Development of lightweight alkali-activated mortar for 3D printing technology

This article aims to develop lightweight alkali-activated mortar for 3D printing. High CaO fly ash (FA) was used as a binder and sodium metasilicate (SM) was used as an alkali-activator at the rates of 3.0, 4.5, 6.0, 7.5 and 9.0% by weight of binder. Moreover, fine aggregate was replaced by bottom ash (BA) at the rates of 50 and 100%by volume of fine aggregate in order to use as an internal curing material and reduce the density of mortar. The flowability of mortar was controlled between 180 –190 mm. Setting times, compressive strength, and 3D buildability of mortar wereinvestigated. The results showed that the water to binder ratio of mortar was decreased with the increase of sodium metasilicate content, resulted in the decrease of setting times. The setting time, density, and compressive strength of mortar were decreased with the increase replacement of fine aggregate with bottom ash. The use of sodium metasilicate at 4.5% combined with 100% replacement of fine aggregate with bottom ash was the suitable mixture of lightweight alkali-activated mortar for 3D printing technology, which had the densityof 1795 kg/m3 and the compressive strength of 24.1 MPa at age of 28 days.