Journal of the South African Institution of Civil Engineering
On-line version ISSN 2309-8775
MOLOISANE, R J and VISSER, A T. Evaluation of the strength behaviour of unpaved road material treated with electrochemical-based non-traditional soil stabilisation additives. J. S. Afr. Inst. Civ. Eng. [online]. 2014, vol.56, n.1, pp. 28-39. ISSN 2309-8775.
Travel along unpaved roads is not always assured, because of their low standards, poor riding quality, impassability in wet weather, and the danger in the quantity of dust that is generated by moving vehicles and wind. Stabilisation with electrochemical-based non-traditional soil stabilisation additives (chemical additives) may offer a solution to this continual problem. The objective of this paper is to report on the strength behaviour of a typical marginal quality weathered quartz gravel material treated with two electrochemical-based non-traditional soil stabilisation additives, enzyme and sulphonated oil to assess their potential value for unpaved road construction under wet and dry conditions. These treated panels were trafficked under 100 vehicles per day. The evaluation was done by means of laboratory tests and field investigations for three years. The characteristics of the natural material and the binding ability of the non-traditional soil stabilisation additives were established from the laboratory testing. Density and moisture, and the strength development of the treated material were determined from field investigations. These two non-traditional soil stabilisation additives appear to have affected the particles and their water component, hence an increase in densities was achieved. The degree of formation and paste surrounding the particles appeared to have varied with time and differed between the additives. An increase in density in the sulphonated oil additive treated panel occurred three months after construction, and a further increase was again noticed eight months after construction (five months thereafter). Up to eight months after construction, the enzyme additive treated panel showed a significant decrease in density, but showed a slight increase thirty-one months after construction. This increase in densities might probably be because of further densification by traffic. The variations in density were attributed to testing variability. In the in situ and soaked DCP-CBR strength measurements, the sulphonated oil additive treated panel reached its maximum in situ strength at two months after construction, while the enzyme additive treated panel reached its maximum in situ strength at five months after construction. Up to eight months after construction, both treated panels indicated a significant decrease in both the in situ and soaked DCP-CBR strength conditions. The decrease was attributed to rain. There was, however, little evidence to show that the additives had improved the material, with the control panel being consistently stronger in both the in situ and soaked DCP-CBR conditions. The importance of considering the time factor in the strength development of non-traditional stabilisation test techniques, as well as the number of tests, was highlighted in the results of this study. The natural variability of the materials used in this type of study is generally high, and the precision of the test method is typically quite low. On this basis, it is usually difficult to draw definite conclusions.
Keywords : Unpaved road material; electrochemical stabilisation; bonding; dry density and moisture content; strength development.