Development of Computer Model for Optimising the Compressive Strength of Concrete Made of Laterised Sand Stones

Abstract

The economic importance of local aggregate in the construction industry, the abundance of the natural deposit in this country, its ever-increasing use by builders, and the ever-increasing cost of construction materials prompted research into local and cheap construction materials.

Granite, the common coarse aggregate in normal concrete is equally affected. Therefore, the search for alternative low-cost materials that can be used as aggregate in concrete without extremely affecting the properties of the concrete is a task on researchers, technologists, engineers, and scientists.

The traditional methods of mix design employ empirical formulae and are very cumbersome, time wasteful and energy consuming. This research was aimed at overcoming these limitations by developing a computer model for optimizing the strength of concrete made from laterized sandstones (local aggregate) in Nsukka, Nigeria. Model for compressive strength based on Henry Scheffe's simplex theory using a quadratic polynomial and a (4, 2) simplex lattice was developed. A QBASIC computer optimization program was equally developed for the model. Using the model, once the user specifies the required strength, the computer provides all the possible mix ratios that can yield such strength. The students't-test statistic confirmed the adequacy of the model. The maximum compressive strength attainable with the model using laterized sandstone aggregate is 43.5N/mm².