One of the major causes of distress in Portland Cement Concrete (PCC) highways is loss of support under slabs. A new mix for High Performance Concrete (HPC) pavement appears to promise an enhancement of pavement lifetime. This new mix includes blast furnace slag, a by-product of manufacturing processes.
The Ohio Research Institute for Transportation and the Environment (ORITE) evaluated the structural performance of three sections of PCC pavement installed as part of the $8 million reconstruction of US Route 33 in Nelsonville. The three test sections compared two different new concrete mixes, each incorporating 30% blast furnace slag recycled from industry and the standard concrete mix as a control. The project also involved comparing two different curing methods, the traditional method using wet burlap and a new method using a spray-on membrane. The testing included monitoring the curing process, measuring the shape of the slabs after curing, conducting non-destructive testing on the finished road, and conducting laboratory tests to determine the mechanical properties and maturity curves of these mixes.
It was determined that one of the new mixes (“Mix B”, with 30% blast furnace slag and #357 aggregate) did indeed perform the best. This mix had the least warping in the slab, the least deflection under load, and the best load transfer between joints. Both methods of curing appeared to work about equally well, with the wet burlap method producing slightly lower warping and the membrane method resulting in slightly lower deflections under load.
As part of the project, ORITE hosted an open house and workshop on June 2, 2004, for Ohio Department of Transportation employees, FHWA employees, transportation officials from other states, local city employees, and contractors to share the maturity test results and provide practical technical information on the design and construction of the new HPC concrete mixes.