Mechanical Properties and Durability of Ultra-High-Performance Concrete with Locally Available Materials

Abstract

Demand for high-rise residential buildings and skyscrapers necessitated the demand for higher strength concrete to reduce the dimensions of concrete structural elements. The rapid deterioration of normal strength concrete under harsh climatic conditions due to deleterious agents' ingress has raised concerns over reinforced concrete (RC) durability in the global construction industry. In the present study, a viable solution to the abovementioned problems, the Ultra-High-Performance Concrete (UHPC) is investigated due to its better mechanical and durability characteristics. Its low porosity and dense microstructures offer high compressive and flexural tensile strengths. Since water and other harmful agents cannot diffuse through the dense structure of UHPC, the durability of RC structures is expected to be enhanced manifolds. UHPC without coarse aggregates are easily fabricated. In this study, a UHPC with similar strength and followability is cast using three types of coarse aggregates up to 12.5% by volume of concrete. Then, the cost of this concrete could be reduced. Also, coarse aggregates make these concrete mixes more viable for the construction industry as for as mixing and shrinkage are concerned. Gabbro, recycled concrete, and steel slag aggregates with the use of micro, macro and hybrid fibers (1% of the volume) are employed to fabricate a 120 MPa in compressive strength after 28 days of curing in UHPC mixes. The strength is achieved in the following order: steel slag, gabbro, and recycled concrete aggregates UHPCs. It is perceived that compressive strength is increased with steel slag aggregates without losing workability. The durability indicators such as resistivity, porosity, rapid chloride penetration test (RCPT), and sorptivity are also enhanced in all types of UHPC mixes. Using steel slag aggregates in the mix also provides better durability properties and gives higher compressive strength values that other aggregates. Moreover, using macro steel fibers provide high flexural tensile strength results and using micro steel fibers give high compressive strength and durability properties. In addition, using micro and macro steel fiber in the same time gives moderate values in terms of mechanical and durability properties. Also, the addition of fibers enhances the flexural strength more than compressive strength.