The effects of curing time and temperature on stiffness,strength and durability of sand-environment friendly binder blends

Agricultural-industrial wastes, like rice-husk ash (RHA) and carbide lime (CL), have great potential applications in such earthworks as the stabilization of slopes and pavement layers and the spread footings and bed of pipelines, particularly in the regions near where the waste is produced. Present research evaluates the potential use of RHA mixed with CL as a binder, improving strength, stiffness and durability properties of a uniform sand. Two different curing temperatures, 23 °C and 40 °C, and curing periods, 7 and 28 days, of compacted sand-RHA-CL blends (distinct dry unit weights and contents of RHA and CL) were evaluated to determine the importance of these changes on the reactions between the materials. The experimental program aims to assess the following parameters: initial shear modulus (G₀), unconfined compressive strength (q_u), and accumulated loss of mass (ALM). Studies have been carried out to quantify these parameters as a function of a novel index called porosity/volumetric binder content (η/B_iv). The results showed higher values of G₀ and q_u, as well as a small rate of ALM with reduction of porosity and with rise of the environment friendly binder content. The latter is achieved either by increasing eith the RHA or the CL content. The curing temperature acts as a catalyser, accelerating the pozzolanic reactions between RHA and CL. Longer curing periods also benefit reactions between materials by enhancing their geotechnical properties. An analysis of variance (ANOVA) was carried and the results showed the dry unit weight, RHA content and curing type are significantly effect the strength results. It was also possible to verify that curing for 28 days at 23 °C and for 7 days at 40 °C are statistically equivalent in terms of strength. The G₀ results after weathering cycles tended to decrease in specimens at a 40 °C curing temperature and increase in specimens at a 23 °C curing temperature.