What is the difference between Hollow Concrete Blocks and Fly Ash Bricks?

Which is better for masonry?

The masonry is there since mankind begins and to date, it is very popular. The stones are used in masonry work for years but now the bricks are widely used material in construction. The reason behind bricks used in masonry is they are economical, durable, easy to handle, and to work with. But bricks have some disadvantages. The conventional clay bricks are made from topsoil which minimizes the land for agriculture. In the making of these bricks the carbon dioxide gas is emitted. The clay bricks are not environment friendly. These days the fly ash bricks and hollow concrete blocks gaining popularity for masonry.

This is the comparison between concrete hollow blocks and fly ash bricks to choose right for your masonry.

Hollow Concrete Blocks

The hollow concrete blocks according to Indian Standard – IS 2185 (Part-1) 2005, the hollow blocks have one or more large holes or cavities pass through the block or do not pass through the block (close cavity). The block has solid material between 50 to 75 percent of total volume from overall dimensions.

Fly Ash Bricks

The fly ash bricks are eco-friendly made from fly ash or pulverized fuel ash. These blocks are 100 percent solid and do not have any cavity.

Which Raw Material is Used?

The hollow concrete blocks have cement, aggregates, sand or gravel, and water. Also, the industrial waste like fly ash, bottom ash is added.

The fly ash bricks are made from fly ash or pulverized fuel ash, cement, sand, lime, and gypsum

Where are they Used?

The hollow concrete blocks are used in masonry for Exterior load-bearing walls, Interior load-bearing walls, curtain walls, partition wall, and panel wall, backing to stone, brick and facing, fireproofing, fire-safe walls around elevators and stairwells, piers, retaining walls, column, etc.

As the fly ash bricks provide strength and durability these bricks are used in various types of construction for load-bearing and non-load bearing walls. These bricks are also used for Raising Infrastructures, Factories, Warehous, Power plant, High rise structures, construction of pavements, water tanks, underwater works, canal lining, and irrigation work, etc.

Advantages of Concrete Hollow Blocks and Fly Ash Bricks?

Hollow Concrete Blocks

These blocks have high durability and less weight. So there is less dead load and saves reinforcement steel in RCC

The masonry practice of hollow concrete blocks is easy and faster than other conventional practices.

These blocks are environment friendly as the waste like fly ash or bottom ash is used as raw material.

The blocks have a rough texture so there is excellent bonding between cement mortar and blocks.

Semi-skill labor can also work with hollow concrete blocks.

These hollow blocks are good sound insulators and provide resistance to earthquakes.

Water consumption of concrete blocks is comparatively less than fly ash bricks

The steel reinforcing is possible with hollow concrete blocks

The weight of the block is less and less steel is required as there is less dead load

These hollow concrete blocks can be used in the construction of load-bearing structure up to 6 stories high with steel

Using the steel there is less dead load so the construction has high earthquake resistance

The special hollow concrete blocks can be used as horizontal reinforcements like lintels and horizontal reinforced concrete can build with blocks

Fly Ash Bricks

These bricks are made using the waste from fly ash which is the waste from a thermal power plants and it is hard to dispose of.

These bricks are high fire insulation

The bricks are very strong and sturdy and almost no breakage in transportation

The bricks have the uniform size so the less mortar is required for joints and plaster

Fly ash bricks provide good thermal insulation

There is no different size of fly ash brick requires for lintel, sill, and jamb

What are the disadvantages of Hollow Concrete Blocks and Fly Ash Bricks?

Hollow Concrete Blocks

The blocks are poor heat insulator as have less thermal mass

The price of the blocks is high compared to fly ash bricks for construction. The price is depending on the availability in the market

Concealed wiring is not possible in hollow concrete blocks

There is a different size of blocks required for lintel, sill, and jamb

Fly Ash Bricks

The mechanical strength of fly ash brick is less but it can improve by adding marble waste of mortar

These bricks can manufacture in limited size and modular size is produced only. The large size of brick has higher chances of breakages

The bricks have a low heat-absorbing capacity. This is can be used in a subtropical region or where the climate is warm.

Bricks are heavy in weight than the hollow blocks

The concealed wiring can be done

The steel cannot be used in the fly ash masonry

How to identify Hollow Concrete Blocks and Fly Ash Bricks?

The hollow concrete blocks are grey in color

The fly ash bricks are generally tan to dark grey

Various Properties of the Concrete Hollow Blocks and Fly Ash Bricks

Hollow Concrete Blocks

Length: 400, 500 or 600 mm

Height: 200 or 100 mm

Width: 50, 75, 100, 150, 200, 250 or 300 mm

Fly Ash Bricks

Standard Modular Size 190 x 90 x 90 mm or 190 x 90 x 40 mm

Standard Non modular size 230 x 110 x 70 or 230 x 110 x 30 mm

Dimensions Tolerance

The hollow concrete blocks have variation in length shall not more than ±5 mm and the height and width of the unit not more than ±3 mm

Fly Ash Bricks

The dimension of the block tested in accordance with IS 12894:2002 with limits of 20 bricks

For modular size

Length 3720 to 3880 mm (3800 ±80 mm)

Width 1760 to 1840 mm (1800 ±40 mm)

Height 1760 to 1840 mm (1800 ±40 mm)

 

For 90 mm high bricks

760 to 840 mm (800 ±40 mm)

For Non-Modular Size

Length 4520 to 4680 mm (4600 ±80 mm)

Width 2240 to 2160 mm (2200 ±40 mm)

Height 1440 to 1360 mm (1400 ±40 mm)

(For 70 mm high bricks)

640 to 560 mm (600 ± 40 mm)

(For 30 mm high bricks)

Dry Density

The dry density of the hollow concrete block varies from 1100 to 1500 kg/m³. This variation is depending on the grade of concrete and the extent of the cavity

Fly Ash Bricks

The fly ash bricks have a dry density that varies between 1700 to 2000 kg/m³.

Weight

Hollow Concrete Blocks

The weight is depending on the density and size of the block

Fly Ash Bricks

This depends on the density and size of the brick

Compressive Strength

The hollow concrete block has a compressive strength of hollow concrete block ranges from 3.5 to 15 N/mm² and depend on the grade of the blocks

Fly Ash Bricks has compressive strength from 3.5 to 35 N/mm² and depending upon the class bricks

Water Absorption

The water absorption of a hollow concrete block does not exceed 10 percent of its weight

The water absorption of fly ash brick should not exceed 15 to 20 % of its weight

Termite Resistant

Concrete hollow blocks and fly ash bricks have good termite resistance

Thermal Conductivity

The hollow concrete block has a thermal conductivity of 0.12 to 0.17 W/m K

The thermal conductivity of fly ash brick is 0.3 to 0.4 W/m K

Sound Insulation

Hollow Concrete Blocks

The sound insulation is the capacity to reduce sound transmission by building elements

It is depending upon the thickness of the wall

The blocks have good sound insulation property as it has a dense structure

Fly Ash Bricks

The fly ash bricks have moderate sound insulation property

Efficiency

Mortar Consumption

Hollow Concrete Blocks

The blocks required less mortar compared to fly ash bricks

Fly Ash Bricks

More mortar is required compared to hollow blocks

Breakage and Utilization

The hollow concrete blocks have negligible breakage and it depends on basic quality

The fly ash bricks have negligible breakage and almost utilization is possible

Cost

The hollow concrete blocks are costlier than fly ash bricks but the overall masonry cost is low. As it consumes less mortar

The fly ash bricks are cheap but the overall cost is high as it requires more mortar than hollow concrete blocks

What is an Environment Impact of Hollow concrete block and Fly Ash bricks?

Hollow Concrete Blocks

The hollow concrete blocks are environment-friendly building material and also energy-efficient as they have proper insulating properties

Fly Ash Bricks

The fly ash brick is also environmentally friendly. It is the waste of thermal power plant and not easy to dispose

There is a very low amount of carbon dioxide is emitted in manufacturing

 

You will know about the comparison between Hollow Concrete Blocks and Fly Ash Bricks. Both products are environmentally friendly and the raw material used is industrial waste. This comparison will help you to choose according to your application.