Unit 5 - Special Concrete

1. CONCRETE TECHNOLOGY
Dr. S. GOPIKUMAR Ph.D. Associate Professor
gopikumar@scadengineering.ac.in
Department of Civil Engineering
SCAD College of Engineering and Technology

2. UNIT V
SPECIAL CONCRETES (9)
Course Outcomes
CO5 - At the end of this unit, students will have the knowledge about polymer concrete, high performance concrete.

3. SPECIAL CONCRETE
• Frequently, CONCRETE may be used for some special purpose for which special properties
are more important than normal concrete
• In order to achieve a special concrete, suitable proportions of chemical and mineral
admixtures are used. This concrete is called as special concrete.
Introduction

4.  • Special concrete is used in extreme weather
 • It has been used in large structures
 • Good cohesiveness or sticky in mixes with very high binder content
 • Comparable flexural strength and elastic modulus
 • Better drying shrinkage and significantly lower creep
 • Good protection to steel reinforcement in high chloride environment
 • Excellent durability in aggressive sulphate environments
 • Lower heat characteristics
 • Low resistance to de-icing salt scaling
 • PC pipes with good resistance to chemical attack
Need for the study

5. 1. First modern use of lightweight concrete (LWC) was recorded in 1917
2. American Emergency Fleet Corporation started building ships with this mixture due to its
high strength and performance.
3. Lightweight concrete is a mixture made with lightweight coarse aggregates such as shale,
clay, or slate, which give it its characteristic low density.
4. Lightweight concrete has higher water content.
5. The use of porous aggregates increases the time it takes to dry.
Light weight concrete

6. • One of the most popular structures built with
lightweight concrete is the Bank of America Building in
Charlotte, N.C.
• LWC utilization in the Wabash River Bridge.
• Produced using porous and lightweight aggregates
including Clay, Shale, Slate, Volcanic Pumice, Ash,
or Perlite.
• Weaker aggregates may also be added to the mixture,
which has an impact on its thermal conductivity
• Lightweight aggregate is perfect for pre-cast concrete blocks or steel reinforcements.
However, denser varieties show better bonding results between steel and concrete, along
with enhanced protection from steel corrosion.

7. Lightweight aggregates are used to reduce the density of concrete.
 Varieties of light weight aggregates are available in natural or artificial source.
Advantages of Lightweight Concrete
a) Reduced dead load of the concrete allows longer span.
This saves both labor and time.
b) Screeds and walls where timber has to be attached by nailing.
c) Casting structural steel to protect it against fire and corrosion or as a covering for
architectural purposes.
d) Gives heat insulation on roofs.
e) Used in insulation of water pipes.

8.  This type of lightweight concrete is also known as gas concrete or foamed concrete, since
it is developed by introducing large voids into the mortar mass or concrete.
 Voids are typically injected through a chemical reaction, or with the use of an air
entraining agent.
 Aerated or foamed concrete does not require flattening, exhibits appropriate thermal
insulation, and is self-compacting. This makes it ideal for use in hard to reach spaces and
sewer systems.
Foam Concrete

9. Aerator or Cellular or Foamed concrete
• This concrete is achieved by introducing of air or gas into mortar so that when the mix sets
and hardens, a uniform cellular structure is formed.
• Due to this cellular structure, the overall weight of the concrete is much reduced.
• Aluminium powders, Zinc are used to produce hydrogen gas.

10. Self-compacting concrete (SCC) is an innovative concrete that does not require vibration for
placing and compaction.
 Excellent self-compacting properties
 Significant water reductions
 Easy and simplified placing
 Excellent flow even around dense reinforcement
 Easy finishing
 High strength
 Consistent slump and flow
Self Compacting concrete

13.  Vacuum concrete is the type of concrete in which the excess water is removed for
improving concrete strength.
 The water is removed by use of vacuum mats connected to a vacuum pump.
1. The final strength of concrete is increased by about 25%.
2. Sufficient decrease in the permeability of concrete is sufficiently decreased.
3. Vacuum concrete stiffens very rapidly so that the form-works can be removed within 30
minutes of casting even on columns of 20 ft. high.
4. This is of considerable economic value, particularly in a precast factory as the forms can
be reused at frequent intervals.
Vacuum concrete

14. 1. The bond strength of vacuum concrete is about 20% higher.
2. The density of vacuum concrete is higher.
3. The surface of vacuum concrete is entirely free from pitting and the uppermost 1/16 inch
is highly resistant to abrasion. These characteristics are of special importance in the
construction of concrete structures which are to be in contact with flowing water at a
high velocity.
4. It bonds well to old concrete and can, therefore, be used for resurfacing road slabs and
other repair works.

15. 1. Fiber Reinforced Concrete is a composite material consisting of fibrous material which
increases its structural integrity.
2. It includes mixtures of cement, mortar or concrete and discontinuous, discrete, uniformly
dispersed suitable fibers.
3. Fibers are usually used in concrete to control cracking due to plastic shrinkage and to
drying shrinkage.
4. They also reduce the permeability of concrete and thus reduce the bleeding of water.
Fibre Reinforced concrete

17.  Ferro cement is a type of thin wall reinforced concrete, commonly constructed of hydraulic
cement mortar, reinforced with closely spaced layers of continuous and relatively small
size wire mesh.
 The mesh may be made of metallic or other suitable materials.
Ferro Cement

18. ACI Committee 549, 1980
 Cement mortar is reinforced with layers of continuous and small diameter wire meshes
 Mortar provides the mass and wire mesh imparts tensile strength and ductility
 Italian engineer Pier Liugie Nervi is credited with inventing ferro cement in the 1940’s
Materials used in Ferro cement
 Cement mortar mix
 Skeleton steel
 Steel mesh reinforcement or Fibre-reinforced polymeric meshes
Applications of Ferro cement
1. Marine applications
2. Water supply and sanitation
3. Agricultural
4. Residential buildings
5. Rural energy
6. Other structures
7. Boats, fishing vessels, barges, cargo tugs, catamarans, yachts and flotation buoys
8. Key criteria for marine applications: light weight, impact resistance, thickness and water
tightness

19.  RMC is a type of concrete, which is a mixture of Portland Cement, Water, Fine (Sand) and
Coarse aggregates. It is manufactured in a cement factory or batched plants in specific
proportions and transported in a Transit-mixer to the construction sites.
 RMC is eco-friendly compared to site mix concrete because mixing is done in closed
chambers as it reduces the noise and air pollution.
Types of Ready-Mix-Concrete
1. Transit mixed concrete - truck mixed concrete
The first RMC plant in India was set up in Pune, 1992.
2. Shrink-mixed concrete
Shrink the volume of the concrete.
3. Central-mixed concrete
Wet batch plants
Ready Mix Concrete

20. Advantages of Ready-Mix Concrete
 Better quality concrete is produced as it is made from consistent methods and in
advanced equipment.
 No need to store construction materials at the site.
 Labour associated with the production of concrete is eliminated, thereby reducing labour
cost.
 Wastage of basic materials at the site is avoided.
 Reduce the time required for construction.
 No delays in completing major projects like constructing dams, roads, bridges, tunnels.
 Economy in the use of raw materials results in conservation of natural resources.
 Safe work practices - No disruption in the project schedules.
 Environment-friendly.

21.  SIFCON (Slurry Infiltrated Fiber Concrete) is a relatively new composite material utilizing
steel fibers in a cement-based matrix.
 It differs from conventional steel-fiber-reinforced concrete (SFRC) in which the steel fibers
are added directly to a typical concrete mix in the ratio of 0. 5 to 1. 5 percent by volume.
SIFCON, on the other hand, starts with a bed of preplaced steel fibers in the range of 5 to 20
percent by volume.
The fiber bed is then infiltrated with a low viscosity cementitious slurry.
The resulting composite material possesses a very high compressive strength as well as
ductility.
SIFCON has the potential for many applications in the building industry.
SHIFCON

24. Shotcrete is a mortar or high performance concrete conveyed through a hose and
pneumatically projected at high velocity onto a backing surface.
 It is the force of this spraying action that leads to compaction of the concrete or mortar
which then forms layers of concrete to the required thickness .
 Shotcreting has proved to be the best method for construction of curved surfaces.
 Tunnel linings and domes are now much easier to construct with the advent of shotcrete
technology.
 Shotcrete is a widely accepted and used way of placing material that is cementitious in
nature for a vast variety of applications.
In the mining sector, the demand for shotcrete for underground support has skyrocketed in
recent years.
The simultaneous working of multiple heading, unusual filling conditions and difficulty
in access are some of the problems which are distinctive to underground mining and which
require new and innovative applications of shotcrete technology.
Shotcrete

25. Shotcrete materials
1. Cement, water, sand and aggregate are the basic materials used in shotcrete along with
various plasticisers and admixtures to enhance its functioning.
2. High water-cement ratio gives slow setting and influences end quality, while moisture
content in sand/aggregate is also keenly measured.
3. Optimal W/C ratio is around 0.45.
4. Composition of sand/aggregate depends upon water demand, workability, accelerators,
rebound, shrinkage and durability.

26. Properties of shotcrete
 As is the case with conventional concrete, shotcrete properties vary dramatically
depending on water-cement ratio, aggregate quality, size, and
type, admixtures used, type of cement used, and construction practices.
 The proper use of admixtures, fibers, silica fume, and polymers can improve
certain properties. Depending on the needs of the particular application, properties of
the shotcrete materials and mixtures should be tested prior to final application.

27. 1. Polymer concrete is the composite material made by fully replacing the cement hydrate
binders of conventional cement concrete with polymer binders or liquid resins, and is a
kind of concrete-polymer composite.
2. For hardening of polymer concrete, most liquid resins such as thermosetting
resins, methacrylic resins and tar-modified resins are polymerized at ambient or room
temperature.
3. The binder phase for polymer concrete consists only of polymers, and does not contain
any cement hydrates.
4. The aggregates are strongly bound to each other by polymeric binders.
5. The advantages and disadvantages of polymeric binders are directly given to the polymer
concrete.
6. Accordingly, in comparison with ordinary cement concrete, its properties such as
strength, adhesion, watertightness, chemical resistance, freeze-thaw
durability and abrasion resistance are generally improved to a great extent by polymer
replacement.
7. Since the bond between polymeric binders and aggregates is very strong, its strength
properties depend on those of the aggregates.
Polymer Concrete

28. Applications of Polymer Cement Concrete
 Bridge deck coverings
 Floor construction
 Precast construction
 Used as patching compounds

29. The American Concrete Institute defines High Performance Concrete as “Concrete that meets
special performance and uniformity requirements that cannot always be obtained by using
conventional ingredients, normal mixing procedure and typical curing practices.”
In simpler words, HPC is a concrete that has atleast one outstanding property viz.
Compressive Strength, High Workability, Enhanced Resistances to Chemical or Mechanical
Stresses, Lower Permeability, Durability etc. as compared to normal concrete.
For example, Self- compacting Concrete is a specific part of High Performance Concrete,
which distinguishes itself with self-consolidation properties coupled with high flowability.
Table 1 shows the Properties and Areas of application of High Performance Concretes.
Table 1a shows some properties and areas of Application of HPCs.
High Performance Concrete

30. Table1: Properties and Areas of Application of HPC
Property Types of Concrete Areas of Application
Compressive Strength High Strength Concrete
Construction Elements
in High Rise Buildings
Workability
Self Compacting
Concrete
Precast Industry
Filigree Construction
Elements
Durability
High Resistance
Concrete
Chemical-Mechanical
Natural Draught Cooling
Tower
Tank Bund Areas
Density
High Density Concrete
with low Permeability
Marine Structures

31. Table 1a: Properties and Areas of Application of HPC
Properties of HPC Areas of Application of HPC
1.Increase of Durability by lowering of Permeability
2.Increase of Concrete Density
3.Increase of Compressive Strength
4.Improvement in ratio of Flexural Strength to
Compressive Strength
5.Increase of resistance to Corrosion Attack
6.Increase of Chemical Resistance
7.Improvement of Abrasion Resistance
8.Reduction of Segregation and Bleeding
9.Increased resistance to Alkali-Silica-Reaction
(ASR)
10.Improved sulphate resistance and low chloride
ion penetration
1.Production of High Strength Concrete
2.Production of highly Durable Concrete
3.Guniting and Shotcrete Applications
4.Underwater Concreting
5.Concrete in Marine Environment
6.Concrete for Nuclear Projects
7.Concretes for Sewage Treatment
Plants
8.Concrete for Underground Structures
9.Highly Abrasion and Chemical Attack
Resistant Concrete
10.Concrete to take Thermal Stresses

32. High Performance Waterproof Concrete
For a fast developing nation like India, the future focus will be to reduce maintenance costs
of structures.
 We will NEED to adopt a stance to prevent deterioration of structures by using the latest
available material technology.
Taking into consideration today’s general concrete manufacturing and placing process, it
becomes imperative to waterproof the concrete as insurance against its deterioration.
If manipulating the properties of concrete itself can prevent water ingress through the
concrete, the longevity of the structure can be maintained.
This method will ensure that the concrete is protected against water and aggressive media
and the structure is protected from failure through its design life.
Quite simply this can be achieved by blocking the pores and capillaries in concrete using
one of the following methods:
1. Using high performance PCE polymers to reduce water cement ratio of concrete
2. Use of materials like Silica-fume or Aluminosilicate slurries in concrete
3. Use of highly specialized latest generation Integral waterproofing compounds that work
on process of Dynamic SynCrystallization® (DySC) technology

33. Iowa Boasts First Ultra-High Performance Concrete Highway Bridge in United States
Iowa’s Wapello County boasts the first ultra-high performance concrete(UHPC) highway
bridge in the United States, completed in May 2006.
Although a simple, single-span bridge with a three-beam cross section, the Mars Hill Bridge is
a significant step toward “The Bridge of the Future” – utilizing 110-feet UHPC girders that do
not have any rebar for shear stirrups.
The project was one of 96 presented at the 2006 Concrete Bridge Conference held in May in
Reno, Nevada.

34. 1. Geopolymer concrete combines an alkaline liquid with a geological source material
containing silicon and aluminum to form a binder that does not use any Portland cement.
2. Because the chemical reaction that takes place is a polymerization process, the material
is called a geopolymer.
3. The geological source material can come from naturally occurring materials such as
kaolites and clays or by-product materials such as fly ash, silica fume, slag, rice-husk ash,
etc.
4. Fly ash, being one of the most abundant source materials with the necessary properties,
is the most commonly used source material for geopolymer concrete.
5. The alkaline liquids come from soluble alkaline metals such as sodium or potassium such
as combinations or sodium hydroxide and potassium hydroxide and sodium silicate or
potassium silicate.
Geo polymer Concrete

35. The mechanical properties of geopolymer concrete is similar to that of Portland cement
concrete, and therefore can be used as a substitute for Portland cement.
Geopolymer concrete gains strength similar to Portland cement concrete, is resistant
to sulfate attack, has good acid resistance, and undergoes very little creep and drying
shrinkage.
It is ideal where durable concrete is a must. Structural tests on reinforced concrete
elements such as beams and columns demonstrate similar behavior to ordinary Portland
cement concrete.
One drawback is that the alkaline liquid is expensive to manufacture, and thus geopolymer
concrete has not been commercialized to replace ordinary Portland cement concrete.
However, some companies have commercialized it for specialty applications where high
fire or chemical resistance is required.
Obviously, if the process could be made more economical, it would provide an excellent
opportunity to lower the environmental footprint of concrete construction.

36. Depending upon the special properties of concrete, it can be classified
1. Lightweight concrete
2. High strength concrete
3. Fibre reinforced concrete
4. Ferrocement
5. Ready mix concrete
6. SIFCON
7. Shotcrete
8. Polymer concrete
9. High performance concrete
10. Geo polymer concrete
Conclusion

37. THANK YOU