Fabrication of Geopolymers from Untreated Kaolin Clay for Construction Purposes

A new geopolymeric material has been fabricated from local Saudi Arabian resources using inorganic mineral polymerization technique. In this technique, the mineral polymer is synthesized from the following components: naturally occurring kaolin clay mineral, silica sand, sodium hydroxide, and water. Homogeneous samples of known amounts of clay minerals and silica sand were mixed with different ratios of clay and sand and sodium hydroxide solutions ranging from 13 to 19.7 mol/l. To accelerate the chemical polymerization reaction, the molded reactants were cured at 80 °C in an oven for 24 h to form stable and hard geopolymeric material. The synthesis parameters of mass of clay mineral, sand, NaOH and water were varied according to a statistical analysis design of experiment. The optimum amount of water is limited by the plastic limit of the clay, which is determined to be around 25%. Based on the results of the experimental design a geoploymer with a compressive strength of 27.1 MPa was achieved by sand to kaolin ratio of 1.5, water to kaolin ratio of 0.25 and NaOH to kaolin ratio of 0.17 under dry conditions and 18.1 MPa under wet conditions.