Proportioning RCCP mixes under hot weather conditions for a specified tensile strength

Hisham Y. Qasrawi, Ibrahim M. Asi and H. I. Al-Abdul Wahhab
^a Civil Engineering Department, Faculty of Engineering, Hashemite University, Zarqa 13115, Jordan
^b Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
Abstract

The work presented in this paper introduces the use of roller-compacted concrete pavements (RCCPs) as a substitute to the traditional asphalt concrete pavements that suffer from severe rutting and cracking due to heavy loading and hot weather which prevail in most of the Middle East countries. A soil compaction method (Kneading compaction) was used in this research to simulate compaction in the field. The variables affecting the mix proportioning of RCCP in hot weather have been evaluated and discussed. The variables included in this research were cement content, aggregate-to-cement ratio, water-to-cement (W/C) ratio, and degree of compaction. The effects of these variables on the density, tensile, and compressive strengths have been studied. Various plots and tables showing the interrelations between the studied variables were included in the paper.

Results showed that under hot weather conditions, slight alterations in material proportions should be made to arrive at the required properties of RCCP mixes. A W/C ratio of 0.45 has been found to produce the optimum density and tensile strength for concrete in hot weather under the conditions of the experiments. One of the major findings was that the main factor that controlled most of the fresh and hardened properties is the cement content. Another important factor is that, unlike normal concrete, lowering the W/C ratio below an optimum value may not result in increase in the strength. Based on the results, simple relationships and equations have been obtained to predict the tensile strength of RCCP using the proportions of the mix. In addition, it has been found that a simple relationship, similar to the one presented in the ACI 325.10 state-of-the-art report, exists between the compressive and the tensile strength of concrete. The equation is presented in the simple form:

Based on the extensive study, the paper proposed a method of mix design that is suitable for RCCP in the Middle East. However, the method can be extended for other situations.

Author Keywords: Concrete; Mix design; Roller-compacted concrete