CONCRETE TO SLABS ON PILES
BY
KANOKPITCH NOPHPORNPHITAK
AN INDEPENDENT STUDY SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE
OF MASTER OF ENGINEERING (ENGINEERING TECHNOLOGY)
SIRINDHORN INTERNATIONAL INSTITUTE OF TECHNOLOGY THAMMASAT UNIVERSITY
ACADEMIC YEAR 2021
COPYRIGHT OF THAMMASAT UNIVERSITY
Independent Study Title Application Potential of Expansive Concrete to Slabs on Piles
Author Kanokpitch Nophpornphitak
Degree Master of Engineering (Engineering
Technology)
Faculty/University Sirindhorn International Institute of Technology/
Thammasat University
Advisor Professor Somnuk Tangtermsirikul, D.Eng.
Academic Years 2021
ABSTRACT
Cracking in concrete structures occurs when the shrinkage stress exceeds the tensile capacity, which is called drying shrinkage cracking and is commonly found in reinforced concrete structures. A solution to this problem is to apply expansive concrete. This independent study is aimed at surveying the overviews of the application of expansive concrete and expansive additive and its mechanisms to prevent restrained shrinkage cracking by introducing expansion in the expansion concrete. Some related existing standards are compared. Examples of construction projects of slabs on piles are surveyed and some typical characteristics such as slab thickness and reinforcement ratio are summarized.
Keywords: Expansive concrete, Expansive additives, Slab on piles, Standards
ACKNOWLEDGEMENTS
In successfully completing this project, I would like to extend my sincere respect and appreciation to Professor Somnuk Tangtermsirikul and Assistant Professor Ganchai Tanapornraweekit. I am very grateful for their suggestions and guidance which are very helpful.
Finally, I also like to take this opportunity to express to my family. It would have been difficult and challenging to complete my project without them. Lastly, I want to thank my supportive friends for being by my side throughout all of this.
Kanokpitch Nophpornphitak
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TABLE OF CONTENTS
Page
ABSTRACT (1)
ACKNOWLEDGEMENTS (2)
LIST OF TABLES (4)
LIST OF FIGURES (5)
LIST OF SYMBOLS/ABBREVIATIONS (6)
CHAPTER 1 INTRODUCTION
1.1 Background 1
1.2 Problem Statement 2
1.3 Objectives 2
1.4 Scopes and Limitations 2
CHAPTER 2 REVIEW OF LITERATURE 3
2.1 Applications of Expansive Concrete 3
2.2 Properties of Expansive Concrete 4
2.3 Performance of Shrinkage-Compensating Concrete in Slabs 6
2.4 Differences in Standardization 6
CHAPTER 3 CONSTRUCTION PROJECT IN THAILAND 8
CHAPTER 4 CONCLUSION 10
REFERENCES 11
LIST OF TABLES
Tables Page
2.1 Advantages and disadvantages of Expansive cement and Expansive Additive 7
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LIST OF FIGURES
Figures Page
3.1 Calculation of construction project in Thailand 9
LIST OF SYMBOLS/ABBREVIATIONS
Symbols/Abbreviations Terms
ACI American Concrete Institute
CaSO4 Calcium Sulfate
CaO Calcium Dioxide/ Lime
CaO-Al3O2-SO3 Calcium Sulfoaluminate
C3A Tricalcium Aluminate
EA Expansive Additive/ Agent
FA Fly Ash
JIS Japanese Industrial Standard
LP Limestone Powder
MgO Magnesium Oxide
SCC Shrinkage-Compensating Concrete
Ref. code: 25646322040533RDE
CHAPTER 1 INTRODUCTION
1.1 Background
If the restrained tensile stress or restrained tensile strain exceeds the tensile strength of the concrete, respectively, the concrete begins to crack. There are many types of shrinkage, we mainly focused on shrinkage caused by drying and autogenous shrinkage. Beginning with autogenous shrinkage, it is brought on by water consumption in the capillary pore during the hydration of cement inside the concrete without loss to the outside environment. While drying shrinkage is induced by the evaporation of water to the outside environment. According to the definition of JIS A6202, expansive additives are admixtures that produce ettringite or calcium hydroxide when mixed with cement and water, and cause the mortar and concrete to expand. Also, the admixtures that are sold as powders and are used in concrete.
(Gagné, 2016) and ACI 223R-10 state that a concrete with an expansive agent is also referred to as shrinkage compensated concrete or expansive concrete. By utilizing the expansive agent, two different ways to produce expansive concrete can be distinguished. The first technique, known as expansive cement, is created by combining Portland cement with an expansive additive. It is widely used in the USA.
The second method is to use the expansive additive as a mineral admixture in concrete which can be varied based on the country, for example, Thailand also uses fly ash as a mineral admixture which can enhance the expansion of expansive concrete.
Expansive additives are frequently used, for instance in Japan, Thailand, China, and other countries. Cracking can be prevented by providing a sufficient amount of expansion. The sufficient early expansion can compensate for the subsequent shrinkage and the expansive concrete applying this concept is called Shrinkage-Compensating Concrete.
In this independent study, we will mainly focus on drying shrinkage and/or autogenous shrinkage that affects the slab on piles, representing the examples of slab application using expansive concrete or expansive additive. Surveying the mechanical properties of expansive concrete/ expansive additives was conducted together with
describing the difference in standard between ACI and JIS and providing information on examples of slab on pile construction projects in Thailand.
1.2 Problem Statement
According to the structure, thin slabs are usually subjected to restrained shrinkage, and studies on the application of expansive concrete to slabs on piles are still none in Thailand
With the issue of cracking commonly appearing on reinforced concrete structures, the use of expansive concrete reduces cracks by its volumetric expansion properties and reduces shrinkage before the cracks can occur. The Type K, M, and S expansive cement types that are defined by the American Concrete Institute (2010, pp.3), while also identifying the Type K, M, S, and G expansive component systems.
This study focuses on drying shrinkage and/or autogenous shrinkage on slabs on piles, with the application of normal concrete and expansive concrete in construction projects provided by CPAC. Lastly, this study will also survey the properties of expansive concrete and expansive additives and find the advantages and disadvantages of using standards; ACI and JIS. Summarize the information on the construction projects of slabs on piles provided by CPAC.
1.3 Objectives
The study will survey the mechanism and behavior of expansive concrete or expansive agents. Also, surveying the standards of expansive concrete and expansive additives. Lastly, summarize the examples of the situation of slabs on piles in Thailand.
1.4 Scopes and Limitations
1.4.1 The study will mainly focus on the slabs on piles that are affected by drying shrinkage and/or autogenous shrinkage
1.4.2 Comparing the advantages and disadvantages of expansive concrete and expansive additives
1.4.3 Summarize the example of slabs on piles projects in Thailand provided by CPAC
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CHAPTER 2
REVIEW OF LITERATURE
2.1 Applications of Expansive Concrete
Concrete made with an expansive cement or component system is shrinkage compensated concrete. American Concrete Institute (ACI, 2010) classifies expansive concrete into two types, the type of using expansive cement and the type of using an expansive component system. There are 3 types of expansive cement:
1. Type K expansive cement: a mixture of Portland cement, anhydrous tetracalcium trialuminate sulfate (C4A3S), Calcium sulfate (CaSO4), and lime (CaO)
2. Type M expansive cement: interground or blended mixtures of Portland cement, calcium-aluminate cement, and calcium sulfate suitably proportioned.
3. Type S expansive cement: a Portland cement containing a high composition of tricalcium aluminate (C3A) and an amount of calcium sulfate above the usual amount found in Portland cement.
Next, there are four types of expansive component systems which are combinations of Portland cement and expansive components.
1. Type K expansive component: a blend of calcium sulfoaluminate and calcium sulfate that produces ettringite when mixed with portland cement and water.
2. Type M expansive component: a blend of calcium-aluminate cement and calcium sulfate that produces ettringite when mixed with Portland cement and water.
3. Type S expansive component: a blend of tricalcium aluminate (C3A) cement and calcium sulfate that produces ettringite when mixed with Portland cement and water.
4. Type G expansive component: a blend of calcium dioxide and aluminum dioxide that produces calcium, hydroxide platelet crystal when mixed with Portland cement and water.
The use of shrinkage-compensating concrete, which complies with ACI 223R-10, is mandated in order to reduce structural movement and cracking in concrete that results from drying shrinkage. (ACI, 2010)
2.1.1 Expansive additive
Many different types of concrete construction use expansive cement concrete as “shrinkage-compensating concrete” or “chemical prestressing concrete”. (Nagataki and Gomi, 1998) Expansive concrete expands more when the amount of expanding additive is increased and the pores formed in the hardened structure are caused by the expansive cement concrete’s expansion mechanisms, which involve increasing the expansive ingredients by absorbing water. On the basis of cement minerals like calcium sulfoaluminate (CaO-Al3O2-SO3), calcium oxide, and iron powder, expansive admixtures are used (CaO). The calcium sulfoaluminate series is the main group.
There are three uses for expansive concrete: shrinkage-compensating concrete for cast-in-place concrete, shrinkage-compensating concrete for factory products and chemical prestressing concrete, and filling concrete for placement inside cavities created by pre-existing concrete, steel pipes, and rocks. (Nagataki and Gomi, 1998)
2.2 Properties of Expansive Concrete
2.2.1 Expansion and Compressive Strength of Concrete with Expansive Additives This study examined the effects of expansive additive (EA) quantity, binder type—Limestone powder (LP) and Fly Ash (FA), water to binder ratio, curing conditions, and restraining ratio—on expansion and compressive strength using the CaO-type expansive additive. (Trong Lam, Sahamitmongkol and Tangtermsirikul, 2008)
The results show that EA hydrates more quickly than cement. Fly ash pastes set faster when EA was used with fly ash concrete. When the water to binder ratio rises, expansive concrete's free expansion also rises, which is the effect of the water to binder ratio on expansive concrete.
With the same amount of EA, the effect of the type of binder on the free expansion of expansive concrete is that when the FA content increases, so does the free expansion of the concrete.
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Free expansion of expansive concrete is influenced by curing conditions in a similar way to sealed curing and water curing, but after being kept in the air, free expansion starts to decrease due to shrinkage. Water is therefore required for the formation of expansive products.
When it comes to the effect of expansive additive quantity and fly ash content on free expansion of expansive concrete, the results indicate that EA is more effective in fly ash concrete than in cement-only concrete. When FA content develops, EA also expands the free expansion at the same rate.
In conclusion, using EA content with FA concrete improves its ability to control cracks. The effect of EA content on the restrained expansion of concrete is still greater in FA concrete than in cement-only concrete under restrained conditions.
When comparing the relationship between the quantity of expansive additive and the compressive strength of expansive concrete without restraint.
Finally, the results indicate that FA concrete solves the problem of strength loss when high EA content, while EA has a significant impact on compressive strength when it comes to the relationship between the amount of expansive additive and the compressive strength of expansive concrete without restraint.
2.2.2 Effects of Curing Conditions on Physical Properties of Mortars Blended with Expansive Agent
It is generally accepted that curing temperature or changes in curing temperature have a significant impact on expansion characteristics. (Takuya et al., 2019) The materials used in this study include an ettringite-type expansive agent that is primarily used in Japan and a lime-based expansive agent. The influence of the curing temperature demonstrates that expansive material or not, the compressive strength is high. The expansion coefficient of the lime-type expansion material was higher than the expansion coefficient of the ettringite-type expansion material.
2.2.3 Shrinkage and Expansive Strains of Concrete with Fly Ash and Expansive Agent
When MgO expansive agents are used in concrete, they can cause shrinkage and expansive strain that can be reduced by fly ash. To counteract temperature
shrinkage, MgO expansive agent can form the delayed expansive strain. (Gao, Lu and Tang, 2009)
2.3 Performance of Shrinkage-Compensating Concrete in Slabs
It is well known that shrinkage-compensating concrete can lower drying shrinkage cracking. (Russell, 1978) The performance of concrete slabs made with Type S, Type K, and Type M shrinkage-compensating cements is examined in this report. The experiment's results demonstrated that all slabs with shrinkage compensation had lower final net drying shrinkage than slabs made with type I cement. Different types of shrinkage-compensating cement provide varying degrees of expansion. As reinforcement is added, slab expansion is decreased, and shrinkage is decreased.
2.4 Differences in Standardization
Three different kinds of expansive cement and four different kinds of expansive component systems were offered by the American Concrete Institute (ACI 223R-10). By combining expansive cement and expansive component systems with concrete, expansive concrete is created. As a result, expansive cement/ expansive component systems are convenient to control and manage the expansion rate.
The expansive additive is defined by the Japanese Industrial Standard (JIS A6202) as the mineral admixture of mortar or concrete that, when combined with cement and water, generates ettringite or calcium hydroxide as well as other hydration products.
The comparison between ACI and JIS standard provides the advantages and disadvantages in the table below.
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Table 2.1Advantages and disadvantages of Expansive cement and Expansive Additive
Type Advantages Limitations
Expansive Cement
● Easier to control the quality
● Low risk of self-deterioration
● The only way to adjust the expansion rate is to change the amount of cement
● Maximum expansion rate is rather fixed
● Not cost-effective
Expansive Additive
● Enable customization of mix proportion for specific demand
● More cost-effective
● Enable more advanced material like Chemical Prestressed Concrete (CPC), material for repair section, etc.
● Need well-trained practitioner
● Error in design or construction may cause serious damage to structures
CHAPTER 3
CONSTRUCTION PROJECT IN THAILAND
According to the situation in Thailand, there are very few constructions that mixed expansive admixtures into concrete. From the following table, examples of data of construction using slabs on piles were provided by CPAC, as shown in Figure 1.
There are 13 projects of slabs on piles using normal concrete construction.
Only the 24-shopping projects includes both normal concrete and expansive concrete The data in Figure 1 indicate that the characteristics of the slabs on piles are as follows.
a. The slab thickness ranges from 20 - 30 cm.
b. The applied compressive strength of concrete are 280, 350, and 400 ksc.
c. Center-to-center of the pile ranges from 2 - 3.5 m.
d. The percentages of reinforcement at midspan are as follows.
The maximum percentage in x-direction is 1.005 The maximum percentage in y-direction is 1.005 The minimum percentage in x-direction is 0.302 The minimum percentage in y-direction is 0.302
e. The percentages of reinforcement at the pile cap are as follows.
The maximum percentage in x-direction is 1.759 The maximum percentage in y-direction is 1.759 The minimum percentage in x-direction is 0.361 The minimum percentage in y-direction is 0.361
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Figure 3.1Calculation of construction project in Thailand
CHAPTER 4 CONCLUSION
Throughout the literature review conducted on the application of expansive concrete and expansive additives as mineral admixtures , the importance of expansive additives/agents has been surveyed in this independent study, as well as the properties and mechanisms of expansive concrete/ expansive additives to solve restrained shrinkage cracking problem in concrete. For the standards, the differences between ACI and JIS are addressed. For ACI, they use expansive cement. On the other hand, JIS uses expansive agents, and this concept is widely used in Japan and Thailand. It is also recommended to mix in an appropriate amount of the expansive agents and provide a good curing process. Characteristics of some slab-on-pile projects, provided by CPAC, are summarized.
Ref. code: 25646322040533RDE
REFERENCES
American Concrete Institute. (2010). Guide for the Use of Shrinkage-Compensating Concrete.
ACI Committee 223, 1-16.
https://www.concrete.org/Portals/0/Files/PDF/Previews/223R-10web.pdf
Gagné, R., 2016. 22 - Expansive agents. In P.-C. Aïtcin & R.J. Flatt (Eds.), Science and Technology of Concrete Admixtures(441-456): Woodhead Publishing
Gao, P., Lu, X. and Tang, M., 2009. Shrinkage and expansive strain of concrete with fly ash and expansive agent. Journal of Wuhan University of Technology-Mater. Sci. Ed., 24(1), 150-153.
Japanese Society of Civil Engineers. (2007). Standard Specifications for Concrete Structures - 2007 “Materials and Construction”. JSCE Guidelines for Concrete, 16, 1-530.
https://www.jsce-int.org/system/files/JGC16_Standard_Specifications_Materials_and _Construction_1.1.pdf
Japanese Standards Association. (1980). Japanese Industrial Standard, Expansive Additive for Concrete. JIS A 6202 - 1980, 1-31.
Nagataki, S. and Gomi, H., 1998. Expansive admixtures (mainly ettringite). Cement and Concrete Composites, 20(2-3), 163-170.
Russell, H., 1978. Performance of shrinkage-compensating concrete in slabs. [Skokie, Ill.]:
Portland Cement Association.
Takuya, H., Sudo, H., Hashimoto, S. and Date, S., 2019. Effect of Curing Conditions on Physical Properties of Mortar Blended with Expansive Agent. MATEC Web of Conferences, 278, p.01002.
Trong Lam, N., Sahamitmongkol, R. and Tangtermsirikul, S., 2008. Expansion and Compressive Strength of Concrete with Expansive Additive. Research and Development, 19(2).
