Cheap, robust and quick to construct, block work is still a staple element of most new buildings. When looking to reduce the environmental impact of block work, look for high levels of recycled aggregates, lower levels of cement and increasingly available alternatives to concrete.
Block work is something of a necessity in a building. Almost all buildings will feature concrete blocks in one way or another. According to the Concrete Block Association 60million square metres of dense and lightweight concrete building blocks are produced each year.
There are three main types of blocks; dense, lightweight and aerated. Dense concrete blocks with their properties of durability and strength are typically selected for load bearing walls. Often chosen for infill, lightweight blocks offer greater savings in time and cost, but are less strong. Aerated concrete blocks have commonly been used in the UK since the 1960s and provide both structure and insulation. They are produced by adding aluminium powder to the mix, which allows a chemical reaction to occur, producing air bubbles in the concrete.
Walls usually make up the largest surface area of a building, so ensuring good thermal mass and low U-values is important. The use of block work offers the potential for high thermal mass, especially if used to create not just the external walls, but also internal partitions.
Concrete has long been criticised for its environmental impact. However, the industry is making improvements; through encouraging the use of alternatives to cement, the environmental impact is being reduced. Ground granulated blast furnace slag (GGBS), can typically be used to replace up to fifty per cent of the cement in a concrete mix. Another common alternative is pulverised fuel ash, a waste product of combustion in coal fired power stations. For optimum strength, this can replace fifteen per cent of the cement in standard blocks, and up to fifty per cent in aerated blocks.
There is a growing market of alternatives to concrete. Natural and renewable materials are beginning to be utilized. Clay honeycomb blocks have been used on the continent for years, but are now becoming more common in the UK. They are formed with a cellular structure, which traps air, acting as an insulant. Hemp blocks offer high levels of insulation with breathability whilst providing structure. They are also highly sustainable due to their ability to sequester carbon, but are yet to become common place in the UK building industry.
Thermalite Hi-Strength Smooth Face
Hanson’s Thermalite blocks are lightweight, meaning they can be laid more quickly. The aerated concrete blocks contain pockets of trapped air providing good compressive strength, high levels of thermal insulation and moisture resistance.
Manufacturer: Hanson
Application: walls, partitions
Material: pulverised fuel ash, sand, cement, lime, aluminium and water
Recycability: reusable
Recycled content: 50 per cent pre-consumer pulverised fuel ash
Face dimensions: 440 x 215mm
Block widths: 100mm and 140mm
Density:730kg/m3
Strength:7.3N/mm2
Thermal conductivity: 0.18W/mK
UK distribution base: West Midlands and Kent
Thermalite Turbo
The Thermalite Turbo block is suitable for all blockwork applications, including use below DPC level. By using a minimum 215mm width block, Turbo can be used in external solid wall applications where low u-values are required.
Manufacturer: Hanson
Application: external walls, partitions and foundations
Material: pulverised fuel ash, sand, cement, lime, aluminium and water
Recycability: reusable
Recycled content: 50 per cent pre-consumer pulverised fuel ash
Face dimensions: 440 x 215mm
Block widths: 100mm, 115mm, 125mm, 140mm, 150mm, 190mm, 200mm, 215mm, 265mm, and 300mm
Density: 470kg/m3
Strength: 2.9N/mm2
Thermal conductivity: 0.11W/mK
UK distribution base: Kent
Enviroblock Lightweight
Enviroblock has a minimum of 80% recycled aggregates. They can be used both internally and externally and are available in both a standard and a paint grade finish.
Manufacturer: Aggregate Industries UK
Application: walls, partitions
Material: cement, china clay and water
Recycability: reusable and recyclable
Recycled content: minimum 80%
Face dimensions: 440 x 215mm
Block widths: 100mm and 140mm
Density: 1450kg/m3
Strength: 7.3N/mm2
Thermal conductivity: 0.84W/mK
Life expectancy: 10 years
UK distribution base: Aberdeen, Leicestershire, Wiltshire and Cornwall
Enviroblock Dense
This block is suitable for use both above and below the DPC. It is available in a paint grade finish, which is suitable for use where a consistent and close textured face is required.
Manufacturer: Aggregate Industries UK
Application: walls, partitions
Material: cement, china clay and water
Recycability: reusable and recyclable
Recycled content: minimum 80%
Face dimensions: 440 x 215mm and 290 x 215mm
Block widths: 100mm and 140mm
Density: 1950kg/m3
Strength: 10.4N/mm2
Thermal conductivity: 1.37W/mK
Life expectancy: 10 years
UK distribution base: Aberdeen, Leicestershire, Wiltshire and Cornwall
Masterdenz Fairfaced Solid
This block is designed to have a consistent high quality finish, making it particularly well suited to facing blockwork. It is available in a natural buff or grey finish, created naturally, without the use of artificial pigmentation.
Manufacturer: Aggregate Industries UK
Application: walls, partitions
Material: concrete
Recycability: reusable and recyclable
Face dimensions: 440 x 215mm
Block widths: 75mm, 100mm and 140mm
Density:1900kg/m3
Strength:7.3N/mm2
Thermal conductivity: 1.31W/mK
Life expectancy: 10 years
UK distribution base: Lancashire, Wiltshire, Leicestershire, Cornwall and Scotland
ThermoplanZiegel Blocks
The ThermoplanZiegel Block is a honeycomb clay block, which provides high insulation and low psi values. The system is suitable for buildings up to four storeys in height.
Manufacturer: Natural Building Technologies
Application: external walls
Material: clay
Recycability: reusable
Face dimensions: 250 x 250mm
Block widths: 300mm, 365mm, and 425mm
Density: 650kg/m3
Strength: 6N/mm2
Thermal conductivity: 0.09W/mK
Country of manufacture: Germany
UK distribution base: London and Buckinghamshire
Hemp HC Block
Made from industrial hemp, the Hemp HC block has a number of eco credentials. They offer the advantage of carbon sequestration, as the hemp takes in carbon as it grows.
Manufacturer: Hemp Construct
Application: External walls and partitions
Materials: Hemp shiv, slaked lime, hydraulic lime and water
Face dimensions: 600 x 300mm
Block widths: 300mm
Density: 340kg/m³
Strength: 10.8N/mm²
Thermal conductivity: 0.53W/mK
UK distribution base: Essex
Celcon Standard Grade Blocks
Alongside being used for wall applications, Celcon Standard Grade Blocks can also be used below DPC levels as infill for beam and block floors.
Manufacturer: H+H
Application: internal and external walls, partitions, beam and block floors, and foundations
Material: pulverised fuel ash, aggregates, aluminium powder
Recycability: can be recycled for use as aggregate
Recycled content: contains upto 80% recycled material
Face dimensions: 440 x 215mm
Block widths: 75mm, 100mm, 115mm, 140mm, 150mm and 215mm
Density:600kg/m3
Strength:3.6N/mm2
Thermal conductivity: 0.15W/mK
Life expectancy: over 35 years
UK distribution base: Yorkshire
Celcon Standard Grade Foundation Block
Designed for use below DPC level, this block is suitable for the support of cavity or solid walls, framed construction or suspended floors, including beam and block floors.
Manufacturer: H+H
Application: foundations
Material: pulverised fuel ash, aggregates, aluminium powder
Recycability: can be recycled for use as aggregate
Recycled content: contains upto 80% recycled material
Face dimensions: 325 x 215mm, 440 x 215mm and 610 x 140mm
Block widths: 215mm, 275mm, 300mm, and 355mm
Density: 600kg/m3
Strength: 3.6N/mm2
Thermal conductivity: 0.25W/mK
Life expectancy: over 35 years
UK distribution base: Yorkshire
Jumbo Bloks
Jumbo Bloks allow 1m2 of wall to be completed using six blocks, increasing speed and productivity. These blocks are around two and a half times the size of a traditional block.
Manufacturer: H+H
Application: partitions, internal and external walls
Material: pulverised fuel ash, aggregates, aluminium powder
Recycability: can be recycled for use as aggregate
Recycled content: contains upto 80% recycled material
Face dimensions: 610 x 270mm
Block widths: 100mm and 140mm
Density: 600kg/m3
Strength: 3.6N/mm2
Thermal conductivity: 0.15W/mK
Life expectancy: over 35 years
UK distribution base: Yorkshire
Fairfaced Concrete Blocks
These blocks are designed to be outer facing, offering both structural integrity and a high quality finish. They fairfaced block is available in nine different colours.
Manufacturer: Forticrete
Application: external facing walls
Material: concrete
Face dimensions: 400 x 215mm
Block widths: 90mm, 100mm, 140mm and 215mm
Density: 2100kg/m3
Strength: 17.5N/mm2
Thermal conductivity: 1.56W/mK
Cellular Dense Concrete Blocks
These cellular blocks are a low weight alternative to dense concrete blocks. They can be sued for both the inner and outer leaf of cavity walls upto three storeys high.
Manufacturer: Thomas Armstrong
Application: external and internal walls
Material: concrete
Recycled content: upto 30%
Face dimensions: 440 x 215mm
Density: 2100kg/m3
Strength: 10.4N/mm2
Thermal conductivity: 0.92W/mK
Fibotherm Lightweight Concrete Blocks
Fibotherm concrete blocks offer speed in their construction, due to their lightweight nature. They provide high levels of insulation, and the surface acts as a good key for plaster.
Manufacturer: Stowell Concrete
Application: external and internal walls, cavity walls and partitions,
Face dimensions: 440 x 215mm
Block widths: 75mm, 100mm, 140mm and 190mm
Density: 850kg/m3
Strength: 3.6N/mm2
Thermal conductivity: 0.29W/mK
UK distribution base: Bristol, Cheddar and Weston Super Mare
Durisol D365/120
Durisol blocks are made from cement bound woodchip. For structural stability concrete must be poured into the cavity, surrounding steel reinforcement bars. They achieve a BRE Green Guide rating of A+.
Manufacturer: Durisol
Application: external walls
Material: Recycled and treated timber, cement and PFA
Recycled content: 80% recycled wood
Face dimensions: 500 x 250mm
Block widths: 365mm
Strength: determined by the concrete core
Thermal conductivity: 0.19W/mK
UK distribution base: South Wales
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