Investigation of the spatial variability in oyo-iwa limestone deposit for quality control

The continuing expansion of Nigeria construction industries coupled with the large importation of cement despite huge limestone deposits scattered all over the country is of great concern. This study investigates the spatial variability of OyoIwa limestone deposit using the cement raw materials variables (such as Calcite) as well as cement quality parameters (Lime Standard, Silica Modulus and Alumina Modulus). In order to achieve this objective, exploratory borehole data were obtained, processed and analysed to examine the spatial pattern of the selected variables within the deposit. Statistical studies indicated that all the variables used in this research came from the same parent population. Due to skewness of the plotted histograms of the variables, normal transformation was applied to the variables. Also, the correlation matrix obtained showed that the considered variables shared low correlation with each other. The omni-directional variogram of each of the limestone variables were later constructed and systematically fitted both in the vertical and horizontal planes. Moreover, the directional variograms were also developed and this show neither severe geometric nor strong zonal anisotropy exist in the limestone deposit. The models were verified through cross validation and proved to be valid with the variance of the standard error, varying from 0.9796 to 1.0250 between the estimated and real data of the limestone variables. Also, the mean of the standard error of the cross validation varies from -0.0079 to 0.0336.The result of this research work will be informative and beneficial especially in the characterisation with modelling as well as reserve estimation of Oyo-Iwa limestone deposit