Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam Full Depth Reclamation of Highways in Vietnam Mai Trieu Quang, Civil Engineer, General Director of BK Engineering & Construction Company Associate Fellow of ASEAN Academy of Engineering and Technology (AAET), Vietnam Abstract: The total length of road network in Vietnam is over 20,000 kilometers, in which the total length of National Highway is 17,000 kilometers Every year in Vietnam, hundreds of kilometers of road need to be rehabilitated, that requires a huge quantity of road materials The conventional road rehabilitation method in Vietnam is to remove and dispose old road materials Old asphalt and base materials are not recycled, and they must be disposed of or stockpiled, increasing transportation costs and utilizing valuable landfill space In some locales, old asphalt can no longer be landfilled Environmental laws are becoming stricter, thus adding to the expense of mining new materials and landfilling old Full-Depth Reclamation (FDR) is a full pavement rehabilitation process in which the pavement and a portion of the subbase material are uniformly crushed, pulverized and blended This process rebuilds worn out asphalt pavements by recycling the existing roadway The old asphalt and base materials are pulverized, mixed with additive such as Portland cement, foam bitumen or emulsion and water, and compacted to produce a strong, durable base for either an asphalt or concrete surface This report presents the overall figures on pavement recycling in Vietnam, and provides some findings on the first large scale pavement recycling by using Full Depth Reclamation in 18 kilometers of National Highway No.5 from Ha Noi to Hai Phong, a heavy traffic highway in the North of Vietnam This will contribute to accelerate the application of pavement recycling in road maintenance and rehabilitation projects in Vietnam Basic Information on Reclamation of Asphalt Pavement in Vietnam Hundreds of kilometers of road needed to be upgraded and rehabilitated each year require millions of cubic meters of materials for pavement construction and rehabilitation In the conventional technology of pavement construction, the removal and disposal of the old pavement’s concrete are costly and waste much time while adversely affecting the environment due to the transport of disposed materials of the old pavement Hence, it is imperative for us to apply a new technology in pavement upgrading and rehabilitation Since 1998, when Vietnam started upgrading and rehabilitating key national highways, utilizing ODA loans from international organizations, the technology of regenerating pavement has been experimentally applied in the projects for National Highway 1A in Vietnam * Pavement recycling of National Highway 1A crossing Binh Thuan province under ADB1 Project, 1998 * Pavement recycling of National Highway A crossing Da Nang city and Quang Nam province under WB2 Project, 2002 * Pavement recycling of National Highway 1A crossing Quang Ngai province and Phu Yen province under ADB3 Project, 2003 These experimental projects have reached positive results and brought useful experience to Vietnamese Engineers and Authorities However, due to the unavailability of complete construction equipments system, the construction prices of this option at this moment is quite high in comparison with conventional method, so the new technology has not been deployed on a large scale Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam The Ministry of Transport of Vietnam recently has conducted trial sections of pavement cold in place recycling in highways, as follows: * In 2007, with the support of Sakai Company (Japanese), a trial for road stabilization with the Ministry of Transport tested the technology in which the cold regeneration (regenerate pavement’s foundation) was used with special bitumen additive and cement at the two sections of the National Highway at Ha Nam Province Figure 1: Trial for Pavement Recycling by Sakai Road Stabilizer * In August 2010, a trial of the new Wirtgen Recycler on an 800 meter long (4.75m width) stretch of road in An Suong, the busiest highway linking Ho Chi Minh city to the Mekong Delta has been successfully made The Department of Public Works of Ho Chi Minh city commissioned the trial with the support of Vietnam Ministry of Transport Vietnam Ministry of Transport has approved the outline and directed the assessment of the testing result since July 2010 After 18 months of monitoring, the trial pavement met the quality requirements, and Vietnam Ministry of Transport issued Decision No 1162/QD-BGTVT on May 23rd, 2012 regarding “Temporary regulations on design, construction, and inspection of the cold generated pavement with foam bitumen combined with cement in pavement structure of roads”, which is currently allowed to be experimentally deployed on a large scale Figure 2: Trial for Pavement Recycling by Wirgen Road Stabilizer in An Suong * Later on in March 2011, Vietnam Ministry of Transport has organized another trial section for the Full Depth Reclamation by using Engineering Emulsion in National Highway No.1A in Long An province The technology has basically met the requirements Based on the result of test monitoring, Vietnam Ministry of Transport issued Decision No 2969/QD-BGTVT on November 16th, 2012 Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam regarding “Temporary regulations on design, construction, and inspection of the in-place removed materials of the cold generated pavement with engineering emulsion asphalt in pavement structure of roads” Figure 3: Trial for Pavement Recycling by Hall Brothers Road Stabilizer in NH1A-Long An province Generally speaking, with the above-mentioned temporary regulations issued by Vietnam Ministry of Transport in late 2012, the legal corridor has been through for the deployment of the pavement recycling technology in transportation projects in Vietnam on a larger scale Full Depth Reclamation in National Highway No.5 Ha Noi to Hai Phong The National Highway No.5 (NH-5) links the capital of Hanoi with the international ports of Hai Phong in the East with a length of 106 kilometers The highway plays the most important role in the road transportation system of Northern Vietnam as a socio-economic artery joining the two cities and surrounding cities along the highway With the economic growth that started in the 1990s as a result of the reform, it was estimated that both cargo and passenger traffic volumes on the NH-5 would significantly increase in the near future Along NH-5, there are some crossing roads such as NH-1A (KM0), NH-3(KM59) and NH-10 (KM77) for connecting with other provinces/cities According to the field survey, pavement condition of NH-5 is deteriorating quickly caused by heavy and overloaded vehicles and it needs more attention for maintenance activities The pavement from Hai Phong to Ha Noi is being damaged more seriously than the opposite road lanes, creating rutted damages because most of vehicles traveling from Hai Phong to Ha Noi are overloaded as shown in Figure Also, the section from Km76-Km94, the pavement condition toward Ha Noi is damaged more seriously Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam Figure 4: Overload trucks in the direction from Hai Phong to Ha Noi have caused serious pavement damages in NH5 Ha Noi - Hai Phong 47 percent of good pavement, 44 percent of pavement to be maintained and carpeted, and percent of pavement to be improved Hai Phong - Ha Noi percent of good pavement, 82 percent of pavement to be maintained and carpeted, and 15 percent of pavement to be improved Source: Vietnam Road Administration (2006) Note that rates of and for good and poor pavement conditions, respectively As per the initial design that have been approved by Vietnam Ministry of Transport, the pavement in National Highway No.5 will be rehabilitated by applying conventional design in two alternatives: To repair all damages in the existing asphalt pavement, seal all cracks, pave leveling layer and after that overlay with some layers of new asphalt concrete with the calculated thickness Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam To remove all existing damaged asphalt pavement and replace with new asphalt concrete layers All pavement structures, with the passage of time and traffic, wear out In the past, it was convenient to overlay these roadways with additional layers of materials, thereby extending their service lives Eventually, however, due to many factors, these roadways deteriorate to a point that conventional maintenance and/or repair and overlay practices become expensive and not perform well due to the condition of the underlying structure It is at this stage in a pavement’s lifecycle that costly roadway reconstruction is typically specified However, due to the evolution of high horsepower road reclaimers with state of the art computerized additive systems, FDR is one of the fastest-growing rehabilitation techniques being specified by pavement engineers around the world FDR conserves previous investments of in-situ materials while resolving the issues and minimizing the costs in-situ material disposal common with conventional pavement reconstruction practices The process has been proven on a wide range of flexible pavement structures to produce quality results at substantially lower costs and considerably shorter construction periods than conventional reconstruction practices After technical issues review and cost comparison, the Full Depth Reclamation has been selected to be applied for two of five Pavement Rehabilitation Contract Packages of National Highway No.5, with the total length of 18 kilometers Full-Depth Reclamation (FDR) is a full pavement rehabilitation process in which the pavement and a portion of the subbase material are uniformly crushed, pulverized and blended This revitalized gradation can be mixed with an asphalt emulsion and/or Portland cement to increase the stability of the rejuvenated material This process completely rehabilitates and reinforces the structural strength of the underlying base of the road It addresses reflective cracking problems by completely recycling base and sub-base structural deficiencies Full-depth reclamation uses the old asphalt and base material for the new road There’s no need to haul in aggregate or haul out old material for disposal Truck traffic is reduced, and there is little or no waste Full Depth Reclamation (FDR) is distinguished from other rehabilitation techniques like Cold Planing (CP), Cold In-Place Recycling (CIR) or Hot In-Place Recycling (HIR), by the fact that the rotor or cutting head always penetrates completely through the asphalt section into the underlying base layers, thereby erasing deep pavement crack patterns and eliminating the potential of reflective cracking With today’s innovative equipment and vast range of stabilizing additives, FDR can be utilized to depths exceeding 12”, although it is typically performed at 6”- 9” The pulverized layers and additive(s) become a homogeneous well graded (2”/50 mm minus) material with improved structural characteristics Site Investigation The site has been investigated to determine the cause of failure Pavement cores and test holes was used to determine layer thicknesses and to obtain samples of the material to be recycled (asphalt surface, base course aggregate) Falling weight deflectometer (FWD) testing was carried out on the National Highway No.5 prior to and following construction to determine the change in the overall strength of the pavement structure FWD testing applies an impact load to the pavement surface and measures the surface deflection using geophones at set distances from the loading plate The data is recorded and can be used to backcalculate the material properties of individual layers of known thickness Table No.1 List of sections with average Ep and Mr and SN of existing pavement No Chainage Lane direction Km76+000 – Km76+800 Km76+800 – Km77+750 Km77+750 – Km78+850 Km78+850 – Km80+500 Km80+500 – Km 82+050 Direction from Ha Noi to Hai Phong (Right lanes) Ave Ep ( Mpa) 559 565 682 493 625 Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Ave Mr ( Mpa) 161 143 143 81 95 Structural Number SNeff 5.30 5.32 5.67 5.08 5.50 Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam 10 Km76+000 – Km76+900 Km76+900 – Km78+000 Km78+000 – Km80+050 Km80+050 – Km81+050 Km81+050 – Km82+050 Direction from Hai Phong to Ha Noi (Left lanes) 343 324 407 768 412 63 63 71 149 67 4.50 4.42 4.77 5.89 4.79 Lab Evaluation Material samples from the site have been pulverized in the lab to create an aggregate-soil mix that will be similar to that expected from the recycling process This includes the determination of maximum dry density and optimum moisture content and other properties as stipulated in the Vietnamese Temporary Regulations on Design, Construction, and Inspection of Full Depth Reclamation with Engineering Emulsion Asphalt in Pavement Structure of Roads Table No.2 Required Properties of Recycling Sample in the Laboratory Table No.3: Requirement in Vietnamese Pavement Design Specification 22TCN 211– 06 STT Required property in the Elastic Modulus of material sample, curing at 400 C in 72 hours, testing at 250 C, Mpa Required value ≥220 Testing Code Remark 22 TCN 211-06 and For reference Appendix A in the Temporary Regulations Scarification and Pulverization Road Stabilizer from Hall Brothers has been used for the FDR This machine is capable of pulverization without scarification first The depth of pulverization in this section is 20 cm include all of the asphalt surface, plus some part of the base course To achieve the proper gradation after pulverization, two pass of the equipment has been applied Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam Shaping and Grading The pulverized material is shaped to the desired cross-section and grade by a motor grader Water Application Water is added to bring the aggregate-soil mixture to optimum moisture content (water content at maximum dry density as determined by ASTM D558), either in front of the pulverizer/reclaimer or in the mixing chamber Mixing The aggregate-asphalt-cement-water-binder mixture is combined and blended with the pulverizing/mixing machinery Compaction The mixture is compacted to the required density of at least 96% of standard Proctor density (ASTM D558) The compaction is performed with a Hamn padfoot vibrating roller, following by a smooth-wheeled vibratory rollers A pneumatic-tired roller is follow to finish the surface The field density and moisture are monitored for quality control purposes Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam Curing The surface is kept moist by periodically applying water to the surface, to make sure it does not become dry This is done continuously through the curing period in seven days until the base can support traffic without deforming The application of the prime coat should occur as soon as possible to ensure that moisture is sealed inside the base Pavement Surface The new pavement surface consisting of one layer of hot-mix asphalt, cm thick is constructed to complete the recycling process Field Test after Full Depth Reclamation After completion of FDR process, elastic modulus measured by FWD and Benkenmal beam has been carried out to check the result and compare with the one measured before FDR and the requirements in the current Vietnamese Design Regulations Table No.4: Elastic Modulus by Benkelman beam on the top of pavement before and after FDR No Chainage Direction Hai Phong - Ha Noi Km 77+900-:- Km 78 + 100 – Lane Km 77+900-:- Km 78 + 100 – Lane Km 77+900-:- Km 78 + 100 – Lane Direction Hai Phong - Ha Noi Km 77+900-:- Km 78 + 100 – Lane Km 77+900-:- Km 78 + 100 – Lane Km 77+900-:- Km 78 + 100 – Lane Required Elastic Modulus after 30 days Ebenkelman Elastic Modulus before FDR, Edh (MPa) Days after completion of FDR Elastic Modulus after FDR (Mpa) 123 120 127 11 11 11 210 221 173 120 131 121 18 18 18 164 175 175 130 MPa Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam Table No.5: Summary of FWD measurement in the FDR in National Highway No.5 No Location of FWD measurement Traffic lane Km 78 + 100 – Km 79 + 100 Km 78 + 100 – Km 79 + 100 Km 78 + 100 – Km 79 +100 Cars Trucks Ave Ep, Mpa Ave Mr , Mpa 313.1 346.9 380.0 66.8 65.3 66.1 Structural Number SN 4.48 4.23 4.36 Required SN after 30 days 3,87 FWD testing will be carried out on an annual basis in this section as a means of monitoring the longterm pavement performance of the pavement in this first large scale constructed FDR in Vietnam Existing data show that the pavement in FDR section met all requirement of current specifications Conclusions Pavement recycling technology is new to Vietnam but it will be a very successful solution for road maintenance where problems with both base and surface exist The recycler mills both asphalt and sub-base to the depth of 30 cm max, mixes with binding agents in its mix chamber (foamed bitumen or bitumen emulsion) and lays the finished base back down in a single pass Speeds of up to 6m/min and a working width of 2.4m mean fast renovation of roads Hardening of the base takes from hours allowing traffic to flow immediately, prior to laying the final asphalt layer Full-Depth Reclamation (FDR) is a popular, economically effective and high technology which has been used in many countries throughout the world Advantages of this technology are quick construction time, costly saving, unnecessariness to raise the pavement too highly, environmentally friendly and low transportation costs However, it requires high techniques, expensive specialized equipments The use of pavement recycling technology will help to solve the problems about costs, time and minimize the naturally environmental impact The cost for rehabilitation of pavement by using FDR in the National Highway No.5 is 15% less than by using the conventional method The materials for pavement construction in Vietnam are not widespread throughout Vietnam, quarries are mainly distributed at the Northern mountainous and Central regions, so exploiting conditions are very difficult, there are not many qualified, transportation distance is long and the costs are high As natural resources are limited, the use of the existing materials is a cost and time saving solution, which helps to minimize naturally environmental impact Full-Depth Reclamation (FDR) has met the above mentioned requirements With initial success of pavement recycling technology on the National Highway No.5 and legal corridors on Specifications and Guidelines which are set up at the Ministry level, and monitoring valuation to be made in the coming time on the above-mentioned sections of road, it is hoped that this technology will be more widely applied in pavement maintenance and rehabilitation projects for Vietnam road network, especially urban roads in big cities because of its advantages such as unnecessariness of raising the pavement elevation in constrained area, minimum of natural resources waste Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang / 10 Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam REFERENCES Second Highway Rehabilitation Project, National Highway No.1 from Dong Ha to Quang Ngai - Vietnam Pavement Report - Part 2: Pavement Recycling, prepared by Hyder Consulting Ltd - 2002 Applying of the Cold In-place Recycling Technology Using Asphalt Engineering Emulsion for Base and Surface Course of Pavement in Vietnam - Doan Minh Tam, Richard Kisner and Pham Chat International Workshop: Transport Infrastructure for Sustainable Development in Vietnam TISDV-2013 Developing Standards and Specifications for Full Depth Pavement Reclamation - FINAL REPORT May 2012 by Quality Engineering Solutions, Inc Commonwealth Of Pennsylvania Department Of Transportation Mai Triệ u Quang – Công ty Cổ phầ n Tư vấ n ĐTXD ECC Trang 10 / 10 .. .Công nghệ tái chế mặ t đư ng bê tông nhự a Việ t Nam The Ministry of Transport of Vietnam recently has conducted trial sections of pavement cold in place recycling in highways, as... support of Vietnam Ministry of Transport Vietnam Ministry of Transport has approved the outline and directed the assessment of the testing result since July 2010 After 18 months of monitoring, the... Later on in March 2011, Vietnam Ministry of Transport has organized another trial section for the Full Depth Reclamation by using Engineering Emulsion in National Highway No.1A in Long An province