Toward improved performance of unpaved roads: laboratory tests and field investigation of a soil-byproduct base layer

In this study, the performance of two steel slag byproducts is investigated to produce mixtures for base layers of unpaved roads. The basic physical properties including Atterberg limits, grain size distribution, California bearing ratio and expansion tests of eight different mixtures of soil-byproduct are investigated in laboratory to understand the engineering properties of the mixtures. The byproducts are mixed in different proportions from 50% to 80% by weight with a local (clayey) subgrade soil. Subsequently, two selected mixtures are used to build an experimental road section along an unsurfaced road. Results demonstrate that the gradation and strength of the samples satisfy the requirements for base layers. Furthermore, the mixtures are shown to be of low-plasticity at higher byproduct content and non-expansive. Field investigations show that 12 roller passes at the standard Proctor and 14 at the intermediate Proctor are enough to reach 100% of the degree of compaction.