CE 471 – ADVANCED CONCRETE
TECHNOLOGY
1 - Introduction
Asst. Prof. Dr. Şevket Can Bostancı
1.1. Introduction
• Concrete is a manmade building material that looks like stone. The
word “concrete” is derived from the Latin concretus, meaning “to
grow together.”
• Concrete is a composite material composed of coarse granular
material (the aggregate or filler) embedded in a hard matrix of
material (the cement or binder) that fills the space among the
aggregate particles and glues them together.
Introduction
• Depending on what kind of binder is used, concrete can be
named in different ways.
- Non-hydraulic cement,
- Hydraulic cement,
- Asphalt concrete.
• Both non-hydraulic and hydraulic cement need water to mix in
and react. They differ here in the ability to gain strength in
water. Non-hydraulic cement cannot gain strength in water,
while hydraulic cement does.
• Non-hydraulic cement concretes are the oldest used in human history
(6500 BC).
• It was the Romans who refined the mixture’s use. The nonhydraulic
cements used at that time were gypsum and lime. The Romans used a
primal mix for their concrete. It consisted of small pieces of gravel and
coarse sand mixed with hot lime and water, and sometimes even
animal blood. To trim down shrinkage, they were known to have used
horsehair.
History
• Historical evidence shows that the Assyrians and Babylonians used clay
as the bonding material. Lime was obtained by calcining limestone.
• The Egyptians used gypsum mortar in construction, and the gypsum
was obtained by calcining impure gypsum. (3000 BC)
• The Chinese also used lime mortar to build the Great Wall in the Qin
dynasty (220 BC).
• A hydraulic lime was developed by the Greeks and Romans using
limestone containing argillaceous (clayey) impurities.
• In 1756, John Smeaton was commissioned to rebuild the Eddystone
Light house off the coast of Cornwall, England. Realizing the
function of siliceous impurities in resisting water, Smeaton
conducted extensive experiments with different limes and
pozzolans, and found that limestone with a high proportion of
clayey materials produced the best hydraulic lime for mortar to be
used in water.
• Portland cement was invented by Joseph Aspdin of England. The
name Portland was coined by Aspdin because the color of the
cement after hydration was similar to that of limestone quarried in
Portland.
• It was in Germany that the first systematic testing of concrete took
place in 1836.
• The second generation of concrete refers to steel bar-reinforced
concrete. Francois Coignet was a pioneer in the development of
reinforced concrete. (1855)
• Reinforced concrete was further developed by Hennebique at the end
of the 19th century, and it was realized that performance could be
improved if the bars could be placed in tension, thus keeping the
concrete in compression. Early attempts worked, with the beams
showing a reduced tendency to crack in tension, but after a few
months the cracks reopened.
• The first reinforced concrete bridge was built in 1889 in the Golden
Gate Park in San Francisco, California.
• To overcome the cracking problem in reinforced concrete, prestressed
concrete was developed and was first patented by a San Francisco
engineer as early as 1886. Prestressed means that the stress is
generated in a structural member before it carries the service load.
• Prestressed concrete became an accepted building material in Europe
after World War II, partly due to the shortage of steel.
• Nowadays, with the development of prestressed concrete, long-span
bridges, tall buildings, and ocean structures have been constructed.
• As a structural material, the compressive strength at an age of 28 days is
the main design index for concrete. There are several reasons for choosing
compressive strength as the representative index.
• First, concrete is used in a structure mainly to resist the compression
force. Second, the measurement of compressive strength is relatively
easier.
• Finally, it is thought that other properties of concrete can be related to its
compressive strength through the microstructure.
• Hence, a high compressive strength could be achieved by reducing the
w/c ratio. However, to keep a concrete workable, there is a minimum
requirement on the amount of water; hence, the w/c ratio reduction is
limited, unless other measures are provided to improve concrete’s
workability.
• Since the 1960s, the development of high-strength concrete has made
significant progress due to two main factors: the invention of water-
reducing admixtures and the incorporation of mineral admixtures,
such as silica fume, fly ash, and slag.
• Water-reducing admixture is a chemical admixture that can help concrete
keep good workability under a very low w/c ratio.
• 1960’s; 30 Mpa is high strength concrete
• In 1972, the first 52-MPa concrete was produced in Chicago (Mid-
continental Plaza)
• In 1972, a 62-MPa concrete was produced, also in Chicago (Water
Tower Place)
• In the 1980s, the industry was able to produce a 95-MPa
West Wacker Drive building in Chicago Water Tower Place in Chicago
• Concrete produced after the 1980s usually contains a sufficient
amount of fly ash, slag, or silica fume as well as many different
chemical admixtures, so its hydration mechanism, hydration
products, and other microstructure characteristics are very different
from the concrete produced without these admixtures.
• There have been two innovative developments in contemporary
concrete: self-compacting concrete (SCC) and ultra-high-
performance concrete (UHPC).
• High-performance concrete is a concept developed in the 1980s.
• It is defined as a concrete that can meet special performance and
uniformity requirements, which cannot always be achieved
routinely by using only conventional materials and normal mixing,
placing, and curing practices.
• The requirements may involve enhancement of the characteristics
of concrete, such as placement and compaction without
segregation, long-term mechanical properties, higher early-age
strength, better toughness, higher volume stability, or longer
service life in severe environments.
• SCC was initially developed by Professor Okamura and his students
in Japan in the late 1980s earthquake zone, concrete structures are
usually heavily reinforced, especially at beam–column
joints. Hence, due to low flowability, conventional concrete could
hardly flow past the heavy reinforced rebars, leaving poor-quality
cast concrete and leading to poor durability.
• In the 1990s, a new “concrete” with a compressive concrete
strength higher than 200 Mpa was developed in France. Due to the
large amount of silica fume incorporated in such a material, it was
initially called reactive powder concrete and later on changed to
ultra-high-strength (performance) concrete (UHSC).
• The ultra-high-strength concrete has reached a compressive
strength of 800 MPa with heating treatment. However, it is very
brittle, hence, incorporating fibers into UHSC is necessary. After
incorporating fine steel fibers, flexural strength of 50 MPa can be
reached.
1.2. CONCRETE AS A STRUCTURAL
MATERIAL
• Concrete is the most widely used construction material in the world, and
its popularity can be attributed to two aspects.
• First, concrete is used for many different structures, such as dams,
pavements, building frames, or bridges, much more than any other
construction material.
• Second, the amount of concrete used is much more than any other
material.
• In a concrete structure, there are two commonly used structural
materials: concrete and steel.
• Steel is manufactured under carefully controlled conditions, always
in a highly sophisticated plant.
• The quality of cement, the binder of concrete, is guaranteed by the
manufacturer in a manner similar to that of steel.
• Concretes have been widely used to build various structures.
High-strength concrete has been used in many tall building
constructions.
• Dams are other popular application fields for concrete. The first
major concrete dams, the Hoover Dam and the Grand Coulee Dam,
were built in the 1930s and they are still standing. The largest dam
ever built is the Three Gorges Dam in Hubei province, China.
Concrete has also been used to build high-speed railways.
• In addition, concrete has been widely applied in the construction of
airport runways, tunnels, highways, pipelines, and oil platforms.
China
Concrete runway
Spain
1.3. CHARACTERISTICS OF CONCRETE
1.3.1. Advantages of Concrete
• Economical
• Ambient temperature-hardened material
• Ability to be cast
• Energy efficient
• Excellent resistance to water
• High temperature resistance
• Ability to consume waste
• Ability to work with reinforcing steel
• Less maintenance required
1.3.2. Limitations
• Quasi-brittle failure mode
• Low tensile strength
• Low toughness
• Low specific strength (strength/density raito)
• Formwork is needed
• Long curing time
• Working with cracks
1.4 Types of Concrete
• 1.4.1. Classification according to unit weight
• 1.4.2. Classification according to compressive strength
• 1.4.3. Classification in accordance with additives
1.5 FACTORS INFLUENCING CONCRETE
PROPERTIES
• w/c ratio (or w/b or w/p ratio)
• Cement content
• Aggregate: maximum aggregate size, aggregate grading,
aggregate shape and texture, sand/coarse ratio,
aggregate/cement ratio
• Admixtures
• Mixing Procedures
• Curing
1.6. Approaches to Concrete Study
References
• Li, Z. (2011) Advanced Concrete Technology. John Wiley & Sons, New Jersey.
• Newman, J. & Choo, B.S. (2003) Advanced Concrete Technology. Butterwoth-
Heinemann, Oxford.
