Pavement ruting problem in viet nam

Rutting is classified into 3 types: Rutting on asphalt concrete AC surface, rutting in subgrade of the pavement structure including road foundation layers and embankment and rutting in b

CÁC GI Ả I PHÁP KI Ể M SOÁT CH Ấ T

Rutting phenomenon, an analysis of incidents in the East-West Highway

Project - Causes and remedies

Mai Triệu Quang

Deputy Secretary General of Vietnam Soil Mechanics & Geotechnical Engineering

Associate member of the Institute of Science and Technology in Southeast Asia

General Director of BK ECC JSC (Da Nang)

Co Project Director of Supervision Consultant for Deo Ca Pass Tunnel - Consulting Consortium of Apave-Dohwa-Tedisouth

Rutting status on roads and transport works (TW) has recently become very popular with very serious damages According to the report of MOT at the workshop of "Progress and quality of transport works" organized by Transport Newspapers on 15 th of Novermber, rutting phenomenon occurs on almost of arterials which have big traffic flows such as National Highway no.1, National Highway no.5, the East – West Highway, the Belt Road no.2 in Hanoi This phenomenon has been also occuring

on the surface of the approach road and the begining point of Thanh Tri bridge, even if the structures have been re-designed and re-constructed carefully, using innovative materials

According to statistics from earlier this year, on National Highway no.1, there are 70km over totally 620km on the section from Thanh Hoa to Hue and 90km out of 953km on the section from Da Nang to Khanh Hoa encountering rutting status On some routes over passes, the ruts mark a difference of 10 - 15cm with respect to the road surface According to statistics of Directorate for Roads of Vietnam, 13-15% of these route sections were constructed 10 years ago, and the settlement appeared after they had been put into use for 6 years The time of settlement is most intense on fierce hot weather days This article provides some analysises of the causes and proposed remedies

A Mechanisms causing rutting on asphalt concrete pavement

Rutting is a form of pavement damage on highways popular in the world as well as in Vietnam in recent years This is a depression in wheelpaths on heavy truck running lanes Generally, the routes loading heavy trucks will encounter rutting when the number of turns of heavy vehicles running through the routes themselves reaches a certain number Around the world, particularly in the states of the United States, there have been a lot of researchs on this phenomenon Therefore, in developed countries, the rutting experiments are included in the design process of the asphalt concrete mixture In Vietnam, rutting experiments have also been included in the process for Polymer asphalt concrete 22 TCN319-04 or in the latest Standard TCVN 8819:2011 for asphalt concrete

Along with the development of economy, the demand for road transport is constantly increasing To meet this demand, a large number of tug-lorries are needed to pull into traffic As a result, the number

of axles and axle load is far greater than initially anticipated

This is one of the causes damaging rapidly structures of road surfaces and the most common are the extrusion and rutting phenomena occurring at intersections and along the road respectively Besides, it should be taken into account the environmental factors of which the most typical in the tropics as our country is the temperature factor Temperature plays a big part in accelerating the process of subsidence of asphalt concrete road surface For viscoelastic materials, such as asphalt, the susceptibility to heat is always a mechanical & physical character which needs to be paid attention to when put the material into use

Rutting is classified into 3 types: Rutting on asphalt concrete (AC) surface, rutting in subgrade of the pavement structure (including road foundation layers and embankment) and rutting in both AC and subgrade

Rutting type 1 Rutting type 2 Rutting type 3 The most common form is rutting on asphalt concrete surface The researchers of asphalt concrete have found three main mechanisms causing rutting:

Local rutting status found on the East-West Highway Project - At the intersection to Cat Lai port

Mechanism 1: Rutting due to shear strain occurs when the load placed on AC layer is bigger than its

bearing capacity In this case, AC layer will not stable then the shearings will occur The AC layer just below the wheels will be uplifted along the edges of the ruts which make the pavement sunken and extruded as the picture above

Mechanism 2: Rutting due to vertical creep deformation This mechanism occurs when the

temperature of AC layer increases and loading duration increases As the temperature increases, the viscosity, stiffness of bitumen will be reduced and rigidity of AC is also reduced correspondingly As the duration increases, the deformation will increase due to accumulated time Creep deformation which is not fully recovered when unloading will cause rutting These explains why rutting phenonmenon has occurred at the intersection positions of heavy vehicles roads, steeps, curves where traffic speed is slow, and often occur in hot season

Mechanism 3: Rutting due to vertically post compaction This mechanism occurs after finishing

compaction but the density of AC not yet achieved The amount of voids in aggregate is high, so under the condition of heavy load combined with high temperature, the aggregate will be rearranged This process helps increase the density that means the volume will be reduced Consequently, AC layer will subside in the wheelpath position This phenomenon will cause rather small ruts

1 Designed pavement structure of the East-West Highway Project

5cm of AC 12.5

7cm of AC 19

15 cm of black macadam (aggregate treated with asphalt)

17cm of base course

30cm of subbase course

2 History of damage

- The road was opened to traffic on August 15, 2010

- After two months of operation, rutting phenomenon was observed near the intersection of Luong Dinh Cua, especially in the eastern lane just before the traffic signal pole, toward Hanoi Highway (mainly on the left - turn waiting lane to Cat Lai port)

The outline of serious ruts on the left- turn waiting lane to Cat Lai port -A short time later, a similar phenomenon occured in the opposite lane in the West just before the traffic signal pole, toward the Provincial Road 25B

- Rutting also appeared on the approach road in the North of Khanh Hoi Bridge, before the Ham Nghi intersection and some other positions

3 Assessment works carried out

After the incident, there have been numerous articles and many experts voicing their conjecture about the causes of damage The parties involved in the project have conducted investigations to find out the causes of rutting, including:

+ Coring the pavement to test the thickness of pavement layers

+ Measuring to track the development of rut depth over time

+ Sampling for visual inspection and testing components of gradation, asphalt content, porosity of asphalt concrete, etc

+ Reviewing Marshall experiments carried out in the design and construction stages

The experiments show that the quality of AC in these sections are not different from the quality of AC

in the neighboring undamaged sections (which are paved on the same day, by the same Contractor and Supervision Consultant, and bear the same traffic flow), although there are some unmet indexes Black macadam layer is slightly warped but the subbase is not damaged

+Placing the automatic weighing system to check the actual axle load of vehicles on the route

The survey results of flow and vehicle axle load by automatic weight show a huge number of overload heavy vehicle: heavy vehicles with maximum axle load (28.4 tons) accounted for over 40% of vehicles occupy the traffic flow

Contractor and Supervision Consultant (both Japanese) have had the same voice to the Client that the cause of damage is the plastic deformation of AC layer due to overloaded vehicles and special bearing conditions at positions where the heavy vehicles change their speeds to stop waiting for traffic signals The Supervision Consultant OC has commented that with overloading conditions as measured, the designed asphalt concrete pavement for these sections will not be able to withstand and suggested using rigid pavement (concrete cement pavement)

Contractors and Consultants then agreed to cut and repair damaged sections and conducted trials for 6 sections with new AC adopting a mixing formula of a Vietnamese prestige organisation in HCM city

Section A1: asphalt concrete 19 for subbase, asphalt concrete 12.5 using the formula 2 for base, according to the Project Design

Section A2: asphalt concrete 19 for subbase, asphalt concrete 12.5 using the formula 2 for base, according to the Project Design

Section A3: asphalt concrete 25 for subbase, asphalt concrete 15 for base, in accordance with Standard 22 TCN 249-98

Section A4: asphalt concrete 25 for subbase (22 TCN 249-98), Polymer asphalt concrete 19 for base, according

to 22TCN 356-06

Section A5: asphalt concrete 25 for subbase (22 TCN 249-98), normal asphalt concrete 20 for base

(249-98 TCN 22)

Section A4: asphalt concrete 25 for subbase (22 TCN 249-98), normal asphalt concrete 20 for base, formula 2 (22 TCN 249-98)

The trial sections are strictly mornitored by the Supervision Consultant, Client and an Independent Third Party mentioned-above The above sections were paved on December 12, 2012, ie nearly a year ago

After 100 days opening these trial sections to the traffic, rutting phenomenon re-occured even on the sections using polymer asphalt concrete which is very expensive, and the ruts are greater than they are

on the sections using normal asphalt concrete

The picture of the left-turn waiting lane to Cat Lai port taken at site on Novermber, 2013

The Supervision Consultant of Project (Oriental Consultant - Japanese) then had a letter sent to the Client reaffirming that only cement concrete pavement can bear the current loading conditions at the intersections and suggested not to test with flexible pavement, which will waste time & money and cause damages to society because the vehicles must travel in uncomfortable conditions

The final conclusion of the authorities at this time (December 2013) was that reinforced cement concrete pavement with 43cm thick slab will be applied for these sections at the intersection with Luong Dinh Cua street

The outline of sections to be recplaced with cement concrete surface of 43cm thickness

C Conclusions on causes of damages occurring at some intersections of heavy vehicle routes

and proposed remedies

1 Special locations of serious damaged position: Located on the sections where the vehicles

change their speeds (reduce speed and stop at the red light then start running when the green light turns on) Although traffic flow was the same and the whole section of the road was paved by one contractor on the same working day, but damages first occured on the sections where the vehicles run slowly and change their speeds Under these conditions, shear forces from the wheel load occuring in the asphalt concrete layer is much larger than on other normal sections, which cause plastic deformation in the asphalt layer and cause rutting sooner than the other segments This actually happened a long time in the world and more than 10 years ago in the highways in Vietnam But at that time, traffic flow and vehicle load were small, rutting did not grow as fast as today With a huge amount of overloaded vehicles which not be controlled, the damages have grown very fast, bringing a serious concern to the society

In Da Nang City, on Cach Mang Thang Tam arterial (NH 14B to the Tien Sa Port 14B) there is

an signalized intersection (intersected with Ong Ich Duong street) which has been also damaged and repaired for many times with asphalt concrete, but it did not last long Finally, the authorities had to apply cement concrete pavement then it has lasted so far The roundabout interchanges on the roads bearing heavy loads in Da Nang now has to be changed to concrete structures after the repeated failure of asphalt texture despite all sorts of improvements

AC pavement damaged in Nga Ba Hue intersection after 3 months of asphalt concrete

pavement Photo taken in August 2002

Cement concrete road surface at the

roundabout of CMT8-Nguyen Tri Phuong (the

arterial to Tien Sa port) - Da Nang City

16-12-2013

Cement concrete road surface at the roundabout of Ngo Quyen - Ho Xuan Huong (the arterial to Tien Sa port) - Da Nang City 16-12-2013

2 With the huge shear forces from vehicles’ load to AC layer at the positions in special operating

conditions as above, it can be said that the application of flexible pavement structure at signalized positions and roundabouts on the heavy vehicle roads is inappropriate and

rutting or extrusion of road surfaces ahead of time calculated will definitely happen, fast or

slow, depending on traffic volume and the actual load Thus, under the conditions that we still not able to take measures to control vehicle load as effective as it is in developing countries, it needs to have a special pavement structure from the design stage or reinforce pavement structure at these posistions (this had happened previously at the ramp to the tollgate on the National Highway and the pavement has almost been replaced with cement concrete pavement) Two solutions can be considered:

- Cement Concrete Pavement

Damage at the intersection of CMT8-Luong

Dinh Cua-Da Nang City (Direction from

NH14B to the Tien Sa Port) - 16-12-2013

Cement concrete pavement at the intersection

of CMT8-Ong Ich Duong street-Danang City (Direction from NH14B to the Tien Sa Port) - 16-12-2013

Cement concrete pavement at the roundabout

of CMT8-Nguyen Tri Phuong (the arterial to

Tien Sa port) - Da Nang City 16-12-2013

Cement concrete pavement at the roundabout

of Ngo Quyen - Ho Xuan Huong (The arterial to Tien Sa port) - Da Nang City 16-12-2013

- Advanced feature brick pavement on aggregate layer reinforced with cement

Damage of AC surface at the intersection of

Nga Ba Hue - Da Nang City (On the Ton

Duc Thang Street)

Application of advanced featured brick pavement; - Apply for continuous damaged sections on Ton Duc Thang Street - Da Nang City

3 For the sections under adverse bearing conditions including roads over passes, slopes,

especially the way up to slopes, curves on the heavy traffic routes (the national highways, the highways, the roads leading to the industrial zones, etc., may still be considered to apply

flexible pavement structure, but the asphalt components should be designed for high resistance to rutting, specifically by adopting the following measures:

- For the asphalt layer, it can increase sliding resistance by:

• Using bigger aggregate and larger macadam content in AC mixture Specifically, do not use AC 12.5 but AC type 19 or 25 for the base of roads bearing many heavy vehicles

AC 37.5 is recommended for the subbase

• Using innovative polymer asphalt instead of conventional asphalt

Among the causes of rutting, the asphalt is the first element needs to be improved, especially with a tropical climatic condition and big traffic flow as in our country

The conventional 60/70 asphalt has a low softening temperature (the best asphalt currently in our country is around over 48oC) and the thermal stability is low (PI index is negative) Besides, the conventional petroleum asphalt virtually has no elasticity which easily leads to irreversible deformation under the effect

of high load and high repetition Thus using Polymer asphalt in sections under special bearing conditions as mentioned is a solution need to be considered

The article of Polymer asphalt concrete on Deo Ca and Deo Ro Tuong The article of Multiphalte asphalt concrete for Hai Van Pass