Abstract: The present invention is directed to methods of preparing biocement. The methods disclosed herein employ microbial or enzymatic means first to generate acid which dissolves CaCO3, and then to degrade urea, producing CO3? ions which increase the pH and lead to the reprecipitation of CaCO3. The precipitation of CaCO3 acts as a cementation process which can bind together particulate materials to yield mortars, concretes and suchlike. The invention further provides construction materials formed by the methods of the invention, and bacterial strains which can be used in the methods of the invention to generate organic acids.