Application of Ferrophosphorus Powder as a Replacement for Natural Aggregate Filler in Microsurfacing Treatment: Mix Design and Performance Analysis

Abstract

Growing environmental concerns and the depletion of natural resources have led to a significant rise in the demand for waste material utilization. This study primarily aimed to explore the potential use of ferrophosphorus powder (PSP) as a filler in microsurfacing mixtures, evaluating its performance in comparison to natural aggregate fillers (NAFs). For this purpose, wet cohesion tests, wet abrasion tests, loaded wheel test (LWT)-sand adhesion tests, and LWT-displacements were conducted on five varying types of microsurfacing mixtures containing 10% NAF, 8.5% NAF + 1.5% PSP, 7% NAF + 3% PSP, 5.5% NAF + 4.5% PSP, and 4% NAF + 6% PSP based on the total aggregate weight. Then, the toxicity characteristic leaching procedure (TCLP) experiment was performed to evaluate the mixture’s environmental impact. Subsequently, analysis of variance (ANOVA) was performed to examine the PSP effect on the microsurfacing performance. The findings demonstrated that the use of PSP improves microsurfacing performance. Among the mixtures, the sample containing 4.5% PSP resulted in an increase in cohesion of 25% and 28.6% after 30 and 60 min, respectively, a reduction in vertical displacement by 30.1%, an improvement in abrasion resistance by 47%, and a decrease in bleeding by 39.1%. The ANOVA results validated the significant effect of PSP on the mixture properties through F-value and P-value parameters, demonstrating significant impacts on adhesion enhancement ( η 2 = 0.889 ) and deformation resistance ( η 2 = 0.981 ). The TCLP test results demonstrated that PSP-incorporated specimens were eco-friendly mixtures, as the leaching of all examined heavy metals remained below permissible limits. Therefore, their use in microsurfacing as a filler replacement, up to 6%, is considered acceptable. The optimal PSP replacement rate was determined to be 4.5%, which not only improved mechanical properties and reduced binder consumption but also provided an environmentally sustainable alternative to conventional fillers in microsurfacing applications.