۱- Introduction

۲- Materials and methods

۳- Experimental results and discussion

۴- Conclusions

References

Abstract

This paper aims to develop and evaluate the performance of steel fiber-reinforced concrete made with recycled concrete aggregates (RCA) and desert dune sand. Different fresh and hardened properties of RCA concrete mixtures with and without steel fibers were evaluated and compared with those of a mixture made with natural coarse aggregates (NA). Test parameters included the RCA replacement percentage and steel fibers (SF) volume fraction (vf). Test results showed that the substitution of 30% of NA with RCA in plain concrete mixes did not reduce the design cylinder compressive strength (f′c), whereas the use of higher percentages of RCA replacement compromised the fresh and hardened properties of the concrete. The addition of SF significantly reduced the adverse effects caused by the inclusions of RCA in the mixes. RCA-based concrete mixtures having 70 and 100% RCA replacements could be produced with f′c values comparable to that of a NA-based concrete, when minimum vf values of 1, and 2% were added, respectively. The RCA replacement increased the water absorption and sorptivity but decreased the ultrasonic pulse velocity, bulk resistivity, and abrasion resistance. The addition of SF improved the hardened properties of RCA-based concrete mixes to an extent of exceeding some of those of the NA-based counterpart, as in the case of abrasion resistance. Analytical regression models were introduced to correlate different concrete properties to the 28-day cylinder compressive strength.

Introduction

Concrete is one of the most consumed construction materials. It uses significant amount of non-renewable natural resources in the production of its components, aggregates and cement. To sustain the continuous population growth and construction development, more concrete will be required. Consequently, the increasing demand for aggregates raises concerns of the depletion of their current sources and the availability of new sources. At the end of its service life, a concrete structure is demolished, creating massive amounts of construction and demolition waste (CDW) [1]. The concrete waste is mostly disposed of in landfills, instigating serious environmental hazards. The limited space for landfills to contain CDW and the scarcity of natural resources for natural aggregates (NA) promote the concept of reusing this waste by manufacturing RCA as a potential substitute to NA. This promising approach is considered an innovative means to promote the use of sustainable materials in construction. The usage of concrete made with RCA has been limited to nonstructural applications such as roadway subbase [2,3]. This is because RCA has lower strength and elastic modulus and higher water absorption and porosity compared to NA [4,5]. As a result, the incorporation of RCA in concrete mixtures causes a decrease in its mechanical performance compared to its conventional counterpart [6–۸]. Çakır [9] studied the effect of using a 100% RCA replacement on the concrete compressive strength. It was concluded that the compressive strength of concrete with a 100% replacement of RCA decreased by approximately 24% compared to that of concrete made of NA.