Development of lightweight mortars targeted on the high strength, low density and low permeability

This article presents a mix design methodology for the development of cement-based lightweight mortars. Expanded-glass lightweight aggregates were used in this study as the lightweight material. The mix design was developed applying the packing theory using the modified Andreasen and Andersen model to obtain the optimal grading curve of all the solids in the mixture. Two self-compacting and one conventionally vibrated mortar were designed. The developed mortars had a low thermal conductivity while retaining good mechanical properties. The permeability of the developed mortars was quantified based on the measurements of the capillary water absorption, water penetration under pressure and chloride transport properties. The results of the tests indicate that the produced self-compacting mortars are very permeable, while the permeability of the vibrated mortar is very low. When fine fractions of the lightweight aggregates were used, the produced composites were very permeable. On the other hand, a low-permeable lightweight mortar was developed by combining cement paste of a good quality (low water/cement ratio) with normal-density sand and only coarse fractions (1 – 4 mm) of lightweight aggregates.