CMT-Lesson 9

• Hollow Blocks


  A hollow concrete block is a block made of concrete that has hollow spaces (also called as core) between its walls
• Applications of Hollow Blocks

  • walls
  • partitions
  • fences
  • dividers
• Raw materials for High-Density Hollow Blocks

  • Portland Cement
  • Aggregate
  • Fine Gravel
  • Sand
• Raw materials for Low-Density Hollow Blocks

  • Fly Ash
  • Bottom Ash
• Standard Sizes of Hollow Concrete Blocks (Philippines)

  • Length: 40cm, Height: 20cm, Width: 10cm (4'')
  • Length: 40cm, Height: 20cm, Width: 13cm (5'')
  • Length: 40cm, Height: 20cm, Width: 15cm (6'')
• Full-size Hollow Blocks


  Two cores
• Half-size Hollow Blocks


  Cubical and have one core
• Advantages of Hollow Concrete Blocks

  • Affordability - reduce the construction cost as it has a large size which reduces the number of joints
  • Durable - can provide long-lasting stability and durability for buildings and structures
  • Ease of Construction - relatively easy to install, and no special tools or equipment are required
  • Fire Resistance Rating - resistant to high temperatures, helping to limit the spread of fire through a building
• Disadvantages of Hollow Concrete Blocks

  • IF NOT made with the appropriate materials and right amounts, it can lead to poor thermal insulation
  • The blocks' Hollow Core/s can make them susceptible to water damage
  • Improper installation makes the material prone to cracking
  • Heavier compared to other modern building material
• Compressive Strength


  Ability of material or structure to carry the loads on its surface without any crack or deflection
• Compression Testing Machine (CTM)


  • The machine is designed to have a piston that moves up and down inside a cylinder, applying the load to the sample
  • Comes in two types: Digital and Manual
  • Used to measure the compressive strength of a material
  • Used in construction industries to test the quality of concrete
  • Can also be used to measure other materials such as: bricks, rocks, and metals
• Compressive Testing


  • Able to determine the material's behavior or response under crushing loads
  • To measure the plastic flow behavior and ductile fracture limits of a material
• Plastic Flow


  A deformation process that occurs when a material under severe stress starts to behave like a Newtonian fluid (permanent change in shape due to stress)
• Ductile Fracture


  A type of material failure that occurs when a material is stretched and deformed beyond its elastic limit
• Process of Determining Compressive Strength

  1. It is first checked during mix design to make sure that the quality of concrete that was taken into account is of standard quality

  2. The average compressive strength of a concrete masonry block is typically measured using eight blocks

  3. After being collected at the lab, the blocks should be analyzed within three days

  4. Each block will be allowed to cure for 28 days
• Procedure for Testing Concrete Blocks

  1. Concrete masonry units are topped with sulfur and granular materials or gypsum plaster

  2. Half of the predicted maximum load is applied continuously once the unit is placed in the testing machine; the remaining load is applied in no less than two minutes

  3. Concrete block compressive strength is determined by dividing the maximum load for a given masonry unit by the unit's total cross-sectional area

  4. Test the remaining 7 blocks, the final compressive strength is the average of the strengths of all 8 blocks
• First CHB was design in 1890 by Harmon S. Palmer in United States
• First Dimension of CHB were: 8 in x 10 in x 30 in
• Standard Size Rectangular Hollow Blocks is also known as Cinder Blocks or Breeze Blocks