When taking on a building project, understanding concrete block density is a crucial piece of the puzzle. Not only does the density of blocks impact the weight, but it also impacts the strength of the blocks, and therefore what it is good at, what it can be used for, and its properties.
As a general rule, heavier (and denser) concrete blocks mean stronger walls, while lightweight (particularly aerated blocks) mean weaker walls. However, this doesn’t mean that lightweight blocks are not suitable for being used as load bearing walls in houses, and there is some nuance to be aware of before you jump into a project regarding fire resistance, flood resistance, reinforcement, and more.
To find out more about concrete blocks at PPC Concrete Products, why not check out our blogs about installing interlocking concrete blocks, benefits of concrete blocks in waste management, if they can be used for temporary structures, and how these blocks stay in place.
What Is Concrete Block Density?
Concrete block density simply relates to how dense a concrete block is. This is how compact the block is in relation to its size and weight, and is shown in kilograms per cubic metre (kg/m³) or sometimes pounds per cubic foot (lb/ft³). Density is directly related to the strength of concrete blocks, and the reason why dense blocks are better suited for foundations, load bearing walls, and other areas of construction where a lot of support is required.
Understanding concrete block density is crucial for all kinds of projects, and choosing the right one from the get-go will save you time, effort, and money, while also ensuring that the structural integrity of whatever you choose to build maintains. It is important to know that different block densities have different strengths and weaknesses, and where one might excel, another could fail spectacularly for any number of reasons.
Types of Concrete Blocks by Density
There are three primary types of concrete block density—lightweight, medium-density, and high-density blocks. Each of these types has a different density range, which is impacted by the materials that are used to make them (which can also impact how eco-friendly they are).
For example, there is a stark difference between lightweight and high-density concrete blocks, where the denser blocks can weigh close to 30kg, while lightweight blocks are less than half of that. As a result, high-density blocks are much stronger and excellent for load bearing walls, while lightweight blocks are weaker, and better suited for firewalls and many non load bearing walls.
Lightweight Concrete Blocks
Lightweight concrete blocks are made using lightweight aggregates such as pumice, ash, or expanded clay, and have a density between 650 and 1,200 kg/m³. These are then mixed with cement, water, and sand, to create a block that is light, easy to handle, and excellent for thermal insulation.
Weight-wise, these blocks can vary depending on specific density and size. However, most lightweight blocks will weigh between 8–12kg. It is common for 100mm blocks to weigh under 12kg, and 140mm ones to be under 20kg, making them the perfect option for easy and safe manual handling.
Benefits of lightweight blocks:
- Easier manual handling
- Improved thermal insulation
- Improved sound insulation
- More recycled materials are used
- Low self-weight
- A1 fire rating
Medium-Density Blocks
Medium-density concrete blocks are denser (with a general range between 1,100 to 1,600 kg/m³) due to the materials and aggregates used to make them. In these blocks, expanded clay, perlite, furnace bottom ash, and various other approved lightweight aggregates are mixed with cement, sand and water to form the balanced block.
These medium-density blocks generally weigh between 14–16kg, with exact weights depending on the precise aggregates used and their ratios. While they are fairly light, medium-density blocks should be handled with care and caution to prevent injury and strain.
Benefits of medium-density blocks:
- Improved impact-resistance
- Great sound insulation
- A1 fire rating
- Airtight (especially if the surface gets painted)
High-Density (Dense Aggregate) Blocks
High-density concrete blocks have a general density of between 1,800 to 2,100 kg/m³, making them weigh far more, and more difficult to handle. Like other concrete blocks, cement, sand, and water are used to make these blocks, as well as dense aggregates like gravel and limestone to make them heavier and sturdier for their purpose.
These blocks can weigh up to 28.5kg each, but there will be variations depending on the exact size and materials that are used to create the blocks. Because they can weigh so much, it is crucial to be careful when working with them, and adhere to safety standards and methods to avoid injury.
Benefits of high-density blocks:
- Very strong and durable
- Sufficient thermal insulation
- Excellent for soundproofing
- A1 fire rating
- Versatile and suitable for many wall types
How Does Density Affect Strength and Load-Bearing Capacity?
Concrete block weight and density directly impact the strength of the block and its load-bearing capacity. Dense aggregate blocks are excellent for load bearing walls and foundations thanks to their structure, while lightweight blocks are highly effective for fire break walls and separating walls, but can also be used for load bearing walls in many cases.
Weight Considerations for Handling and Transport
Any blocks that are 20kg or more require manual handling risk assessments, and are likely to need mechanical equipment for movement and use in order to keep everyone safe. This means that most, if not all, high-density concrete blocks may require equipment in order to be used, while lightweight blocks will not. The vast majority of medium-density blocks will be safe for manual handling, but it ultimately comes down to the size of block you are using, and the specific aggregates that contribute to the weight of it.
Concrete block density is crucial in understanding safety in building—even a block that might look small can weigh a lot and be unsafe to manually handle, and you need to know when to alter your methods to ensure safety.
How to Choose the Right Density for Your Project
To choose the right concrete block and density for your project, you need to have a good understanding of your project type, the dimensions of it, and what it will be used for. Consider the level of soundproofing or thermal insulation required, and load bearing aspects. As a rule, denser blocks are perfect for commercial projects, but it is always best to get the opinion of professionals in the field to make the right choice for you.
Lightweight blocks are suitable for:
- Load bearing walls
- Non-load bearing walls
- Inner and outer leaves of external cavity walls
- Separating walls
- Infill for block and beam flooring
- Fire break walls
Medium-density blocks are suitable for:
- Internal walls
- Infill for block and beam flooring
- Partition walls
- Inner and outer leaves of external cavity walls
High-density blocks are suitable for:
- Foundations
- Load-bearing walls
- Retaining walls
- Block and beam floors
- Partition walls
- Inner and outer leaves of external cavity walls
Other Block Types to Be Aware of
There are some other types of blocks to be aware of, including paving, hollow, aerated, and decorative blocks. These blocks are typically used for specific things, and are not suitable for construction, like the other blocks we have discussed are.
- Paving blocks – usually used for floors, driveways, and paths, but can be used for façades and other wall types
- Hollow concrete blocks – these can be filled with concrete and are ideal for methods of strengthening such a rebar, making them a good choice for load bearing walls and other structures that benefit from strength
- Aerated concrete blocks – light and weak, not suitable for load bearing walls, but are excellent for firewalls and preventing heat from passing through
- Decorative concrete blocks – creates with different patterns and textures, perfect for being used in gardens and other decorative ares what will not be for load bearing purposes
PPC Concrete Products: Supplying Blocks to Match Every Build
Now that you understand concrete block density, you should have a good idea of what you need for what you are working on. Need the right concrete block for your project? Contact PPC Concrete Products today for expert advice and high-quality blocks tailored to your build.
Contact us on 01706 580106 or by emailing us at info@ppcconcreteproducts.co.uk, or learn more about construction through our blog with posts about how to enhance construction site security with Jersey Barriers, how interlocking concrete blocks help marine life, or if you can paint these blocks.
