Concrete pouring is an integral part of many building projects; however, the runny, grey goo is more challenging than it looks. Especially in form reo pour projects where the formwork and reinforcement parts of the project cumulate with the concrete pour.
In this article, we will give you some advice on regular mistakes that are made, what to avoid and as a ‘Plan B’, how to fix or correct the mistake if it has already been made.
To make the most of your next concrete pouring project, here are some tips that should help you get it right the first time.
Inadequate Site Preparation
Fault
If the working area is not properly prepared, the surface can remain uneven, pools of water can develop, and parts of the structure can become weak.
How To Avoid
Clean and dry the base properly. Use the correct-sized gravel and place it at a depth that will ensure a solid base. Set forms level and strap the forms down with hardware cloth fastened to the side with wires.
Fixing or Correcting
If the forms are not properly prepared, remove them and regrade the site. Make sure the base is thoroughly compacted and check it for levelness before attempting another pour.
Incorrect Concrete Mix
Fault
Using the wrong mix can affect the strength and durability of the concrete.
How to Avoid
Proper concrete mix for the job. The mix depends on load, conditions, and finish.
Fixing or Correcting
If the mix is off, it might need to be removed and replaced. For lesser problems, reworking the course by adding incidental materials such as cement, emulsions, organic stuff or graded material is needed, but always consult a structural engineer.
Poor Weather Conditions
Mistake
Pouring concrete in extreme weather conditions can hinder the curing process.
How to Avoid
Check the weather forecast, and avoid pouring in very hot or cold temperatures. Additives can help concrete set correctly in less-than-ideal temperatures.
Fixing or Correcting
During and after a pour, when weather conditions aren’t cooperating, use blankets or plastic sheeting to protect the concrete until the concrete sets. If damage occurs, assess and consider grinding or resurfacing.
Adding Too Much Water
Mistake
Excess water can weaken the concrete mix, leading to cracks and structural issues.
How to Avoid
Follow the manufacturer’s suggested mixing ratio – generally between 6:1 and 8:1 water-to-cement. The mix should be workable, not overwet.
Fixing or Correcting
The concrete is still too wet. Remove, re-level and tamp out excess water. If the concrete has not already been set:
1. If possible, rake out all the excess water.
2. Use a screed board to level out the topping mix. For future pours.
3. Use a moisture meter or other reference tool to accurately set the water ratio for the mix.
Rushing the Curing Process
Mistake
Not allowing concrete to cure properly can compromise its strength.
How to Avoid
Cure the concrete thoroughly by keeping it wet and covered for at least seven days; doing so will prevent excessive moisture loss, preventing cold, weak and unsightly concrete.
Fixing or Correcting
If the concrete has not been adequately cured, it will be weak and brittle. Keep the area covered and watered for the rest of the cure. If the concrete has already been set, a structural assessment will determine whether it can stay in place.
Inadequate Reinforcement
Mistake
Neglecting to use or incorrectly placing reinforcement can lead to cracks.
How to Avoid
First of all, concrete can’t anticipate future damage, so you need to be alert about it. You should use reinforcing bars or mesh, as appropriate, or ensure that anything embedded in the concrete is at the right depth and is sufficiently concentrated for the job at hand.
Fixing or Correcting
If reinforcement is missing or misplaced before the concrete becomes set, stop the pour and put the reinforcement in place. Otherwise, consult a structural engineer about possible solutions, which could include installing additional external reinforcement.
Improper Finishing Techniques
Mistake
If you repeat motions too many times, this surface can lose its power, or you might not be able to finish the entire surface to paint on the lower edge. This might make your newspaper pool with water from the plaster and buckle the piece. It can also cause surface problems and imperfections.
How to Avoid
Do the finishing (use the correct tools and procedures). Wait for the bleed water to evaporate, then do the finishing.
Fixing or Correcting
If the finish is poor, you may have to resurface or grind. Apply a concrete resurfacer or sealant if the surface is just slightly messed up. Proper technique and formwork are essential here (sufficient fall and compaction, etc).
TIP - By avoiding common mistakes that occur during the concrete pouring process and employing best practices, you are sure to reap the benefits of a successful concrete pour (its strength and aesthetic appeal) while also avoiding costly errors that can result from a poor quality or negligent pour.
Australian Legislation
In Australia, mixing concrete is controlled by legislation and regulations that refer to the specifications.
Let's take a look at the main points:
Australian Standards: The preparation of the concrete mix follows the Australian Standard AS 3600, which deals with concrete structures.
National Construction Code (NCC): The NCC has requirements specified in Part 3.2.3 for concrete mixing that enable concrete to be manufactured to meet relevant strength and quality classes.
Concrete Mix Design: Comprehensive prescriptions for concrete mix design are contained in industry documents such as the ‘Guide to Concrete Construction’ (2010) by the Cement Concrete Aggregates Australia (CCAA), which complies with AS 1379 and its Supplement.
Such regulations make sure that cement, sand, rocks and water are mixed together and used for concrete construction throughout Australia, maintenance the same standard in durability, safety and performance.
While companies need to deal with concrete mixing and concrete pouring on a greater scale, they have to be fully aware of the regulations and strictly abide by them.
Summary
Most of us are familiar with concrete and how to mix it and for some concrete pouring, unforeseen circumstances can lead to varying problems on-site that are not necessarily your fault. However, having the knowledge to identify the problem or know in advance what not to do so you end up there is vital. We hope these seven-pointers will stand you in good stead with your next project. Good luck!
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