Tóm tắt: Nghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt Nam

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT THUYLOI UNIVERSITY DINH HOANG QUAN RESEARCH ON CONCRETE USING ACTIVATED FLY ASH - BLAST FURNACE SLAG BINghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt NamNghiên cứu bê tông sử dụng chất kết dính kiềm hoạt hóa tro bay – xỉ lò cao làm việc trong điều kiện biển Việt Nam

MINISTRY OF EDUCATION

AND TRAINING

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

THUYLOI UNIVERSITY

DINH HOANG QUAN

RESEARCH ON CONCRETE USING ACTIVATED FLY ASH - BLAST FURNACE SLAG BINDERS FOR MARINE CONDITIONS IN VIETNAM

ALKALINE-Specialization: Hydraulic engineering

Code No: 9580202

ENGINEERING DOCTORAL THESIS SUMMARY

HANOI, 2024

This scientific work has been accomplished at: ThuyLoi University

Scientific supervisor 1: Assoc.Prof.Dr Nguyen Thanh Bang

Scientific supervisor 2: Assoc.Prof.Dr Nguyen Huu Hue

Review No.1: Assoc.Prof.Dr Nguyen Thanh Sang, University of Transport and Communications

Review No.2: Dr Tran Minh Duc, Vietnam Institute for Building Science and Technology

Review No.3: Assoc.Prof.Dr Hoang Pho Uyen, Hydraulic Construction Institute

This Doctoral Thesis will be defended at the meeting of the University Doctoral Committee at ThuyLoi University, 175 Tayson str., Dongda, Hanoi, Vietnam

At 8:30 a.m on February 11, 2025

This dissertation is available at: - The National Library

- The Library of ThuyLoi University

INTRODUCTION

1 Statement of the Problem

Climate change and environmental protection are urgent issues, especially in developing countries With a commitment to achieve net zero emissions by 2050, Vietnam faces a major challenge as greenhouse gas emissions increased from 150.9 million tons of CO2 in 2000 to 563.8 million tons in 2020 The cement industry accounts for 8.6% of the total national emissions and it is harmful to the environment during production Fly ash from thermal power plants and blast furnace slag from metallurgical plants are also increasing rapidly, threatening the environment if not treated effectively The use of alkaline binders activated from fly ash and blast furnace slag to partially replace traditional cement is of great significance, helping to reduce greenhouse gas emissions and make use of industrial waste materials With a long coastline affected by climate change, building sustainable coastal protection works is necessary Alkaline activated fly ash – blast furnace slag (AAFS) binder has the ability to resist erosion in marine environments but has not been widely applied due to lack of regulations, short setting time, and high cost Therefore, the author has chosen the dissertation title

“Research on Concrete Using Alkaline-Activated Fly Ash - Blast Furnace Slag Binders for Marine Conditions in Vietnam”

2 Aim of the Study

To design and manufacture AAFS concrete components that meet technical and cost requirements for applicability in construction projects in Vietnam, with a particular focus on structures in marine environments

3 Research Object and Scope

AAFS concrete produced from fly ash (FA) and ground-granulated blast-furnace slag (GGBFS), applied to construction projects, particularly those in marine environments, using locally available materials in Vietnam

5 Research Approach and Methodology

Figure 1 illustrates the research framework, approach, and methodology of this

thesis

Figure 1 Research framework of the thesis

6 Scientific and Practical Significance

- Scientific Significance: (1) Establishing the relationships between input factors and the physical and mechanical properties of AAFS concrete using mathematical and machine learning models; (2) Proposing a composition design method for AAFS concrete to achieve the required strength and workability, tailored to the available materials in Vietnam; (3) Identifying suitable activators and additives to extend the setting time of AAFS concrete, meeting practical construction time; (4) Evaluating the durability of this concrete in corrosive marine environments through experimental testing

- Practical Significance: (1) Evaluating the environmental benefits of AAFS concrete by recycling fly ash and blast furnace slag, contributing to greenhouse gas reduction; (2) Proposing a production method for AAFS concrete that optimizes economic and technical performance, demonstrated through successful application in a sea dike section, helping to introduce this innovative material to

the construction market

CHAPTER 1 OVERVIEW OF CONCRETE USING ACTIVATED FLY ASH AND BLAST FURNACE SLAG BINDERS 1.1 Overview of Alkali-Activated Binder

ALKALINE-1.1.1 Key Milestones in the Development of Alkali-Activated Binders

Research on Alkali-Activated Binders (AAB) began in the 1940s with Purdon

In 1967, Glukhovsky advanced this research by developing AAB from blast furnace slag, which he called “soil-cement”, later standardized as “Alkali-Activated Slag Cement” In 1978, Davidovits introduced an AAB made from metakaolin, coining the term “Geopolymer” In 2010, AAFS concrete saw its first practical application in construction in Australia

1.1.2 Classification of Alkali-Activated Binders

Based on the chemical composition of input materials: (1) Alkali-earth enriched

aluminosilicate materials (e.g., ground granulated blast furnace slag, Class C fly

ash); (2) Aluminosilicate materials (e.g., Class F fly ash, metakaolin) Based on the primary reaction products: (1) Blast furnace slag (Si + Ca) activated by a

mild alkaline solution, primarily producing C-S-H as the reaction product; (2) Fly ash and metakaolin (Si + Al) activated by a medium-to-strong alkaline solution, resulting in a product commonly referred to as “Geopolymer” with an

amorphous polymer structure Based on the form of activator and production technology: (1) Binder and activator solution are separate components, known

as two-part AAB; (2) Both binder and activator are in solid form and pre-mixed, requiring only water for use, known as one-part AAB

1.2 Scientific Basis for Combining Fly Ash and Ground Granulated Blast Furnace Slag to Create AAFS Binder

1.1.3 Reaction Mechanism of Alkali-Activated Fly Ash Binder

The reaction mechanism of alkali-activated fly ash binder begins when fly ash comes into contact with an alkaline solution, such as NaOH or KOH This process breaks the Si-O-Si and Al-O-Al bonds within the fly ash, releasing silicate and aluminate ions These ions then migrate and rearrange, forming an

amorphous polymer network known as a geopolymer, with a structure similar to that of zeolite This network subsequently hardens and gains strength over time

1.1.4 Reaction Mechanism of Alkali-Activated Slag Binder

The reaction mechanism of alkali-activated slag binder occurs when granulated blast-furnace slag is activated by an alkaline solution, allowing it to rapidly harden and gain high strength The primary reaction products are C-S-H, AFm, and hydrotalcite, with no formation of Ca(OH)2 or ettringite The C-S-H gel in this binder forms more quickly and has a plate-like structure, unlike the needle-like C-S-H gel found in Portland cement

ground-1.1.5 Scientific Basis for Combining Fly Ash and Ground-Granulated Blast

Furnace Slag to Produce AAFS Binder

The combination of fly ash and ground-granulated blast-furnace slag to produce alkali-activated binder is an effective solution Fly ash-based binders offer high strength but require heat curing, while slag-based binders can harden at room temperature but are prone to shrinkage This combination helps to overcome the limitations of each material, resulting in a durable binder that minimizes shrinkage and micro-cracking while developing strength under ambient temperature conditions

1.2 Overview of Research on AAFS Binders

1.2.1 Composition of AAFS Binder

The composition of AAFS binder includes fly ash, ground-granulated furnace slag, an activator, and water Overview research shows that increasing the slag content (%XLC) speeds up setting and enhances strength However, an excessively high %XLC may lead to shrinkage and cracking Liquid activators such as Na₂SiO₃ + NaOH yield higher strength than other types Parameters like

blast-%Na2O, indicating activator concentration, and the silica modulus Ms, representing the Na₂SiO₃/NaOH ratio, significantly impact the properties of AAFS binder However, the optimal ranges for these parameters remain broad,

so further studies are needed to determine their reasonable value range Additionally, AAFS binders activated by Na2SiO3 + NaOH or Na2SiO3 alone

have rapid setting times, reducing formwork removal time, making them suitable for precast components, particularly in coastal protection structures However, for conventional concrete structures, rapid setting poses a challenge for transportation and handling, requiring adjustments

1.2.2 Mix Design Methods for AAFS Concrete

Previous AAFS concrete mix design methods have limitations and are not suited to Vietnamese conditions, such as: not considering the specific gravity of the material; only applicable to Na2SiO3 with Ms=2.0 while Na2SiO3 in Vietnam has Ms ranging from 1.5 ÷ 2.7; replacing the R28~Water/Cement chart in the Portland cement concrete mix design standard with R28~Activator solution/Binder is inappropriate, as increasing Activator solution/Binder raises the Water/Binder ratio (reducing strength) while also increasing activator concentration (enhancing strength); not paying attention to the issue of reasonable cost (low-strength concrete is sometimes costlier than high-strength);

well-or the process is simple but fix impwell-ortant variables Thus, the use of machine learning for AAFS concrete mix design is gaining interest Several models have been developed to predict compressive strength and slump, yet limitations remain, including small sample sizes, lack of consideration for activator solution, water content, aggregate effects, and fly ash/slag ratios Therefore, developing a machine learning-based AAFS concrete mix design approach, considering key input material factors as outlined in this dissertation, is essential

1.2.3 Durability of AAFS Concrete in Marine Environments

The sulfate resistance of AAFS concrete is better than traditional Portland cement, even surpassing sulfate-resistant cement AAFS concrete is more resistant to MgSO4 than Na2SO4 environments The chloride resistance and rebar corrosion protection of AAFS concrete are still unclear as studies have shown that this material has good resistance to chloride penetration, while some studies have shown the opposite Research on its abrasion resistance remains limited Laboratory studies examining durability under single or combined attack of sulfate, chloride, and carbonate indicate that the optimal fly ash/slag ratio is

around 50/50 However, further research is needed to assess AAFS concrete's durability in real marine environments for more accurate evaluations

1.3 Characteristics of Vietnam’s Marine Environment and Degrading Agents

The seawater in Vietnam, similar to other oceans, typically contains about 3.5% dissolved salts with a pH around 8.2–8.3, which leads to significant corrosion of concrete and reinforced concrete, particularly in tidal and wave-impacted zones Researches indicate that concrete in marine environments can deteriorate due to physical, chemical, and biological effects, as well as reinforcement corrosion The lifespan of concrete structures in marine environments generally reaches only 10–50% of their designed service life, depending on environmental conditions, characteristics, and location of the structure Therefore, it is essential

to study durable concrete materials like AAFS concrete to improve longevity

Conclusion of Chapter 1

(1) Clarifying the scientific basis for choosing the combination of fly ash and ground-granulated ground blast furnace slag in the manufacture of AAFS binder; (2) Key input factors affecting AAFS binder properties include %XLC, %Na2O, and Ms However, the reasonable value ranges for these parameters remain unclear, necessitating further research to define these ranges;

(3) Current mix design methods for AAFS concrete, both globally and in Vietnam,

face some limitations and are not entirely suitable for local conditions Thus, developing a tailored mix design method for AAFS concrete in Vietnam is crucial;

(4) AAFS concrete activated with Na2SiO3 + NaOH or Na2SiO3 has a quick setting time, making it suitable for precast concrete or for coastal protective concrete repairs However, for conventional concrete structures, this rapid setting time needs adjustment to allow sufficient time for construction and transportation;

(5) AAFS concrete has the potential to replace Portland cement concrete in

marine-exposed concrete and reinforced concrete structures Nevertheless, further in-depth studies, especially in real marine environments, are needed to draw accurate conclusions about the durability of this binder

CHAPTER 2 MIX DESIGN METHOD FOR ALKALI-ACTIVATED FLY ASH – BLAST FURNACE SLAG BINDER CONCRETE

2.1 Approach and Research Process

2.1.1 Approach

This dissertation proposes a mix design method for AAFS concrete using an aggregate ratio approach that aims to achieve maximum density based on the particle packing density theory The composition of input materials is determined using predictive models for slump (Sn) and 28-day compressive strength (R28) of AAFS concrete The particle packing density theory, which is based on the principle that smaller particles fill the voids between larger particles to create a densely packed structure, is applied here using the modified Toufar model for its accuracy and simplicity The excess paste theory describes the flow behavior of the concrete mix, dividing the paste into three parts: filling voids, coating aggregate particles to achieve initial slump, and adding extra paste to reach the required slump The average thickness of the excess paste layer around the aggregate particles (tpaste) significantly influences the mix's slump

2.1.2 Research Process

The research process for Chapter 2 is illustrated in Figure 2.2

Figure 2.2 The research process for Chapter 2

2.2 Development of Material Calculation Formulas

2.2.1 Materials Used in the Research

This study uses three types of Class F fly ash (FA): from Hai Phong Power Plant (LOI = 11.32%), from Pha Lai Power Plant (LOI = 10.93%), and from Formosa Power Plant (LOI = 1.83%) The ground-granulated blast furnace slag (GGBS)

is sourced from Hoa Phat Steel Joint Stock Company, with an HM index greater than 1.4 The alkali activator solution consists of Na2SiO3 (NS) and NaOH (NH), with 99% purity flake NaOH, and Na2SiO3 solution containing 26.7% SiO2, 9.84% Na2O, and 63.46% H2O, with a silica modulus of 2.7 The aggregates used comply with TCVN 7570:2006 standards, similar to those in traditional Portland cement concrete

2.2.2 Study on the Influence of Material Characteristics on the Properties of

Alkali-Activated Binder

The primary characteristic factors for the input materials include %GGBS,

%Na2O, Ms, W/B, and tpaste Experimental planning results on AAFS mortar samples indicate that the Ms factor has a relatively minor impact on compressive strength compared to %GGBS and %Na2O (see Appendix 1) Therefore, Ms is kept constant at 1.2 to reduce experimental workload

2.2.3 Calculating Characteristic Factors from Basic Input Material

Parameters

Table 2.4 The calculation formulas for determining characteristic factors from

the basic parameters of input materials

Using the adjusted Toufar model, the optimal aggregate mixing ratio was determined to maximize the particle packing density, ∅A, which in turn defines the aggregate surface area Based on the “absolute volume” theory and the adjusted Toufar model, formulas were developed to calculate characteristic factors from basic input material parameters and vice versa (Tables 2.4 and 2.5) Table 2.5 Formulas for calculating input material composition from

characteristic factors

Total Binder m Binder

[1 − (∅1

𝐴 + 𝑡 𝑝𝑎𝑠𝑡𝑒 𝑆𝑆𝐴 𝑜 10 −6 )−1] / [%𝐺𝐺𝐵𝑆.(1−%Na2O−Ms.%Na2O).(

%𝑆𝑖𝑂 2𝑁𝑆 ) Added Water m Water 𝑚 𝐵𝑖𝑛𝑑𝑒𝑟 ∗ 𝑊/𝐵 − 𝑚 𝑁𝑆 ∗ %𝐻 2 𝑂 𝑁𝑆

to establish artificial neural network and mathematical models for predicting slump and 28-day compressive strength of AAFS concrete, is summarized in Table 2.6 and randomly split into training and testing sets at an 80/20 ratio

Bảng 2.6 Description of the dataset used in the study

%Na 2 O %GGBS W/B t paste (μm) S n (mm) R 28 (MPa)

2.4.1 Development of an Artificial Neural Network (ANN) Model to Predict

Slump and Compressive Strength of AAFS Concrete

(a) (b)

Hình 2.9 Permutation importance of the inputs in

ANN models for predicting (a) the slump, (b)

compressive strength of AAFS concrete

Hình 2.11 Effect of tpaste

and W/B ratio on the slump

Hình 2.10 Effect of %GGBS, %Na2O and W/B ratio on the compressive strength

The ANN model was established with input variables %Na2O, %GGBS, W/B, and tpaste, and outputs of either slump (Sn) or 28-day compressive strength (R28) Genetic algorithms combined with K-fold cross-validation were used to optimize the model’s hyperparameters The results showed high accuracy for R28 and Sn

predictions on both the training and testing sets, with R values of 0.956 and 0.974 for compressive strength, and 0.928 and 0.931 for slump, respectively Both MSE and MAE were very low, indicating the model’s reliability and accuracy Permutation importance analysis was used to identify the significance

of each factor Results indicated that %GGBS, %Na2O, and W/B were the primary influencing factors for compressive strength (Figure 2.9b), while W/B and tpaste significantly affected slump (Figure 2.9a)

Contour plots in Figure 2.10 illustrate the impact of %GGBS, %Na2O, and W/B

on R28 The findings suggested that an optimal %GGBS range is between 30% and 60%; beyond 60%, the increase in compressive strength slows, and it may even decline when exceeding 70% To ensure high compressive strength and cost efficiency, %Na2O should remain within the range of 3.5% to 6.5% Lower W/B values correspond to higher compressive strength due to a reduction in excess water in the concrete mix Additionally, contour plots in Figure 2.11 demonstrate the influence of tpaste and W/B on slump (Sn) The slump of the AAFS concrete mix depends not only on the W/B ratio but also significantly on the tpaste value (Figure 2.11)

2.4.2 Developing Mathematical Models to Predict Slump and Compressive

Strength of AAFS Concrete

The mathematical models for predicting the slump and compressive strength of AAFS concrete were developed using the Gene Expression Programming (GEP) method GEP automatically generates mathematical expressions through selection, recombination, and mutation, enabling predictions of slump and compressive strength The accuracy of these models was evaluated using the coefficient of determination (R²), achieving 0.88 and 0.95, respectively Mathematical models for Sn and R28 are expressed in following formulas:

𝑆 𝑛 =[(𝑡𝑝𝑎𝑠𝑡𝑒 −1.344).𝑡 𝑝𝑎𝑠𝑡𝑒 ]0.24

0.209 (5.94𝑊/𝐵) − 4.265%𝐺𝐺𝐵𝑆𝑡

𝑝𝑎𝑠𝑡𝑒 + %𝑁𝑎2 𝑂 4.994(𝑊/𝐵−0.33) +𝑡𝑝𝑎𝑠𝑡𝑒 (%𝑁𝑎 2 𝑂−1.679)(𝑡 𝑝𝑎𝑠𝑡𝑒 𝑊/𝐵−21.781)