ABSTRACT
Semi-flexible pavements are manufactured by producing a very open porous asphalt skeleton and filling the voids with selected cementitious grouts. The resultant composites, referred to as “grouted macadams”, combine the flexibility of the bituminous component with the strength and rigidity of the cementitious component. In this investigation, a range of cementitious grouts was formulated using a variety of binders including ordinary Portland cement, silica fume and fly ash. The grouts were designed to provide improved strength and performance characteristics with reduced water/binder ratios, whilst maintaining high workability. This was achieved with the aid of chemical admixtures that allowed the grouts to penetrate the porous asphalt skeleton under gravity action (i.e. without vibration). The properties of the grouted macadam composites were assessed using a range of engineering, deformation and performance tests. These included compressive strength, stiffness modulus, creep resistance, shrinkage, porosity and permeability up to the curing age of 28 days.
The formulated cementitious grouts attained high strength characteristics (90–120 MPa at 28 days), with the pozzolanic materials (silica fume and fly ash) having improved permeability and shrinkage properties. When the grouts were impregnated into the porous asphalt skeleton, the resultant grouted macadam composites showed superior strength to conventional asphalts and much higher resilient properties than that of concrete pavement materials. In addition, the grouted macadams exhibited much lower porosity (<8%) indicating enhanced durability performance.
