Experimental evaluation on the influence of cement-treated base materials components on physical and mechanical properties

The rapid traffic growth, the consumption of natural resources, and environmental concerns are directing the design of future infrastructures to be economical and sustainable. In this regard, cement-treated base material increases pavements' bearing capacity and improves the load distribution to the underlying foundation. Its combination with an asphalt layer has excellent potential to guarantee a long life with minimum maintenance. Although several studies have been conducted to investigate the properties of cement-treated base material, the influence of its components is not totally clear to fully exploit this material's potential. Therefore, the primary purpose of this study is to evaluate the variation of mechanical and physical properties of cement-treated base materials at the variation of some parameters, such as the lithic skeleton, the cement content, the water content, and the dimension of specimens. To achieve this object, a campaign of experimental tests is carried out in the Road Material Laboratory of the Polytechnic of Turin. By looking at the lithic structure, four granular mixtures were designed: GM1, GM2, GM3, and GM4. The first two were made by combining three aggregate classes (0/8, 8/18, and 18/30 mm) and were characterized by a very low fine content, while the other two were optimized by adding mineral filler. Two cement-bound mixtures, CBM1 and CBM4, were designed starting from two selected granular mixtures to evaluate the influence of the cement dosage, which was varied in the range from 1,5% to 3,5%. A Proctor study on each considered mixture was conducted to investigate the influence of lithic skeleton and cement dosage on the optimum water content and dry density. Unconfined compressive tests and indirect tensile tests were performed on the cement-bounded mixtures to evaluate the effects of cement dosage on mechanical strength. Finally, additional tests were made on selected mixtures on specimens of different sizes, compacted through the gyratory shear compactor, to derive some empirical relationship. In conclusion, the effect of adding mineral filler, aside from a significant rise of the granulometric curves' tail, is an increase in dry density. Instead, for what concerns the effects of cement dosage, its increase is translated to an augment in the mixtures' dry density and mechanical strength. On the other hand, the mechanical strength linearly reduces by increasing the water content in the mixtures.