Restrained Expansion and End-Zone Stress Compensation in a Pretensioned Precast Concrete Pavement Slab: Full-Scale Strain Monitoring and Mechanical Assessment

Pretensioned precast pavement slabs exhibit reduced compressive stress near their free ends owing to the finite transfer length of prestressing strands. This study investigated an 800 mm self-stressing concrete end segment using five mixtures containing 0%, 6%, 10%, 12%, and 18% expansive agent and a 3700 mm × 975 mm × 240 mm instrumented slab monitored during strand release and for 180 days thereafter. The E10 and E12 restrained specimens developed calculated self-stresses of 1.36 and 1.53 MPa, respectively, whereas the E18 specimen exhibited a visible longitudinal crack. At 28 days, the expansive mixtures attained compressive and flexural strengths of at least 59.2 and 7.7 MPa, respectively. In the slab, strand-induced compression was approximately 0.50 MPa at 125 mm from the end and 1.25 MPa in the interior, indicating a local deficit of 0.75 MPa. The mean end-segment strain 24 h before release was 221.23 με, corresponding to 1.86 MPa of calculated restraint stress. Total compression at 125 mm reached 2.24 MPa immediately after release and was estimated at 1.58 MPa on day 140 before thermal correction. A full-length compatibility model estimated the end-plate device contribution at 0.12 MPa after release and 0.07 MPa on day 140. The monitored release response indicates that restrained expansion restored compression in the slab end relative to the interior reference.