This chapter presents the preparation of a new kind of biocement based on the biophosphate minerals, which have cementation, by the bacteria reacting with the substrate. Ammonia/ammonium can be changed into environment-friendly struvite when the soluble phosphate is added to biocarbonate cement. After that, struvite and carbonate, which can be considered as composite cements, are applied to cement loose particles. The biocement is environmentally friendly, which has important application prospects. Based on mixing-precipitation process, the injection process was adopted to bind loose sand particles. Permeability, porosity, compressive strength, and internal microstructure of the biosandstones cemented by composite cement were determined under different number of injections. Mixing-precipitation process was inferior to injection process according to compressive strength of the biosandstones caused by the particle size and morphology of composite cement. Permeability, porosity, compressive strength, and fixation ammonia ratio of the biosandstones were compared when three different formulations of composite cement (CJ1, CJ1.5, and CJ2) were adopted to bind sand columns. The results show that the CJ2 has the best overall performance. The molar ratio of K2HPO4·3H2O and urea was 2:1 in the CJ2 formulation.
Part of the book: Sustainable Construction and Building Materials