Evaluation of Spent diatomaceous earth as mineral filler in hot mix asphalt concrete

Abstract

The integration of waste materials into construction practices has garnered attention due to its potential to lower costs, conserve natural resources, and address environmental concerns. This study explores the use of spent diatomaceous earth (DES) as an alternative mineral filler in Hot Mix Asphalt (HMA), contributing to both sustainable waste management and advancements in road construction technologies. With the alarming rate of 1,212,500 kg/year of DES discharged from four beer factories in Ethiopia, the need for effective waste management solutions is evident. The research aims to evaluate the impact and viability of replacing crushed stone dust (CSD) with varying percentages of spent DES in HMA mixtures. The study employs different proportions of DES (ranging from 0% to 50%) to replace CSD. The composition of the HMA mixture encompasses diverse sizes of aggregates, bitumen of 80/100 penetration grade, CSD, and DES mineral fillers. A total of 105 specimens were prepared for testing. laboratory tests were conducted to assess material quality and engineering properties, including Marshall stability, flow, moisture susceptibility, and rutting performance. Through the utilization of the MS-2 method with curve plotting and common range selection, the optimum filler content (OFC) and optimum bitumen content (OBC) were determined. The OFC was established at 4%, while the OBC was ascertained to be 5.0%. The laboratory results revealed an optimal replacement range of 5-15% DES for CSD filler. Stability tests demonstrated values of 14.9 KN for 100% CSD, 14.7 KN for 5% DES, 15.1 KN for 10% DES, and 15.2 KN for 15% DES. Corresponding flow values were recorded as 3.10 mm, 3.20 mm, 3.30 mm, and 3.40 mm, respectively. Tensile strength ratios (TSR) were found to be 89.9% for 100% CSD, 87.02% for 5% DES, 86.10% for 10% DES, and 82.87% for 15% DES at optimum conditions. The rutting resistance, evaluated by subjecting mixtures to 10,000 loading cycle wheel track tests, showed promising results, with rut depths within specifications. The rut depth measurements were 3.09 mm for 100% CSD, and 3.17 mm for 10% DES with 90% CSD. The investigation recommends the utilization of spent diatomaceous earth in conjunction with crushed stone dust as fillers in HMA. The approach holds the potential for enhancing asphalt mixture performance while aligning with sustainable waste management goals. Further research, focusing on the long-term rheological properties of bituminous mixtures containing spent diatomaceous earth fillers, is suggested for comprehensive understanding and continued improvement of this innovative practice.