Mechanical Properties of Alkali Activated Material Based on Red Clay and Silica Gel Precursor

The search for alternative alumosilicates source for production of alkali activated materials (AAM) is intensively researched. Wide spread of natural materials such as clays and waste materials are one of potential alternatives. In this research AAM was made from local waste brick made of red clay and calcined low-carbonate illite clay precursor and its properties evaluated. Waste silica gel containing amorphous silica from fertilizer production plant was proposed as additional raw material. 6 M and 7 M NaOH alkali activation solutions were used to obtain AAM. Raw materials were characterized by X-ray diffraction, laser particle size analyser, DTA/TG. Raw illite clay was calcined at a temperature of 700 to 800 °C. Waste brick was ground similar as raw clay and powder was obtained. Replacement of red clay with silica gel from 2–50 wt.% in mixture composition was evaluated. Results indicate that the most effective activator was 6 M NaOH solution and AAM with strength up to 13 MPa was obtained. Ground brick had the highest strength results and compressive strength of AAM reached 25 MPa. Silica gel in small quantities had little effect of AAM strength while significant strength reduction was observed with the increase silica gel content. The efflorescence was observed for samples with silica gel.