CRACKING

Cracking rates were obtained by compiling the crack lengths using mapping measure from test sections. The results shown in figure 5 are expressed in m/m2. The cracking rates are presented per 150-m section and represent the mean rate of the three lanes and the left shoulder for Highway and of the three lanes for Highway.

During the first winter season, that is four months after opening to traffic, the rate of cracking is similar for the four test sections. Afterwards for Highway , the progression remains significant yet less markedly so. 30 months after reconstruction, the cracking rates are 0.83 and 0.89 m/m2 respectively for sections 1 and 2 of Highway . These mean cracking rates are similar to the minimum allowable crack width criteria used for the design of the reinforcement of Highway (1.07 m or 3.5 feet). To verify this result in terms of the effective crack spacing on site, calculations were made using the June 2002 mapping measurements. Approximately 9% of the spacings were in the range of 0.2 to 0.6 m, 20% in the 0.5 to 0.8 m range, 60 % in the 0.8 to 3-m range and 8% were over 3 m. A certain proportion of the crack spacing is inferior to design limit values, something that will have to be closely monitored in the months to come. However, to date, the CRCP has not revealed any damage whatsoever. On Highway , three crack-width measurements were made using a so-called comparative method. The crack widths taken between spring (17.5^oC) and winter (- 22.5^oC) were 0.183, 0.057 and 0.055 mm for a mean of 0.098 mm. Another measurement was taken in June 2003 at a temperature of 37^oC. There was a 0.1-mm difference with the winter opening measurement, which is far lower than the width specified in the design (1- mm). The 0.1-mm value reported is very similar to that published by the Belgians for temperatures oscillating between -1^oC and 19^oC .

Smoothness:

A profile survey to evaluate the pavement’s smoothness, that is, the irregularity of the longitudinal profile in the wheel paths compared to a perfectly smooth reference surface. The index used by MTQ to rate the smoothness is the IRI (International Roughness Index). For a paved surface, the scale ranges from 0 to 12, 0 being a perfectly smooth surface. Note that a surface rated 1.2 is the allowable limit indicated in the specifications, and anything beyond that may bring about a penalty. On Highway , grinding was forbidden for values up to 1.8 so this was not the case for Highway . Figure 6 shows the mean IRI values in the three lanes for the entire sector in CRCP for Highway (2 km) and for a JPCP section (1.5 km) immediately adjacent to the CRCP section. The mean values for the entire three lanes of Highway are also presented on the same figure. Immediately after reconstruction of Highway, the IRI values of two of the three lanes with JPCP are higher than those of CRCP. Three years later, there is little change in the smoothness of the CRCP whereas there is a 0.2 increase in the values of the JPCP. For Highway, we observed a slight increase in the first winter.

4. CONCLUSION

1.Compared to flexible pavement, CRCP gives additional design life of at least 10 years. Further, it offers much better riding quality, less dislocations to traffic movement and substantial saving in vehicle operating cost comprising reduced consumption of fuel, lubricants etc.

2.Considering durability and maintenance free service of CRCP it is desirable to construct all these concrete roads with CRCP.

3.Thermo mechanically treated, TMT, bars are desirable for CRCP pavement. Corrosion resistant TMT bars may be used in corrosion prone areas.

4.The demerit of CRCP is its high initial cost & difficulty in repair works required to be done if not constructed properly.

5.Jointless concrete pavement, CRCP offers excellent smooth Riding surface for the vehicles that maximizes the comfort for the passengers.

6.It needs minimum cost of maintenance and rehabilitation. It minimizes the detrimental dynamic loads that are applied to the vehicles and pavement. Air and noise environment improve along the thickly populated existing corridor. Concentrations of CO and NOX are expected to reduce by around 70 % and 45% respectively. The noise level would reduce substantially.

7.Concrete can withstand even the heaviest traffic loads. There’s no need to worry about ruts, shoving effects common with asphalt pavement.

8.Concrete’s hard surface makes it easier for rolling wheels. Studies have even shown that this can increase truck fuel efficiency. Savings in fuel to the extent of 20%, may be considered ultimately reducing the vehicle operating cost.

9.Concrete roads facilitate increased speed and thereby savings in time and money. Almost maintenance free service reduces traffic disturbances and thus reduces man-hour loss to the road users.

10.Use of CRCP drastically can reduce import of bitumen there by leading to saving of foreign currency.