Concrete Blocks
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Concrete Blocks in the History of Jarfel // Sahara
Concrete blocks have been evolving since the 1940s — the same decade when Sahara Tecnologia, represented by Yoshio Sahara, arrived in Brazil in 1942 from Japan, specifically to manufacture concrete block machines using Japanese technology.
In 1978, Jarfel, led by its director Francisco Carlos Aguilar, believed in concrete blocks — which at the time were considered something of the future and close to becoming a reality due to not requiring firing in their production process — and acquired Sahara Tecnologia. Today, it is one of the largest companies in the field of equipment manufacturing for concrete products.
And that vision became reality. Starting in the year 2000, many ceramic industries began to shut down in large numbers due to increased inspections. These companies failed to comply with regulations related to the firing process and the use of unregulated raw material extraction.
Concrete blocks are the reality of 21st-century construction. In the past, ceramic materials dominated the construction industry, especially in low-income housing projects. However, due to environmental concerns, ceramics are increasingly falling out of use in Brazil. In addition, there are more viable alternatives in terms of investment and sustainability, such as concrete blocks, soil-cement bricks, and precast elements.
After the 2015 crisis, the ceramics sector experienced a major downturn of around 30%. As a result, the price per thousand units dropped by more than 20%, significantly reducing profit margins and making the business less lucrative for entrepreneurs in the sector. Meanwhile, concrete block manufacturing continued to grow.
It can be observed that a large number of ceramic industries that once existed in Brazil — as well as in other countries — have ceased to exist. Much of this is due to their failure to adapt to market demands. This lack of adaptation goes beyond just modernizing equipment; it also involves diversifying product lines to serve other segments of the construction industry.
Nowadays, there is a strong emphasis on ecological responsibility — such as avoiding environmental pollution and recycling materials. These are duties we all share, to help the planet and improve quality of life for humanity.
When sustainability is combined with cost-effective investment, it benefits everyone — from producers, sellers, and builders to, most importantly, the people living in homes built with these advantages. The Brazilian home of Dona Dalvina was named the best house in the world by ArchDaily, and it was built entirely from blocks and concrete — best of all, it cost only R$ 150,000.00.
What are the characteristics of concrete blocks?
Concrete blocks are widely used in Brazil. They were the first type of block to have a Brazilian standard for structural masonry design.
Their compressive strength is considered good, ranging from a minimum of 4.5 MPa to 16 MPa, as required by Brazilian technical standards.
High-strength levels are typically found only in large-scale factories, which have machinery with hydraulic compaction and equipment designed to improve the mixing of the aggregates that make up the concrete block.
Brazil already has buildings with more than 20 floors built using structural masonry with concrete blocks. As with other structural systems, walls made with concrete blocks serve both as structural support and enclosure, eliminating the need for columns and beams and reducing the use of reinforcement bars and formwork.
A block must provide both quality and cost-effectiveness to buildings. This means it should have: appropriate dimensions and shapes, compactness, strength, good geometric finish, and a visually appealing appearance—especially when the design does not include wall coverings. In addition, it should ensure thermal and acoustic insulation. These parameters are essential for the quality of the blocks and have their limits established by appropriate technical standards.
There is a comprehensive set of standards from ABNT (Brazilian Association of Technical Standards) focused on the quality of materials and the construction system of structural masonry using concrete blocks. The main ones are:
- NBR 15873/2010 – Modular Coordination for Buildings
- NBR 6136/2008 – Hollow Concrete Blocks for Masonry – Requirements
- NBR 7184:1992 – Determination of Compressive Strength
- NBR 8215/1983 – Prism of Hollow Concrete Blocks for Structural Masonry – Preparation and Compressive Strength Testing
- NBR 15961-1/2011 – Structural Masonry – Concrete Blocks – Part 1: Design
- NBR 15961-2/2011 – Structural Masonry – Concrete Blocks – Part 2: Execution and Quality Control
- NBR 12118/2011 – Hollow Concrete Blocks for Masonry – Test Methods
- NBR 14321 – Structural Masonry Walls – Determination of Shear Strength
- NBR 14322 – Structural Masonry Walls – Verification of Flexural or Flexural-Compression Strength
- NBR 10837:1989 – Design of Structural Masonry with Hollow Concrete Blocks
- NBR 8798:1985 – Execution and Quality Control of Structural Masonry Works with Hollow Concrete Blocks.
What is the compressive strength of concrete blocks?
Compactness depends on the mix design criteria, which directly influence the block’s strength as well as its absorption rate.
Curing is a determining factor in the compressive strength of the blocks and should be evaluated after 28 days of the curing process.
Strength is the ability of the masonry wall to withstand the various mechanical actions foreseen in the design, such as structural loads, wind, deformations, impacts, etc. This strength is directly related to several factors, including: the characteristics of the components and joints, the overall bond between elements, the slenderness of the wall, the connection between walls, among others.
What is the water absorption rate of a concrete block?
The determination of the total absorption of structural concrete blocks is covered by NBR 6136. The absorption index is used as an indicator of durability. The individual absorption of concrete blocks must be less than or equal to 10%.
The initial absorption (determined according to ASTM C 67) corresponds to the block’s suction capacity. It is an important indicator for defining the block’s potential adhesion with a mortar that has adequate water retention. Concrete blocks generally have an initial suction absorption rate of around 0.265 g/cm²/min.
This absorption is influenced by the porosity of the blocks, being higher for more porous blocks. Therefore, it is important to find the balance point, since absorption in the right amount favors the penetration of binders which, when hardened, make the assembly of blocks, mortar, and coating monolithic.
However, when absorption is too high, it can compromise the chemical reactions necessary for hardening. To ensure this balance, it is important to use a mortar with adequate water retention characteristics.
How to control the surface of the concrete block?
The blocks must be homogeneous, compact, and have sharp edges (an indicator of dimensional accuracy). They should be free of cracks and fractures so as not to compromise their laying, strength, and durability.
The surface texture is important both for masonry without finishing, where the block serves as the finish, and for masonry with finishing, where it must have adequate roughness, texture, and surface porosity to ensure adhesion with the mortar and promote monolithicity of the assembly. In general, the texture varies from smooth to rough depending on the materials used and the manufacturing conditions.
How to use special concrete blocks?
In addition to the standard block, there is also the half block, which allows masonry to be built with a bonding joint, eliminating the need to cut blocks on site. Other special types include U-shaped blocks (channels) that facilitate the construction of beams, lintels, and counter-lintels, as well as J-shaped blocks, which aid in building the support beam for slabs.
Concrete blocks can be made with or without a closed bottom. Blocks without a bottom facilitate the passage of electrical conduits and hydraulic pipes through their interior without the need to cut the masonry.
How to carry out the bonding (tie) process with concrete blocks?
The bonding process is used to join walls without the need to cut whole blocks. For this process, compensating blocks are used. For the 29 family, the block used for “L” shaped bonding is 14x19x29 cm. For “T” shaped bonding, the 14x19x44 cm block is used. In the 39 family, the “L” shaped bonding is done with the 14x19x34 cm block, and the “T” shaped bonding with the 14x19x54 cm block, as shown in the figures below:
Which blocks are the most common in civil construction today?
Partition Block
It is widely used to close openings, using the reinforced concrete method.
Structural Block
It is commonly used by construction companies for building structures, where a project is based on structural masonry. It also has the benefit of allowing the block’s hollow core to be filled with grout (creating pillars), providing safety and stability. Its use is not limited to just houses.
Ecological Block
Concrete blocks do not necessarily have to be made from top-quality raw materials. Depending on the strength required for your product, it is possible to incorporate some recycled aggregates to make the product more sustainable and economical.
Brasileirinho Concrete Block
Today, as an alternative piece in civil construction, we have the Brasileirinho Concrete Block, which introduces a new perspective on concrete blocks by being lightweight and easy for humans to handle.
The Brasileirinho is a great innovation in the concrete products segment because it combines the advantages of concrete blocks but is much lighter and modular, which further facilitates construction and requires much less physical effort to handle.
How are concrete blocks made?
It is possible to produce concrete blocks in various ways, using manual molds, manual machines, pneumatic machines, and hydraulic machines. What will change for each manufacturing method is the amount of aggregates you invest in order to achieve the desired strength.
About us
For over 53 years, in the market for manufacturing machines for the production of ecological bricks, blocks and concrete pavers, JARFEL is also the inventor of the solo cement ecological brick presses.
