It is not uncommon to find most roads constructed in Tanzania facing one form of structural defects or the other. What however, surprises one is the billions of Tshs allocated on road construction, rehabilitation or repairs without commensurate effect both on its viability or long term sustainability. The reason for this is not far–fetched. All those involved in road construction in Tanzania, from the government which awards such contracts to contractors, either fake or third rated, who dot the country only pursue short term interests for the road constructed, pocketing millions of Tshs. In the end one finds, for example, a 25km road constructed barely 6 months ago fast washing off due to government/contractor malfeasance.
This writer is of the belief that the basis for road construction has lost its tempo where government is known to embark on extravagant spending on roads which in the end wash off in months. Road construction should ordinarily appear like a medical doctor who attends carefully to his patient, where before he prescribes a drug, he firstly examines and in turn diagnoses his illness, failure for which such patient may develop complications. This should be the similitude of Tanzania roads vis-à-vis the contractor.
There are however, many causes of road failures in Tanzania among which include poor construction or lack of drainage system, poor subgrade, gradation, permeability/damage, capillarity, plasticity, in-zone outside the tropics, frost susceptibility of the soils, slope stability, general drainage (especially storm water, side drains and culvert/bridges), erosion control, poor CBR or weak base soil and material failure against the axial loading. All these have been instrumental or the reason behind why many roads today in the country do not last for long. The remedial measure therefore, against failure is that the road should be properly aligned or designed much that failure to adhere to road construction standards and rules quickly lead to the road being washed off or damaged.
It is worthy to note that most roads in Tanzania fail because the designs are defective from the start. This is evident from the soil tests which are not done properly, a situation which eventually leads to series of problems. Aside this, there are standard requirements for each layer of road (sub-grade, sub-base, base and surface) which needs to be met before approving the use of the material for each layer. Any road contractor who uses sub–standard or poor materials should be penalized. This is because such roads at the end of the day wear off, leading to road accidents or long hold ups which is usually detrimental to the socio-economic life wire of the country.
Having said this, it should be noted that, if the asphalt thickness on the road, for instance, is thin between 30–50mm and placed on improper compacted laterite, the combination cannot stay together, hence, such a road will fail in no time. According to rules guiding road construction, the Asphalt thickness ought to be 100mm thick, 4.50–6.50% bitumen content for binding course, 5.0–8.0% bitumen content for wearing course, with mix composition passing a British standard sieve size fitting in the standard envelop. Likewise to the Stone Base, it has its own standard control and also the rest of the materials used for road construction.
Harped on the need for quality control of roads to ensure that the service life of the road is attained, it is pertinent that the nation must embark upon reforms, especially in the area of civil engineering to bring them at par with their peers in the developed world. Constructing good roads have other multiple effects especially as it deals with sustainable socio-economic development either in the area of agriculture, industry, education, defence, commerce, trade and investment. It is the opinion of the writer that special consideration must be given to quality control while local capacity development is required to build and sustain the natural infrastructure such that not taking cognisance of all these factors may lead to our roads becoming deficient, un-motor able and appear as death traps.
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