Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam. Nghiên cứu bê tông có độ bền ăn mòn cao sử dụng muội silic cho kết cấu công trình ở môi trường biển Việt Nam.NhËn xÐt 3 §å thÞ h×nh 4 MINISTRY OF EDUCATION AND TRAINING UNIVERSITY OF TRANSPORT AND COMMUNICATIONS NGUYEN LONG KHANH RESEARCH ON HIGH CORROSION RESISTANCE CONCRETE USING SILICA FUME FOR BUILDING S.
Trang 1MINISTRY OF EDUCATION AND TRAINING
UNIVERSITY OF TRANSPORT AND COMMUNICATIONS
NGUYEN LONG KHANH
RESEARCH ON HIGH CORROSION RESISTANCE CONCRETE USING SILICA-FUME FOR BUILDING STRUCTURES EXPOSED TO MARINE ENVIRONMENT
Trang 22 The thesis was completed at:
UNIVERSITY OF TRANSPORT AND COMMUNICATIONS
Instructors:
1 Assoc Prof Dr Nguyen Thi Tuyet Trinh
2 Prof Dr Pham Duy Huu
Reviewer No.1: Prof Dr Nguyen Dong Anh
Reviewer No.2: Assoc Prof Dr Khuc Dang Tung
Reviewer No.3: Dr Do Huu Thang
The thesis is defended in front of the Doctoral Dissertation Judging Committee meeting at the University of Transport and Communications at … of …/…/ 2023
The thesis can be found at:
- National Library of Vietnam
- Information and Library Center, University of Transport and Communications
Trang 3In the world in the 1970s, the problem of the corrosion resistance of concrete structures began to be researched However, it was not until 2005 that the Netherlands began a formal research program, conducted under the supervision of Committee B23
of the CUR (Global Council for Postgraduate Research), which surveyed sixty results
structure at different ages Research shows that the biggest cause affecting the durability of concrete structures is the corrosion of reinforcement due to Cl- ion penetration, mainly in old structures with relatively low protective concrete layer [Wiebenga 1980]
Vietnam is a country with more than 3,200 km of coastline Faced with the urgent requirements of the construction and protection of seas and islands, the Party and State pay special attention to the socio-economic development of coastal and island regions with many priority policies for development That includes infrastructure development
In fact, the problem of improving the quality and longevity of concrete constructions in the sea or coastal areas is mainly solving the problem of improving the corrosion resistance of concrete in the structure
From the above analysis, the thesis selected the topic "Research on high corrosion
resistance concrete using silica-fume for building structures exposed to marine environment of Vietnam" to research, analyze and test concrete types Concrete uses
silica-fume admixture to enhance the durability of Cl- ion waterproofing for concrete structures in the marine environment
2 Objectives of the research
The research objective of the thesis is to study the use of silica-fume concrete with high corrosion resistance for building structures exposed to marine environment of Vietnam, specifically as follows:
Determining the effect of the ratio of Water/Binder (W/B), silica-fume content on compressive strength, Cl- ion permeability, Cl- ion diffusion coefficient to evaluate compressive strength, Cl- ion impermeability of silica fume concrete in marine environment
Determine the relationship between the W/B ratio, the silica-fume content, the compressive strength, and the Cl- ion permeability to serve as a basis for building a method for designing silica-fume concrete components taking into account the durability of ionic waterproofing Cl-
Determine the change of pore volume over time to analyze the influence of pore volume on the durability of silica-fume concrete
Evaluation of the time of onset of corrosion for silica-fume concrete and Portland cement concrete structures in the marine environment of Vietnam Application of silica fume concrete mix design for building structures in the marine environment of Vietnam through assessment of corrosion initiation time
3 Object and scope of research
The research object of the thesis is concrete using silica fume with specific strength
Trang 42
> 60 MPa and Cl- ion permeability < 1000 Coulomb
The scope of the thesis is to study the influence of the W/B ratio and the silica-fume content in order to evaluate the durability of Cl- ion waterproofing of concrete in the marine environment, at the high and low tide in the environment sea school
4 Research Methods
The method of combining theory and experiment in the laboratory, namely:
Theoretical methods are based on the results and contents of studies in the world and in the country, from which appropriate methods and data are selected to be included
in the research
Experimental research method, Taguchi method for planning, processing experimental data, combined with the use of Life-365 software to evaluate the time of onset of corrosion of structures in the marine environment Room
The test method is a laboratory test method based on Vietnamese and foreign standards to determine the strength and pore volume characteristics of concrete
5 Scientific and practical significance
Scientific significance: (1) Give more clear evidences on the influence of W/B
ratio, silica fume content on the durability of concrete (compressive strength, Cl- ion permeability, Cl- ion diffusion coefficient) ; (2) Establishing the relationship between the ratio of W/B, the silica fume content, the compressive strength, and the Cl- ion permeability of the silica fume concrete Thereby proposing a method to design silica fume concrete considering the durability of Cl- ions; (3) Evaluation of the influence of pore volume on the durability of silica fume concrete over time; (4) Proposing the grade
of silica-fume concrete for structures in the marine environment of Vietnam to meet the requirements of durability
Practical significance: (1) Contributing to perfecting the method of designing
silica-fume concrete components in the marine environment to improve the durability
of Cl- ion waterproofing; (2) Promote the utilization of silica-fume materials from industrial products for the construction of transport infrastructure works in the marine area, contributing to reducing environmental pollution, increasing economic and technical efficiency
6 Thesis layout
The thesis consists of an introduction, 04 main chapters, conclusions, recommendations and directions for further research, references and appendices
CHAPTER 1 OVERVIEW OF CONSTRUCTION WITH HIGH CORROSION
RESISTANCE IN THE MARINE ENVIRONMENT
1.1 Overview of marine environment effect on durability of concrete
1.1.1 Conception of the marine environment
According to the research of K Mehta (France), corrosion in the marine environment is divided into three main areas [94] : The area is constantly flooded; The tidal zone (including the breaking wave); Atmospheric regions of the sea and the coast The marine environment contains many factors that adversely affect the quality and durability of concrete, reducing the life of the structures In fact, more than 50% of concrete and reinforced concrete structural parts are corroded, severely damaged or destroyed after only 10-30 years of use The aggressive impact of the marine
Trang 53 environment on the durability of concrete and reinforced concrete works is mainly as follows:
+ Carbonation process
+ The process of permeation of SO42- ions into concrete
+ The process of diffusion of oxygen, Cl- ions and moisture into concrete
+ Corrosion process caused by microorganisms, by waves
In the world
The earth's surface area is covered 71% by water bodies and of which nearly 96,5%
is covered by sea water
Vietnam has a coastline of more than 3200 km from 8o37' to 21o32' North with hot and humid conditions typical of Vietnam's climate [40]
1.1.2 Influence of the marine environment on the durability of concrete
The marine environment has many harmful effects on the durability of concrete, but the main effects can be summarized as follows:
Corrosion of steel reinforcement caused by Cl- ions
The actual survey shows that the reinforced concrete works after a period of use all show signs of rust in the reinforcement at different levels, leading to no guarantee on the life of the works
Effects of magnesium salts
The typical MgCl2 content of seawater is 3200 ppm, which is enough to cause the deterioration of Portland cement's workability due to the invasion of Mg2+ ions
Effects of sulfate invasion
Sulfate ions from seawater react with the hydrate products of Portland cement and cause deterioration of concrete structures
1.1.3 Requirements for strengthening concrete in marine environment
Requirements on input material selection
Requirements on design, concrete composition
Requirements on manufacturing and construction technology [40]
1.2 Overview of durability of concrete
1.2.1 Concrete durability
According to ASTM E 632, "durability" is the ability to maintain the usability of a product, structure, or structure for a specified time Service life usability is considered the ability of components to perform the function for which they were designed, built The durability of concrete is divided into two main groups: mechanical strength (erosion, washout, freezing/thawing ) and chemical resistance (corrosion of reinforcement due to Cl- ions, corrosion of concrete, etc.) tones due to the phenomenon
of carbonation, sulphate invasion, etc.)
1.2.2 Research on corrosion of steel reinforcement caused by Cl - ions
Trang 64 The characteristic of corrosion of reinforcement due to Cl- ions is to create "holes"
on the metal surface (micropilc), making the ratio of cathode/anodic area large, so the local corrosion current density is very high Only Cl- ions in free form cause corrosion
of reinforcement and their diffusion in the porous structure of concrete This process is illustrated in Figure 1.7 From that, Fe2O3 and Fe(OH)3.3H2O are formed, which are products of the electrochemical process
Figure 1.7: Mechanism of electrochemical corrosion of steel in concrete exposed to
Cl - ions [21]
According to Nielsen A (1985), Fe2O3 has twice the volume of the steel it replaces But when converted to Fe(OH)3.3H2O, it expands to 6.5 times, causing cracking and breakage of the protective concrete
1.2.3 Research on the mechanism of influence voids effect on durability of concrete
Cl- ions penetrate into concrete through pores and micro-cracks Furthermore, as concrete is a heterogeneous material, the porous properties are directly related to the permeability of concrete [127], including pore structure, strength, curing conditions and environmental factors [77] Therefore, the voids of concrete is also an important criterion to evaluate the durability of the structure
1.3 Overview of silica fume concrete with high corrosion resistance in marine environment
1.3.1 Conception of concrete with high corrosion resistance in marine environment
Concrete with high corrosion resistance is essentially high quality concrete Compared with ordinary concrete, in the composition of high-quality concrete, there is
an indispensable ingredient, which is mineral admixture There are many types of mineral additives of natural and artificial origin (silica-fume, fly ash, blast furnace slag ) However, silica-fume is one of the most common pozzolans, adding them to the concrete mix results in lower porosity, permeability and water separation because their oxides (SiO2) react with Ca(OH)2, is created from the normal hydration of Portland cement to produce the product C-S-H which is the main component of the strength of concrete
1.3.2 Effect of silica fume on concrete
Silica-fume is a kind of pozzolanic mineral additive, which has some characteristic properties such as very small particle size (about 0.1 µm), spherical shape, amorphous structure and high SiO2 content Studies on silica-fume [54], [59] show that the influence of soot on concrete properties is caused by two chemical and physical effects The chemical effect is related to the ability to form calcium calcium silicate hydrogen product CSH, which is the binder that gives strength to concrete On the other hand, the physical effect of silica-fume is the microaggregation effect to fill the gaps between the aggregate particles and between the cement particles, making the concrete denser and
Trang 75 stronger These are the main effects of silica-fume on the strength and durability properties of concrete
Previous studies related to the use of silica fume in concrete have shown that the optimum silica-fume content used is from 5% to 15% by weight of cement to achieve the required strength [110]
1.3.3 Research situation on concrete with high corrosion resistance using silica fume
In the world, research on corrosion, solutions to increase durability for concrete - reinforced concrete works in general has been interested since the beginning of the 19th century In developed countries in Europe and America and Nordic countries Some famous scientists in the field related to corrosion of concrete - reinforced concrete structures in the marine environment can be named as P.K Mehta, V.M Malhotra, J P Olivier… [94], [89] with many scientific publications, many reference books, monographs on durability and corrosion resistance of concrete
In Vietnam, the research problem of concrete with high corrosion resistance has also been studied before These include the studies of Dao Van Dinh [15], Ho Van Quan [33], Ho Xuan Ba [11], Ngo Van Thuc [33] However, the authors have only focused on researching and evaluating the Cl- ion waterproofing ability of concrete using silica-based mineral admixtures, there have been no in-depth studies on the Cl- ion diffusion coefficient and the effect of silica fume on voids and concrete strength over time Also,
no method has been given to design concrete components with regard to durability
1.3 Conclusion of Chapter 1
- In Vietnam, the hot and humid marine climate conditions contain a high concentration of Cl- ions, so reinforced concrete structures are often corroded and degraded at a relatively fast rate Therefore, for concrete used as structures in the marine environment in Vietnam, higher requirements are required in terms of strength and durability of Cl- ion waterproofing
- Infiltration of Cl- and SO42- ions are thought to be the two main causes of the destruction of reinforced concrete structures However, the corrosion caused by SO42-ions takes place after a long time, so the corrosion caused by Cl- ions is the biggest threat to reduce the service life of reinforced concrete structures in the marine environment
- From the overview analysis, the thesis focuses on the research direction affecting the composition factors, pore volume on the resistance to Cl- ion penetration of silica fume concrete Proposing a method to design silica-fume concrete taking into account the resistance to Cl- ion penetration and assessing the corrosion initiation time of reinforced concrete structures in the marine environment.1.5 Thesis's research direction From the analysis in Chapter I, the thesis has identified specific research directions
as follows:
Study on the influence of composition factors such as W/B ratio, silica-fume content
on compressive strength, Cl- ion permeability of silicon black concrete
Developing a method to design silica-fume concrete components taking into account the durability of Cl- ion waterproofing
Study on the influence of silica-fume on the pore volume of concrete Thereby analyzing the influence of pore volume on the durability of concrete over time
Trang 86 Evaluation of the corrosion initiation time of structures when using silica-fume concrete and conventional concrete in the marine environment From there, it is proposed to match the requirements of the corrosion initiation time of 100 years for works in the marine environment
CHAPTER 2 THEORETICAL BASIS FOR ASSESSING THE DURABILITY
OF SILICA FUME CONCRETE
2.1 Theoretical basis for assessing resistance to Cl- ion penetration of silica-fume concrete
2.1.1 Cl - ion penetration resistance of concrete
Cl- ions can be present in concrete constituents, especially in sand and water According to European Standard EN 206-1 (2001) [141], the Cl- ion content per mass
of cement should not exceed 0.4% for reinforced concrete or concrete with steel core Cl- ions can be present in concrete as ions in the liquid phase
2.1.2 Test methods for Cl - ion penetration resistance of concrete
Long-term experiment: Salt Ponding Test – AASHTO T259); Bulk Diffusion Test (ASTM C1556)
Long-term experiment: Rapid Chloride Permeability Test – ASTM C1202); Electrophoresis engineering; The Rapid Chloride Migration Test - AASHTO TP64 2.2 Theoretical basis for evaluating the influence of pore volume on the durability of concrete
2.2.1 Effects of pore volume on the durability of concrete
Many studies have shown that porosity is the space between C-S-H and small capillary pores that does not cause permeability for high-quality concrete In contrast, when the degree of hydration increases which leads to a significant increase in the void volume due to the increase of the space between the C-S-H layers and the capillary voids, the permeability decreased sharply Therefore, there is the existance of a direct relationship between permeability and pore volume greater than 100 nm This may be because in the pore system, which includes many small pores, there is a tendency to discontinuity (discontinuous) which affects the durability of concrete
2.2.2 Method to determine the pore volume of concrete
The pore volume of concrete was determined by the N2 adsorption-desorption isotherm method (Brunauer - Emmett - Teller/BET method) This method is used to determine properties of capillary materials such as specific surface area, pore volume, pore size distribution as well as surface properties
From the results of the BET method, the Barret - Joyner - Halenda (BJH) method is applied to determine the pore volume distribution and pore size, thereby determining the pore distribution in concrete
2.3 Introduction to the Taguchi method
2.3.1 Experimental design according to Taguchi's method
The Taguchi method combines experimental planning and data processing to figure out the relationship between the input variable and the objective function In particular, the experimental matrix design applied in many technical fields for high efficiency is simple The experimental matrices are designed based on fixed orthogonal matrices The process is done as follows:
Determine the parameters
Trang 97 Determine the levels of each parameter Select a suitable OA orthogonal array Assign parameters to columns of orthogonal array
Conduct experiments Analyze data
2.3.2 Building regression equation according to Taguchi method
In the Taguchi method, to build the relationship between the objective functions and the input variables, the analysis of the model variance, the consideration of the model's correlation coefficient, and the determination of the terms in the model are supported by the Minitab software [23]
The overall regression equation has the following form [23]:
Where: y is the hypothetical function
xj, xu are hypothetical variables
bju: are the coefficients that estimate the change of the hypothetical function for each unit change of the hypothetical variables
2.4 Conclusion of Chapter 2
- Studying the theoretical basis of Cl- ion penetration resistance and the influence of pore volume on the durability of concrete, studying methods to determine permeability,
Cl- ion diffusion coefficient and pore volume voids of concrete
- Selecting method to determine Cl- ion diffusion coefficient through rapid Clpermeation method and rapid electrophoresis method
Selecting the Taguchi method combined with Minitab software to analyze the data, building the correlation between the W/B ratio and the intensity of silica fume, Cl- ion permeability
- Selecting the method of adsorption - desorption (BET/BJH) to determine the pore volume of concrete
CHAPTER 3 RESEARCH ON THE EFFECT OF COMPOSITION FACTORS
ON THE DURABILITY OF SILICA-FUME CONCRETE
3.1 Design and manufacture of silica-fume concrete
3.1.1 Applied standards and scientific basis in selecting design components of silica-fume concrete
Applied standards
Applying TCVN 10306:2014 on High-strength concrete – Design of cylindrical sample components [9] and other national standards specifying specifications for concrete components
Scientific basis for selecting components in the design of silica-fume concrete
Trang 108 Design of silica-fume concrete composition with compressive strength at 28 days greater than 60 MPa (cylindrical sample) and Cl- ionic permeability < 1000 Coulomb
3.1.2 Materials for making silica-fume concrete
Coarse aggregate (crushed stone)
- Origin: Sunway quarry - Luong Son - Hoa Binh
- The intensity was determined at the laboratory of the University of Transport Technology
Small aggregate (yellow sand)
- Origin: Red River (Viet Tri)
- The physico-mechanical parameters of sand were determined at the laboratory of the University of Transport Technology
But Son Cement PC40 according to TCVN 2682 - 2009
Specifications are provided by the manufacturer
Silica-fume mineral additive
Sikacrete PP1 silica-fume product from Sika, conforms to ASTM C1240-03
Superplasticizers
Sika Viscocrete 3000-20, grade G, meets ASTM C494
Water for pouring concrete
The tap water of Hanoi's domestic water supply system meets the quality standard TCVN 4506: 2012 – Water for concrete and mortar
3.1.3 Calculation, design and fabrication of silica-fume concrete
Input parameter selection
Based on the analysis of previous research in Vietnam and in the world, the thesis selects input parameters for the research as follows:
- Substitute silica-fume content: 8% – 10 % – 12%
- W/B ratio: 0,25 – 0,30 – 0,35
Experimental design according to Taguchi's method
- Objective function: Compressive strength and Cl- ion permeability
- Input parameters:
Substitute silica-fume content: 8% – 10 % – 12%
W/B ratio: 0,25 – 0,30 – 0,35
Experimental arrangement according to Taguchi's method
According to the Taguchi quality technical manual [117], the case of 2 factors, 3
levels each, the selection of L9 type planning with 09 experimental levels, the combination of experiments arranged orthogonally
Design of the composition of silica-fume concrete
Within the scope of the research, the thesis does not consider the influence of aggregates, only focuses on the composition of the binder in silica fume concrete including the composition of the binder and the amount of water used Applying TCVN 10306:2014 with silica fume content (8% - 10% - 12%) and W/B ratio (0.25 - 0.30 - 0.35), calculating the design of components concrete mix as follows:
Table 3.13: Silica-fume concrete components used in the research
(kg)
N (liter)
MS (kg)
C (kg)
Đ (kg)
PG (liter)
Trang 119 8MS 0,25W/B
0,25
8 552 150 48 612 1100 8,3 10MS 0,25W/B 10 540 150 60 612 1100 8,1 12MS 0,25W/B 12 528 150 72 612 1100 7,9 8MS 0,30W/B
0,30
8 460 150 40 692 1100 6,9 10MS 0,30W/B 10 450 150 50 692 1100 6,8 12MS 0,30W/B 12 440 150 60 692 1100 6,6 8MS 0,35W/B
0,35
8 395 150 34 745 1100 5,9 10MS 0,35W/B 10 386 150 43 745 1100 5,8 12MS 0,35W/B 12 377 150 52 745 1100 5,7 0MS 0,30W/B 0,30 0 500 150 00 692 1100 6,8
In addition to the grades using silica-fume, the thesis selected an additional one (without silica fume) with the ratio W/B=0.30 as the control sample
Notes: X: Cement; N: Water; MS: Silica-fume; C: Sand; A: Crushed stone; W/B: Ratio
of Water/Adhesive; PG: Superplasticizer
Manufacturing of silica-fume concrete
Table 3.14: Summarizing the number of test samples
Number of cylindrical samples 150 x 300 (mm) (for compression test)
Number of cylinders of size
100 x 50 (mm) (for the test to determine the permeability)
Figure 3.5 Image of concrete mixing and curing process
3.2 Study on the influence of the compositional factors on the compressive strength of silica-fume concrete
3.2.1 Test to determine the compressive strength of silica-fume concrete
- Testing to determine the compressive strength of concrete according to the standard TCVN 3118:1993 at the Laboratory of the University of Transport Technology
Trang 1210
- The results of compressive strength are averaged from the results of measuring 9 test pieces/grades at 28 days of age, as follows:
Table 3.15: Test results to determine compressive strength
MS (%)
Average compressive strength at 28 days
Figure 3.6: Relationships of W/B ratio, silica fume content and compressive
3.2.3 Building a regression equation describing the relationship of the W/B ratio, the silica-fume content and the compressive strength of the silica-fume concrete
by the Taguchi method
Building a regression equation describing the relationship of the W/B ratio, the fume content and the compressive strength using Minitab software The equation is as follows:
Trang 13 Evaluation of the fit of the regression equation by Minitab software
Table 3.19: Results of analysis of variance of correlation model
Regression 4 600,498 150,124 1777,79 0,00001 W/B 1 18,868 18,868 223,43 0,00012
MS 1 17,465 17,465 206,82 0,00014 (W/B)2 1 10,276 10,276 121,68 0,00038
R-sq(adj)
(Adjusted correlation coefficient)
R-sq(pred) (Predicted correlation coefficient)
The correlation coefficients of the regression equation, R-sq = 99,94%, R-sq(adj) = 99,89%, R-sq(pred) = 99,72% (Table 3.44) show that regression has a strong correlation with experimental data Therefore, this equation can be used to predict the compressive strength of silica fume concrete
b Evaluating the fit of the regression equation through the experimental results Table 3.21: Comparison of experimental compressive strength and predicted
compressive strength according to Taguchi Method
R n 28 according to Taguchi method (MPa) (2)
Difference between (1) and (2)