Modeling of compressive strength of roller-compacted concrete containing reclaimed asphalt pavement using response surface methodology (RSM)

Reclaimed asphalt pavement material (RAP) that are known as reconstruction and asphalt milling debris, constitute a major part of the waste materials. One of the applications that have been considered recently, is the use of these materials (RAP) in mixes such as roller-compacted concrete (RCC). Therefore, in this study, after experimental studies and making 141 concrete samples, 47 unique data of the compressive strength of RCC containing RAP was obtained. Then, response surface methodology (RSM) was used to build a model to predict the compressive strength. The regression coefficient (R2) of 0.9668 for the developed model, indicated the accuracy of the model. The model showed that in addition to all the basic variables other than fine aggregate, interaction between cement and fine RAP, coarse aggregate and curing time, fine RAP and curing time, curing time square and temperature square, can also be effective in predicting the compressive strength values. Also according to the results of the sensitivity analysis, it was observed that the amount of compressive strength will be increased by increasing the amount of cement and the slope of this increasing in higher amounts of fine RAP was far less. In addition, decreasing the fine RAP or increasing the curing time in a fixed amount of coarse aggregate, will lead to an increase in compressive strength. And also, curing time will have a greater effect on the compressive strength in lower percentage of fine RAP.