Summary of Doctoral thesis: Research on components, mechanical properties and the applicability of epoxybitumen binder for asphalt mixtures in Vietnam

For the purpose of researching on the applicability of BTNE in the field of transport Works, the thesis focuses on the component, mechanical properties, technical standards and the workability of BTNE.

UNIVERSITY OF TRANSPORT AND COMMUNICATIONS

TRAN THI CAM HA

RESEARCH ON COMPONENTS, MECHANICAL PROPERTIES AND THE APPLICABILITY OF EPOXY- BITUMEN BINDER FOR ASPHALT MIXTURES IN

VIETNAM

Field of study: Transport engineering

Code : 9580205

Speciality: Highway and urban road engineering

SUMMARY OF DOCTORAL THESIS

HANOI – 2020

University of transport and communications

Supervisors:

1 AssocProf.Dr Tran Thi Kim Dang

University of Transport and Communications

2 Prof.Dr Bui Xuan Cay

University of Transport and Communications

Reviewer 1: Prof.Dr Nguyen Xuan Truc

Reviewer 2: Prof.Dr Nguyen Thuc Tuyen

Reviewer 3: Prof.Dr Pham Cao Thang

The thesis will be defended before Doctoral-Level Evaluation Council at University of Transport and Communications

at …… on …….th …… 2020

The thesis can be read at:

1 National Library of Vietnam

2 Library of University of Transport and Communications

1 Tran Thi Cam Ha, Tran Thi Kim Dang (2017), “A study on several

mechanical properties of epoxy bitumen”, Transport Journal No 5/2017

2 Tran Thi Cam Ha, Bui Xuan Cay (2018), “Experimental research on static

elastic modulus and flexural strength of epoxy asphalt concrete”, Transport

Journal No 5/2018

3 Tran Thi Cam Ha (2018), “Experimental research ondynamic shear

modulus of bitumen- epoxy”, Transport Journal No 11/2018

4 Tran Thi Cam Ha, Nguyen Quang Tuan, Tran Anh Tuan, Hoang Viet Hai (2018), “Shear behavior of epoxy asphalt concrete coating and epoxy

adhesive on steel deck”, Transport and Communication Science Journal No

66

INTRODUCTION

I Research background

In fact, the use of asphalt pavements on main national road in Vietnam showed that there was a lot of premature deterioration of asphalt pavements such as rutting in National road No 5, National road No.1, East – West boulevard, the access road to Thanh Tri bridge, Ring road No.3; the deterioration of the overlay on Thanglong bridge; deep rutting on the road linked to Cat Lai port This deterioration greatly affected the socio-economic development, so the government had to spend a lot of money to repair these deterioration Moreover, this also affects the physical and mental well -being of road users

In many countries in the world such as UK, USA, Japan, Ukraine , the research and the use of modified asphalt mixtures with epoxy-bitumen binder

as the surface layer for heavy roads and steel bridges have achieved good results These modified asphalt surface significantly reduced the deterioration compared with asphalt pavements using conventional bituminous binders Vietnam has also had a project using epoxy asphalt concrete (BTNE) as the surface of Thuan Phuoc bridge – Danang city Unfortunately this first application was not successful This epoxy asphalt concrete surface on Thuan Phuoc bridge has therefore been replaced almost entirely by the modified asphalt mixture (BTNP) using polymer modified bitumen The researches about this material before applying for Thuan Phuoc bridge were also quite limited

Currently, in Vietnam, epoxy can be supplied by domestic and foreign suppliers, but there has not been any study about the applicability of epoxy -bitumen binder for modified asphalt mixtures

Therefore, the thesis "Research on components, mechenical properties and the

applicability of epoxy-bitumen binder for asphalt mixtures in Vietnam ” is

scientific and practical

II Research o bjective

For the purpose of researching on the applicability of BTNE in the field of transport Works, the thesis focuses on the component, mechanical properties, technical standards and the workability of BTNE

III Reseach content s

The thesis contents include:

1 Overview study of BE and BTNE;

2 Empirical research to determine the properties of BE materials, evaluate the applicability of BE binders for BTNE mixtures using in road pavement structures; analysis and selection of epoxy content for BE binder for BTNE mixtures;

3 Empirical research in the laboratory to determine the physical and mechanical properties of BTNE as a basis for assessing the applicability and scope of use of BTNE materials;

4 Proposing some typical pavement structures using BTNE material as surface layers

IV Scientific and practical contribution

 Scientific contribution: The thesis studies mechanical properties of BE

binder and BTNE mixture, analyzes the advantages and disadvantages and the scope of application of this new material in Vietnam conditions Systematizing testing standards for quality assessment of BE binder and BTNE mixture

 Practical contribution: Based on experimental research results of BTNE

mixture compared with other types of asphalt mixtures, thereby proposing the method of designing mixed components, proposing experiment al standards for quality assessment of BTNE mixture; From mechanical properties of BTNE, the thesis proposes some road pavement structures using BTNE surface course in Vietnam

CHAPTER 1

LITERATURE REVIEW

Chapter 1 provides an overview of the use of BE and BTNE as the basis for the selection of epoxy for empirical studies in the following chapters

1.1 Epoxy bitumen and epoxy asphalt mixture

1.1.1 Overview of additives to improve the performance of bitumen

Main components of modified

bitumen are bitumen and

additives The additives using for

bitumen includes 3 basic groups:

non-polymer, polymer and the

chemical additive (create

chemical reactions when

blending) The types of polymer

additives is shown in Table 1-1

1.1.2 Epoxy resin

Epoxy resins are a class of

thermoset materials – transformed into solid form under the action of heat or a chemical reaction that is then not melted or dissolved again Epoxy offer high strength, low shrinkage, excellent adhesion to various substrates, chemical and solvent resistance and low toxicity Epoxy resins are used as glues, coatings, packaging, molding materials and adhesives, etc

Fig 1-1 Basic chemical structure of epoxy group

An epoxy resin are made by mixing three basic components: basic resin (main resin), curatives, and the modifiers For a simple mixing formula, an epoxy resin only includes a single epoxy resin and curative Other formulas can include various epoxy resins, modifiers and a combination of curatives

1.1.2.1 Basic resin (main resin)

The term “epoxy resin” describes a broad class of

thermosetting polymers in which the primary cross

linking occurs through the reaction of an epoxy

group In general, an epoxy resin can be thought of

as a molecule containing a three-membered ring,

consisting of one oxygen atom and two carbon

atoms (Fig 1-1)

Two branches connected to two carbon atoms of the ring can be very diverse, thereby creating different types of epoxy resins

1.1.2.2 Epoxy Resin Curatives

Epoxy resins will react with a large number of chemical species called curatives or hardeners The most commonly used chemical classes of curatives are amines, amine derivatives, and anhydrides Cure times can range from seconds to days, even months to years at room temperature The materials have been separated into the general categories of room temperature cure, room - or elevated-temperature cure, elevated temperature cure, and miscellaneous curatives

1.1.3 Epoxy bitumen

Epoxy bitumen (BE) is a two-component (two-phase) chemical system in which a part is thermoset epoxy (continuous phase) mixed with ordinary bitumen (dispersed phase) Bitumen is a heat sensitive adhesive, which becomes flexible when heated and hardens when cooled Epox y is a thermoset material that becomes permanently hard after curing Epoxy bitumen is a thermosetting material that has both the rigidity of epoxy and the flexibility of bitumen The percentage of epoxy in BE usually ranges from 15% to 50% by weight

1.2 Studies of epoxy-bitumen (BE) and epoxy asphalt mixture in the world

A lot of studies about BE and BTNE have been done around the world For example, the BE pilot project with the participation of 7 countries including Denmark, France, Germany, New Zealand, Ukraine, United Kingdom and USA was implemented from 2006 to 2008; the research project of BTNR using local materials in China in 2002; Studies about BE and BTNE in Japan in the late 70s of the 20th century These studies have shown that BTNE material has high fatigue resistance (10 times higher than conventional asphalt concrete BTN), high rutting resistance (almost no rutting in wheel track tests), good tensile strength and good anti-skid resistance

1.3 Some applications of BTNE all over the world

BTNE mixture can be used as an overlay on the bridge deck, surface layer of long life pavements, airport runway pavements, roads on port area, asphalt surface layer for inproving pavement texture

1.4 Some researches and applications in Vietnam

Until now, Vietnam also has the project “Thuan Phuoc Bridge - Da Nang city” which used BE and BTNE The overlay on the steel plate deck is a 41mm thick BTNE layer The water-proof layer use a type of BE binder which is also an adhesive layer between the steel plate surface and the above BTNE layer BE used in the project is Epoxy Asphalt Id of Chemco System (USA)

Thuan Phuoc Bridge was opened to traffic on July 14, 2009 By the hot season

of 2013, the asphalt overlay on the bridge deck was seriously damaged on a large scale It greatly affected traffic on the bridge The observation results during the 4 years showed that the worst status of the asphalt surface layer occured after each hot period in June and July every year, so it can be confirmed that high temperature was a main factor causing damage to the overlay The asphalt layer on Thuan Phuoc steel deck surface suffered from disadvantages relating to working temperature due to heat accumulation effect

in the 655m long closed steel

box beam without ventilation

system In summer,

temperature inside the steel

box beam can be up to

70-800C This makes the overlay

and the adhesive layer always

worked at a disadvantage

In 2013, Thuan Phuoc bridge

was conducted to repair the

overlay: Digging away the old

BTNE layer After that a new overlay included 2 asphalt layers of BTNP PMB3 The thickness of total 2 layers is 800 mm Adhesive layer between BTNP layer and steel plate with two-component epoxy resin of Chemco System (USA) was still used Adhesion strength was enhanced by welding steel ribs 80cm apart on steel deck Between 2 layers of BTNP was reinforced

by fiberglass mesh layer with tensile strength of 100 kN

After repaired, the overlay was still damaged after 5 years of the operation and

is being continued to be repaired

1.5 Problem statement

The thesis focuses on solving the following issues:

- Researching on componets of epoxy-bitumen and modified asphalt mixtures using epoxy-bitumen in order to suit with climatic conditions and construction technology level in Vietnam;

Hình 1-21 Các hư hỏng do hiện tượng xô dồn bề mặt, mất sự liên kết với bản thép sau 4 năm khai thác

Fig 1-21 Damages on Thuan Phuoc bridge surface after 4 years

- Initially proposing technical properties of epoxy-bitumen (with particular components) and BTNE mixture using BE binder for road pavement’s surface layers

BE binder compared with some bitumens used commonly in Vietnam

2.1 Determining components and method of manufacturing BE binder

2.1.1 Selection of epoxy resin

Epoxy resin used in this research is

provided by TAIYU KENSETSU,

JAPAN This type of epoxy is

widely used in Japan, China and

even in Korea Epoxy resin

includes two main components:

basic resin and curatives

(hardener) The technical

characteristics of each component

and mixing ratios shown in Table

2.1.2.1 Content of epoxy in epoxy - bitumen

The technical properties of BE binder vary with different contents of epoxy in binders In this study, the properties of BE binders were be tested with epoxy contents of 15%, 20%, 30%, 35%, 40%, 50% by weight They were abbreviated respectively: BE15, BE20, BE30, BE35, BE40, BE50

2.1.2.1 Steps of mixing epoxy-bitumen

- Step 1: Producing epoxy resin: Blending main resin with curatives in proportion

of 56:44 during one minute in order to produce epoxy resin for the research

- Step 2: Producing BE binder: Mixing bitumen 60/70 with epoxy resin made

from step 1 in a paricular proportion during 4 minutes BE binder obtained from this process will be poured into a mold and dried at 1500C for 1 hour

- Step 3: Maintaining BE sample (As shown in section 2.1.4)

2.1.3 Setting out a time interval and temperature level of epoxy -bitumen sample curing before testing

In this study, BE binder was cured at two different temperature levels: 600C (corresponding to the temperature of pavement surfaces in very hot summer areas and on steel plate bridges); 250C (corresponding to average temperature

in Vietnam) For the cured samples at room temperature of 250C, tests for them were carried out at different curing time intervals: 2h, 4h, 24h, 48h, 72h, 96h and 168h., tests for them was conducted after curing during 96h for cured sample at 600C

2.2 Selecting technical specifications and testing methods for BE binders

In Vietnam, TCVN 7493: 2005 "Bitumen-technical requirements" are used to assess the quality of bitumens All 7 technical characteristics to evaluate bitumens according to this specification were applied to BE binders In addition, viscosity and dynamic shear modulus (DSR) of BE binders were al so performed in this study Testing methods comply with current sta ndards Using Minitab software to design general experiments T he number of common repetitions is 3 ANOVA analysis and post-editing analysis used to detect differences according to Tuckey standard Carrying out the evaluation to remove outliers according to ASTM E178; evaluating the precision according

to ASTM C670 with the acceptable limits specified by the respective standard tests

Penetration tested in accordance with TCVN 7495: 2005 The total number of experimental sample groups was 49

By precision analysis in accordance with ASTM D5 -2013, it could be confirmed that penetration test results me t the precision requirements

Fig 2-1 Relationship between

penetration and epoxy content and

different curing conditions

Fig 2-2 Penetration values of epoxy bitumen

- Penetration (Pe) decreases with increasing epoxy content In the case of epoxy content less than 30%, the reduction rate of Pe is about 6,5 ÷ 15 (1/10mm) corresponding to increasing by 15% epox The average decrease is 3,64 (1/10mm)/5% increase of epoxy content) The rate of reduction in Pe is significant (average reduction of 6.7 (1/10mm)/5%) if the epoxy content increases from 30% to 35% In the case of epoxy content greater than 35%, the rate of reduction returned to the original lev el with an average of 3,64 (1/10mm)/5% [see fig 2-5 and fig 2-6]

- PE of BE binders in all types of content decreases with increasing cur ing time, but for the epoxy content below 35% this reduction is negligible and almost stable at 96h; At 35%, 40% and 50%, this reduction is obvious with increasing curing time (see fig 2-6)

- PE of samples cured at 600C for 96h were lower than those of samples cured

at 250C for 168h For samples with 50% epoxy content and curing at 600C for 96h, Pe was lower than 20 (1/10mm) (see fig 2-5)

The reduction of PE or the increased hardness of the BE binder compared with conventional bitumen is due to epoxy resin as a thermoset component In BE binders, epoxy is a three-dimensional continuous phase that is hard and becomes harder when heated As epoxy content increases, the mixtures with more hard components reduce their Pe, while BE bin der cured at higher temperature makes it harden faster Long curing time makes BE continue to complete dispersion phase of epoxy and increase the hardness of BE binder Setting up the second regression equation showing the relationship between Pe and variables (BE and T) in research limit as follows :

Pe = 79,62 – 1,0153 BE – 0,06700 T + 0,00990 BE*BE + 0,000283 T*T – 0,003223 BE*T (2-1)

The equation ensures reliability with the adjustment coefficient R2đc = 97,68%, p-value of all parameters is less than 0,05

2.4 Softening point (ring-and-ball apparatus)

This test was carried out according to TCVN 7497:2005 - ring-and-ball apparatus Total number of sample groups was 49

Precision analysis of softening point test results according to ASTM D36 -2014 showed that their precision was satisfactory

Fig 2-9 Relationship between softening

point and epoxy content and different curing

10 ÷ 600C, corresponding to an average of approximately 70C for every 5% increase in epoxy content This is shown in the slope of the straight lines in the graph of the relationship between SP and epoxy content which increases significantly at 30% epoxy content (See Fig 2-10 and Fig 2-9)

As sample curing time at room temperature increased, SP of all epoxy bitumen with different epoxy contents increased However, when the epoxy content was below 35%, the increase was negligible and almost no longer increased after 96 hours With epoxy contents of 35%, 40% and 50%, the increase is noticeable as sample curing time increases Of the three types of

-BE (with expoy contents as above), the growth rate of 50% epoxy sample is the largest, 35% epoxy sample is the smallest (see Fig 2-10)

- SP of curing samples at 60°C for 96 hours is higher than that of curing samples at 250C for 168 hours With 50% epoxy content and curing at 600C for 96h, BE does not soften even at 120oC (see Fig 2-9)

- Samples are cured at 250C and 168h after mixing, SP of BE35 is equivalent

to PMB-II, of BE40 is equivalent to PMB -III and of BE50 is up to 1170C The theoretical basis for change of SP is similar to that for Pe Thermoset epoxy component included in BE binder increases temperature resistance, maintains hardness of BE in high temperature A higher epoxy content expands thermosetting continuous phase which increases the stiffness of BE rapidly under high temperature As with Pe, curing samples at high temperatures rapidly increases the hardness of BE Long service time has the effect of developing a dispersed thermoset phase, thereby increasing SP of BE binder The longer curing time is, the more dispersed thermoset phase develops, thereby increasing SP of BE binder

Setting up the second regression equation showing the correlation between SP and BE and T variables within the study limits as follows :

The correlation equation ensures the reliability with the adjusted determination

R2đc = 94,61% and the p-value of the parameters are less than 0,05

2.5 Proposal for selection of BE components

From the test results for penetration and softening point of BE binders, the following conclusions are drawn:

- Epoxy content ≤ 30%: The rate of reduction of Pe and increase of SP is not significant; PE of BE binders with all tested curing conditions ranges from 40-65 (1/10mm), only equivalent to PMB -II and PMB-III; when expoy content is lower than 30%, SP of BE binders in all curing conditions is lower than 600C which is lower than PMB-I; With an epoxy content of 30%, if cured at room temperature (250C), SP only reaches 60,250C with curing samples for 168h and if cured at 600C for 96h, SP reaches 61,550C, which is equivalent to PMB I

- With epoxy content of 35% or more, Pe and SP of BE are superior to those

of bitumen 60/70 With 50% epoxy content, these two properties are still superior to those of PMB-III Details are as follows:

+ With BE35: if curing samples at 250C for 168h or curing at 600C for 96h,

SP of them is equivalent to PMB-II (higher than 700C);

+ With BE4: if cured at 250C from 72h to 96h, SP is equivalent to that of PMB-II (higher than 700C); if curing samples for 168h or curing at 600C for 96h, SP is equivalent to that of PMB -III (higher than 800C);

+ With BE50: if cured at 250C for 96h, its SP is equivalent to PMB III; Especially, if curing time reaches 168h or curing at 600C for 96h, its SP can be up to 1200C - superior to PMB-III

+ Pe is lower than that of PMB-III (below 40 1/10mm) when cured above 96h at 250C with BE35 and BE40, over 72h at 250C with BE50

From the above conclusions, choosing 02 types of BE binders (BE35 and BE50) corresponding to 35% and 50% epoxy by total weight of BE mixing to conduct further studies in the thesis

2.6 Experiment on basic properties of

BE binder

Experimental results of other basic

properties of BE35 and BE50

according to TCVN 7493:2005 in

table 2-13 show that properties of

both tested BE35 and BE50 meet the

requirements for 60/70 bitumen

2.7 Dynamic shear modulus of BE binder

- DSR test results of original BE15, BE35 and BE50 binders are equivalent to PG70, PG76 and PG82

- PG of BE35 and of BE50 after RTFO remain the same as the original BE resin, respectively PG76 and PG82

- PG of BE15 after the RTFO decreases by one level compared to PG of corresponding original BE, from PG70 to PG64, which is equivalent to PG of ordinary bitumen 60/70 (BE0)

2.8 Conclusion for chapter 2

 BE binders using epoxy supplied by TAIYU, Japan meet the requirements for bitumen used in construction according to TCVN 7493:2005 With an epoxy content of 35% or more, SP of BE binder is significantly higher than that of conventional bitumen With epoxy content up to 50%, this property is also superior to that of PMB III It is recommended to use BE type with a minimum epoxy content of 35% by weight of BE

 SP and Pe of BE binders are affected by curing time and temperature The higher the epoxy content is, the greater the influence of these factors on SP and Pe

 At an air temperature of 250C, after mixing for 4 hours, there is any significant difference between properties of BE binder and of bitumen 60/70, so the use of BE as a binder for asphalt mixtures will not meet difficulties in the process of blending in asphalt mixing plant and in construction

 The decline of Pe to approximately 20 -25 (1/10mm) during the use of pavements is a risk for cracking by hardening of bitumen Therefore, it is necessary to study the effect of increasing hardness of bitumen on crack resistance by fatigue testing for asphal t concrete using BE binder

 PG of BE15, BE35 and BE50 are based on |G*|/sin of original BE and after RTFO are PG64, PG76 and PG82 respectively

CHAPTER 3

EXPERIMENTAL RESEARCH ON MECHANICAL AND PHYSICAL

PROPERTIES OF BTNE USING BE BINDER

Chapter 3 focuses on the study of technical properties of BTNE to assess the quality of them, analyze pavement structure s with BTNE surface layers in Vietnam In addition to common mechanical properties (Marshall stability and flow, static elastic modulus, ), other properties (fatigue life, dynamic modulus ) of BTNE were also analyzed and evaluated

3.1 Mix design of BTNE mixtures and reference mixtures