Properties of cement–lime mortars vs. cement mortars containing recycled concrete aggregates

• The replacement of natural aggregates with recycled aggregates in mortars was studied.
• Cement and cement–lime mortars were compared.
• Recycled aggregates worsen the properties of cement mortars.
• Cement–lime mortars characteristics improve by recycled aggregates addition.

Cement based materials have a very special presence amongst building and construction materials, and therefore their recycling is of capital importance. In this research, concrete wastes were used as replacement of natural aggregates in cement and cement–lime mortars. The mortars were cured for 28-days with an increasing substitution of fine natural aggregates with recycled aggregates and have been prepared as well as characterized. The results show that, as expected, cement mortars always have better mechanical properties than the corresponding cement–lime mortars. A worsening of mechanical properties is observed upon increasing the amount of recycled aggregates in the cement mortars; on the contrary, cement–lime mortars show an improvement in mechanical properties of up to 60% when increasing the amount of recycled aggregates. The experimental results suggest that this improvement could arise from a synergic effect of lime hydraulicity and the filler effect due to the fine fraction of recycled aggregates within the mix, that lead to better densification of the lime mortars by blocking the capillary pores.