CURRENT ISSUES IN CONCRETE MIXING RESEARCH

Easy and economical use of some new materials in civil engineering is slowed down by their production cost due to mixing difficulties. The aim of mixing research at LCPC is first to appraise the production process and second to understand the phenomena which occur during mixing. The final goal is to reach an optimal association between material and mixing system. We present herein a summary of three recent research projects carried out at the LCPC Mixing Station, a scale-1 ready mix plant, i) By studying the residence time of each particle inside the mixer, a global model for the continuous mixing process of an unbound roadbase material is obtained, ii) The effect of the form of mineral admixture (either added to the mix or incorporated in the cement) on mixing time requirement has been investigated. There is a very slight advantage to use blended cement, although mixtures containing two-thirds of blast-furnace slag (as compared to the total binder) added in the concrete mixer exhibit excellent properties, iii) Tests performed on High-Performance and Self-Compacting Concretes show that the mixing time required is governed by water and cement dosages, that the compressive strengths increases in inverse of mixing time, and highlight some influences of the mixing system on the mixing time required.

• INTRODUCTION

• MIXING RESEARCH AT LCPC

• CONTINUOUS MIXING OF UNBOUND ROADBASE MATERIAL

• MIXING OF EVERYDAY STRUCTURAL CONCRETE

• MIXING OF SUPERPLASTICIZED MIXTURES

• CONCLUSION

• ACKNOWLEDGMENTS

• REFERENCES