Application of Ultra-Thin Whitetopping (UTW) on Bituminous Pavements in Factory Areas. An Italian Experience

The paper describes an application of ultra-thin white-topping on a bituminous factory pavement. Different road cement concrete mixes were studied: high-strength concrete, concrete with PP fibres added, concrete modified with latex, concrete made by tyre-rubber grains instead of natural aggregate and steel fibre reinforced concrete. The binder was CEM II/A-L 42.5R; super-plasticiser and silica fume were added to the mix. Mixes were tested by mechanical trials after 1 to 60 days: adhesion of concrete to bituminous surfacings, compressive and flexural strength, hygrometric shrinkage, CTOD/CMOD tests, indirect tensile strength, dynamic elastic modulus. Mechanical characterisation of the mixes suggested the use of cement concrete with PP fibres added (because they reduce incoming cracking), latex (in order to reduce slab fragility) and water-reduction additives (for higher and faster mechanical resistance) and steel fibre reinforced concrete. The application was done on a 20 cm macadam pavement with bituminous wearing course, laid in a factory area pavement. The slabs were constructed according to ACPA standards. Strain gauges and LVDT were inserted in the pavement. The experimental data revealed acceptable behaviour of whitetopping: the slabs appear monolithic and have a good response to static and dynamic stresses due to commercial vehicles.