Study of natural hydraulic lime-based mortars prepared with masonry waste powder as aggregate and diatomite/fly ash as mineral admixtures

NHL-based mortars were prepared by using waste marble powder (WMP) as aggregate and introducing diatomite and fly ash to partially replace natural hydraulic lime (NHL). Physical property evaluation showed that compressive and flexural strength of mortars prepared with diatomite were greatly enhanced, fly ash addition had noticeable improvement on mortars' flexural strength. Diatomite had a more positive effect on mortars' compressive strength than fly ash and 20% mineral addition made mortars achieve better mechanical properties. Apparent density of prepared mortars was decreased after introduction of diatomite and fly ash. Acid and sulfate resistance properties of mortars were improved by the presence of mineral. Diatomite was more effective than fly ash in improving the sulfate resistance of mortars. Microstructure, ultrasonic velocity and thermal properties characterization suggest that the improvement of mortars' properties could be attributed to pozzolanic reaction between mineral admixtures and calcium hydroxide (Ca(OH)2) which mainly occurred during curing period at the range of 14-28 days.