Blocks

History of Blocks  

Blocks

   A concrete block can be used as a building material in the construction of walls. It is also defined as a concrete masonry unit (CMU). A concrete block is one of several precast concrete products used in construction. Most concrete blocks have one or more hollow cavities, and their sides may be cast smooth or with a design. Concrete blocks are stacked one at a time and held together with fresh concrete mortar to form the desired length and height of the wall.

     Concrete mortar was used by the Romans as early as 200 B.C. to bind shaped stones together in the construction of buildings. During the reign of the Roman emperor Caligula, small blocks of precast concrete were used as a construction material in the region around present-day Naples, Italy.  The English stonemason Joseph Aspdin developed portland cement, which became one of the key components of modern concrete from the year of 1824.

     In 1890, the first hollow concrete block is designed by Harmon S. Palmer in the United States. Palmer's blocks were 8 inches by 10 inches by 30 inches. They were so heavy. Therefore, they had to be lifted into place with a small crane. There is an estimated number which is 1,500 companies were manufacturing concrete blocks in the United States by the year of 1950.

     These early blocks were usually cast by hand. The average output was about 10 blocks per person per hour. Nowadays, concrete block manufacturing is a highly automated process that can produce up to 2,000 blocks per hour.

    Blocks are generally larger than bricks in term of size. Due to this reason, a block normally requires both hands to lift it up for laying process. For the same reason, it can be laid more quickly than bricks, but the larger size also means less versatility in laying process especially when structure ends, corners and laying to curves. Thus, blocks are generally intended to be plastered.

There are 2 types of blocks, which are clay blocks and concrete blocks where concrete blocks are more widely used.

Manufacture Process:

• Concrete  or clay is casted into mould, vibrated and cured.
• The addition of aluminium powder to a fine mix of sand, lime, fly ash and Portland cement are form most aerated blocks
• The dissolution of the metal powder produces a non-interconnecting cellular structure is to generate the hydrogen gas.
• The process is accelerated by pressure steam curing in an autoclave.

CONCRETE BLOCKS 

Type of concrete block:

• Solid

Solid concrete blocks are also called dense aggregate blocks. Solid concrete blocks are mostly used in the work-horse of the construction industry. Their distinctive properties of durability and strength make them an ideal and cost-effect solution for all types of load bearing walls

• Cellular

It can be defined as lightweight aggregate block. Produced in greater volume, but less strong than solid concrete blocks, cellular concrete blocks are used in both internal and external walls where loading is slightly more restricted or as infill blocks in beam and block flooring. Their main advantage over solid concrete blocks comes from a combination of higher insulating properties and a lighter unit weight. The cellular block enables time and material cost savings through easier handling and larger units.

• Hollow

It is known as aerated concrete or "aircrete" block. Hollow concrete blocks are the lightest weight among all types  the concrete blocks.  They are distinguished by their capacity to perform a dual structural / insulation function.  Though, it is limited to the structural applications in low-rise construction and partitions as well  as a component of curtain walling in higher buildings, hollow concrete blocks can perform a similar range of functions as solid and cellular concrete blocks.

Properties:

1.      Density and Strength

For the British Standard BS 6073-2: The range of aircrete and aggregate concrete blocks can be listed by common compressive strengths of 2.9, 3.6, 7.3, 8.7, 10.4, 17.5, 22.5, 30.0, and 40.0MPa.

The majority of concrete blocks fall in the range from 2.8 to 30MPa, with associated densities of 420–2200 kg/m3 and thermal conductivities from 0.10 to 1.5W/mK at 3% moisture content.

In the range of 0.03-0.05% is considered to the drying shrinkages.

2.      Durability

Dense concrete blocks and certain aerated lightweight blocks are resistant to freeze conditions below damp-proof course (DPC) level.

3.      Fixability

Aerated and lightweight concrete blocks has a good background for fixings.

Nails to a depth of 50mm are efficiency in the light loads.

Wall plugs and proprietary fixings are suitable for the heavier loads.

Both of these two fixings should avoid the edges of the blocks.

4.      Thermal insulation

The limiting area-weighted U-value standard for wall elements in new building is 0.35W/m²K.

The range of 0.27-0.30W/m²K is to achieve the Target Emission Rate overall.

5.      Phase change material blocks

Phase change materials (PCMs) incorporated into aerated concrete blocks offer some additional thermal stability to the internal environment by absorbing excessive summer heat, which is then released during the cooler periods.

The phase change at 26^◦C effectively increases the thermal capacity of the lightweight blocks.

6.      Fire resistance

Solid unplastered 90mm blocks can achieve up to 60 minutes’ fire protection.

Certain 150mm and most 215mm solid blocks can achieve 360 minutes’ fire protection.

Therefore, concrete block offers good fire resistance.

7.      Sound insulation

Concrete blocks can achieve minimum airborne sound insulation of 45Rw dB for separating walls and 40Rw dB for internal bedroom or WC walls.

CLAY BLOCKS 

In general, clay blocks are extruded hollow units. It is manufactured with the same materials that used in production of clay bricks. Through the process of firing, these blocks are becoming dense, hard, and brittle which make them to be easily cut and fixed. During the manufacturing, clay is added with sand, straw or other recycled materials to enhance its unique properties as it is fired, dried and extruded. As the blocks are burned off during firing process, innumerable tiny holes and connecting pores are occurred which the air will be trapped these pores and it helps to resist against hear and reduce the sound transmission. Additionally, clay block is not only resisting against fire, yet it also resists against the insects attack. Clay blocks are highly eco-friendly materials as it has less environmental impact during their manufacturing process compare to other materials and it provides a very high insulation.

Types of Clay Blocks

• Fire-clay blocks 

Fire-clay blocks are combining structural strength, insulation and when externally rendered as well as moisture protection. For masonry clay honeycomb blocks, it can be used as single skins for external load bearing walls. Besides, for its internal part, it is usually finished directly with gypsum plaster. They are actually manufactured to natural, riven, and textured finish in a range of colours, which is including terracotta red, ochre, buff and blue as well as to high gloss or satin finish in pastel shades.

• Unfired-clay blocks 

Unfired-clay blocks are manufactured from clay and sometimes incorporating straw might be used for non-load bearing partition walls. These blocks are easily to cut and to create many architectural features. Due to this, it is normally finished with a skin coat of clay plaster. However, its internal walls are sufficiently strong to support shelving and other features. Apart from that, it is actually recyclable or biodegradable and it has advantage of absorbing the odours and stabilizing internal humidity as well as temperature by its natural absorption and release moisture and heat.

• Gypsum blocks 

Gypsum blocks are generally made from natural crystalline rock. It is generally used as non-load bearing partitions and internal insulation of walls. Additionally, they are actually good in sound insulation. Thus, they are used to infill rather than used as load-bearing wall. The sound insulation properties are in relation to its thickness and block density. 

Properties:

• Low density: 600 – 800 kg/m³
• Medium density: 800 – 1100 kg/m³
• High density: 1100 – 1500 kg/m³

Typical Clay Blocks

The minimum average compressive strengths for clay blocks are;

• Non-loadbearing walls/partitions              1.4 N/mm2
• Facing and common blocks                     2.8 N/mm2
• Blocks for loadbearing internal walls        2.8 N/mm2

Omni Blocks (Green Material)

Omni Block

Nowadays, there are some high-rise buildings started to use green materials as its main materials which will insure a return on their construction investment. One of the green materials to be used in construction is Omni Block, an insulated 'stand-alone' structural wall system. For its advantage, it does not require and furring strips, additional insulation, or sheetrock to complete the wall, even though numerous finishes are added for its aesthetic purpose. 

Properties:

Omni Block is re-engineered "age-old" regular cinder block with unique cells, which are easily filled with uniformly molded Expanded Polystyrene foam insulation inserts.

Its insulation inserts are manufactured using safe, clean, non-toxic, and non-polluting processes, which in turn, result in a product that is environmental friendly. Its raw material is a by-product of oil refinery waste. The Block units are manufactured utilizing inorganic elements that are in abundant supply and locally quarried.