Mortar with different rice husk ashes in partial replacement of Portland cement: Pozzolanic activity index and hardened state properties.

Reference	Presenter	Authors (Institution)	Abstract
04-095	Camila Crauss	Crauss, C.(Universidade de Santa Cruz do Sul); Krann, M.L.(Universidade de Santa Cruz do Sul); Basegio, T.M.(UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL); dos Santos, P.M.(Universidade de Santa Cruz do Sul); Rodriguez Lopez, D.A.(Universidade de Santa Cruz do Sul); Rodriguez, A.L.(Universidade de Santa Cruz do Sul);	The use of rice husk ash (RHA) as an addition in substitution for Portland cement may have an impact both on mortar properties and environmental aspect of this material, since RHA is a residue of rice husk burned for energy production. Portland cement manufacture uses non-renewable raw materials, consumes energy mainly in the kilns for cement clinker formation and emits large amounts of CO2 during the process. Cement’s partial substitution for an agroindustrial waste can minimize the environmental impacts generated by the final product. The combustion method of the rice husk and also the granulometric composition of the ash influence its pozzolanic activity. In this study, RHA from three different sources were analyzed: 1) controlled burning temperature and milling, obtained from fluidized-bed combustion; 2) without controlled burning temperature and without milling obtained from the combustion in furnaces of a local ceramic industry; 3) burning with controlled temperature in laboratory furnace and without milling. Pozzolanic activity indexes of the RHA with lime and cement were analyzed to determine if the ashes without treatment had similar performance to that ones with controlled burning temperature and milling. XRF and XRD analyzes indicate that the ashes are composed basically of SiO2 for the ash with controlled burning temperature with amounts greater than 93%, and amorphous phase. Granulometry and specific surface area of the three types of ash were also analyzed. Properties of the hardened mortar for volume composition 1: 1: 6 and 10% of replacement of cement by RHA were analyzed by flexural strength, compressive strength, density in hardened state, capillary absorption, immersion absorption and voids index. It is possible to relate the characteristics of the chemical and morphological composition of the RHA with their pozzolanic activity index with lime and cement, and the modification in the properties related to the behavior of the hardened mortar.
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