Abstract

Unpaved roads are designed with a small input and are constructed from the nearest available materials as possible. It requires routine and periodic maintenance, and its condition can be significantly affected by a period of excessive traffic volumes or inclement weather conditions. The accurate estimation of maintenance cost is difficult. Many problems occur in the economic analysis of unpaved roads in comparison with paved roads. D effects that may affect unpaved roads are dusty, potholes, stoneness, corrugations, and rutting. Hence, it needs to apply a sufficient stabilization method to strengthen and increase the durability of the unpaved road. Mechanical stabilization is an important application in engineering for different types of construction to improve the performance of road construction materials. The objective of this research was to determine the Engineering properties of natural gravel materials by mechanical stabilization method to be used in subbase material for the unpaved road. The methodology carried out in this research study includes: (a) field visual inspection and sampling of natural gravel materials from three quarry sites around the Jimma area; and (b) laboratory tests to identify the physical and mechanical properties of natural gravel. Based on the laboratory test results, natural gravel materials from the Seka quarry site has an excellent Abrasion resistance of 35.26%, Plasticity Index of 13% a little bit above the upper limit, and good gradation (coarser and less subtle or binder materials), right CBR value. While the Jiren quarry site has a little Abrasion resistance of 52.09%, medium plasticity index, poor gradation (moderate fine material), CBR value of 28.90% which was below 30% minimum requirement, but had good MDD. On the other hand, the Merewa quarry site comprised of a very poor Abrasion resistance of 78.3 4%, Plasticity Index of 2 3.90% which was beyond the upper limit plasticity index of 1 2%, and poor gradation (more fine materials), poor CBR value and poor MDD. Therefore, it is concluded that the natural gravel from the Seka quarry site is suitable for the subbase course. But since road construction around Jimma is booming, the natural gravel from this quarry site would be soon depleted. About this, mechanical stabilization is recommended by blending the natural gravel from the Seka quarry site with 54% by weight with Jiren natural gravel of 46% by weight to meet the minimum requirements for subbase materials.

Abstract

At the time of industrial development, the production of large amounts of wastage required proper disposal. To reduce the disposal problem, utilization of wastage in construction works is a very important aspect. The reuse of industrial waste had gained high momentum for achieving sustainable waste management locally and globally. Keeping this in mind, research carried out to assess the utilization of molasses, lime, and molasses-lime for improving natural gravel for sub-base and base course construction from the Jimma Jiren quarry site. The natural gravel from this quarry site is known to have poor quality since it did not satisfy the ERA standard specification for sub-base and base course construction. To use Jiren natural gravel as a sub-base or base course construction material, it is necessary to improve its engineering properties. The laboratory test matrix in each test plan included variations in additive type, additive content, and curing period. It was established 8% cane molasses by weight of dry soil as the maximum for effective stabilization of natural gravel for sub-base construction, but not suitable for a base course layer. Results indicated that the natural gravel specimens from the Jiren quarry site stabilized with lime provided higher CBR values than molasses used alone. On the other hand, replacing 50% of lime content with molasses indicated better results than the performance of either individual additive. Therefore, the natural gravel blended with the molasses-lime combination is much better when it used for sub-base and base course construction to treat such an inferior quality of natural aggregates.