Concrete Timeline
More Concrete
Concrete Concrete laitance
Formwork
Wall formwork
K-Lock Slab Formwork
Beam-Slab formwork
Flying Formwork
Types of Forms: Special Forms: Slipform, Economy in Formwork
Accuracy Standards
Portland Cement Concrete Aggregate Gradation
Cement Making Process
Concrete Technology
Hydration of (Typ) Portland Cement ASTM Types of Portland Cement
More Concrete
Concrete Concrete laitance
Formwork
Wall formwork
K-Lock Slab Formwork
Beam-Slab formwork
Flying Formwork
Types of Forms: Special Forms: Slipform, Economy in Formwork
Accuracy Standards
Portland Cement Concrete Aggregate Gradation
Cement Making Process
Concrete Technology
Hydration of (Typ) Portland Cement ASTM Types of Portland Cement
FAQ's for Cement & Concrete
Isolation/Expansion Joints: Isolation joints are used to relieve flexural stresses due to vertical movement of slab-on-grade applications that adjoin fixed foundation elements such as columns, building or machinery foundations, etc. Expansion joints are used primarily to relieve stress due to confinement of a slab. If the slab is placed adjacent to structures on more than one face of the slab an expansion joint should be placed to relieve stress. For example, if a slab were placed between two buildings, an expansion joint should be placed adjacent to the face of at least one of the buildings. Confinement on three faces would normally be handled by placing expansion joint on all three faces, and confinement on four faces should be isolated on all faces. This allows for thermal expansion and contraction without inducing stress into the system.
Contraction (control) joints are placed to control random cracking. Contraction joints should be placed at 2 times the slab thickness in feet for a maximum aggregate size of less than ¾”.
For example for a 5” slab with a ¾” coarse aggregate the maximum joint spacing would be 10’. When the maximum coarse aggregate size is greater than ¾” the spacing could be increased to 2 ½” times the thickness. For the prior example this would increase to 13’.
Applications that require thick slabs of 8" or more and good load transfer across joints, due to heavy loading, should be limited to 15' contraction joint spacing to ensure aggregate interlock.
Construction joints are stopping places in the process of construction. Construction-joint types (a) and (b) are also used as contraction joints.
The credits in this page is as indicated in the links
Concrete is a mixture of:
Water (1)
Portland cement (2)
Fine aggregate -SAND (3)
Coarse aggregate -GRAVEL OR CRUSHED ROCK
Uncontrolled concrete work
1:3:5
(1) One part of cement
(2) Three parts of aggregate sand
(3) Five parts of coarse aggregate crushed rock or gravel
Concrete laitance
Types of Forms: Special Forms: Slipform,
Economy in Formwork
Accuracy Standards
Portland Cement
Hydration of Typ Portland Cement
ASTM Types of Portland Cement
Prestressed Precast Concrete Part 2
CONCRETE QUIZ 1
Distinguish between cement and concrete.
Name at least three items you have encountered today which are concrete. Answers will vary.
What are the major ingredients for concrete, and what role do they play? cement- reacts with water to form "glue"
water- reacts with cement, the amount also determines strength
aggregate- makes concrete stronger, more durable, and less costly
What is meant by "workable?" Why is it important for concrete to be workable?
Cement which is workable is able to be poured into forms without difficulty. A slump test is used to measure workability.
Give an example of an aggregate. What is the practical use for this aggregate in making concrete? gravel, sand, vermiculite, perlite,
Aggregate makes the concrete stronger and cheaper.
Cement is a component of concrete. Cement and water make the "glue" which holds concrete together.
CONCRETE QUIZ 2
What can be used to slow the hardening of concrete (give example?) Why would slowing this process be desirable?
What can be used to speed the hardening of concrete (give example?) Why would speeding up this process be desirable?
Calcium chloride solution can be added to speed the hardening of concrete. For example, in cold weather it is desirable to speed up the hardening process and produced higher heat of hydration.
Suppose you were in charge of building a skyscraper. What would be your choice for aggregate and why? The aggregate would depend upon how the concrete is to be used in the building. Lightweight aggregates like shale are used for insulating properties. However, normal weight aggregate would be required for strength. Availability and economy of aggregate are important, too.
Sugar can be added to the concrete to retard hardening. For example, if the concrete needs to be transported a long distance, then a retarding admixture would be desired.
CONCRETE QUIZ 3
What will happen to concrete if it dries out too quickly?
Suppose you were to be the chief designer in charge of building a concrete ship to carry people overseas. What aggregate might you choose to put in your concrete and why?
A lightweight aggregate would be desirable for building a ship needing to float. However, the boat would be dangerous because of poor tensile properties of concrete. It would have to be reinforced to be safe.
Explain what the dormancy period of fresh concrete is. How do contractors make use of the dormancy period? The dormancy period of fresh concrete is the period during which the concrete is in a plastic state and the reaction is very, very slow. This state lasts from 1 to 3 hours and allows contractors to transport concrete to the job site and consolidate it before it hardens. After the dormancy period, the hydration reaction accelerates, and the concrete sets and becomes hard.
Explain how can you measure the consistency of freshly mixed concrete?
A slump test can be performed on freshly mixed concrete to determine its consistency. This is done by pouring it into an inverted cup with the bottom cut out. Once the cup is removed, the concrete is observed. It is desirable that the concrete stay 50-75% of its original height for good workability.
Concrete will most likely crack due to drying shrinkage. The hydration reaction which strengthens concrete will be halted from lack of water resulting in weaker concrete.
CONCRETE QUIZ 4
Briefly discuss the importance of a proper water to cement ratio.
Explain the purpose of a superplasticizer in making concrete.
A superplasticizer is an admixture which is used to make concrete more workable with the use of less water. Using a superplasticizer will result in a stronger concrete because less water is used.
Why should gloves be worn when mixing concrete? Be specific.
Gloves should be worn while mixing concrete because one of the products of the hydration reaction is calcium hydroxide, a base. In fact, upon mixing concrete, the pH rises to 12 which means the solution is strongly basic. This can burn, irritate, and dry out the skin.
Water is important in making concrete, however, it can also be harmful to concrete. Explain this statement. Water transports harmful substances that lead to concrete degradation. Water is the central issue in freeze-thaw damage of concrete.
The water to cement ratio determines the strength of concrete. The less water that is used to obtain a workable concrete, the more strength the resulting hardened concrete will have. However, remember that workability is lost if water to cement ratio is too low.
GLOSSARY
Accelerators: Admixtures that decrease the setting time by increasing the rate of hydration.
Admixture: A material other than water, aggregates, or cement that is used as an ingredient of concrete or mortar to control setting and early hardening, workability, or to provide additional cementing properties.
Aggregate: Inert solid bodies such as crushed rock, sand, gravel.
Binder: Hardened cement paste.
Bleed: To have water seep to the surface of the cement paste due to settling.
Calcination: Decomposition due to the loss of bound water and carbon dioxide.
Cement: Finely powdered mixtures of inorganic compounds which when combined with water hardens with hydration.
Cement paste: Cement plus water. When the mass has reacted with water and developed strength it is called hardened cement paste.
Clay: Type of soil consisting of very fine particles.
Clinker: The material that emerges from the cement kiln after burning. It is in the form of dark, porous nodules which are ground with a small amount of gypsum to give cement.
Compression: Forces acting inwardly on a body.
Concrete: A hard compact building material formed when a mixture of cement, sand, gravel, and water undergoes hydration.
Cure: To keep concrete moist during initial hardening.
Deformation: The process of changing the dimensions of a structure by applying a force.
Dormancy period: Time period that concrete retains it workability. (1-3Hr)
Elasticity: The ability of a material to return to its original shape after being stretched.
Forms: Holders in which concrete is placed to harden.
Gypsum: Calcium sulfate dihydrate, CaSO4.2H2O added to cement to regulate setting.
Hydration: The reaction of cement with water to form a chemical compound.
Kiln: High temperature oven.
Limestone: Mineral rock of calcium carbonate.
Mortar: Cement paste mixed with sand.
Pozzolan cement: Volcanic rock powdered and used in making hydraulic cement.
Porosity: The amount of empty space in concrete.
Portland cement: A cement consisting predominantly of calcium silicates which reacts with water to form a hard mass.
Retardants: Admixtures that increase the setting time by slowing down hydration.
Set: Transformation of cement paste or concrete from a fluid-like consistency to a stiff mass.
Slump test: Test used to determine workability.
Tension: The stress resulting from elongation.
Workability: How easily fresh concrete can be placed and consolidated in forms.
Historical Timeline of Concrete Historical Timeline of Concrete form Auburn
3000 BC - Egyptian Pyramids
The Egyptians were using early forms of concrete over 5000 years ago to build pyramids. They mixed mud and straw to form bricks and used gypsum and lime to make mortars.
300 BC - 476 AD—Roman Architecture
The ancient Romans used a material that is remarkably close to modern cement to build many of their architectural marvels, such as the Colosseum, and the Pantheon. The Romans also used animal products in their cement as an early form of admixtures. Admixtures, additions to the mix used to achieve certain goals, are still used today
1824—Portland Cement Invented
Joseph Aspdin of England is credited with the invention of modern Portland cement. He named his cement Portland, after a rock quarry that produced very strong stone.
1836—Strength Testing
In 1836, the first test of tensile and compressive strength took place in Germany. Tensile strength refers to concrete's ability to resist tension, or pulling apart forces. Compressive strength refers to concrete's ability to resist compression, or pushing together forces.
1867— Iron-Mesh reinforced flower pots
Joseph Monier French gardener is credited
1889— Alvord Lake Bridge
Alvord Lake Bridge was built in 1889 in San Francisco, CA. This bridge was the first reinforced concrete bridge, and it still exists today, over one hundred years after it was built!
1891— Concrete Street
In 1891, the first concrete street in American was built in Bellefontaine, Ohio. This is a modern photo of the historic street.
1882—1902 Reinforced concrete
Francois Hennebique patented
1903—The Ingalls Building
The first concrete high rise was built in Cincinnati, Ohio, in 1903. The Ingalls Building, as it is called, has sixteen stories, making it one of the great engineering feats of its time.
1908—Concrete Homes
In 1908, Thomas Edison designed and built the first concrete homes in Union, New Jersey. These homes still exist today. Edison envisioned that his design would meet great success, and that before no time everyone in America would be living in a concrete home. However, his vision did not become a reality as soon as he expected; in fact, concrete homes are just starting to gain popularity now, one hundred years later.
1913—Ready Mix
The first load of ready mix was delivered in Baltimore, Maryland in 1913. The idea that concrete could be mixed at a central plant, then delivered by truck to the job site for placement, revolutionized the concrete industry.
1915—Colored Concrete
Lynn Mason Scofield founded L.M. Scofield, the first company to produce color for concrete. Their products included color hardeners, colorwax, integral color, sealers, and chemical stains. Colored concrete has done nothing but grow in popularity since.
1918—Water-Cement ratio
Duff A. Abrams developed this metod
1920—Trabeated system of monolithic columns and beams
Auguste Perret (his student was Le Curbosier, proposed that concrete's ability to resist tensile stresses)
1928—Patented Long-Span bridge design
Eugine Fressinet used high strenght steel wire to counter the effects of creep in concrete
1928—London's Royal Horticultural Hall completed
1930—Air Entraining Agents
In 1930, air entraining agents were used for the first time in concrete to resist against damage from freezing and thawing.
1936—Hoover Dam
The Hoover Dam, completed in 1936, is located on the Colorado River, bordering Arizona and Nevada. Up to this time, the dam was the largest scale concrete project ever completed.
1938—Concrete Overlay
John Crossfield was the first to receive a patent for a concrete overlay. He add latex to portland cement, aggregate, and other materials to make a covering for ship decks.
1950's—Decorative Concrete Developed
Brad Bowman developed the Bomanite process, the original cast-in-place, colored, textured and imprinted architectural concrete paving, in the middle 1950's in Monterey, California.
1963—Concrete Sports Dome
The first concrete domed sports arena, known as the Assembly Hall, was built at the University of Illinois in 1963.
1970's—Fiber Reinforcement
Fiber reinforcement was introduced as a way to strengthen concrete.
1980's—Concrete Countertops
Buddy Rhodes, the father of the concrete countertop, cast his first countertop in the mid '80s. Around the same time, Fu-Tung Cheng also cast his first concrete countertop.
1990—Concrete Engraving
Darrel Adamson designed the Engrave-A-Crete ® System in 1990.
1992—Tallest Concrete Building
The tallest reinforced concrete building was built in Chicago, Illinois. The 65-story building is known only by its street address, 311 South Wacker Drive.
1999—Polished Concrete
HTC, originally a Swedish company, introduced concrete polishing to the United States. The first installation in the US was a 40,000-square-foot warehouse floor for the Bellagio in Las Vegas. The popularity of polished concrete has soared in just the few short years it has been around, it is now being used in retail locations and even residential homes.
Code of Hammurabi
Portland Cement is a type of cement, not a brand name. Many cement manufacturers make Portland Cement.To find out more about what concrete is made of, concrete mix designs, admixtures, and water to cement ratios, read our section "What Is Concrete?"
Portland Cement Association |
I.- Type 1 - STANDARD: Normal portland cement.
Type 1 is a general use cement.
II.- Type 2 - MODIFIED: Is used for structures in water or soil containing moderate amounts of sulfate, or when heat build-up is a concern.
For slow setting and less heat.
III.- Type 3 - HIGH EARLY STRENGTH: Used when high strength are desired at very early periods.
For quick setting and early strength.
IV.- Type 4 - LOW HEAT: portland cement. Used where the amount and rate of heat generation must be kept to a minimum.
For very slow setting (little heat)
V.- Type 5 - SULFATE RESISTANT: portland cement. Used where the water or soil is high in alkali.
For alkaline water and soils.
Types IA, IIA and IIIA are cements used to make air-entrained concrete.
They have the same properties as types I, II, and III, except that they have small quantities of air-entrained materials combined with them.
These are very short descriptions of the basic types of cement. There are other types for various purposes such as architectural concrete and masonry cements, just to name two examples.
Your ready mix company will know what the requirements are for your area and for your particular use. Simply ask them what their standard type of cement is and if that will work fine for your conditions.
CONCRETE MIX DESIGN
Types of concrete
Brick Masonry Engineering
Procedure for slump test
1. Dampen the slump test mold and place it on a flat, moist, nonabsorbent, rigid surface, like a steel plate.
2. Fill the mold to 1/3 full by volume (about 2 1/2 inches), and rod the bottom layer with 25 evenly spaced strokes.
3. Fill the mold to 2/3 full (about 6 inches), and rod the second layer with 25 strokes penetrating the top of the bottom layer.
4. Heap the concrete on top of the mold, and rod the top layer with 25 strokes penetrating the top of the second layer.
5. Strike off the top surface of the concrete even to the top of the mold.
6. Remove the mold carefully in the vertical direction (take about five seconds).
7. Immediately invert an place the mold beside the slumped concrete and place the rod horizontally across the mold, and measure the slump, in inches, to the nearest 1/4 inch. The slump test should take approximately 2 1/2 minutes.
What is Concrete?
Brain Storming Activity 1: Concrete Survey
When was concrete first made?
9000 BC 500 BC 100 AD 1756 1824
Circle the possible components of concrete.
water cement gravel sand air steel rods
What is the purpose of cement in concrete?
What role does water play in producing concrete?
Why does concrete harden?
Why does concrete set (harden) slowly?
How can you make concrete set:
faster
slower?
Is concrete stronger in compression, tension, or the same in either?
How strong can concrete or cement be (in pounds per square inch (psi))?
50,000 20,000 5000 2000
How long can concrete last (in years)?
50,000 5000 500 50
scores: 8-10 materials science major; 5-7 concrete contractor; 2-4 concrete laborer;
0-1 home owner
Concrete Survey (Key)
When was concrete first made?
9000 BC 500 BC 100 AD 1756 1824
Circle the possible components of concrete.
water cement gravel sand air
What is the purpose of cement in concrete?
It acts as a primary binder to join the aggregate into a solid mass.
What role does water play in producing concrete?
Water is required for the cement to hydrate and solidify.
Why does concrete harden?
The chemical process called cement hydration produces crystals that interlock and bind together.
Why does concrete set (harden) slowly?
It takes time for the hydrated cement crystals to form
How can you make concrete set:
faster? add calcium chloride or "accelerator"
slower? add sugar or "set retarder"
Is concrete stronger in compression, tension, or the same in either?
It is stronger in compression.
How strong can concrete or cement be (in pounds per square inch (psi))?
50,000 20,000 5000 2000
How long can concrete last (in years)?
50,000 5000 500 50
scores: 8-10 materials science major; 5-7 concrete contractor; 2-4 concrete laborer;
0-1 home owner
(Note: Correct answers are given in bold.)
Concrete- An artificial stone-like material used for various structural purposes. It is made by
mixing cement and various aggregates, such as sand, pebbles, gravel, shale, etc., with water and allowing the mixture to harden by hydration.
Here are just a few facts to help convince you that the topic of concrete deserves to become a part of your science curriculum:
Concrete is everywhere!! Roads, sidewalks, houses, bridges, skyscrapers, pipes, dams, canals, missile silos, and nuclear waste containment. There are even concrete canoes and Frisbee competitions.
It is strong, inexpensive, plentiful, and easy to make. But more importantly, it's versatile. It can be molded to just about any shape.
Concrete is friendly to the environment. It's virtually all natural. It's recyclable.
It is the most frequently used material in construction.
Slightly more than a ton of concrete is produced every year for each person on the planet, approximately 6 billion tons per year.
By weight, one-half to two-thirds of our infrastructures are made of concrete such as: roads, bridges, buildings, airports, sewers, canals, dams, and subways.
Approximately 60% of our concrete highways need repair and 40% of our concrete highway bridges are structurally deficient or functionally obsolete.
Large cities lose up to 30% of their daily water supply due to leaks in concrete water pipes.
It has been estimated that the necessary repairs and improvements to our infrastructures will cost $3.3 trillion over a nineteen-year period. $1 trillion of that is needed for repairing the nation's concrete.
Cement has been around for at least 12 million years and has played an important role in history.
Brainstorming Activity 2: Why is Concrete Important?
Objective: Students will create a list of the importance of concrete and explain how it affects their lives.
Procedure:
"Why concrete is important?" In a large group students will create a list of the importance of studying concrete.
Upon completion of their list, students will develop acronyms for concrete based on their list of concrete's importance. (See example below.)
Students will discuss the implications that would occur if we could no longer make concrete. (i.e. increasing levels of CO2 production or federal regulations)
Brainstorming Activity 3: Applications of Concrete
Objective: Students will create a list of the past, present, and future applications of concrete and how these applications affect their lives and lifestyles.
Procedure:
In small groups, the students will list applications for concrete:
In the past:
Students will create a list of past applications for concrete that has influenced their lives and/or lifestyles.
Currently:
Students will describe common applications of concrete that they encounter daily. Label these as present applications of concrete.
In the future:
Students will create a list of future applications of concrete by predicting how concrete will affect their lives in the future.
Students will present their lists to the class in the form of a collage or a mobile displaying the correlation between their lives and lifestyles with the applications of concrete throughout their lives.
1918 Duff A. Abrams Water-Cement ratio
