1. Chapter 11 Recent Advances of cement-based materials

2. 2 High-strength concrete
1 Definition
2 High-strength concrete
3 Self-Compacting Concrete
Advanced
Concrete
4 High-Performance Concrete
5 Shrinkage-Compensating Concrete
6 Fiber-Reinforced Concrete

3. 7 Concrete Containing Polymers
Advanced
Concrete
8 Heavyweight concrete
9 Mass Concrete

4. 1 Preview
Ordinary concrete----made with natural aggregate, has a low strength-weight ratio compared to steel.
Disadvantage----tall buildings, long-span bridges, and floating structures.

5. 1 Advanced concrete Advanced the density can be reduced
the strength can be raised
combine the first two approaches
above of three approaches

6. 2 High strength concrete
2.1 Definition
Strength of the matrix
Strength of the interfacial transition zone
Concrete strength

7. 2 High strength concrete
2.1 Definition
O.C
H.S.C
S.S.C
Compressive strength 60 80
MPa
Ordinary concrete:
Compressive strength <60 MPa.
High-strength concrete:
Compressive strength>60 MPa.
It is applied largely to the high-
rise building, large span bridge
and high-strength prefabrication
component and so on.
Super-strength concrete:
Compressive strength>80 MPa.

8. 2.2 Choice of HSC Raw material
2 High strength concrete
2.2 Choice of HSC Raw material
Binding Material
Characteristics of cement
kinds and grades
mineral composites and fineness
Quantity of cement

9. 2.2 Choice of HSC Raw material
2 High strength concrete
2.2 Choice of HSC Raw material
Kinds and Grades
Normally, these kinds of cement, can obtain higher final strength is applied in improving consistent strength.
such as
high-mark Portland cement
ordinary Portland cement
slag Portland cement
pozzolan Portland cement

10. 2.1 Choice of HSC Raw material
2 High strength concrete
2.1 Choice of HSC Raw material
Kinds and Grades
In the past, it was difficult to mix high-strength concrete. That is, the mark of cement should be higher than strength grade of concrete, or sometimes be slightly lower than strength grade of concrete.
In our country, at present, it is much easier to mix high-strength concrete with the modification of material properties and craftworks especially the wide use of admixture.

11. 2.1 Choice of HSC Raw material
2 High strength concrete
2.1 Choice of HSC Raw material
Mineral Composites and Fineness
Fineness of cement can influence strength of concrete.
surface area is cm2/g.
The finer levigating, the large surface area, the more sufficient hydration reaction, the higher strength

12. 2.1 Choice of HSC Raw material
2 High strength concrete
2.1 Choice of HSC Raw material
Quantity of Cement
The quantity of binding material is so important to produce HSC that it directly influences the cohesion between hardened cement paste and border surface.
Construction requirement also needs certain feasibility. In order to increase the proportion of binding material in mortar, the usage of cement is large usually in the range of kg／m3.
But it is recommended not out of this range otherwise it is easy to cause slow heat radiation and large shrinkage in hydration.

13. 2.1 Choice of HSC Raw material
2 High strength concrete
2.1 Choice of HSC Raw material
Excellent Aggregate
fine aggregate
Sand modulus of fineness lower than 3.0 and reduce sand rate
Concrete admixture should not be too dry or hard.
In the composites of HSC, fine admixture percentage is smaller than that of the ordinary concrete. It is better to use quartz river sand as the chemical composite of sand.

14. 2.1 Choice of HSC Raw material
2 High strength concrete
2.1 Choice of HSC Raw material
Excellent Aggregate
coarse aggregate
Concrete strength is influenced by coarse aggregate by the following factors, cement paste, cohesion of mortar and aggregate, aggregate elasticity, stress concentration around the aggregate. For HSC coarse aggregate has good performance in compressive strength, surface, maximum grain-size.

15. 2.1 Choice of HSC Raw material
2 High strength concrete
2.1 Choice of HSC Raw material
Superplasticizer
HSC can be obtained by high grade cement and superplasticizer.
Polycarboxylate Superplasticizer
Reducing water usage

16. 2 High strength concrete
2.2 Application
JinMao Tower，C60
Skyscraper
E-Tower building,Brazil

17. 3 Self-Compacting Concrete
3.1 Problem
How to produce concrete mixtures possessing a high workability?
Development of high-workability concrete mixtures that are known by self-compacting concrete

18. 3 Self-Compacting Concrete
3.2 Definition
The self-compacting concrete (SCC) may be defined as a flowing concrete that can be cast into place without the use of vibrators to form a product.

19. 3 Self-Compacting Concrete
3.2 Development
Although superplasticizing admixtures are expensive, the ability to place concrete rapidly and to consolidate it with little or no cost presents savings that may equal or even exceed the cost of the superplasticizer, while producing a better quality end product.

20. 3.2 Materials and mixture proportions
3 Self-Compacting Concrete
3.2 Materials and mixture proportions

21. 3 Self-Compacting Concrete
3.3 Properties
--Superior rheological characteristics
--Slump value in excess of 200 mm
--Slump-flow value in excess of 600 mm
--Be placed and compacted without the help of vibrators

22. 3 Self-Compacting Concrete
3.4 Applications
Europe and Japan---underwater concreting and for the construction of heavily reinforced structures
North America --- precast concrete plants where there is a high degree of quality control
China--- long-span bridge,
high-rise buildings
Sutong Bridge，2008

23. 4 High-performance Concrete
high workability
high durability
high ultimate strength
High-performance concrete (HPC) for concrete
mixtures possessing high workability, high
durability and high ultimate strength.

24. 4 High-performance Concrete
4.1 Definition
ACI defined high-performance concrete as a
concrete meeting special combinations of
performance and uniformity requirements that
cannot always be achieved routinely using
conventional constituents and normal mixing,
placing, and curing practice.
1990 The first international conference in USA

25. 4 High-performance Concrete
4.2 Characteristics
Examples of characteristics that may be considered critical for particular application are:
---Compaction without segregation
--- Early age strength
---Long-term strength and mechanical properties
--- Permeability
--- Density
---Heat of hydration
---Toughness
---Volume stability
---Long life in severe environments

26. 4.3 Structure and properties
4 High-performance Concrete
4.3 Structure and properties
Fly ash
Slag
Silica

27. 4 High-performance Concrete
4.4 Applications
Long span bridges
Highway
CCTV Building
Steel fiber reinforced self-compacting concrete

28. 5 Shinkage-Compensating concrete
5.1 Definition
According to ACI, shrinkage-compensating concrete is an expansive cement concrete which, when properly restrained by reinforcement of other means, will expand an amount equal to or slightly greater than the anticipated drying shrinkage. Because of the restraint, compressive stresses will be induced in the concrete during expansion. Subsequent drying shrinkage will reduce these stresses.

29. 5 Shinkage-Compensating concrete
5.1 Definition
Concrete containing a hydraulic cement, water, aggregate, and discontinuous discrete fibers is called fiber-reinforced concrete.
Containing pozzolans and other admixtures
Fibers of various shapes and sizes produced from steel, plastic, glass, and natural materials are being used, steel fiber is the most commonly used of all the fibers.

30. 6 Fiber-reinforced concrete
6.1 Type of fiber
The type of fiber and its volume fraction has a marked effect on the properties of fiber reinforced concrete. It is convenient to classify the fiber reinforced composites as a function of their fiber volume fraction:

31. 6 Fiber-reinforced concrete
6.2 Type of fiber
Low volume fraction (<1 percent). The fibers are used to reduce shrinkage cracking. These fibers are used in slabs and pavements that have a large exposed surface leading to high shrinkage cracking.
Moderate volume fraction (between 1 and 2 percent). The presence of fibers at
this volume fraction increases the modulus of rupture, fracture toughness, and impact resistance.

32. 6 Fiber-reinforced concrete
6.2 Type of fiber
High volume fraction (greater than 2 percent).
The fibers used at this level lead to strain-hardening of the composites.

33. 6 Fiber-reinforced concrete
6.2 Type of fiber
High volume fraction (greater than 2 percent).
The fibers used at this level lead to strain-hardening of the composites.

34. 6.2 Type of fiber

35. 6 Fiber-reinforced concrete
6.3 Properties
Workability. For most applications, typical mortar or concrete mixtures containing fibers possess very low consistencies; however, the placeability and compactibility of the concrete is much better than reflected by the low consistency
Strength. It can be seen that increasing the length of fibers up to a point increases strength as well as toughness.

36. 6 Fiber-reinforced concrete
6.3 Properties
Toughness and impact resistance. The greatest advantage in fiber reinforcement of concrete is the improvement in flexural toughness consistency. Related to flexural toughness are the impact and fatigue resistance of concrete, which are also increased considerably.

37. 6 Fiber-reinforced concrete
6.3 Properties
Elastic modulus. Inclusion of steel fibers in concrete has little effect on the modulus of elasticity.
Durability. Fiber-reinforced concrete is generally made with a high cement content and a low water-cement ratio. When well compacted and cured, concretes containing steel fibers seem to possess excellent durability as long as fibers remain protected by the cement paste.

38. 6 Fiber-reinforced concrete
6.3 Properties
Figure 10 Factors affecting properties of fiber-reinforced concrete: (a) influence of increasing fiber volume; (b) influence of increasing the aspect ratio.

39. 6.4 Development of ultra-high-performance fiber-reinforced composites
6 Fiber-reinforced concrete
6.4 Development of ultra-high-performance fiber-reinforced composites
Compact reinforced composites. Researchers in Denmark created compact reinforced composites using metal fibers, 6 mm long and 0.15 mm in diameter, and volume fractions in the range of 5 to 10 percent. These short fibers increase the tensile strength and toughness of the material.

40. 6.4 Development of ultra-high-performance fiber-reinforced composites
6 Fiber-reinforced concrete
6.4 Development of ultra-high-performance fiber-reinforced composites
Reactive powder concrete (RPC). The material can obtain a compressive strength of 200 MPa when cured in hot water at 90°C for three days and a compressive strength of 800 MPa when cured at 400°C.

41. 6.4 Development of ultra-high-performance fiber-reinforced composites
6 Fiber-reinforced concrete
6.4 Development of ultra-high-performance fiber-reinforced composites
Reactive powder concrete (RPC). The material can obtain a compressive strength of 200 MPa when cured in hot water at 90°C for three days and a compressive strength of 800 MPa when cured at 400°C.

42. 6.4 Development of ultra-high-performance fiber-reinforced composites
6 Fiber-reinforced concrete
6.4 Development of ultra-high-performance fiber-reinforced composites
Reducing the deadweight of structure
Improving the durability of structure
Good toughness
High temperature resistance
Fire resistance

43. 6.4 Development of ultra-high-performance fiber-reinforced composites
6 Fiber-reinforced concrete
6.4 Development of ultra-high-performance fiber-reinforced composites
Slurry-infiltrated-fibered concrete (SIFCON). The processing of this composite consists of placing the fibers in a formwork and then infiltrating a high w/c ratio mortar slurry to coat the fibers. Fibers with high surface area are used. Compressive and tensile strengths up to 120 and 40 MPa.

44. 6.4 Development of ultra-high-performance fiber-reinforced composites
6 Fiber-reinforced concrete
6.4 Development of ultra-high-performance fiber-reinforced composites
Engineered cementitious composite (ECC). The material has a very high strain capacity and toughness and controlled crack propagation .
Ductility，500 times
Light，40%

45. 7 Polymer concrete 7.1 Definition
Polymer concrete (PC) is a mixture of aggregates with a polymer as the sole binder. To minimize the amount of the expensive binder, it is very important to achieve the maximum possible dry-packed density of the aggregate.
It was important to use dry aggregate because the presence of moisture caused a serious deterioration in the properties of the polymer concrete.

46. 7 Polymer concrete 7.1 Definition
Polymer concrete (PC) is a mixture of aggregates with a polymer as the sole binder. To minimize the amount of the expensive binder, it is very important to achieve the maximum possible dry-packed density of the aggregate.
It was important to use dry aggregate because the presence of moisture caused a serious deterioration in the properties of the polymer concrete.
Polymer conctent : in the range of 5-20%
Application: Repairing of pavement and others

47. 7.2 Mechanism and properties
7 Polymer concrete
7.2 Mechanism and properties
Mechanism
The density of polymer concrete can be increased because the pores and microcracks are filled by the polymers.
Properties
High strength
Permeability resistance
Frost resistance
Corrosion resistance

48. 8 Heavyweight concrete 8.1 Definition
Concrete is commonly used for biological shielding in nuclear power plants, medical units, and atomic research and testing facilities. Heavyweight concretes are produced generally by using natural heavyweight aggregates. The concrete unit weights are in the range 3370 to 3840 kg/m3, which is about 50 percent higher than the unit weight of concrete containing normal-weight aggregates.

49. 8 Heavyweight concrete 8.2 Properties
Heavyweight concrete can be pumped or placed by chutes over short distances only, because of the tendency of coarse aggregate to segregate.
Unit weights of concrete containing barite, magnetite aggregate are in the range of 3450 to 3760 kg/m3; when hydrous and boron ores (which are not of high density) are used as partial replacement for heavyweight aggregate, the unit weight of concrete may come down to about 3200 to 3450 kg/m3.
2000 to 2800 kg/m3

50. 8 Heavyweight concrete
8.3 Applications
Nuclear power plant

51. 9 Mass concrete 9.1 Definition
ACI has defined mass concrete as concrete in a massive structure, for example, a beam, columns, pier, lock, or dam where its volume is of such
magnitude as to require special means of coping with the generation of heat and subsequent volume change.

52. 9 Mass concrete 9.1 Definition
Thermal stress and temperature control is crucial in mass concrete structure.
Temperature rise in concrete due to heat of hydration, and subsequent shrinkage and cracking that occurred on cooling
If they are several meters thick and are made of high-strength concrete mixtures (high cement content), the problem of thermal cracking can be as serious as in dams

53. Thanks for your attention!