Influence of the Autoclaving Conditions on Some Properties of Lightweight Building Blocks

摘要

Various mixes composed of 75 % filler (sand) and 25 % binder (15 % lime + 10 % OPC) had been used for the preparation of cellular building units using hydrothermal method (autoclaving) at different autoclaving conditions namely, 10, 12 and 14 atmospheres for different periods. All samples had been tested using different techniques: the compressive strength and density measurements, in addition, XRD, DTA and SEM investigations were conducted. The results indicated that at a given autoclaving pressure, the mechanical strength of the products increases with the autoclaving period to a maximum, beyond which the compressive strength declined. The results of XRD and DTA confirm the formation of tobermorite as the main binding agent. Also, the maximum strength was achieved either at shorter periods under higher pressures or for longer periods under lower autoclaving pressures. The results of SEM revealed that the changes in morphology of the binder (tobermorite) explained the consecutive changes in mechanical properties.