Effect of the ratio of water to binder and sand to aggregate on the hardness of concrete mixtures and compressive strength of roller-compacted concrete

Abstract

In roller-compacted concrete technology, due to the use of low water and cement content, the concrete mixture after kneading has high hardness and compaction equipment must be used to shape the product. Therefore, the content of mixing water, binder, and aggregate is considered a decisive factor, greatly affecting the properties of roller-compacted concrete in both fresh and hardened states. The article uses the mathematical method of two-factor rotatable central compositional planning to simulate the effect of volumetric ratios of water-binder (V_N/V_CKD) and sand-aggregate (V_C/V_CL) on the objective functions of the test. The selected objective functions are the hardness of the concrete mixture and the compressive strength of the roller-compacted concrete at the age of 28 days. From the obtained objective functions, it is shown that both control variables V_N/V_CKD and V_C/V_CL have a significant influence on the values of the experimental model. When the V_N/V_CKD ratio increases, the water content contributes to increasing the plasticity and reducing the hardness of the concrete mixture. At the same time, excess water exists in the concrete in the form of pores, reducing the compressive strength of the product. Furthermore, the V_C/V_CL ratio of the aggregate that is too small or too large tends to cause the compressive strength of the concrete to decrease.