Performance-based testing of new cements for concrete pavements

Abstract

During the last years we can see big trends in reduction of the clinker factor in cement production with the aim of “low carbon cement”. In addition to that, a shortage of blast furnace slag on the market led to various new blended cements, which are also proposed to be used in pavement construction as a replacement of conventional cements. Performance-based and technological testing is needed to assure the proper usage of the new cements for concrete pavements. In the experimental project, financed by Directorate of Motorway in The Czech Republic, number of new cements were tested, covering coarsely-ground Portland cement, and various GGBS- and limestone-blended cements. Cements with slow hydration kinetics performed the best in the ring shrinkage test, with minor influence of blended mineral admixture. Crack resistance during restrained drying was found the most influential factor, related to volume deformations caused by chemical and drying shrinkage. Then selected cemetns were tested in concrete mixes for lower and top layer of concrete pavement. Limestone-blended cements showed decreased freeze/thaw resistance and workability problems with added fines. Testing with deicing salts generally correlated with freeze/thaw resistance. The best results were obtained on coarsely-ground clinker with separately ground GGBS, keeping low initial strength gain and chemical shrinkage.