The Mechanical and Binding Potentials of Fresh Cow Dung (FCD) for Gravel Roads Construction

Among the developing nations, unpaved (gravel and earth) roads form a disproportionately large percentage of the road network when compared to the paved roads. For instance, in Kenya earth roads account for 47% of the road network, while the gravel roads account for about 38%. The most significant problem associated with gravel and earth roads is dust emission, which contributes to the deterioration of the road surface. In addition, the dust causes road safety, human health and the environmental quality issues. In order to minimize dust emission dust suppressants are applied annually. Dust suppressants, for example, Magnesium or Calcium Chlorides solutions are expensive and hence not widely used in developing countries like Kenya. In many Kenyan rural homes and in most African countries, fresh cow dung (FCD) is used as dust suppressants in madhouses. Therefore, this study seeks to explore the mechanical and binding potentials of FCD for gravel roads construction as a dust suppressant, improvement of mechanical and resilience properties of lateritic soils for gravel roads construction. The effect of FCD on gravel soils was determined at various percentages (0%, 3%, 6%, 9% and 12%) by weight. The Index properties, compaction properties, plasticity requirements and bearing strengths {Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR)} were determined. The results show that Maximum Dry Density (MDD) reduced while the Optimum Moisture Content (OMC) increased with the increase in dosages of FCD. The UCS test results were 257 kN/m2 (0%), 257 kN/m2 (3%), 300 kN/m2 (6%), 267 kN/m2 (9%) and 213 kN/m2 (12%) while, the CBR test results were 21%, 39%, 54%, 34%, and 24% for 0%, 3%, 6%, 9% and 12%. The research concludes that FCD at 6% by weight can be used for mechanical stabilization of gravel soils for road construction. FCD is cheaper, readily available, sustainable and environmentally friendly. This will go a long way in the economic development of low and middle-income countries.

Development of a Simplified Agency Life-Cycle Costing Tool for Gravel Roads

Understanding how roads behave is necessary both for their design and also to make sure that suitable and appropriate maintenance is programmed and carried out effectively. The problem is that this is not an easy task because there are many variables that affect road performance, and these differ from place to place. This is true of both paved and unpaved roads. Most countries have a large network of rural unpaved roads that require regular maintenance at relatively high total cost over many years. If the performance of such roads can be improved, especially in whole life terms, their costs can be reduced. Decision support tools such as the highway development and management system have been developed based on several studies in different countries. The performance models developed as a result of these studies often contain many variables and require extensive data collection before they can be used. This is often beyond the resources available. To improve this situation and to develop better understanding of the performance of gravel roads, this study was undertaken in six countries. It was found that two material characteristics, namely plasticity product and grading modulus, had a major effect on the performance of gravel roads, and were found to predict the performance of gravel roads to an acceptable level of accuracy. The results of the study were used to develop a simple life-cycle costing model for gravel roads that allows engineers to improve the performance of gravel roads and to reduce whole life costs.

Laboratory Method to Assess Efficacy of Dust Suppressants for Dirt and Gravel Roads

Particulate matter (PM) generated from dirt and gravel roads is a concern for both human and environmental health. To help reduce the amount of PM generated, many states allow the use of water coproduced from oil and gas wells (i.e., brines) as road dust suppressants. However, few methods exist to quantify the effectiveness of these brines and other dust suppressants. Here we designed and tested a bench-scale method to test the efficacy of dust suppressants on dirt and gravel road materials. The Standard Proctor test was modified to create discs of road aggregate that could be treated with dust suppressant, dried, and then tumbled in a mechanical drum attached to an aerosol monitor that measured PM generated within the drum. Using two types of road aggregate (DSA and 2RC) and a combination of nine simulated brines, the effects of brine total dissolved solids (TDS), and sodium adsorption ratio (SAR) on dust suppression were calculated. The effects of moisture content and aggregate type were also observed. Higher TDS and lower SAR were found to be good predictors of dust-suppression effectiveness, with the degree of effectiveness partially dependent on the type of road aggregate. The test method provides a means to quickly and reproducibly compare effectiveness of dust suppressants, with other variables such as aggregate type and moisture content, to accurately estimate dust suppression. Comparisons of dust measurements collected within the laboratory and vehicle-based measurements offer the ability to relate laboratory results to conditions encountered on dirt and gravel roads.