Chemically Prestressed Precast Concrete Box Culvert with Expansive Additives

This study discusses application of expansive additives for concrete to improve the serviceability of precast box culvert by inducing chemical stress. For this purpose, both expansive concrete slabs and normal concrete slabs are tested to verify the effect of expansive additives. Then the failure tests of the full-scale precast box culverts are carried out and the critical aspects of the structural behavior are investigated. The result of the material tests shows that the optimal proportion of expansive additives is 13% of cement weight, and the properties of expansive concrete are the same as those of normal concrete in that proportion. Both the experimental cracking load and service load of the expansive concrete members are increased in comparison with those of the normal concrete. In addition to the above results, the deformation of expansive concrete member is less than that of normal concrete member, and permanent strain result from cyclic load is decreased. It can be concluded that the use of expansive additives to induce chemical prestress in precast box culvert greatly improves the serviceability.