Although the terms cement and concrete often are used interchangeably,
cement is actually an ingredient of concrete. Concrete is basically a mixture
of aggregates and paste. The aggregates are sand and gravel or crushed stone;
the paste is water and Portland cement. Concrete gets stronger as it gets
older.

Portland cement is not a brand name, but the generic term for the type of
cement used in virtually all concrete, just as stainless is a type of steel and
sterling a type of silver. Cement comprises from 10 to 15 percent of the
concrete mix, by volume. Through a process called hydration, the cement and
water harden and bind the aggregates into a rock like mass. This hardening
process continues for years meaning that concrete gets stronger as it gets
older.

So, there is no such thing as a cement sidewalk, or a cement mixer; the
proper terms are concrete sidewalk and concrete mixer.

It’s simple. Concrete is used for the finished products, such as sidewalks,
foundations, and the surface of many roads. Concrete contains sand, gravel and
cement. Cement is the special hardening ingredient (the gray powder) that makes
concrete harden. Cement is usually made of 60% lime (limestone), 25% silica, 5%
alumina, and 10% other materials, such as gypsum and iron oxide. (Content
provided by the Mineral Information Institute, © 2002

No. Concrete is made by mixing cement, aggregates and water together. When
the water comes in contact with the cement a chemical reaction starts to take
place. This chemical reaction is called hydration. Hydration is the reaction
between the chemicals in water and the chemicals in cement. This reaction forms
new compounds and crystals interlocking themselves and the aggregates together.
A majority of this reaction takes place over the first month after placing the
concrete. Small amounts of additional reaction and strength gains could take
place for years as long as moisture is still present to cause more hydration.
Actually, when the concrete does finally dry out, it stops gaining strength.

Not really; it varies from city to city and region to region. If you are
estimating a project, call our local ready-mix concrete company, and they can
give you an estimate.

Curing is
one of the most important steps in concrete construction, because proper curing
greatly increases concrete strength and durability. Concrete hardens as a
result of hydration: the chemical reaction between cement and water. However,
hydration occurs only if water is available and if the concrete’s temperature
stays within a suitable range. During the curing period-from five to seven days
after placement for conventional concrete-the concrete surface needs to be kept
moist to permit the hydration process. new concrete can be wet with soaking
hoses, sprinklers or covered with wet burlap, or can be coated with
commercially available curing compounds, which seal in moisture.

Yes. Concrete must comply with local building codes, ACI, and ASTM.

Temperature
extremes make it difficult to properly cure concrete. On hot days, too much
water is lost by evaporation from newly placed concrete. If the temperature
drops too close to freezing, hydration slows to nearly a standstill. Under
these conditions, concrete ceases to gain strength and other desirable
properties. In general, the temperature of new concrete should not be allowed
to fall below 50 Fahrenheit (10 Celsius) during the curing period.

Good concrete can be obtained by using a wide variety of mix proportions if proper mix design procedures are used. A good general rule to use is the rule of 6’s:

A minimum cement content of 6 bags per cubic yard of concrete,

A maximum water content of 6 gallons per bag of cement,

A curing period (keeping concrete moist) a minimum of 6 days, and

An air content of 6

Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 500 millionths. Translated into dimensions-this is about 1/16 of an inch in 10 feet (.4 cm in 3 meters). The reason that contractors put joints in concrete pavements and floors is to allow
the concrete to crack in a neat, straight line at the joint when the volume of
the concrete changes due to shrinkage.

Concrete is tested to ensure that the material that was specified and bought is the same material delivered to the job site. There are a dozen different test methods for freshly mixed concrete and at least another dozen tests for hardened concrete, not including test methods unique to organizations

like the Army Corps of Engineers, the Federal Highway Administration, and state departments of transportation.