TITLE:
Optimisation of Mine Dust, Clay and Recycled Polyethylene Proportions for Improved Mechanical and Physical Properties of Lightweight Construction Composites
AUTHORS:
Caleb Masese Obiko, James Mutua, Brian Odero, Fredrick Mwema
KEYWORDS:
Mine Dust, Recycled Polyethylene, Clay, Taguchi Optimisation, Lightweight Composite
JOURNAL NAME:
Open Journal of Civil Engineering,
Vol.16 No.4,
October
28,
2026
ABSTRACT: Mine dust from dimension-stone quarrying and expansive clay excavated during construction accumulate as unmanaged by-products in peri-urban Kenya, while post-consumer polyethylene continues to burden landfills. This study determined the proportions of mine dust, clay and recycled polyethylene that give the best combined mechanical and physical performance in a ternary composite intended for lightweight, non-load-bearing partitions. Nine formulations were prepared for each polymer type following a Taguchi L9 orthogonal array with three control factors, recycled polymer, clay and mine dust, at three levels each. Composites were produced by melt intercalation at 170˚C for high-density polyethylene (HDPE) and 140˚C for low-density polyethylene (LDPE), and then evaluated for compressive strength (ASTM D695-15), surface roughness (ISO 4287) and water absorption (ASTM D570-98). Signal-to-noise ratios, analysis of variance and linear regression were used to identify the optimal proportions and to quantify the contribution of each constituent. The optimal formulations were 400 g polymer, 10 g clay and 80 g mine dust for HDPE, equivalent to 82%, 2% and 16% by mass, and 200 g polymer, 10 g clay and 80 g mine dust for LDPE, equivalent to 69%, 3% and 28% by mass. The polymer fraction governed HDPE behaviour, contributing 81.92% to compressive strength, 91.20% to surface roughness and 95.09% to water absorption, whereas mine dust governed LDPE behaviour, contributing 93.98%, 88.81% and 85.71% respectively. Regression models reproduced the measured responses with coefficients of determination above 0.9. Confirmation specimens produced at the optimal settings reached compressive strengths of 1.63 MPa (HDPE) and 2.48 MPa (LDPE) and gained no more than 0.002 g after immersion, indicating adequate strength and dimensional stability for partitions and facade infill panels.