Roads are used in our day to day life. However little thought is put into how the road was made. Which method was used? What materials were used? How long did it take for the whole process and how long will it serve you. In this article you will get all the answers and get to know the techniques used. The most common modes of construction are Earth road method, Gravel road, bituminous road; water bound macadam and concrete cement method.
- Earth road method.
This technique is most popular in semi-rural and rural areas. The raw material used is earth like the name suggests. It does not require much skill for it to be put into place. All you need is the right machinery i.e. excavators and rollers.
However, a downside to this method is that it has a low bearing capacity hence it cannot hold heavy traffic. This road is prone to weather conditions if it is rainy it tends to get slippery, when hot it gets dusty. On the other hand when heavy vehicles use the road there is likelihood it will get dents and in the long run deteriorate. To make this type of road more long-lasting soil stabilisation must be used, but this can only be implemented if the design and implementation are done professionally.
- Gravel Road
This is an advancement of the earth road. It is common in semi-rural, semi urban and rural areas. Here you use the same process as the earth road but you add a layer of gravel after the earth is compacted.
One major advantage that this road has is the lack of dust and that it does not get slippery when it rains. Its maintenance cost is also low and its construction is not complicated.
The downside of this technique is that it cannot hold heavy traffic. If you take a long trip on such a road you will find the ride uncomfortable. Lastly, it deteriorates quite easily.
- Bituminous Road
Bitumen is the key material in this method. This method is the most preferred due to its flexibility. It made of four layers of bitumen. The bottom layer is the thickest and the subsequent three layers keep on thinning as the get to the top.
One major advantage is its elasticity as it tends to acquire the shape of load above it. This one factor gives it an edge over the two previous techniques because it can hold heavy traffic. Weather has nothing on this method, if rainy the bitumen is water proof thus maintenance is a non issue. In the event of a pot hole it can be repaired.
However, comparing this method to the other two, it needs expertise. Time is also a factor as all this cannot be completed in a month
- Water Bound Macadam
This method involves interlocked broken aggregates that are bound with water and filler material where the base course is well compacted.
WBM is considered high quality due to the compacted mass. The aggregates impart enough strength thus no void is left behind. It is also cheaper compared to the bituminous option.
- Concrete Road.
This method uses a mixture of Portland cement and asphalt. They are most common in urban areas. The edges are made thicker than the middle part.
Concrete roads are made to handle heavy traffic flow. This is an all weather road. It built to last up to ten years as it has lower maintenance issues. You do not have to worry about potholes because it is water proof.
Unlike the bitumen roads this does not bend to accommodate the heavy load thus making it vulnerable to deterioration. When it comes to expenses, this is quite costly compared to the other methods discussed earlier.
Whether in an urban area or semi rural one the choice is vast for the kind of method you will use to construct the road. Ensure that you know your budget and terrain well.
Before any type of road construction method is considered, soil testing must be carried out, which is known as cbr testing or The California bearing raito. This test is performed by measuring the pressure required to penetrate the soil or aggregate with a standard area plunger. The harder the surface the higher the CBR. For example a CBR value of 4.75 equates to moist clay while moist sand could have CBR value of 10. The standard material used is crushed limestone which as a value of 100, so it is possible to get readings of over 100 in well compacted areas.