Development of Practical Technology for Maintenance-oriented Concrete Overlay With a Life Expectancy of 20 Years
Development of Practical Technology for Maintenance-oriented Concrete Overlay With a Life Expectancy of 20 Years
▲ Research Fellow Nam Jeong-hee, Department of Highway & Transportation Research, KICT
Prologue
According to Yearbook of Road Statistics (2020) published by Korea’s Ministry of Land, Infrastructure and Transport (MOLIT), the length of cement concrete pavement has steadily increased since 2000, accounting for approximately 65.63% (12,956 km) of the total length of highways (primary roads). However, it is worth noting that a significant portion of this pavement, as much as 19.51% (2,528 km), is targeted in mid- to long-term remodeling plans due to aging.
The increased aging of cement concrete pavement inevitably leads to an increase in maintenance budget requirements. Considering that the budget for highway maintenance, which was KRW 34.9 billion in 2001, had increased to KRW 154.7 billion by 2020, a staggering 4.43-fold rise, it is clear that there is now an urgent need to establish effective maintenance measures.
Over the past four years, we have conducted research on the development of an overlay method for cement concrete paving, which can overcome the limitations of partial cross-sectional repair and ensure longevity and high durability by using materials in the same series as the existing deteriorated cement concrete paving. One of our major achievements in this area is the successful practical application of an overlay method that maximizes durability through reinforcement of continuously reinforced concrete pavements, enabling an expected service life improvement of over 20 years through maintenance. Currently, we are in the process of negotiating a technology transfer.
Development of Technology for Practical Application of Continuously Reinforced Concrete Pavement (CRCP) Overlay Maintenance Method
Known for its excellent durability and cost-effectiveness, the Bonded Concrete Overlay (BCO) method is a pavement maintenance technique in which concrete is overlaid after cutting the deteriorated existing concrete layer. Compared to asphalt overlay methods, it has a relatively long service life and superior load-bearing capacity for increased traffic volumes and heavy vehicles, resulting in a significant reduction in maintenance frequency and costs. Additionally, it is evaluated as an economical maintenance alternative since it has material properties that are similar to the existing concrete pavement, resulting in less pavement damage after maintenance.
The existing concrete overlay method for Jointed Plain Concrete Pavement (JPCP) involves placing concrete on top of the deteriorated JPCP and installing joints in the same position as those of the existing pavement. However, the joint area is the weakest part of the concrete pavement, and from the perspective of repair and reinforcement, installing joints in the same position as those of the existing pavement may ultimately have limitations when it comes to improving usability for public use.
Accordingly, we have developed an innovative method for overlaying joint concrete pavements with longer service life compared to conventional methods, called the Ultra-Thin Continuously Reinforced Concrete Pavement maintenance method (hereinafter referred to as “UT-CRCP”), which employs reinforcing materials such as steel bars to restrict joint movement and eliminate them. UT-CRCP involves cutting the deteriorated surface of existing pavement and overlaying it with a thin layer of concrete. This method induces the two pavement layers (overlay and existing pavement layers) to behave as a single unit by completely bonding them together using continuously reinforced steel bars. The key concept of this method is the removal of deteriorated areas and improvement of the surface of the pavement while enhancing its structural capacity with reinforcement materials. An important prerequisite for achieving this is that the existing pavement must maintain sufficient support for loads, and the overlay layer must be completely attached to the existing pavement. Considering that the reality in Korea is that concrete pavement is frequently damaged at joint areas, it is important to disperse stress concentration on existing joint areas through the effective placement of continuous reinforcement bars during overlay, and to enhance long-term durability through limited joint width movement. The core idea of the construction aspect for practical application is the development of the one-lane paving method for reinforcement installation, which enables maintenance using only one lane to minimize one-lane paving closures and the associated traffic congestion that inevitably occurs when maintaining and repairing deteriorated concrete roads used by the public.
One of our major research accomplishments in this area is the large-scale test construction carried out over four occasions for the practical application of the UT-CRCP. The 1st and 2nd test constructions were conducted at the SOC Demonstration Research Center of the Korea Institute of Civil Engineering and Building Technology (KICT) in Yeoncheon, Gyeonggi-do, where a 60m-scale UT-CRCP was constructed. Through this test construction, the constructability of the equipment developed for the one-lane paving closure method was evaluated, and the field applicability of normal reinforced concrete using type 1 cement was also verified. In addition, the service life of the UT-CRCP under environmental and axle loads was assessed using buried-type sensors. Analyzing the movement behavior of the existing JPCP and UT-CRCP before and after construction under changing environmental loads, it was found that the crack width behavior of the UT-CRCP was reduced by approximately 88% compared to the existing JPCP joint behavior, which clearly can be attributed to the continuous reinforcement effect. This phenomenon shows the possibility that the joint behavior of the existing JPCP can be transformed into the crack behavior of the CRCP through maintenance.
Based on the results of the two previous test constructions, the 3rd test construction made an extension of approximately 102 m at the Ribisagori section of National Route 37 in Paju through cooperation with the Ministry of Land, Infrastructure and Transport (MOLIT) and the Uijeongbu National Highway Management Office, and the 4th test construction was completed in May 2022 on a national highway in Hongcheon. These test constructions have demonstrated excellent performance to date.
Provision of High-Quality Road Services Focused on User Needs through Maintenance
In this paper, we introduced the characteristics and advantages of a new type of maintenance method that can be applied to aging cement concrete pavement. In other words, this method not only can extend the structural lifespan of deteriorated roads through cement concrete pavement overlay maintenance, but also can provide additional services such as improving driving comfort for users and reducing road noise due to continuous construction. Ultimately, we hope that the outcome of this study will present a new vision for the future of concrete pavement through practical application.
