Use of Correlation and Regression Analyses as Statistical Tools in Green Concrete Research

Correlation and regression in this paper were employed as analytical tools to study the degree of relationship as well as
the nature and strength of the relationship between green concrete properties and percentage replacement of cement
with civil engineering materials. Pearson product-moment method and Spearman’s correlation coefficient were
extensively used to show how correlation analysis can be practically applied in green concrete research. Least square
regression line method for both linear relationship and non-linear relationship was also used to analyse the nature of the
relationship between percentage replacement of cement with a pozzolana and green concrete properties like
compressive strength and water absorption. The results of correlation analysis showed that Pearson product-moment is
a better method for analysing green concrete properties when compared with Spearman’s correlation coefficient, since
Pearson’s method takes cognizance of the actual data values unlike Spearman’s use of data positions. The results of
regression analysis also revealed that, for data whose trendline is polynomial in shape with the highest power of its
assumed equation higher than that of quadratic equation, it is better to analyse such data using least square regression
line method for linear relationship than least square regression line method for non-linear relationship. This is supported
by the substantial difference in the predicted values of 40.79MPa and 36.20MPa for linear and non-linear relationship
respectively for 35% replacement of cement with rice husk ash along with fly ash.