INFLUENCE OF FILLERS ON THE HYDRATION OF TERNARY BINDER

While the interaction between the cement-based binders and different types of fillers is described sufficiently, the behaviour of composites, containing gypsum and any type of filler was studied less frequently and studies focused on the interaction between the composite binder and filler are rare. We studied ternary binder composed from gypsum, lime and silica fume in combination with several types of fillers (sand, expanded perlite, expanded clay and waste polyurethane). The strength of the composites was measured in 7 and 28 days. While in the pure gypsum the maximal strength is achieved very quickly (in hours), in the ternary materials it increased between the 7 and 28 days at about 10 to 20%, because the pozzolanic reaction is slower than hydration of pure gypsum and the type of the used filler influences the hydration as well. Composites with sand and expanded clay achieved the compressive strength over 10 MPa (15.9 and 12.7 respectively), the strength of material with expanded perlite was 8.3 MPa and material with waste polyurethane achieved about 3.6 MPa. The images obtained by electron microscopy showed the different structure of hardened materials and different shape of gypsum crystals in materials with different types of filler. The environmental impact of the material with the waste polyurethane was lowest from all tested materials, while its properties allowed it to be used for less demanding purposes.