USE OF ULTRA-THIN WHITE TOPPING FOR PAVEMENT

Abstract

With the advent of new fast track concrete pavement technologies that allow the opening of a concrete pavement within short duration of initial paving, white topping technology is advancing. Ultra Thin White Topping (UTWT) is the next generation concrete pavement. UTWT can be defined as: "A concrete overlay 50 mm to 100 mm thick with closely spaced joints bonded to an existing bitumen/concrete pavement". It is made up by the use of high strength concrete (HSC). By bonding the UTWT to the existing asphalt/concrete surface, the UTWT forms a composite pavement section with the underlying surface, which reduces the stresses in the concrete layer. There is no absolute definition of HSC. It depends upon the present technology, requirement and geographical basis. However; AC1 defines HSC as cylinder strength equal to or greater than 41 MPa at 28 days of age using normal weight aggregates. The main objective of this study was to illustrate the design methodology of high strength fly ash concrete (HSFC) mixes and to investigate the feasibility of its use as overlay. To study the difference in behavior using fly ash by (i) Partial replacement of cement (ii) Partial replacement of fine aggregate (20% fly ash, 30% fly ash, 40% fly ash). with same water-cement ratio and dosage of superplasticizer for target strength is of 60 MPa as per AC1 211 and various tests were performed to determine the structural properties such as compressive strength, flexural strength, modulus of elasticity, stress strain behaviour. The feasibility of use of HSFC in pavement was carried out by laying slab and then carrying out semi full scale laboratory study. The slab was tested under different loading conditions (Central, Edge & Corner) and corresponding deflections and strains were measured. The overall performance of high strength concrete used in ultra thin white topping was found to improve at 20% replacement of cement by fly ash. The load carrying capacity of 40 mm thick slab was found to be more than permissible single wheel load (30 kN) for low volume road.