Study on Comparision of Life Cycle Cost Between White Topping and Btiuminuos Overlays

Abstract

The focus of the present study is on construction of long-lasting and better performing pavements. Usually, with respect to the rehabilitation of the pavement, the construction agencies go with the bituminous overlays as their first priority without considering the condition of the existing pavement structure. But the advantages of cement concrete (CC) pavements that have proved to perform better and are considered to be long-lasting must be explored. The use of Thin White Topping (TWT), and Ultra-Thin White Topping (UTWT) pavements is currently gaining popularity in the area of pavement construction.. And hence it is the era where the Thin and Ultra-Thin White Topping methods are gaining their popularity. The present study provides details on the approaches adopted in measuring the performance of TWT and UTWT pavement surfaces built of plain cement concrete, cement in cement concrete replaced by 50% ground granulated blast furnace slag, cement in cement concrete replaced by an admixture called Conplast NC, and 50% of cement in cement concrete replaced by GGBS and Conplast NC. The study also includes comparison of strength of composite beams of various thicknesses when subjected to repeated wheel loads under Modified Immersion Wheel Tracking Equipment when supported by a 50mm thick bituminous layer below. The performance results on the tests on the specimens of 150mm thick admixture-added CC beam and the 100mm thick GGBS-cum-Admixture-added CC beam were almost the same. This indicated that the thickness of cement concrete slabs could be reduced by 50mm by replacing 50% of cement in cement concrete with GGBS-cum Admixture-added CC beam. Based on the study on cement concrete, and composite beams, and the study of life cycle costs, it was observed that a road surface with cement concrete overlay would be more appropriate when compared to a bituminous concrete (BC) overlay. Together, these findings suggest that the concrete overlay acts as the most economic method.

Introduction

I. INTRODUCTION

White topping is the concrete layer laid over a deteriorated asphalt pavement. The main aim of concrete overlay is to enhance the strength of the existing asphalt structure by rebuilding it.

While achieving this, the overlay also brings back the functional requirement of the existing structure which had undergone deformations like rutting and also brings back the texture. Bituminous roads have been widely used in the world from many years due to the availability of bitumen at a lower cost, and the ease of construction. Bu the adoption of refined petroleum processing technology has resulted in a reduction in the availability of bitumen, coupled by increased import costs. In the meanwhile, concrete technology, and its applications have improved. Also, apart from the initial cost of investment, the impact of life-cycle costs also need to be considered. 

A. Types of White Topping

White Topping technology can be classified as follows based on the types of bondage provided and the thickness of overlay.

1. Ultra-Thin White topping (UTWT): It is a Portland Cement Concrete overlay of below 100 mm thick. It is mandatory to obtain the bond between the overlay & the below asphalt layer.
2. Thin White topping (TWT): It is a Portland Cement Concrete overlay of thickness 100 to 200 mm. It can be designed either by considering or without considering the bond between the overlay & the underlying bituminous layer.
3. Conventional White Topping: It is a Portland Cement Concrete overlay of 200 mm thick or higher than 200mm. It can be designed and constructed without the consideration of bonding between the two layers (composite action is not assumed).

Hence the UTWT and TWT methods are considered as Bonded overlays which are normally used for the resurfacing and also for rehabilitation of the distressed pavements.

II. LITERATURE REVIEW

1. A K Sehgal et al;[1] have studied the advantages and benefits of Thin White Topping over bituminous overlays and have done comparison between the two considering the sustainability as the main criteria. The other factors considered are design life, life cycle cost and other environmental factors. Their study concludes that TWT overlays are considered more environmentally and economically sustainable as compared to that of bituminous overlays. But the study does not presnt the comparisio between the cost of construction and maintenance with a flexible overlay.
2. V K Sinha et al;[2] attempted to bring forth the concept of white topping over existing bituminous pavement. They computed the thickness for the bituminous overlay as well as for the concrete overlay and cost estimation for both. In their study, comparison is done based on total life cycle cost. And from the paper, it is noted that the savings in the construction cost of doing white topping against bituminous overlay is evidently convincing and hence life cycle cost is more economical.
3. Mustaque Hossain;[3] carried out the study to build up a design catalogue for existing roadway which is to be overlaid with the TWT. The 3-D Finite Element (FE) analysis was used to expand the design catalogue. The results obtained from this study showed that the interface bonding condition between the overlay and the existing layer is the most important factor which affects the behavior of thin white topping.
4. Dr. Abhijith C.C;[4] study dealt with the performance of UTWT overlays of different combinations over bituminous concrete layer. From this study, the direct tensile test indicated that the ROFF cement interface improved the bond strength in all the combinations when compared to that of plain cement concrete beams. Also the results of Modified Immersion Wheel Tracking test indicated that the performance of composite beams directly depended upon the thickness of the cement concrete layer (as the thickness increases, yields very low rut value), radius of stiffness of the composite beams and also the admixture used and its percentage. But the statement of decrease in the rut value with the increase of thickness shall be checked for various combinations of the the concrete mix.

The research gaps from the above studies leads to find the new insights to carry out the  study such as i). performance study various combinations TWT and ULTW layers along with a flexible layer below  ii). Assessing the best combination from the performance study iii). Comparision  of cost analysis between  the best combination and the bituminous overlay.

III. OBJECTIVES AND METHODOLGY

The main objectives of this study are;

1. To evaluate the suitability of various composite-beam specimens based on tests using the Immersion Wheel Tracking equipment in the laboratory.
2. To compare the results of beam specimens made of CC, and specimens made with added admixtures and slag.
3. To arrive at the most economic option out of various combinations with respect to the cost and the strength.
4. And to compare the life cycle cost of best performing concrete overlay with the bituminous overlay of a distressed road.

The Methodology invovled is as follows;

a. Basic tests on all the materials (Bitumen, Aggregates, Cement and mix design for BC mix and CC mix)  to be  used

b. BC layer of 50mm representing the flexible surface has been casted and compressed using an I section girder plate.

c. Above the flexible layer, Concrete layers of varying thickness (50mm, 100mm and 150mm) have been casted.

d. Composite beams are cured.

e. And tested for performance under a Modified Immersion Wheel Tracking Equipment.

f. Design of concrete overlay for the best perfomring combination.

g. Design of a flexible overlay as well

h. Compriosn of life cycle cost between the rigid overlay and flexible overlay.

From the estimation of life cycle cost for the rigid and the flexible overlay, it is known that the initial cost or construction cost is very high for the rigid overlay when compared to that of flexible one. But the concrete overlay behaves more economic when the life cycle cost is considered. The maintenance cost for the flexible overlay is very high when compared to that of rigid overlay.

V. STUDY LIMITATIONS AND FUTURE SCOPE OF WORK

1. The present work can be extended by studying the performance with the application of bonding agent between the layers.
2. The performance results can also be assessed by other tests like pull out test, fatigue test etc.
3. The performance results can also be assessed in immersion condition using the same equipment.
4. Study can be furthered continued by replacing the conventional concrete by geo polymer concrete.
5. Study can be furthered continued by replacing the conventional concrete by Engineered Cementitious Concrete.

VI. ACKNOWLEDGMENT

We are overwhelmed in all gratefulness and humbleness to acknowledge my depth to all the people who have helped me to put these concepts, well above the level of simplicity and into something creative. We would also like to express my special thanks of gratitude to my internal guide as well as external guide who gave me the opportunity to carry out this creative work on White Topping, which also helped us in doing a lot of Research and we came to know about so many new things. We are really thankful to them.

Conclusion

1) From the performance results it is known that the rut value decreases with the increase in the thickness of the beam. 2) And hence it is observed that the performance of the slab increases with the increase in the thickness of the slab. 3) The correlation values are less than or close to 1 for each combinations of concrete at a tyre pressure of 8kg/cm2 on the slab, which signifies that deflection and repetitions are strongly correlated. 4) By comparing the performance results of various concrete combinations it is known that the GGBS + Admixture combination had performed well. 5) The GGBS added concrete has the least performance when compared to all other combinations. 6) From the performance results it is observed that the performance results of 150mm thick Plain CC beam and 100mm Admixture added beam has almost the same value. 7) And hence it can be concluded that the slab thickness can be reduced by 50mm with the addition of admixture. 8) And also the performance results of 150mm thick admixture added CC beam and the 100mm thick GGBS & Admixture added CC beam has almost the same value. 9) Hence it can also be concluded that the slab thickness can be reduced by 50mm by replacing 50% GGBS to the Admixture added CC beam. 10) From the cost analysis it is known that the construction cost is very high for the Rigid overlay than the flexible overlay. 11) But the maintenance cost is very low for the rigid overlay. 12) Rigid overlay has the most economic life cycle cost when compared with that of flexible overlay.

References

[1] White Topping – An excellent solution for pavement rehabilitation – Dr. V Ramachandra, Zonal Head, UltraTech Cement Ltd, Bengaluru [2] A review of using Thin White Topping overlays for rehabilitation of Asphalt Pavements - Ankush kumar Sehgal and SN Sachdeva, NIT Kurukshethra [3] White Topping – A cost effective rehabilitation alternative for preserving Bituminous pavements on long term basis - V.K Sinha, Satendar Kumar and R.K Jain [4] Extending Asphalt Pavement Life Using Thin White Topping - Mustaque Hossain, PhD., P.E, Professor, Department of Civil Engineering, Kansas University [5] Studies on the performance of Ultra Thin Cement Concrete overlays on Flexible pavements - Dr. Abhijith C.C, Former Director at Alps Consulting Engineers [6] Conplast NC – FOSRAC – Constructive solutions manual [7] IS 10262-2009 – Concrete Mix Design [8] Highway materials and Pavement testing manual – S.K Khanna, C.E.G Justo, A. Veeraraghavan [9] Ministry Of Road Transportation and Highways (5th revision) [10] IRC SP 76 2008 – Tentative guidelines for conventional, thin and ultra-thin white topping [11] IRC 58 2011 – Guidelines for the design of plain jointed rigid pavements for highways [12] KPWD S.R 2014 – 2015 of PWP and IWTD, Bengaluru circle, Bengaluru [13] ASTM 6433-11 (Calculation of PCI) [14] IRC 81-1997 - Guidelines for strengthening of flexible pavement using Benkelman Beam Deflection Technique

Copyright

Copyright © 2023 Rashmi SM. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.