Saturday, 15 April 2017

The Red Road: How to construct Estate Roads with Lateritic pavers - Engr. Osaz’ ENOBAKHARE

In-tune Developers and Estate Owners with an eye for budget-friendly yet aesthetically-appealing, stable, strong and durable estate infrastructure are already exploring the option of adopting the ‘red road’ technology. With the abundance of cheap and good quality laterite deposits in various parts of the country on the one hand and the prevalent rising cost of construction materials on the other, the use of lateritic pavers for estate road construction in place of concrete interlocks and asphaltic (tarred) roads may just be the real deal.

In structural/highway engineering terms, the Red Road is designed as a light and medium-traffic road with individual unit of paver having the same compressive strength as that of Grade M40 concrete (i.e. 40N/sqMM) as obtainable in concrete pavers for the construction of similar road types. Light and medium traffic roads includes car parks, office driveways, housing estate roads, rural roads, farm houses, office/commercial complexes, boulevards, city streets, small market roads, intersections/rotaries, utility cuts on arteries, service stations, etc. If properly constructed, the red road sufficiently satisfies nearly all known functional requirements for roads with durability potential believed to span beyond 50 years during which only little maintenance is needed. 

Because one of the main constituent material, Laterite which usually amounts for more than 50% by volume of the mix in the red pavers normally contains up to 70% clay -which is known to be ‘plastic’ in nature, the thin gaps or voids between interlocking pavers allows for expansion and contraction across various seasons and at different temperatures; although a suitable infill material which does not affect this natural process can also be used to seal the void. Some engineers also lay damp proof membrane (dpm) beneath the bed in areas with high water table. 

As applicable with concrete pavers, pavers for red roads are built on good bedding usually made of highly-draining sand spread uniformly to form a longitudinal bearing throughout the surface area of the road up to a thickness of 100mm or more depending on the subsoil conditions. Stoppers are installed at the edges of the road with protected linkages to the adjourning drainage to prevent the bedding sand from washing off. In areas where highly compressive soils like clay and peat are encountered at near surface levels, the poor soil is first excavated and a more stable earth fill is used to replace it before the bedding is made. The bedding in any case must be properly leveled and compacted before the lateritic pavers are laid to avoid depressions, bulges and over-settlements at various sections as they receive varying degree of stresses from live loads.  
Red roads are built from lateritic pavers made of a stable mix of laterite, crushed stone/stone dust and cement. The proportion of each constituent material known as the mix ratio largely depends on the expected bearing capacity of the road. For instance, the percentage by weight of stone dust in the mix is often higher for pavers to be used in main arterial roads (i.e. the road(s) leading from the main estate entrance gate to the streets) than the pavers used on the streets (or branch roads) because the load bearing requirements are relatively different.

Recently (March 2017), a kilometer of dual carriage red-road to be constructed by an indigenous firm in Garki, Abuja has already been estimated to cost some 37% less compared to the use of conventional methods. Interestingly also, for lovers of road ‘black’, the red road can also be sprayed black with hot black soot material at an extra fractional cost and still maintain its functionality. As it stands now, Red-roads may soon become a part of our road life.

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