Plastic Shrinkage Cracking of Full-Scale Concrete Slabs Under Field-Production Conditions: Observations on Mix Design, Environmental Exposure and Curing

PE sheeting produced the most consistent crack-free final observations under the investigated conditions. This study investigated the combined effects of mixture composition, water-reducing admixture system, environmental exposure, surface finishing, reinforcement configuration, and curing method on the early-age cracking and mechanical performance of concrete under full-scale production conditions. Seven concrete mixtures were investigated, and 28 full-scale reinforced concrete slabs were produced and monitored for plastic shrinkage cracking. Fresh-concrete workability, slump retention, 28-day compressive strength, environmental conditions, and surface evaporation rates were evaluated. The actual water-to-cement ratio ranged from 0.58 to 0.85, and increasing water demand following the reduction or elimination of water-reducing admixtures resulted in a decrease in 28-day compressive strength (150 mm cube specimens) from 41.4 to 24.6 MPa. Under the investigated full-scale field-production scenarios, visible plastic shrinkage cracking varied with the combined material, environmental, construction, and curing conditions. The unprotected W4-P1 slab, cast during severe hot and dry exposure, developed 19 visible cracks, whereas 4 cracks were recorded for W5-P1 under more moderate conditions. Because these slabs also differed in mixture composition and reinforcement configuration, this comparison is interpreted as an association rather than a single-factor environmental effect. The estimated evaporation rate was 0.71 kg/m2/h for the initial W4 conditions and 0.22 kg/m2/h for W5. Surface-finishing and reinforcement comparisons were based on individual slabs and are therefore reported only as case-specific observations. PE sheeting showed the most consistent performance under the investigated conditions: all nine PE-protected slabs were free of visible cracks at final inspection, while the two water-cured slabs developed zero or one crack. These findings show that visible plastic shrinkage cracking in full-scale production cannot be interpreted from mixture composition or w/c ratio alone and should be assessed in the context of the complete field-production scenario.