Published on 8/8/2017
Published by firstname.lastname@example.org
Why did my concrete crack?
Who's fault is it?
Cover Photo by Michał Grosicki on Unsplash
Why is my concrete cracking?
The age old question of why concrete cracks is often asked by clients and customers around the world, in situations where their newly paid for concrete, is not all that its cracked up to be. After blaming the concreter, who then blames the concrete plant, who then blame the quarry, the cement company and the concreter again, we end up in a game of pass the parcel. No one ends up winning and the customer is left holding the baby.
Yet holding the baby can provide us with a sound analogy from which to explain the very reason why concrete tends to crack. In short fresh concrete requires handling with care, or with "kid gloves", as the saying goes. You wouldn't leave your baby out in the sun without sunscreen on for fear of burning. Nor should fresh concrete be exposed to the elements. Exposure to heat, rain and wind are major contributors to concrete cracking. Water is an integral part of fresh concrete, for it contributes to the process known as hydration. During hydration the cement paste in your mix, when added with water, glues together with the rocks and sand in your mix to form concrete. However in circumstances where water evaporates from your slab surface, due to temperature, relative humidity and wind, your cement paste becomes somewhat ineffective. The small cement particles in the paste are unable to hydrate then connect and bind with other particles unless water is present in the mix. And remember, its not just hot weather that causes water to evaporate from your slab surface, cool weather with low humidity and wind has the same effect.
Photo Source : Vincent Burkhead on Unsplash
Controlling the rate of evaporation from your concrete slab's surface is key to avoiding concrete cracks. The most common form of cracking in Australia is called plastic shrinkage cracking. Plastic shrinkage cracking, as it is known, whilst not effecting the integrity of the slab, isn't all that great to look at. For no one whats to come home to a sea of small cracks scattered at intervals throughout their front driveway. And it is not too comforting to know that these cracks may over time impact on the structural integrity of your slab, as water now has the potential to penetrate and force its way into the core of your concrete.
So how do we avoid this type of cracking?
Controlling concrete cracking
1. Try to watch out for pouring on days when excessive evaporation may occur. Hot temperatures, strong winds, rainy days and days in which there is relatively low humidity are all days to avoid. Pouring early in the morning may mitigate the likelihood of cracking occuring, though it may be best to just postpone your pour if possible.
2. Erect wind breaks where required and ensure the fresh concrete is moist and kept damp at all times.
3. Apply aliphatic alcohol to the surface when placing and finishing. Aliphatic alcohol when sprayed on fresh concrete creates a thin layer or film upon the surface, protecting it from the elements, in much the same way as your baby is protected when dosed with sunscreen and taken outside with a hat on. This reduction in evaporation from the slab surface ensures the concrete can set evenly throughout, without the need for water to escape from the surface into the atmosphere.
4. Commence curing your concrete when you have completed finishing the surface. Same day sealers, 28 day concrete sealers, curing compounds and agents can all be purchased from most good concrete accessory suppliers, concrete wholesale and retail outlets.
Another thing to keep in mind is that concrete cracks under load. Where concrete is in tension, flexure or shear, structural cracks can appear. In other words, driving over your new concrete in a heavy vehicle or with a load on isn't advisable. Your steel reinforcing mesh may mitgate the risk of your slab cracking, however make sure the surface has fully cured before you start "moving in".
If you are looking for suppliers of laiphatic alcohol, sealers and curing agents, you can find them on our website at:
Whilst if you are looking to repair cracks in your concrete we have many concreters listed in addition to concrete resurfacers and resealers such as https://www.concretebroker.com.au/riksresealingandresurfacing
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Tags: aliphatic alcohol concrete cracking concrete cracks concrete sealer crack control crack repair cracking curing concrete