Road construction is one of the important topics that falls under the civil engineering department. There isn’t any direct information available on the Internet, it seems and this gives us an opportunity to discuss what are the latest and the best technological developments being used for the road constructions.

New technology has been developed by Israel that involves changing of soil density by treating it with a special enzyme. The technology allows using existing roads without having to excavate it to fill the underlying layers with asphalt along with selected materials.

Road Surfacing
Soil improvement in its broadest sense, is the alteration of any property of a soil to improve its engineering performance. This may be either a temporary process to permit the construction of a facility or may be a permanent measure to improve the performance of the completed facility. The result of an application of a technique may be increased strength, reduced compressibility and permeability, or improved ground water condition.

Need for Stabilization of Earth Roads
An earth road’s foundation and wearing surface is composed solely of the natural soil present originally on the site. Soils can be classified into two categories– cohesion less and cohesive soils. It has been observed that regions that are predominantly clayey, do not usually have sandy materials. Clays must be considered as very important and often determining soil component since it has two objectionable qualities that make it the most troublesome of the materials to be dealt with. It swells when subjected to wetting, and shrinks with drying.

Clays and silts are low-grade construction materials, which find use in impervious elements such as cores (dams), cut-offs, and are poorly drained alog with the characteristic of shrinking and swelling. Also, clays when wet lose all strength, and are highly compressible, producing undesirable settlement as sub-grades of highways. Sands, though, having good drainage properties are also not suitable, as they lack cohesion and spread laterally under vertical loads. Thus, either of the two types alone cannot take the traffic independently. Therefore, combination of the two in certain specific proportions and thorough compaction with or without the use of additives may result in a stable sub-grade. A stabilized material may be considered as a combination of binder-soil and aggregates preferably obtained at or near the site of stabilization, and compacted, so that it will remain in its compacted state without detrimental change in shape or volume under the force of traffic and exposure of weather. Several materials have been used as soil stabilizing agents. Of these, the best stabilizer will be the one involving minimum cost and at the same time providing durable effect. The technique is mainly applied in road construction soil, and is termed as Mechanical Stabilization or Granular Stabilization. The process of Mechanical Stabilization is used both for base-courses as well as surface-courses. A good mechanically stable base or surfacing usually consists of a mixture of coarse aggregates (gravel, crushed rock, slag, etc.), fine aggregates (natural or crushed stone, sand, etc.), silt and clay, correctly proportioned and fully compacted. The use of correctly proportioned materials is of particular importance in the construction of low-cost roads. The principle of grading soils may be applied to the improvement of sub-grade soils of low bearing capacity, by adding to them, materials having particle sizes that are lacking, e.g. sand, can be added to clay sub-grades and vice versa.

STP Road Construction
The common method is to use a mechanical stabilization using a correct mix of various soils and mechanically compacting each layer. This ensures that there is minimal pore volume and post laying settling. Rubberising the seal coat ensures prevention of water erosion.

In Clayey soils, enzyme stabilization helps in increasing wear and performance.

Another aspect of the latest development of Road Construction is to protect Asphalt Wearing surface from water, fuel and other volatile substances ingression. STP’s new development of ShaliSeal RS TC - Coal Tar Based Slurry Seal has solved the problem to a great extent. Coal tar, being highly water & fuel resistance, prevent the Asphalt Wearing surface and reduce the periodical maintenance cost substantially. The same is also recommended to use on Granular Sub-base as Prime Coat to protect the sub-base as well as bonding with the bituminous macadam. It is already been recommended by NHAI, IRC other Road Consultant. MNCs like HONDA and many others had also opted for the same for their internal Asphalt Pavement. STP recommend the use of ShaliSeal RS TC over existing Asphalt Pavement every year just before monsoon to enjoy a Pot-Holes Free wearing surface years after years.

There are many other developments being carried out with various bodies in many other aspects and we hope a smooth riding surface throughout the country in near future.

NBM&CW November 2016