Concrete blocks are a prefabricated material mainly used to build walls. Like bricks, the blocks are stacked together and joined with a mortar, usually consisting of cement, sand, and water. The blocks are hollow inside to allow for steel bars and mortar filling.
These blocks come in a variety of dimensions and textures, from traditional smooth surfaces to fluted or rough finishes, as well as special units for corners or for beams with longitudinal reinforcements. The dimensions of these blocks range from the classic 8x8x16 inches (approx 19x19x39 cm) which is meant for structural use, to a size of 8x3.5x39 inches (approx 19x9x39 cm) for partitioning walls. How can we incorporate them creatively into our designs?
Although the first blocks were manufactured by hand, nowadays they are produced in an automated way and thousands of blocks can be made per hour. However, by not requiring firing, each unit can be manufactured on site by unskilled masons.
In terms of its thermal behavior, a block wall can work well if the appropriate measures are taken. For example, it is essential to ensure the correct placement of the mixture in all the joints to avoid thermal bridges. In addition, insulators –such as EPS or Glass Wool and Polyethylene as a vapor barrier– can be incorporated into the interior of the blocks to use as an exterior insulating plaster.
Broadly speaking, its manufacture consists of 4 processes:
- Mixing : After weighing, the appropriate amounts of water, gravel, and dry cement are mixed and then water is added.
- Molding : In a specialized machine, the mixture is compacted on molds that define the shape and size of its interior cavities and its exterior texture. This process is generally aided by mechanical vibrations.
- Curing : The blocks are put in steam ovens (low or high pressure) to harden.
- Cubing : The dry blocks are stacked in cubes to be stored.
"The concrete commonly used to make concrete blocks is a mixture of powdered portland cement, water, sand, and gravel.This produces a light gray block with a fine surface texture and a high compressive strength," say the creators of the site How Products Are Made . Thus, the blocks have a good mechanical capacity, incombustibility, and acoustic insulation.
The basic block has been changing to provide more complete solutions, such as waterproofing. Some current models include additives added to the mixture that composes them in order to increase the surface tension of the block and hindering the passage of water. There are also blocks with different edges to deflect the water away from its surface.
Before starting, you should consult local building codes and standards.
1. If we use a strip footing, it must have twice the width of the block. Reference lines are placed with thread or chalk and a test is performed without mortar.
2. Mix the mortar and spread it onto the strip footing (which has been previously moistened) over the width of a block. The initial layer should be 1 inch (2.5 cm) thick.
3. The blocks are placed from the corners and mortar is applied to their vertical joints.
4. At the end of each row, check that they are aligned, vertically and horizontally, and hit them to adjust them if necessary. Repeat the process for all the designed walls.
5. The connection of the holes in each unit begins to generate a continuous vertical cavity where metallic reinforcements can be inserted.
6. When verifying that the mortar is hard enough to mark a footprint, you must finish and equalize the joints and clean the excess.
Despite being a widely used material in the world, its design possibilities have not been exploited. Concrete blocks are usually associated with self-construction and low-cost housing, situations that provide a few spaces to explore beyond functional design.
Through impeccable work, the projects of some architects such as Terra e Tuma, Natura Futura, Agustín Lozada or Takao Shiotsuka Atelier, invites us to think of new ways to use this material. In their work, the blocks appear as the protagonists of the spaces, totally exposed and showing their original color, giving a texture and appearance different from brick; more brutal but very adaptable to other materials and elements such as vegetation and water. By using this material, these architects have managed to reduce the costs of their projects without sacrificing spatial and architectural quality.
What other design options seem to arise? Its standard dimensions and its modular nature allow us to design easily, like a "lego", generating topographies that can form furniture or unevenness. By rotating its original position, its perforations can create permeable walls. These are some simple ideas that can deliver good solutions without being unaffordable.
If you have worked with this material, we invite you to share your experience in the comments section below.