Performance Enhancement of Lightweight Concrete Using Surface-Modified Light-weight Expanded Clay Aggregate: A Comparative Experimental Study

Lightweight concrete (LWC) is gaining widespread use for its combined structural efficiency and thermal performance. However, Lightweight Expanded Clay Aggregate (LECA), though advantageous, exhibits high porosity and poor bonding with the cement paste. This study evaluates five surface-pretreatment methods for LECA, cement paste, SBR-modified cement grout, acrylic polymer, Flancoat, and SBR coatings to enhance the performance of aggregates. Treated aggregates were tested for density, water absorption, compressive, and splitting tensile strength. Results showed that density increased to 1723 kg/m³ (+11%), water absorption decreased by 57%, and compressive strength rose from 11.9 to 14.6 MPa (+23%). Splitting tensile strength improved by up to 64% with some treatments. Among the treatments, the cement-paste coating produced the most consistent improvement, increasing compressive strength to 14.6 MPa and reducing water absorption to 2.2%. The modified cement grout with styrene–butadiene rubber exhibited the highest splitting tensile strength, with an increase of approximately 64% compared to untreated LECA. Flancoat yielded the most significant mass gain (8.1%) and excellent water resistance. Acrylic polymer coating moderately improved compressive strength (13.1 MPa) and durability, while styrene–butadiene rubber alone offered smaller gains but still reduced water absorption compared to untreated LECA. The findings confirm that cementitious and polymeric surface modifications of LECA enhance interfacial bonding, reduce water absorption, and improve structural performance. It is a pragmatic approach to extending the use of LECA for producing lasting commercial structures with the highest structural performance and lightweight concrete.