Effects of Portland Cement and Polymer Powder on the Properties of Cement-Bound Road Base Mixtures

This article presents the test results for the physical and mechanical properties and fracture toughness of polymer-modified hydraulically-bound mixtures (HBM) produced with Portland cement for road base layers. The modifier used was a redispersible polymer powder (RPP) based on a vinyl ethylene acetate (EVA) copolymer obtained by spray drying. A three-level full factorial design with two factors was applied to determine the contents of Portland cement and polymer powder in the cement-bound mixture (CBM). Both Portland cement and polymer powder were added at three levels: 0%, 2%, and 4%. The assessment included basic physical properties (water absorption, density, and bulk density) and mechanical properties (stiffness modulus, axial compressive strength, and indirect tensile strength) of the CBM. Particular attention was paid to the assessment of fracture toughness in the semi-circular bending test. The results of the research show that polymer powder positively influenced the mechanical properties of CBM by improving its cohesion while maintaining its stiffness. Another benefit coming from the use of polymer powder was the CBM’s increased resistance to cracking, which is the desired characteristic from the perspective of pavement durability.