Concrete Hollow Blocks – Comprehensive Guide

How to produce concrete hollow blocks?

Concrete hollow blocks are primarily produced using a concrete brick making machine. First, the raw materials for the hollow blocks are mixed in specific proportions, then transported to the machine’s mold. The material is vibrated on the platform, and the upper mold presses down to shape the block.

Hollow blocks made by a concrete brick machine offer high output and efficiency while saving on labor and raw materials. Additionally, the blocks produced have high strength and precise dimensions.

Depending on production requirements, different types of brick-making machines can be used to produce concrete hollow blocks.

What hollow bricks can your brick machine produce?

All our concrete block machines can produce hollow bricks in various sizes. The most common sizes include 8-inch, 6-inch, 5-inch, and 4-inch hollow blocks. A single brick machine can be fitted with multiple molds, allowing it to produce concrete bricks of different sizes.

The main features of concrete hollow blocks

Concrete hollow blocks offer several key features:

• Lightweight
• Fire-resistant
• Sound-insulating
• Heat-preserving
• Impermeable
• Earthquake-resistant
• Durable
• Pollution-free
• Energy-efficient
• Reduce material consumption
• Environmentally friendly building materials

Hollow blocks have become a vital part of modern wall construction, with strong development potential. Typically used in non-load-bearing sections, they have a porosity rate of 35% or higher. Bricks with larger cavities and fewer solid parts are classified as hollow bricks.

Their lightweight nature and efficient use of raw materials have made hollow blocks the top choice for wall materials in the construction industry, highly recommended by national construction authorities.

Grade standard and marking of hollow brick

According to its size deviation, the appearance quality is divided into: excellent products (A), first-class products (B), qualified products (C).

According to its intensity level: MU3.5, MU5.0, MU7.5, MU10.0, MU15.0, MU20.0

Mark in the order of product name (codename NHB), strength level, appearance quality level and standard number.

Examples of a grade tag:

The block with strength grade MU7.5 and appearance quality of excellent product (A) is marked as: NHB MU7.5A GB8239

Technical requirements of concrete hollow brick

The default size of a concrete hollow block is 390mm × 90mm × 190mm, other sizes can be customized according to customer needs.

The minimum outer wall thickness should not be less than 30mm, and the interval between holes should not be less than 25mm. The hollowness should not be less than 25%.

Size tolerance（mm）

Strength Class ( MPa)

Relative water content (%)

Raw Material Standards for Concrete Hollow Blocks

The following are the standards to ensure the quality and durability of the raw materials used in producing concrete hollow blocks.

1. Cement:
   • Must comply with the standards GB/T 175, GB/T 1344, and GB 12958.
2. Fine Aggregate:
   • Must meet the requirements of GB/T 14684.
3. Coarse Aggregates:
   • Crushed stones, pebbles, and heavy slag are acceptable.
   • Crushed stones and pebbles must comply with GB/T 14685 standards.
   • Heavy slag must comply with YBJ 20584, with a maximum particle size of 10mm.
   • If using broken stones like stone chips, the fine stone powder content (particles smaller than 0.15mm) should not exceed 20%.
4. Admixtures:
   • Must meet the standards set by GB 8076.

Production Requirements of Concrete Hollow Brick

The following are the materials needed hollow bricks that meet the requirements,

• Required raw materials for mortar: cement, sand, water.
• Admixture: Lime, the purpose of adding lime is to increase the adhesion between the brick and the setting material.

What is the ratio of mortar for concrete hollow block?

When you use mortar strength M7.5, cement strength 32.5, the ratio of mortar and cement is:

For Mortar Strength M7.5 (Cement Strength 32.5):

• Weight ratio: Cement : Water : Sand = 1 : 0.9 : 6.72
• Amount per cubic meter:
  • Cement: 250kg
  • Water: 220kg
  • Sand: 1680kg

For Mortar Strength M10 (Cement Strength 32.5):

• Weight ratio: Cement : Water : Sand = 1 : 1.07 : 6.35
• Amount per cubic meter:
  • Cement: 260kg
  • Water: 280kg
  • Sand: 1650kg

Additional Masonry Requirements for Concrete Hollow Blocks

1. Masonry Below Indoor Floor:
   • Use small blocks of ordinary concrete and cement mortar with a strength grade of at least M5.
2. Bottom Walls of Civil Buildings (Five Floors or More):
   • Small blocks with a strength grade of at least MU5 and M5 masonry mortar are required.
3. Painting and Waterproofing:
   • Concrete hollow block walls should be double-painted.
   • Outdoor footings should be coated with cement mortar for protection.
4. Moisture-Proofing for Humid Environments:
   • In humid conditions, walls made from lightweight aggregate concrete small blocks should be plastered with cement mortar for effective moisture-proofing.
5. Thermal Insulation for Cold Regions:
   • In northern cold regions, when using light aggregate concrete small blocks for exterior walls, additional thermal insulation measures should be applied where the insulation performance is weakened, such as around ring beams, lintels, and core columns.

These guidelines ensure the structural integrity and long-term durability of concrete hollow block masonry in varying conditions.

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