Mechanical behaviour of adsorbent pervious concrete using iron slag and zeolite as coarse aggregates

Abstract

Using low-cost industry waste and mineral adsorbentsto produce Adsorbent Pervious Concrete (APC) is a sustainable solution with manifold environmental advantages.This study investigates the engineering properties of APC to widen the potential of its further utilization as a post-treatment step in refinery and wastewater treatment plants. For this reason, coarse aggregate in pervious concrete was replaced by coarse iron slag and zeolite in portions of 25%, 50%, 75%, and 100% by volume. The statistical analysis of variance (ANOVA) and visualization of the microstructure of APC using Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Spectroscopy (EDS) were also presented. Experimental results showed that replacing coarse aggregate with iron slag increased the APC’s strength, and the maximum value of compressive strength (16.80 MPa) occurred at 75% of replacement. Alternatively, increasing the zeolite proportion caused the strength reduction of APC, and the minimum compressive strength (9.40 MPa) happened in a sample with only coarse zeolite. The effect of cementitious paste thickness (CPT) on the compressive strength indicated that the iron slag did not markedly change the average of CPT, only a minor reduction compared to the control sample (0.30–1.5 mm), while zeolites caused considerable increase of average CPT (0.00–2.1 mm). Hence, increasing the average CPT resulted in reducing the APC compressive strength. Also, the specific gravity, resistance to compression, rectangular shape, and micropores on the surface of adsorbents affected the mechanical properties, porosity, and permeability of APC. All APC samples had a satisfactory porosity (more than 15%) and permeability (more than 1.17 mm/s), and the APC sample containing 75% of iron slag had the highest values. The role of adsorbents shape affects the porosity and permeability of APC, especially in the replacement portion of 50% and less, while for samples with more than 50% of adsorbents due to homogenization of the mix and having the same size as aggregates, the void content and infiltration rate approached the value of the control sample. Eventually, iron slag and zeolite based APC could potentially be used in wastewater treatment plants for post-treatment of wastewater as a new cleaner production.