Concrete technology is an ever changing science.
What does not change is.
- Cement is required to bind the ingredients together and give the required strength.
- Excessive addition of water reduces the strength and increase shrinkage cracking.
- Cracking will allow water to access the steel reinforcing,causing corrosion and subsequent failure of the structure
ICF is a unique product.
- ICF is the form-work,insulation and soundproofing of the building.
- The concrete is the strength of the structure
- Any act that reduces the strength of the concrete,reduces the strength of the building.
32mpa 7mm 120mm slump block fill mix,with a cement content to allow a slump adjustment to 160mm on site if necessary.
It is important to specify a block fill mix as this is designed to be pumped through a 50 mm line.
Granno mixes are a topping used over existing slabs and are designed to be low shrinkage.[high aggregate content]
True granno mixes are not suitable for ICF
Block fill mixes also have improved flow characteristics which will help ensure that there are no cavities in the wall,especially around lintels and areas with horizontal double steel
When working with some country plants I will specify a minimum of 340 kg/m3 of cement per m3.
Once concrete has began to hydrate the addition of water will reduce the strength of the product.
I also use retarders,depending on the weather,distance from the plant and complexity of the pour.
Not all concrete producers have plasticisers in stock and extra cement will compensate for slump adjustment when using water.
I always use either a 50mm or 40mm hose with a 180 degree 60mm bend on the end to hook over the wall.
I always use a 50mm grate on my hopper to filter out any oversize particles.
32mpa 7mm 120mm slump will just flow through the 50mm grate .
Blocks will only fail if
- Concrete is too wet
- Concrete is placed by boom and allowed to free fall 3m into the block
- Blocks have the rib cut out
- Joins are not properly braced and supported
- It is rare that a fault in the manufacturing process results in a weakened block
- Concrete is placed too fast.
Concrete producers have different design criteria that they operate to.
Cement content may vary from 295kg/m3 to 400kg/m3,depending on materials and the design criteria of
the supplier involved.
Communication is critical.
It is important that the supplier you are using is made fully aware of the project you are placing their concrete into.
It is important they understand that the concrete is the total strength of the structure.
If the producer you have chosen is operated by a Central Dispatch System it is important to speak with a Customer Service Representative or the Technical Manager at their laboratory
Ultimately,you the purchaser of the concrete,need to know that the concrete delivered and placed into your project will perform as the engineer requires and
Be guaranteed by the concrete supplier.
Read and understand the terms and conditions of the Concrete Supplier.
When pouring into the blocks watch that the concrete flows all the way down and into the next cell at least.
Be care full where there is horizontal steel,especially if it is overlapping as this may cause a cavity underneath.
Corners are a concern and need to be watched carefully.
It is sometimes advisable to lift the top layer and replace it when the concrete is insitu.
Take extra care when filling lintels as the extra steel will impede the flow of concrete.
Do not under any circumstance wash the concrete in with a hose as this will dramatically reduce the strength of the finished product
Scaffolding must be high enough allow you to see down into the block,must be stable and comply with OHS regulations.
Bracing of the walls must be sufficient so that the blocks will stay in position and not move.
Wishing you every success with your project
Rod
Rod Northover
Access Concrete Pumping
0418 357 833
