Hydrothermal Reactions between Lime and Aggregate Fines I. Experimental Conditions for Strength Improvement Using Saturated Steam at Atmospheric Pressure

A comparison of the compressive strength has been made through hydrothermal reactions of lime and silica sand. Various additives, such as china-clay, Na2CO3, CaSO4, 2H2O, slate, fire-clay and Na2SiO3 have been employed in order to get the higher strength. The compressive strengths and mineralogy were determined for various mixtures of lime and aggregate fines autoclaved at a steam pressure of 0.1 MPa (100°C) for 6, 12, 18, 24 and 48 hours. A maximum strength of 25.0 MPa was recorded after 48-hours reaction between 80% silica sand, 15% lime and 5% china clay, whereas if the reactants are only silica sand (85%) and lime (15%), they lead to lower 48-hours strength (11.3 MPa). The cementitious product identified was calcium hydro-silicate.