Concrete matters

The significance of a robust road network as an indicator of economic development is well established. A facilitator of economic activities such as ease of movement of raw materials as well as labour and finished goods, the road network in India boasts of a scale that is second only to the US at 5.47 million kms.

The road network transports 64.5% of all goods in the country and 90% of India’s total passenger traffic uses road network to commute.

Economics of Concrete Roads

While the importance of roads is well acknowledged, the economics of road building and maintenance could do with some more thought. The choice of type of roads to be built have conventionally been based on the economies of initial cost, with little emphasis paid to the overall life cycle cost of a road. This has worked in favour of Bituminous Roads, which have been wanting on several counts including durability.

With more durable alternatives available with materials such as cement, the government’s focus has shifted to total life cycle cost as a primary factor for the choice of type road to be built. The move has increased attention to concrete as a preferred material.

What works for concrete are inherent characteristics such as i) longer life (30 – 40 years), ii) very low maintenance, iii) high durability, iv) environmental friendly, v) high resistance to climatic conditions and vi) structural stability in heavy rainfall areas.

On the basis of initial cost of pavement, Concrete Roads are reported to be over 20% costlier than the Bituminous Roads. However, on life cycle cost basis Concrete Roads are estimated to be around 25-30% cheaper than Bituminous Roads.

Fuel Saving

Central Road Research Institute (CRRI), New Delhi, conducted a study to understand the impact of Concrete Roads on the fuel consumption of the vehicles that ply on them. As per their estimates, based on the study, commercial vehicles may save up to 14% fuel, when they ply on Concrete Roads.

A quick back of the envelope calculation reveals that, assuming a truck running 300 km per day with an average fuel consumption of 1 liter for 4 Km will save Rs. 300/4 x 50 (rate of diesel) x 14% = Rs. 577 per day which comes to Rs. 1.9 lakh per year (assuming 330 days of run annually).

Since concrete roads are lighter in colour, compared to bituminous roads and are reflective in nature, they can help reduce power demand for street lighting.

The Ministry of Road Transport and Highways (MoRTH), Government of India has decided to construct the National Highways in Cement Concrete as a ‘default option’ even if they are more than 20% costlier.

The construction of highways reached 9,829 km during FY18 which was constructed at an average of 26.93 km per day. Total length of roads constructed under Prime Minister’s Gram Sadak Yojana (PMGSY) was 47,447 km in 2017-18.

Concrete Roads – Myths & Facts

Myth No. 1: Concrete Roads are uneconomical:

On the basis of initial cost of pavement, Concrete Roads are reported to be around 14-15% costlier than the Bituminous Roads.

However, on life cycle cost basis Concrete Roads, due to their long life of 30-40 years and high durability, Concrete Roads are estimated to be around 25-30% cheaper than the Bituminous Roads. Thus, on a long term basis Concreter Roads are the most economical choice of pavement, which provide long useful life.

A comparison between the Bituminous Roads and Concrete Roads for a 1 Km long, 2 lane, 7 m wide road, based on the estimated life cycle cost is as below:

DescriptionUnit
New RoadOverlay on Existing Road
Bituminous roadNew Concrete RoadBitumen overlayWhite topping
Raw Material:
Cement requirementMT200 MT
(for culverts, kerbs etc.)
1,200 MT
(including 200 MT for edges, kerbs etc.)
Nil460 MT
Bitumen requirementMT170 MTNil100 MTNil
Cost:
Raw Material CostRs./MTBitumen: 40,800
(Increase of
Rs. 800 since 15th Apr. 16)
Cement: 5,000
Initial CostRs. Lakhs208 (Increased to Rs. 209.6)2146179
Maintenance Cost
(For 20 Years)*
Rs. Lakhs18+61+18 = 975+5+5 = 1518+43+18 = 795+5+5 = 15
Total Life Cycle CostRs. Lakhs30522914094

Myth No 2: Concrete Roads are Skid Prone:

This myth arises from the smooth appearance of Concrete Roads. The high reflectivity of the Concrete Road surface makes it look smooth. However, this is not true. Concrete Road surfaces are finished with either transverse or longitudinal grooving at the time of construction either by brushing or tining. This results in a rough surface which prevents any incidence of skidding over the pavement.

The grooving may wear out over a period of time, due to continuous flow of traffic as is the case with any other type of surface (Bituminous Roads). However, results of monitoring the already constructed Concrete Roads have revealed that even with brushing, the grooves effectively sustain up to 10 years. Thereafter, the surface can be easily re-grooved by using Diamond Grinding to provide a fresh grooved surface.

Myth No 3: Concrete Roads result in High Tyre Noise:

Tyre noise is generated with interaction between the tyre and road surface. Air is compressed and released as the tyre rolls over the road surface which makes noise. The noise level depends upon the area of contact between the tyre and the road surface. Thus, greater the contact, higher the noise level.

However, it must be noted that the cause of noise is not the concrete itself but the texture of the Concrete Roads. It has been observed that transverse grooving results in higher noise levels. Longitudinal grooving may help reduce the noise levels.

Myth No 4: Concrete Roads make Tyres Burst:

Another common myth about Concrete Roads is that it is prone to tyre bursts. This myth may also be related to the high level of noise associated with the Concrete Road surface, which in turn is perceived to be the cause of a higher wear rate of the tyres and eventual failure of the tyre itself.

However, this myth doesn’t hold any factual ground, as the reasons for the incidence of tyre bursts are the same for both Concrete Roads as well as Bituminous Roads. At high speeds irrespective of the type of road, the air pressure of the tyre increases due to rise in temperature because of friction between the road and the tyre. Over inflated tyres or worn out tyres may not be able to sustain an increase in tyre pressure and thus, may result in the tyre failure.