Types Of Concrete, Their Uses And Strengths
Concrete broadly falls into four categories: standard prescribed concrete (SPC), designated concrete, designed concrete and proprietary concrete. There are different types of concrete grades:
Standardised prescribed concrete:
- ST1, ST2, ST3, ST4, ST5
Standardised prescribed concrete:
- General concrete: GEN0, GEN1, GEN2, GEN3
- Reinforced concrete: RC2025, RC23/30, RC28/35, RC35/45, RC40/50
- Paving concrete: PAV1, PAV2
- Foundation concrete: FND2, FND3, FND4
Standardised Prescribed Concrete
Standard mixes are a defined list of concretes within BS 8500 which are made with a prescribed quantity of materials as required in the British Standard. These concretes are normally mixed on site on small scale jobs or obtained from a supplier with no quality standards. SPCs are fairly basic mixes and have no strength guarantee, although this can be assumed based on the values contained within BS 8500.
ST1
ST1 or wet lean mix concrete: commonly used in both commercial and domestic projects for a wide range of general, non-structural applications such as kerb bedding, backing, drainage works, haunching and blinding.
Strength: Assume to be 7.5N/mm2 at 28 days
Strength: Assume to be 7.5N/mm2 at 28 days
ST2
An extremely versatile mix used throughout the construction industry for general and housing applications. It is ideal for un-reinforced foundations and bases for houses and extensions, trench-fill, kerbing, patios and unreinforced house floors as long as a permanent finish (such as a screed or floating floor) will be added.
Strength: Assume 10N/mm2 at 28 days
Strength: Assume 10N/mm2 at 28 days
ST3
ST3 is widely used for light duty domestic applications and foundations but not usually suitable as a wearing surface. It can be used to construct internal floor slabs providing they don’t contain embedded metal and is ideal for house floors with no permanent finish (e.g. carpet or laminate) flooring.
Strength: Assume 15N/mm2 at 28 days.
Strength: Assume 15N/mm2 at 28 days.
ST4
ST4 is used for many domestic, agricultural and industrial applications and suitable as a wearing surface for light foot traffic such as garage floors, sheds bases, internal floor slabs, drain/channel bedding and benching.
Strength: Assume 20N/mm2 at 28 days.
Strength: Assume 20N/mm2 at 28 days.
ST5
ST5 is used for many domestic, commercial and agricultural applications. Suitable for light foot and trolley traffic only such as agricultural equipment stores, foundations for posts/columns, traffic posts and reinforced ground floor slabs.
Strength: Assume 25N/mm2 at 28 days
Strength: Assume 25N/mm2 at 28 days
Designated Concretes
Designated concretes have been developed to make the selection of appropriate concrete simpler and more reliable. While they do not cover every application and they restrict or limit the use of certain materials, they are suitable for many housing, agricultural and structural applications.
GEN0
GEN0 or wet lean mix concrete is a versatile mix commonly used in both commercial and domestic projects for a wide range of general applications, non-structural applications such as kerb bedding, haunching, domestic foundations, blinding, mass and cavity fill. GEN0 should not be used externally unless completely encased.
Concrete strength: 7.5N/mm2 at 28 days.
Concrete strength: 7.5N/mm2 at 28 days.
GEN1
GEN1 is an extremely versatile mix used throughout the construction industry for general and housing applications. It is usually used for cavity filling, kerbing, unreinforced domestic foundations in DC-1 soils and haunching. Examples of GEN1 uses are trench-fill foundations, drainage works, pad foundations, kerbing, cavity and mass fill. GEN1 should not be used externally unless completely encased.
Concrete strength: 10N/mm2 at 28 days.
Concrete strength: 10N/mm2 at 28 days.
GEN2
GEN 2 provides the ideal material for domestic flooring when no permanent floor finish will be installed but it will be carpeted or tiled. Examples of GEN2 uses are foundations for walls, sheds or conservatories, paving for steps and paths, un-reinforced strip footings. GEN2 should not be used externally unless completely encased.
Concrete strength: 15N/mm2 at 28 days
Concrete strength: 15N/mm2 at 28 days
GEN3
Gen 3 is commonly used for light duty domestic applications and foundations. It can be used to construct internal floor slabs that contain no embedded metal and will be covered by carpet, tiles or laminate flooring. It is also suitable for domestic garage floors, but we suggest a minimum of RC25/30 should be used if the garage is also used as a workshop. GEN3 should not be used externally unless completely covered or encased.
Concrete strength: 20N/mm2 at 28 days.
Concrete strength: 20N/mm2 at 28 days.
Reinforced Concrete (RC)
RC is used for a series of designated concretes that are used in concrete that will be reinforced, pre-stressed or containing embedded steel. The specifications for the RC-series of designated concretes include requirements for maximum w/c ratio (W/C) and minimum cementitious content (MCC), which makes specification easier and complete.
RC20/25
This type of concrete is suitable for extremely mild exposure conditions for applications such as lightly reinforced house or garage floors which are not designed as suspended and infill to insulated concrete formwork used above ground.
Concrete strength: 25N/mm2 at 28 days.
Concrete strength: 25N/mm2 at 28 days.
RC25/30
This type of concrete is suitable for mild exposure conditions for applications such as lightly reinforced concrete, internal wearing surface for light foot/trolley traffic and reinforced foundations in DC-1 soils.
Concrete strength: 30N/mm2 at 28 days.
Concrete strength: 30N/mm2 at 28 days.
RC32/40
This type of concrete is suitable for moderate to high exposure conditions such as general and agricultural reinforced concrete, livestock and crop store floors, domestic garages used as workshops.
Concrete strength: 35N/mm2 at 28 days.
Concrete strength: 35N/mm2 at 28 days.
RC35/45
This type of concrete is suitable for highly demanding exposure conditions such as agricultural and industrial reinforced concrete, stable floors, floors and walls for silage or brewer’s grain stores or floors for parlours and dairies.
Concrete strength: 45N/mm2 at 28 days.
Concrete strength: 45N/mm2 at 28 days.
RC35/45
This type of concrete is suitable severe exposure conditions such as agricultural and industrial reinforced concrete, stable floors, floors and walls for silage or brewer’s grain stores or floors for parlours and dairies.
Concrete strength: 50N/mm2 at 28 days.
Concrete strength: 50N/mm2 at 28 days.
Paving Concrete
These designations give the concrete the necessary level of freeze-thaw resistance for conditions experienced in the UK and are suitable for almost all external domestic and structural roads, pavements and hard standings. These have specified MCC and W/C but also require the mix to contain a minimum air content which varies dependant on the maximum aggregate size used/specified.
PAV1
This is the most common type of concrete used for domestic pavement construction, where no de-icing salts are used. PAV 1 mixes have an additive that entrains air to create micro sized air bubbles in the concrete. This helps to protect the surface from frost, specifically freeze-thaw cycles, making it especially useful for outdoor paving. Example of PAV1 uses are house driveways, domestic parking/carports, external paving, walkways/patios, hard standings or bases for workshops, houses or extensions. PAV1 is not suitable for powerfloat finishes.
Concrete strength: 35N/mm2 at 28 days.
Concrete strength: 35N/mm2 at 28 days.
PAV2
PAV2 is a substantial, heavy-duty use concrete suitable for commercial and industrial use. PAV 2 mixes have an air entrainment additive to create micro sized air bubbles in the concrete, helping to protect the surface from frost, specifically freeze-thaw cycles, and making it suitable for use with de-icing salts. Examples of PAV2 uses are slabbing/paving for industrial vehicles or machinery and reinforced bases for commercial buildings.
Concrete strength: 35N/mm2 at 28 days.
Concrete strength: 35N/mm2 at 28 days.
Foundation Concrete
The FND designation used for a series of designated concretes that are used in foundation applications where the ground has been found to contain sulfates. These have specified MCC and W/C and also permit only cement types known to provide appropriate resistance to chemicals found in the ground (primarily sulfates). Foundation concrete for use in sulfate containing soils to DC2-DC4 (design chemical class)
- FND2 – (DC-2 Soils)
- FND3 – (DC-3 Soils)
- FND4 – (DC-4 Soils)
Concrete strength: 30N/mm2 at 28 days.
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