THE INFLUENCE OF CLINOPTILOLITE ON THE HYDRATION AND HARDENING OF PORTLAND CEMENT
Keywords:natural zeolite, clinoptilolite, Portland cement, puzzolanic materials, concrete
Effects of the natural zeolite clinoptilolite (Na, K, Ca)2-3Al3(Al, Si)2Si13O36·12H2O on the mechanical properties and strength of Portland cement paste, mortar, and concrete samples were investigated. Incorporation of 0; 5; 7 and 10 % (by weight) of the clinoptilolite in Portland cement paste (W/C = 0.38), mortar specimens using the water-solid ratio (W/C = 0.44) and concrete mixture specimens (W/C = 0.57) were cured at room temperature for 3, 7, 14 and 28 days. The mechanical properties were determined by measuring the bending and compressive strength of the hardened specimens of mixtures. The hydration products of Portland cement mixture specimens were analysed by using an X-ray diffractometer (XRD), the natural zeolite clinoptilolite with a differential thermal analysis DTA and thermogravimetric analysis (TGA). In the examined conditions after 28 days of hydration hardened cement paste samples with 10 % of the natural zeolite replacement had the highest compressive strength. It can be assumed that the natural zeolite (clinoptilolite) pozzolanic properties are not immediate, but its apparent after 28 days of hydration. The bending and compressive strength of mortar samples does not depend on the zeolite replacement content. By using the natural zeolite (clinoptilolite) the economic effect can be achieved because in concretes up to 5 % of clinoptilolite can be replaced the cement without changing mechanical properties of concrete products.