Optimized Strength Model of Cement-RHA-Laterite-Water Mix in Hollow Sandcrete Block [ ]


With the cost of cement and transportation of sandcrete aggregates in Nigeria increasing geometrically, designers now seek more locally available materials for constructing durable structures that still stand the test of time. This paper focuses on modeling and optimizing the compressive strength of a four component mixture of Cement, Rice Husk Ash, Laterite and Water in the production of hollow sandcrete block, at 67/33 Cement/RHA and 100% laterization. The study applies the Scheffe’s optimization approach to obtain a mathematical model of the form f(xi1,xi2,xi3,,xi4), where xi are proportions of the concrete components, viz: cement, RHA, laterite and water. Scheffe’s experimental design techniques are followed to mould various hollow block samples measuring 450mm x 225mm x 150mm and tested for 28 days strength. The task involved experimentation and design, applying the second order polynomial characterization process of the simplex lattice method. The model adequacy is checked using the control factors. A purpose-made software is prepared to handle the design computation process to take the desired property of the mix, and generate the optimal mix ratios.