Prediction of Compressive Strength of Concrete Using the Spearman and PCA-Based BP Neural Network

Table 2

Results of the correlations between the input variables and compressive strength.

Input variables	Correlation coefficient
Cement (kg)	0.836
Water (kg)	0.303
Crushed stone 1 (kg)	-0.749
Crushed stone 2 (kg)	-0.72
Crushed stone 3 (kg)	-0.786
Sand (kg)	-0.696
Fly ash (kg)	7.14
Water reducer (kg)	-0.065
Cementitious material (kg)	0.426
Four aggregates (kg)	-0.756
Water-binder ratio	-0.158
Sand ratio	0.017
Water-cement ratio	-0.47