At the seminar "Sustainable and Cost-effective Road Solutions" held on June 19^th, 2024, in Ho Chi Minh City, Scientists, representatives of management agencies, and contractors all agreed that the application of sustainable solutions in road construction and maintenance is an inevitable trend that needs to be expanded at large scale in Vietnam road projects.

Especially, at the COP26 Conference, Vietnam made a statement to achieve net zero emissions by 2050. The Prime Minister also issued Decision No. 876 dated July 22^nd, 2022, on green energy transition, carbon and methane emissions reduction from the transportation sector.

Picture 1: Seminar overviews

Below is a summary of the outstanding technical solutions presented by the keynote speakers during the seminar:

Session 1: Advancements in Prime Coat Emulsions – A Sustainable Approach to Road Construction in Vietnam

Sharing at the seminar, Associate Professor, Dr. Nguyen Quang Phuc, Department of Roads, Faculty of Civil Engineering, University of Transport and Communication (UTC) said that Emulsified Asphalt Prime (EAP) is a specially designed emulsion as a prime coat layer, with good bonding to the base layer and quick drying for flexibility during construction. There are many large emulsion manufacturers in the world that produce prime coat emulsion products with different names. EAP emulsion is applied worldwide for road construction in many countries such as the USA, Australia, New Zealand, Thailand, etc.

According to the assessment of the National Center for Asphalt Technology (NCAT), using EAP emulsion causes less environmental pollution due to its low volatile content and less risk of fire and explosion compared to cut-back asphalt, convenient when constructing roads because it does not require heating, can be applied at saturated surface dry (SSD). This is a beneficial factor for road construction in Vietnam when our country has a lot of rain.

In Vietnam, EAP emulsion is known and used through the EcoPrime^® product developed and supplied by Asphalt Distribution Company Limited (ADCo) to meet the technical specifications of TCCS 27:2019/TCDBVN as a prime coat layer for road structures.

Picture 2: Assoc.Prof.Dr. Nguyen Quang Phuc

Research results of Dr. Do Vuong Vinh, Road Department, Faculty of Civil Engineering, University of Transport and Communication, at the EcoPrime^® emulsion construction project on Highway 26 Khanh Hoa showed that EcoPrime^® emulsion had deep penetration and quick setting time after 8 hours of spraying on the aggregate base layer in nighttime conditions with the ambient temperature about 23 degrees Celsius.

After 5 hours of spraying, trucks can pass through without peeling or peeling off the prime coat layer. This is a great advantage when using prime coat emulsion in many road projects in Vietnam that are both under construction and exploitation, helping to speed up progress and be flexible in construction.

Dr. Vinh also shared information when comparing the prime coat emulsion with other products such as MC-70 and CSS-1 emulsion at the National Highway 10 expansion project - Thai Binh, that the prime coat emulsion can be opened to traffic without peeling off after 4 hours (daytime) with ambient temperature about 30 degrees Celsius, meanwhile CSS-1 surface was peeled off and MC-70 surface was not dried yet.

Picture 3: Penetration Testing compares CSS-1, EcoPrime and MC-70 in the lab

Session 2: Advancements in Road Surface Preservation – A Case Study of Microsurfacing in Ho Chi Minh City

At the seminar, Mr. Le Ngoc Hung - Head of Product Development Department of ADCo introduced Microsurfacing technology in preventive maintenance of pavements, which is applied when the pavement structure is still stable, however, the surface begins to oxidize and strip slightly.

This technology helps to improve waterproofing, and skid resistance, protect the underlying structure, prolong the life of the road surface, improve traffic safety, and optimize costs, while could be quickly constructed and opened to traffic after about 1-1.5 hours in daytime conditions and after about 3-4 hours in nighttime conditions. Widely used around the world, Microsurfacing has proven its effectiveness in many projects, especially in Vietnam, such as the pilot project on National Highway 21B Nam Dinh applied from 2017 to present and road surface quality remains stable.

The application of Microsurfacing technology has been widely used in many countries around the world. Microsurfacing technology could repair stripping and bleeding defects, improve roughness and rutting conditions, slow down oxidation and aging of the road surface, and prevent water from penetrating the road structure. The outstanding advantage of this technology is that the construction process is fast, opening to traffic after about 2 hours of construction, ensuring good traffic safety.

Speaking at the seminar, Mr. Luong Nhat Binh, Infrastructure Management Department 4, Ho Chi Minh City Road Traffic Infrastructure Management Center of Ho Chi Minh City, said that Ho Chi Minh City Department of Transport is managing 850 routes with 1,365 km bridges and roads with total pavement surface area of asphalt concrete is 16.5 million m2. The amount of maintenance is huge.

To ensure effective maintenance, Ho Chi Minh City has applied many methods such as milling out and overlaying, recycling, deep recycling, and renewing layers of road structure.

Regarding materials, the Department has tested many new materials such as carboncor, open grade asphalt (densiphalt). However, these types of materials are not suitable for road maintenance in Ho Chi Minh City.

Picture 4: Vo Tran Chi Street after Microsurfacing trial

To find a new, more effective solution, Ho Chi Minh City has piloted Microsurfacing technology at Vo Tran Chi Road to find a proactive, economical, effective, and environmentally protective maintenance solution with actual conditions of in Ho Chi Minh City.

On the other hand, the project also tested the ability of Microsurfacing in conditions where the road has high traffic, and many heavy trucks circulating while the road surface of this route is due for maintenance and repair.

Trial results show that, compared to milling out & overlaying new 5cm hot mix asphalt concrete with Microsurfacing technology: Maintenance costs are reduced by 66%, energy consumption is reduced by 91%, greenhouse gas emissions are reduced by 91%, aggregate materials savings by 89%.

After one month of application, the technical criteria on the route are still maintained even though this route has high traffic. The project will continuously be monitored and evaluated so Ho Chi Minh City Transport Department will have a basis for mass application on the city's roads.

Session 3: Cold Recycling Technology – Enhancing Road Rehabilitation Practices in Vietnam

At the seminar, Mr. Christophe Duboscq, Head of Regional Technical Department - TIPCO-COLAS Group, introduced cold recycling technology as an advanced restoration method for pavement applied in the world, including Vietnam, to solve the problems of road surface damage due to climate and traffic. Recycling technology includes hot recycling (using a mixture of asphalt concrete and milled-out materials) and cold recycling (Cold In-place Recycling (CIR) and Cold Central Plant Recycling (CCPR)).

The advantage of these methods is that the materials are mixed at the milling machine or the station along with a specialized emulsion. The effect is that all existing milled-out materials can be reused, without incurring the cost of importing new materials, low energy consumption, reduced transportation costs, saving costs compared to the traditional method of milling out, dumping, and paving with new asphalt concrete. Traffic can be reopened immediately after compaction.

Picture 5: Mr. Christophe Duboscq on the stage

Results from cold recycling technology compared to traditional methods: energy consumption reduced by 44%, greenhouse gas emissions reduced by 58%, saving aggregates by 68%.

Cold in-place recycling technology has been applied to the construction of Highway 13 in Binh Phuoc since 2020. Mr. Vo Phi Bao, Deputy General Director - Binh Phuoc Infrastructure Construction Investment Joint Stock Company said that the Maintenance and Upgradation of National Highway 13 with a length of 32km applying cold recycling technology. The project was completed with technical criteria fully met. After the exploitation process, the road surface remains stable and good quality. Saving costs and construction time compared to traditional methods, from this success, Binh Phuoc plans to expand cold recycling technology to other sections of the province.

In addition, Mr. Bao also shared that he would continue to apply new technologies and new materials with ADCo at the project such as: Elastic modulus asphalt concrete with EME fatigue resistance feature and oil-resistant Polymer asphalt at the intersection projects that have slow traffic speeds.

“Cold recycling technology brings many economic and environmental benefits, suitable for actual conditions in Vietnam. Applying this technology not only helps reduce maintenance costs but also contributes to protecting the environment and improving the efficiency of using resources and energy," said Mr. Vo Phi Bao.

Picture 6: Cold-in-place recycling at HW13, Binh Phuoc

Another Cold Recycling Technology applied on Highway 51 Dong Nai is Cold Central Plant Recycling (CCPR)

Dr. Nguyen Ngoc Lan, Department of Construction Materials - Faculty of Construction Engineering, University of Transport and Communication, said that in Vietnam, standard specifications for cold recycling technology are gradually being finalized. This technology allows for 100% reuse of Reclaimed Asphalt Pavement (RAP) while controlling the quality of storage and mixing materials more effectively.

Cold Central Plant Recycling (CCPR) technology is an effective method for restoring asphalt concrete pavement. This is an advanced technique that has been widely applied in many countries such as the USA, Europe, and China, but is still new in Vietnam.

The trial on Highway 51 includes the steps of road milling, cleaning, and tack coat spraying with CSS-1h emulsion at a rate of 0.8 l/m2.

After that, RAP materials are mixed at the mixing plant and then transported and spread on the road surface. The technical specifications of the cold recycled mixture are evaluated based on Marshall's stability, stripping, and elastic modulus. The results showed that the cold recycled mixture satisfied the required limits according to AASHTO MP31-22 standard.

Environmentally, with the ability to reduce CO2-eq emissions and energy consumption compared to traditional technologies such as hot mix asphalt (HMA), CCPR could reduce energy consumption by up to 51.6%, while hot recycled asphalt only reduces it by 14.2%. CCPR technology is a sustainable and cost-effective solution for road maintenance and reparation. Applying this technology in Vietnam requires the establishment of standards for design, construction, and acceptance, to ensure quality and long-term effectiveness.

Dr. Lan added, “The 2023 research project of the Ministry of Transport proposes the establishment of basic standards for the design, construction, and acceptance of CCPR at mobile batching plants, promoting the application of cold recycled asphalt concrete in our country".

Picture 7: Dr. Nguyen Ngoc Lan presents at the seminar

CCPR technology not only saves costs but also is environmentally friendly, and suitable for the needs of maintaining and upgrading the road system in Vietnam. Continued research and improvement of technical standards will contribute to improving the effectiveness of applying this technology in practice.

Session 4: Exploring Cold Mix Asphalt – An Effective Approach to Road Surface Repairing

Cold mix asphalt technology, with ADCo's Cold Patch^® product, is an effective and sustainable solution for pavement maintenance and repair. This is pre-mixed, bagged asphalt concrete designed for use in road surface maintenance and repair work.

Cold Patch^® has outstanding advantages such as ease of use, long-term storage, and quick construction, and allows traffic to open immediately after application.

Picture 8: Cold mix asphalt – Cold Patch^®

Mr. Hoang Dinh Kien, Head of Technical Department of ADCo, said that Cold Patch^® is highly appreciated for its safety, cost savings, and flexibility. This is an environmentally friendly product with high durability and good water resistance. Cold Patch^® can be applied on many different types of road surfaces such as asphalt concrete or cement concrete.

Cold Patch^® can be used to patch potholes, fill technical trenches, and repair small areas. The construction process is very simple and quick, including steps of cleaning the surface, spraying emulsion if necessary, spreading Cold Patch^® asphalt concrete, leveling, and compacting. After completing these steps, the road can be opened to traffic immediately.

“Cold Patch^® has been used in many projects in Vietnam, including repairing and patching potholes on the Noi Bai - Lao Cai highway project, filling technical trenches in industrial zones, and leveling bridge connection areas of Hanoi - Thai Nguyen expressway. These projects have proven the effectiveness and sustainability of Cold Patch^® technology in real conditions in Vietnam," said Mr. Hoang Dinh Kien.

Source: ADCo - Transport Newspapers