Sustainable alternative aggregates: Characterization and influence on mechanical behavior of basalt fiber reinforced concrete

Abstract

Demands to assess the feasibility of utilizing alternative sustainable aggregates in concrete have been raised because of the rapid depletion of virgin aggregates resources. In this study, a comparison of the physio-chemical properties of commonly used natural gabbro aggregates (NGA) and natural limestone aggregates (NLA) and their possible sustainable alternatives recycled concrete aggregates (RCA) and steel slag aggregates (SSA) is presented. The suitability of these alternate aggregates is assessed through several standardized tests. Chemical compositions, mineralogical and morphological properties of these aggregates are also reported. To determine the possible leachates of hazardous metals into the environment when used as concrete aggregates, the inductively coupled-plasma atomic emission spectroscopy was carried out on acid digestions of these aggregates. Additionally, basalt macro-fibers (BMF) were incorporated to improve the mechanical properties of concrete made with RCA and local NLA which are deemed as weak and unfit for use as aggregates in structural concrete. Experimental results revealed that both RCA and SSA could be used as sustainable alternative aggregates to have a cleaner production of structural concrete. They had acceptable leachate limits of the hazardous elements. The soundness test results and expansion under autoclave of SSA were well below the acceptable limits. The concrete made with SSA showed higher mechanical properties than the concretes made with other aggregate types. As expected, BMF improved the mechanical properties of concrete made with the low-strength NLA and RCA.