Low viscosity metakaolinite based geopolymer binders

The low viscosity metakaolinite based geopolymer binders were prepared by mixing calcined claystone with potassium activators. The effect of the water content (30, 35, 40, 45 and 50%) and the Me:Al molar ratio (0.55, 0.70, 0.85, 1.00, 1.15 and 1.30) on the properties of binders (dynamic viscosity, applicability by ejection needles with different external diameters, compressive strength, elastic modulus and pore size distribution) was investigated. The Si:Al molar ratio was maintained at 1.5 for all geopolymer binders. Composites of geopolymer binders with 30% water with sand (1:1) were also prepared and evaluated. Geopolymer binders had a very low viscosity (8.4 mPa·s to 1.154 Pa·s), excellent mechanical properties (compressive strength up to 88.1 MPa), and all of them were applicable with injection needles having an external diameter of 1.2 mm or less. Increasing water content in the geopolymer binders led to a significant decrease in viscosity, compressive strength and modulus of elasticity and to the growth of pore volume and pore size. Geopolymers with a Me:Al molar ratio 1.0 had the best mechanical properties. The alkali content in the geopolymer binder did not have any noticeable effect on the pore volume, however dependences of the average pore size diameters on the Me:Al molar ratio had a minimum at Me:Al 0.7. The addition of sand to the binder did not have significant influence on compressive strength, but modulus of elasticity was increased 2–3 times compared to non-filled geopolymer binders.