Mechanical Properties of Hydraulically Bound Road Foundation Materials Containing High Volume of Limestone and Steel Slag Waste Dusts

Abstract

The paper presents laboratory test results on hydraulically bound road foundation materials containing high volume of; limestone, steel slag (SS) and granulated blast furnace slag (GBS) dust compared with Type 1 sub base materials normally used by road engineers in the UK as a foundation layer with or without capping. The mixtures incorporating waste dusts were designed as potential hydraulically bound road pavement foundation layer and contain in addition to the dust in the control sub base the following percentage of dust: i) 20% limestone dust, ii) 20% SS dust, iii)
20% limestone dust + 5% GBS and iv)20% SS dust + 5% GBS.
The size of the dust aggregates range from 0-4mm. The addition of the wastes dust was to enhance the stiffness of the road foundation materials, save primary aggregates and hence reduce the cost of road construction.
The unbound and lightly bound materials resilient modulus were predicted using triaxial repeated load tensile tests according to the current European code of practice and compared with type 1 sub base materials at their optimum water contents.
The test results show outstanding increase in the resilient modulus of mixes containing the percentage of dust mentioned in items (iii) and (iv) above. This improvement was found due to the increase in the strength of the mortar paste between the content of these mixtures, namely; waste aggregates dust and primary aggregates. This finding offers the prospect of using these materials in road unbound foundation materials to reduce the use of primary aggregates and thus minimizing the cost of roads and highways construction.