Evaluation of direct shear strength of self-consolidating and conventional concretes

Kellyn Maressa Pufal,Gustavo Henrique Dalposso,Carlos Eduardo Tino Balestra,Sergio Luis González Garcia,Gustavo Savaris

doi:10.1590/s1517-707620210003.13036

Abstract

ABSTRACT The self-consolidating concrete presents properties that improve the constructive process, it has the main characteristic of flowing under its own weight and completely filling the formwork, without the need of compaction. However, the uncertainty about its shear strength, due to the differences in coarse aggregate volume and size of this concrete compared to conventional vibrated concrete, is one of the main barriers to its acceptance. Self-consolidating concrete mixtures requires generally the reduction of coarse aggregate content and addition of fines materials to obtain flowability and the reduction of particles size directly influences the mechanism of aggregate interlock. In this work, two concrete mixtures, conventional and self-consolidating, were used for casting test specimens, submitted to the direct shear test, in order to evaluate the direct shear strength of these concretes. The results showed a reduction of the shear strength for the self-compacting concrete, attributed to the use of coarse aggregate with smaller particle size, the reduced volume of coarse aggregate and the larger fines content in the mixture. The experimental results were compared with equations proposed in the literature, demonstrating that for self-consolidating concrete these equations underestimate the ultimate shear strengths. Thus, this work contributes to the formation of a database aiming the establishment of equations to estimate self-consolidating concrete shear strength.

Highlights

Concretes with special characteristics, such as high strength, durability and flowability, have been developed in the last decades in order to improve the quality of the structures
It was possible to obtain a mixture of selfconsolidating concrete (SCC) from CC with the partial replacement of sand by limestone filler and the reduction of the coarse aggregate content, replaced by equivalent volume of sand
Evaluating the 95% confidence interval highlighted in Figure 4 (1.39; 3,90), it is verified that the means are different because the value zero, which would represent the equality between the means, is not in the interval. This demonstrates that the reduction of coarse aggregate content to produce the SCC influenced the shear strength, confirming the results presented at literature [10, 11]

Summary

Introduction

Concretes with special characteristics, such as high strength, durability and flowability, have been developed in the last decades in order to improve the quality of the structures. Among these innovations, selfconsolidating concrete (SCC) was developed with the characteristic of spreading under its own weight and filling the formworks without the use of vibrators, without segregating even after passing through obstacles [1]. The third method makes a mixture between the first two, replacing the volume of coarse aggregates by fines and using additives to change the fluidity and reduce the water consumption of the concrete, in order to obtain a SCC with reduced cost

Objectives

Results

Conclusion