starch, alg in, agar and high amylose corn starch (HACS). Concrete samples were ma de using each of the four aquagels and perlite. The plastic, cured and oven-dried densities of concrete samples decreased with increasing co ncentrations of aquagel or perlite. Thermal conductivity (k) was stron gly correlated with density. The k values decreased more than three ti mes the rate of the decline in density. Oven-dried density of the samp les ranged from approximately 0.91 g/cm(3) for samples containing the highest concentration of aquagel to 1.95 g/cm(3) 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 con centration of aquagel. Samples made from wheat starch and algin aquage ls had a lower compressive strength than the other samples even at con centrations as low as 0.19 parts aquagel to one part cement. The densi ty of wheat starch aquagel-based concrete remained uniform and unaffec ted by hydrostatic pressures created at depths of up to 3 m. Of the aq uagel materials tested, wheat starch is the lowest in cost and the mos t widely available. (C) 1998 Elsevier Science B.V. All rights reserved .