Continuously Reinforced Concrete Pavement

Abstract

“Continuously reinforced concrete pavement” as the title suggests this type of pavement is reinforced throughout in longitudinal direction. This type of pavement has no transverse joints unless and until there is end of pavement or the pavement comes in contact with some other pavement or bridge. A longitudinal joint exists only if the road is wider than 14 feet. Due to reduction of joints smooth and continuous riding is possible resulting in fuel saving. Also CRCP roads are maintenance free if properly constructed and care is taken while placement of steel. Once CRCP roads are constructed they need not to be taken care of for the next 50-60 years. The principal behind this roads is that “Let the road crack”, exactly opposite as in case of other type of roads where we avoid crack formation at any cost. CRCP is allowed to crack due to which stresses in the pavement are released. The cracks formed are held tightly by the reinforcement, due to which widening and deepening of cracks is restricted. Hence we can conclude that in CRCP controlled cracking is permitted. The initial cost of CRCP is high, but as it is maintenance free, and lasts for decades, overall cost of CRCP is less as compared to other type of reinforced concrete pavements. Study and observations have shown that this type of roads are alarmingly successful, hence CRCP is widely used in USA, GERMANY, BRITAN, and several other developed and developing nations. Use of CRCP will enhance the cement, and steel industries; it will reduce the fuel consumption by vehicles, and will save lots of money required for frequent construction and repairs of other type of pavements.

1. INTRODUCTION

Transport is a vital infrastructure for rapid economic growth of the country. Speedy transportation of natural resources (such as raw materials), finished goods and perishable materials to all parts of the country including the points of export outlets are basic inputs to economic growth. Recently there has been a major shift in transportation mode from Railways towards the Road sector. Now a day’s about 60% of freight and 80% of passenger transport is met by Road transport in India, which demonstrates the need for development of a good road network.

In India flexible pavement (bitumen) is most common for both national and state highways. Majority of roads are also built with conventional bitumen pavements considering its lower initial cost, though the life cycle cost of these pavements are very high compared to rigid pavements due to frequent repairs and also need for complete resurfacing at interval of 4-5 years. Further fuel consumption of vehicles is much higher on this type of pavement than that on rigid pavement. In advanced countries rigid pavement is increasingly being used due to large number of benefits it offers. Considering durability of concrete pavements some portion of Delhi – Mathura and Mumbai – Pune expressway was built with jointed concrete pavement. Continuously reinforced concrete pavement, (CRCP) eliminates the need for transverse joints (other than at bridges and other structures) and keep cracks tight, resulting in a continuous, smooth-riding surface that is virtually maintenance free.

1.1 What is CRCP?

In concrete pavement the longitudinal reinforcing steel is continuous throughout the pavement length. It is a joint less concrete pavement sufficiently reinforced to control cracking, without the aid of weakened transverse joints such as are used in ordinary or conventional type of jointed concrete pavement. Reinforced bars in the concrete are lapped to form continuous reinforcement holding the pavement together in all kinds of weather and preventing formation of large cracks that would otherwise reduce the service life of the pavement. CRCP has all the good features of concrete pavements such as durability, high structural strength, nonskid surface and good visibility at night, wet or dry—features which make concrete, and especially continuously reinforced concrete, a permanent road surfacing material.

In CRCP reinforcement steel is an important element and it offers the following functions:

1. Holds crack tight

2. Facilitates load transfer across cracks

3. Provides stiffness by restraining end movement

1.2. Definitions and Characteristics of CRCP

Continuously reinforced concrete pavement (CRCP) is concrete pavement reinforced with continuous steel bars throughout its length. Its design eliminates the need for transverse joints (other than at bridges and other structures) and keep cracks tight, resulting in a continuous, smooth-riding surface that is virtually maintenance-free. The whole idea of CRCP is based essentially on the “so-let-it-crack” philosophy rather than the difficult concept of avoiding cracks at any price. The principle in CRCP is to confine random cracking to acceptable spacing and crack widths so that the slab performs the same as if no crack exists, i.e. equal deflection at cracks and the mid span of the slab. In an unreinforced slab, cracks which occur will normally widen and get progressively worse under the effects of traffic and climatic conditions. During the contraction of the concrete fine dirt enters the wide cracks , leading to faulting , spalling and cracking and blow-ups develop , requiring extensive repairs and early surfacing to restore the smooth surface. The amount of reinforcement required to control the cracking is relatively smaller for shorter spans. As length of the slab increases amount of steel needed also increases.