National Concrete Pavement Technology Center

Project description

The main objective of this project was to evaluate construction issues and characterize the long-term performance of compacted concrete pavement (CCP). Three CCP test cells were designed and constructed in Scott County, Missouri, as part of a larger construction project. The total pavement length was 42 ft for the three cells. Cell 1 and Cell 2 were prepared without fibers and had a length of 15 and 12 ft, respectively. Cell 3 was prepared with 5 lb/yd³ (pcy) of synthetic fibers and had a length of 15 ft. The moisture content of the concrete was kept between 5% and 6%, and the water-to-cementitious material ratio was maintained between 0.31 and 0.38. Test results showed that the incorporation of fibers enhanced the mechanical properties (compressive and flexural strengths) of CCP mixtures when proper compaction was provided, as in the case of cast-in field samples. Also, fibers changed the flexural failure mode of saw-cut and cast-in-field CCP samples from brittle to ductile failure. The incorporation of fibers had a restraining effect on the drying shrinkage of CCP mixtures. The use of fibers did not have a significant effect on the performance of CCP mixtures, as shown from the falling weight deflectometer (FWD), truck loading tests and curling and warping. This can be mainly related to the extremely dry consistency of the CCP mixtures (Vebe consistency > 60) that can hinder bond strength in the interfacial transition zone with the matrix. This was more accentuated in the saw-cut samples from the paved CCP as the paving process in the field did not provide enough compaction. As for the size of slabs, results showed that the size of CCP slabs was more effective in the curling and warping measurements. The slab with longer length (15 ft) showed higher variations in curing and warping along the diagonal, transverse and longitudinal lengths over time. Therefore, the use of fibers in CCP can be recommended provided that the CCP mixture has adequate workability and sufficient compaction energy applied during construction.