Influence of additional thermal and shrinkage reinforcement to reduce self-induced strain on early-age concrete

Mass concrete deposited in restrained formwork needs special precautions to control superior heat generation, resulting in thermal expansion. High-performance concrete (HPC) requires strict water-to-cement ratio control, linked to autogenous shrinkage domination. Combining those factors with unsteady formwork support may cause significant cracking damage along the span or localized at a specific area. A special case study of existing cracking on the Jogja-Bawen Highway Project was conducted to investigate the link between emerging cracks and inadequate reinforcing steel to withstand thermal and shrinkage during early-age concrete maturing. ACI 318M-14 and AASHTO LRFD Section 5.10.8 suggested additional temperature and shrinkage reinforcement to cope with the cracking risk. Simplified full-scale finite element (FE) models with various amounts of longitudinal reinforcement and configurations were carried out to reveal improved tensile strain performance of additional reinforcing steel. This study discovered the critical role of temperature and shrinkage reinforcement as an important requirement before establishing such structural designs.