Suitability of Laterite Fines as a Partial Replacement for Sand in the Production of Sandcrete Bricks
The provision of affordable housing units from indigenous building materials has been the focus of most researchers in recent times. This paper focuses on the utilisation of laterite fines as replacement for sand in the production of sandcrete bricks as masonry units. With a mix ratio and a water/cement ratio of 1:6 and 0.50 respectively, batches with 0% (control specimens), 10%, 20%, 30%, 40% and 50% laterite fines replacing the sand were adopted in this study. In all, 96 bricks were cast, tested and compared with those of conventional sandcrete bricks (control specimens). Tests studied were density, compressive strengths (wet and dry) and water absorption. Data results revealed that the laterite fines used could satisfactorily replace the sand up to 30% for the production of structural masonry units even though bricks need to be protected when used in waterlogged areas or below ground level.
SDA and laterite applications in concrete: Prospects and effects of elevated temperature
Abstract This research supports green eco-friendly construction through utilization of laterite and sawdust ash as fine aggregate and supplementary cementitious material in concrete. Critical literature review revealed that at fine aggregate replacement by laterite ≤50, 50–75 and 100%, mix ratios 1:2:4:0.56, 1:1.5:3:0.65 and 2:3:6:0.65 respectively are preferable for structural applications. Higher compressive strength losses of 32.81, 28.23 and 32.59% were recorded at elevated temperatures of 200, 400 and 600°C for SDA-modified laterized concrete while lower strength losses of 8.58, 7.91 and 3.74% were recorded for conventional laterized concrete. However, strength gain of 15.9% was recorded at 25°C ambient temperature for SDA-modified laterized concrete. Based on elevated temperature results, 10% SDA-modified laterized concrete at 45% optimum laterite content can only be used for production of load-bearing bricks and blocks and other non-structural applications. Further research efforts on green construction are required.
KINETICS OF THE POZZOLANIC REACTION BETWEEN LIME AND SUGAR CANE STRAW ASH BY ELECTRICAL CONDUCTIVITY MEASUREMENT: A KINETIC-DIFFUSIVE MODEL
Abstract The kinetics of the pozzolanic reaction between lime (calcium hydroxide) and sugar cane straw ash (SCSA) with 20% and 30% of clay burned at 800 and 1000 °C is studied. A simple experimental technique was used in which the conductivity is the experimental variable. For correlating the conductivity with the concentration of calcium hydroxide (CH), a calibration curve was established. We elaborated a mathematical model that allows us to describe the process in either kinetic or kinetic–diffusive regimes. The fitting of the model by computerized methods enables us determine the parameters that characterize the process: i.e. the diffusion coefficient and reaction rate constant. The pozzolanic activity is evaluated according to the obtained values of the reaction rate constant. The results show that SCSA has a good pozzolanic activity comparable to that of the rice husk ash (RHA).