Influence of the Binder/Sand Ratio on the Performance of Geopolymer Mortar

Kaolinitic clay is the most sought-after natural source of aluminosilicate for the production of geopolymers, but it is found in large quantities in the Ivory Coast, but remains little exploited. Thus, this study was carried out to use these clays to produce geopolymer mortars as a substitute for Portland sand-cement. Its objective is to find the binder/sand ratio for the use of these materials in construction. It is in this context that local clay and sand were characterized by granulometric analysis, X-ray fluorescence and DRX (X-ray Diffraction). This clay, calcined at 750˚C, then mixed with an alkaline solution, gives a geopolymer binder. For this geopolymer binder, sand was incorporated according to binder/sand ratios of 0.4 to 1, and mortars were produced. After molding, heat treatment at 80˚C and curing at room temperature for 28 days, these mortars, which have become blocks, are mechanically tested. Their accessible porosity to water and their apparent density were also determined. The results indicate that the clay is made up of 80% kaolinite, to which muscovite and quartz are added. The compressive strength of the mortars increases from 19.11 to 27.09 MPa for ratios increasing from 0.4 to 0.7 and then decreases to 23.55 MPa, while the flexural strength values vary from 4.35 to 5.86 MPa. The measured accessible porosity to water is between 16.18% and 21.14% and the density is between 1.81 and 1.91 g/cm3. Mortars based on geopolymer binder and sand with a B/S ratio of 0.7 have the highest mechanical strength values. They can therefore be used in construction in the same way as sand-cement concrete blocks. This will reduce cement consumption. This B/S ratio of 0.7 will therefore be retained for the rest of the work.