Packing Density Improvement through Addition of Limestone Fines, Superfine Cement and Condensed Silica Fume

J J Chen,L G Li,A K H Kwan,P L Ng

doi:10.4236/msce.2016.47005

Abstract

Adoption of a low water/powder (W/P) ratio is the key to improve the strength and durability of concrete, which relies on a high packing density because fresh concrete requires excess water to offer flowability. To obtain a high packing density, powders with different particle sizes, including limestone fines (LSF), superfine cement (SFC), condensed silica fume (CSF), were added to the cement paste and the resulting packing densities were measured directly by a newly-developed wet packing test. Results demonstrated that addition of powders with a finer size would more significantly improve the packing density but the powders should be at least as fine as 1/4 of the OPC to effectively improve the packing density. Packing density and voids ratio relationship showed that a small increase in packing density can significantly decrease the voids ratio, which could allow the W/P ratio to be reduced to improve the strength and durability of the concrete without compromising the flowability.

Highlights

To improve the strength and durability of concrete, an essential and important strategy is to lower the water/ powder (W/P) ratio [1]-[3]
The wet packing densities and voids ratio of powder paste produced from the ordinary Portland cement (OPC) blended with different amounts of condensed silica fume (CSF) (0% to 25% by volume of the whole cementitious materials) were measured and the results are shown in the Figure 3
With just 5% OPC replaced by CSF, the packing density was already significantly increased by 4.1% from 0.654 to 0.681; while with 10% OPC replaced by CSF, the packing density continued to increased to 0.707; and with CSF replacement content increased to 25%, the packing density kept on increasing to as high as 0.736

Summary

Introduction

To improve the strength and durability of concrete, an essential and important strategy is to lower the water/ powder (W/P) ratio [1]-[3]. The key to the production of high-performance concrete (HPC) lies on minimization of the W/P ratio while keeping satisfactory workability and flowability. Research shows that it is the excess water (water in excess of that needed to fill the voids) that lubricates the cement paste and gives the concrete mix flowability because the water has to first fill up the voids in the bulk volume of the powder in a cement paste [5].

Results

Discussion

Conclusion