Influence of the activator concentration and calcium hydroxide addition on the properties of alkali-activated porcelain stoneware

Abstract

Objective The aim of this research was to investigate the influence of the alkali activator concentration and calcium dosage on the fresh behavior, compressive strength and microstructure of the binder produced by the alkali activation of porcelain stoneware waste, using NaOH and sodium silicate solution as activators.

Materials Porcelain stoneware waste, NaOH and sodium silicate.

Method Tested properties of mortars were the compressive strength and the setting times. Thermogravimetric analyses, microscopic studies, pH measurements, XRD and FTIR tests were used to assess the evolution of the microstructure developed.

Results The results show that the activator concentration and calcium to sodium molar ratio strongly influence the fresh behavior and the hardening process of mortars. A linear evolution of compressive strength with sodium addition was observed when keeping the SiO2 concentration constant. Mortar samples with up to 36 MPa under compression were obtained after curing for 7 days at 65 °C.