Mechanical Performance of Cement Bound Granular Pavement Layers Incorporating Anhydrous Calcium Sulphate Industrial By-Product

ABSTRACT: The research concerns the assessment of the mechanical performance of Cement Bound Granular Material (CBGM) using a secondary by-product Anhydrous Calcium Sulphate (ACS). First, the investigation aims to find the best CBGM mix performing laboratory tests. Five different mixes were studied, varying Portland cement percentages between 1% and 3% and ACS ranging between 0% and 4%. Compression strength (UCS) and indirect tensile strength (ITS) tests were performed on the specimens. In the second phase, two trail sections were constructed in an industrial site, with and without ACS in the CBGM layer. The laboratory results show good mechanical performances compared to traditional CBGM. The overall binder content in the mix (cement and ACS percentages) is kept in the range of 5%. Introducing 2% of ACS in the reference mix, UCS and ITS increased by 23% and 43% respectively. The two pavements of the trial section have been monitored using a dynamic Falling Weight Deflectometer (FWD) over time. The results of the in situ tests point out the significant reductions in the deflections. The mean deflection, under the load axis, is reduced by 38% in the innovative pavement with ACS and with a greater degree of homogeneity. The stiffness modulus of the CBGM with ACS, evaluated through the back-calculation, has a remarkable increase. On the other hand, this type of mix design needs a longer curing time to reach high mechanical standards.