Most people assume that cracks in concrete happen because of problems in the foundation.
The fact is, this might not be caused by improper design, structural failures or bad quality work.
Following is what you need to know about cracks in concrete and how to stop them.
Causes Of Cracks In Concrete
Cracks in concrete can be caused by the following reasons.
- Concrete usually expands and shrinks in different temperatures so cracks are likely to come up as a result of these scenarios.
- They can also happen when the structure is settling.
- If you apply a heavy load to the entire structure, cracks are going to appear.
- If the concrete dries up because of loss of water, some cracks will show up.
- If there’s insufficient vibration at the time of laying the concrete, it will start cracking.
- If there is too little water compared to the cement, it’s going to be hard to work on the concrete so it’s likely to crack.
- Cracks will show up if there is any corrosion of the reinforcement steel.
What Are The Various Types Of Cracks In Concrete?
Some of the types of cracks that start happening before the concrete hardens include the following.
- Construction Movement Cracks – Usually caused by movement in the formwork and subgrade.
- Plastic Cracks – Usually caused by plastic settlement or shrinkage as well as autonomous shrinkage.
- Frost Damage Cracks – These cracks are caused by premature freezing, scaling or crazing.
There are also cracks that happen after hardening and they include:
- Volume Instability Cracks – Usually caused by drying shrinkage, thermal changes and creeps.
- Structural/Design Cracks – Usually caused by design load or overload, design/subgrade or fatigue.\
- Physio-Chemical Cracks – These are caused by steel corrosion, freeze-thaw cycling and much more.
Tips On How To Prevent Cracks In Concrete
You need to take preventive measures when laying the concrete to reduce the cracks that are most likely to happen after formation.
Here are some of the notable ways to reduce cracks in concrete.
- Reduce The Amount Of Water In The Concrete
If there is too much water in the concrete, the overall quality will be affected.
Reduce the amount of water in the concrete to make it stronger and avoid too many cracks from appearing.
The water/cement ratio should be a maximum of 0.5 because if it’s higher, it will reduce the workability of concrete.
You can correct this using superplasticizer or plasticiser. With less water, you can increase the durability of the concrete.
Note that, any changes in moisture will force the concrete to expand or shrink. However, it tends to shrink in most cases and this will result in cracks.
When concrete becomes hard, the excess water evaporates thus causing the shrinkage. Reduce the shrinking by reducing the amount of water used.
- Ensure Proper Concrete Mix Design And High Quality Materials
Make sure the concrete is proportioned and mixed properly. If you use too little cement, there will be cracks.
Also, as mentioned, if you use too much water, the concrete is likely to become weak causing cracks.
You should use high-quality aggregates that will reduce the amount of shrinkage in the concrete.
For instance, you should opt for dense, hard or large top size aggregate for the best results.
Also, you can optimise the gradation of the aggregate for the best results.
If you are using poor quality aggregate, maximising the gradation, size or content will have very little effect on the shrinkage.
Actually, mixing large quantities of aggregate with poor quality mid-size aggregate will increase the shrinkage of the concrete.
Don’t use admixtures that increase the shrinkage such as dirty aggregate or .
This increases the water demand and prompts the usage of cement with high shrinkage characteristics.
- Proper Finishing Of The Concrete Surface
You should use proper finishing techniques and choose the right timing when applying the finishing.
It’s prudent to use flat trowelling and flat floating surfaces for the best results.
Don’t overwork the concrete especially when using vibrating screeds because it causes settling of the aggregate and bleeds the water.
Eventually, the excess fines will start rising.
Don’t finish the concrete with bleed water on the surface because it forces the water back into the concrete causing evaporation and eventually cracking.
- Proper Curing Of The Concrete
You’re advised to cure the concrete slab for several days because if the slab dries up too quickly it will cause cracks.
Once the concrete sets, you need to make boundaries with mortar and fill them up with water.
Use cotton mats to filled up with water to cover the slabs or cover the slab with a curing compound to prevent loss of water.
During the curing period, don’t subject the concrete to any load. Take the relevant time, about a month to prevent any cracks on the concrete surface.
So there you have it, that’s all you need to know about preventing cracks on concrete.
Using these above tips will go a long way to ensuring you achieve the best results when you’re laying and preparing concrete.
If you are looking for a specialist concrete cutting company who uses only the best practices to get the job done right, then please call us at Megasaw on 1300 920 419 or contact us through our website www.megasaw.com.au/contact-us/