Experimental evaluation of formwork type and release agents in relation to strength, durability, and surface quality of concrete

Concrete surface quality plays a critical role in the durability, aesthetics, and long-term performance of exposed concrete elements, particularly in architectural and bridge structures. Numerous studies have investigated the mechanical and durability properties of concrete; however, the combined influence of formwork material, release agent, and curing regime on surface quality and near-surface performance remains insufficiently addressed within an integrated framework. This study experimentally evaluates the coupled effects of concrete type (normal concrete and self-compacting concrete), formwork material (ABS, PVC, wood, MDF, and iron), mold release agent, and curing condition on mechanical performance, durability-related indicators, and surface quality. The study integrates strength-related tests, abrasion resistance, water absorption, Schmidt hammer rebound, water droplet contact-angle measurements, and qualitative surface assessment within a unified experimental program. A comprehensive experimental program was conducted using standardized test methods on laboratory-scale specimens cast under controlled conditions. Compressive strength, rebound index, water absorption, abrasion resistance, and surface wettability were evaluated, and surface appearance was assessed through systematic visual inspection. The results indicate that formwork material and release agent significantly influence near-surface density, abrasion resistance, and aesthetic quality. Polymer molds combined with appropriate release agents generally produced denser surfaces and improved durability-related performance, whereas wooden molds without release agents resulted in inferior surface quality. Although the tested self-compacting concrete mixture exhibited overall favorable trends, certain normal concrete configurations achieved comparable or higher compressive strength depending on mold conditions. Overall, the findings indicate that surface quality and durability-related performance are governed not only by mixture design but also by formwork–concrete interaction and curing practice. This study provides practical guidance for selecting formwork systems and curing strategies in applications involving exposed concrete surfaces.