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Cemento, Materiali Rafforzare, Forms

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Concrete, Reinforcing Materials, Forms
This module introduces the learner to the types of cement, aggregates, and additives used in concrete.

It describes general types of concrete, concrete mixing information, and various concrete tests.

It also covers concrete quantity estimating procedures for various job applications as well as compression specimen casting and slump (consistency) testing of freshly mixed concrete.

Some types of concrete reinforcement material such as steel reinforcement bars, welded-wire mesh, and various reinforcement bar supports are also introduced in this module.

Because it is in a semi-liquid state, concrete must be contained in forms until it hardens.

Forms can be built on the job using lumber and plywood, or they can be prefabricated form systems that the contractor buys or rents.

In this module, the basic job-built forms for concrete walls, footings, and floor slabs are covered.

Click on each term to find out more:
Admixtures
Materials that are added to a concrete mix to change certain properties of the concrete such as retarding setting time, reducing water requirements, or making the concrete easier to work with.

Aggregates
Materials used as filler in concrete; may include mixtures of sand, gravel, crushed stone, crushed gravel, or blast-furnace slag.

Axle-steel
Deformed reinforcing bars that are rolled from carbon-steel axles used on railroad cars.

Brace
A diagonal supporting member used to reinforce a form against the weight of the concrete.

Cured Concrete
Concrete that has hardened and gained its structural strength.

Flatwork
Work connected with concrete slabs used for walks, driveways, patios, and floors.

Footing
The base of a foundation system for a wall, column, and chimney. It bears directly on the undisturbed soil and is made wider than the object it supports to distribute the weight over a greater area.

Forms
Wood or metal structures built to contain plastic concrete until it hardens.

Green Concrete
Concrete that has hardened but has not yet gained its structural strength.

Hydration
The catalytic action water has in transforming the chemicals in Portland cement into a hard solid. The water interacts with the chemicals to form calcium silicate hydrate gel.

Kip
An informal unit of force that equals one thousand (kilo) pounds.

Monolithic slab
Concrete placed in forms in a continuous pour without construction joints. Also referred to as monolithic pour.

Pascal
A metric measurement of pressure.

Piles
Column-like structural members that penetrate through unstable, nonbearing soil to lower levels of load bearing soil. They provide support for grade beams or columns that carry the structural load of a building.

Plastic concrete
Concrete when it is first mixed and is in a semi liquid and moldable state.

Plyform
American Plywood Association’s trade name for a reusable material for constructing concrete forms.

Pozzolan
The name given by the ancient Romans to describe the volcanic ash they used as a type of cement. Today, the term is used for natural or calcined materials (including fly ash and silica fume) or air-cooled blast furnace slag.

Rail-steel
Deformed reinforcing bars that are rolled from selected used railroad rails.

Rebars
Abbreviation for reinforcing bar. Also called rerod.

Screeding
Leveling newly placed concrete to and established grad. Also called striking off.

Shoring
Temporary bracing used to support above-grade concrete slabs while they harden.

Slab-on-grade (slab-at-grade)
A ground supported concrete slab 3 ½ inch or thicker that is used as a foundation system. It combines concrete foundation walls with a concrete floor slab that rests directly on an approved base that has been placed over the ground.

Slag
The ash produced during the reduction of iron ore to iron in a blast furnace.

Slump
The distance a standard-sized cone made of freshly mixed concrete will sag. This is known as a slump test.

Studs
Vertical members of a form panel used to support sheathing.

Subgrade
Soil prepared and compacted to support a structure or pavement system.

Walers
Horizontal pieces placed on the outsides of the form walls to strengthen and stiffen the walls. The form ties are also fastened to the walers.

Water-Cement Ratio
The ratio of water to cement, usually by weight (water weight divided by cement weight), in a concrete mix. The water cement ration includes all cementations -- components of the concrete (including fly ash and pozzolan) as well as Portland cement.