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What is new in ACI 301-20, Specifications for Concrete Construction

Construction Specifier

Photos courtesy American Institute of Concrete. The American Concrete Institute (ACI) published ACI 301-20, Specifications for Concrete Construction , in October 2020. This standard specification establishes criteria for concrete construction that can be incorporated by reference into contract documents.

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TEMPERATURE EFFECTS ON CONCRETE

The Constructor

The size of movement depends upon the change in temperature and the coefficient of thermal expansion o f concrete. The size of movement depends upon the change in temperature and the coefficient of thermal expansion o f concrete.

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STRUCTURAL USES OF PRECAST CONCRETE

The Constructor

Use of Precast Concrete in frames: There are two main types of precast building frame. Use of Precast Concrete for Floors: Each year the industry makes about 5 million square meters of precast floor slabs. Structural frames are mainly used for offices, car parks and retail developments.

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TYPES OF CRACKS IN CONCRETE BEAMS

The Constructor

Cracks in concrete beams due to increased shear stress 2. Cracks in concrete beams due to corrosion or insufficient concrete cover 3. Cracks parallel to main steel in case of corrosion in beams 4.

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REINFORCEMENT COVER AND PRE-CONCRETE CHECKS

The Constructor

When the formwork is erected the concrete can be poured. When the concrete has reached the required strength the formwork can be poured. If the steel had been placed too close to the surface and the concrete had been poured then over time the steel may become exposed to moisture and corrosion will commence.

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BENEFITS OF USING STEEL FIBRES IN CONCRETE

The Constructor

The benefits of using steel fibres in concrete are as follows: 1. It is generally not possible to achieve the same area of reinforcement to area of concrete using steel fibres as compared to using a network of reinforcing bars of wires.

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REDUCING DRYING SHRINKAGE IN CONCRETE

The Constructor

Upon wetting, concrete tends to expand. These moisture-induced volume changes are a characteristic of concrete. If the shrinkage of concrete could take place without any restraint, the concrete would not crack.

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