Sustainable lightweight polymer concrete composite through partial replacement of aggregates with ABS plastic waste...

This study develops a sustainable, lightweight M20 concrete polymer composite by partially replacing natural aggregates with ABS plastic waste (P = 0-15% of coarse aggregate, by weight) and silica aerogel (A = 0-15% of fine aggregate, by weight) at a constant w/c ratio of 0.45. Ten mixes, including a control, were proportioned using IS-10,262 methodology and tested for slump retention (0-90 min), compressive strength (7-90 days), flexural strength, split-tensile strength, water absorption, and rapid chloride permeability (RCPT). Results show a clear optimum at P10A5 (10% ABS + 5% aerogel): compared with the control, compressive strength increased from 27 to 29 MPa at 28 days and 29 to 31 MPa at 90 days; flexural strength rose to 3.5 MPa at 90 days; and split-tensile strength improved by 8 to 12% at 28 days. Workability remained high, as initial slumps were within 100-120 mm, and P10A5 exhibited superior slump retention (≥ 90 mm at 90 min). Durability indicators followed the same trend: water absorption reached a minimum of 5.0% for P10A5 versus 6.0% for the control (17%), and RCPT charge dropped from 2800 to 2300 C at 28 days and 2200to 1850 C at 90 days, moving toward the ASTM "Low" permeability band. Beyond the optimum, higher aerogel (≥ 10%) or ABS (≥ 15%) increased porosity and reduced mechanical performance. Therefore, P10A5 offers the best balance of strength, workability, and durability, and is recommended for structural-grade, lightweight, and resource-efficient polymer concrete composite.