A designer’s perspective on unplanned shrinkage cracking in plain concrete road pavements

Unplanned shrinkage cracking in plain concrete pavements can be prevented by adequate jointing design, material selection and the use of good construction practice. This paper provides a series of notes on the construction challenges and design aspects that need to be considered to avoid unplanned cracking when constructing a new plain concrete pavement or widening an existing pavement.

One of the most critical factors influencing crack occurrence is the control of slab length in conjunction with shape ratio and corner angles. It is important to not to exceed the joint spacing to be more than six times the radius of relative stiffness. The review presented in this paper confirms that the current joint layout requirements specified in NSW for plain concrete pavements are based on sound principles.

High early strength concrete has been used in overnight slab replacement work in Sydney for quite some time with good results. Considerable experience has been gained to date in producing high early strength concrete without incurring into unplanned cracking.

Neither the cracking model based on the concept of relative stiffness nor the fatigue model based on Miner’s hypothesis can adequately predict shrinkage cracking. Raw material properties and mix design need also be considered.