Moisture and pH changes are the leading cause of damage to concrete in all its forms around the world. Owing to its porous structure moisture can seep into concrete relatively easily contributing to changes in pH level and also increasing the onset of what is known as carbonation.
How pH Affects Concrete
The pH scale ranges from 0 to 14, with 7 being a neutral or ‘basic’ pH. A number lower than 7 indicates acidity and the lower the number, the more acidic. On the other hand, a number higher than 7 means that whatever is being measured is alkaline and the closer readings are to 14, the more alkaline it is.
Concrete uses a binding agent called Portland cement, which has a pH of 11, and if this pH varies too much then it loses its binding properties as it is broken down. This will create more cracks and pores in the concrete speeding up the process exponentially leading to more problems and a swifter deterioration.
When it comes to the production of the concrete there can be issues regarding pH and moisture levels. Depending on the area, water can have a different pH and this can alter the pH level of the overall concrete mix, this problem can be accelerated if there is too much water used when creating the concrete.
If the pH of the concrete drops below 7 there will be noticeable degradation and surface damage as the cement loses its ability to bind the concrete together. If left unattended, it will continue to become more acidic and that will eventually result in the concrete losing all structural integrity and needing to be replaced.
Aside from problems that may arise during the mixing and production of the concrete, there are a number of natural occurrences that can affect the pH level of the concrete. Depending on the location concrete can face issues with anything that increases the moisture level.
Acid rain, for example, is a large contributor as it will have a pH below 7, drastically reducing the overall pH level of the concrete mixture. Another big issue is salt, often used as a countermeasure to combat icy conditions. The salt will get into the pores and any cracks in the concrete and act in the same way as the acid rain, corroding the surrounding materials and lowering the pH.
Even without the addition of acids through saltwater or acid rain, there is a process that slowly degrades the structure of the concrete. This can occur through any water seeping into the porous concrete or even just through the reaction between the carbon dioxide in the air and the cement in the concrete. Carbonation also lowers the pH of the concrete and can have a more serious reaction on any reinforcements inside the concrete causing them to expand, cracking the surrounding concrete and eventually causing the structure to crumble.
There is no way to completely halt the pH decrease in concrete, however, there are plenty of ways to increase the longevity of concrete. Regional guidelines regarding humidity levels, water pH concentration, and the amount of rainfall expected should be taken into account.
Following these guidelines while mixing and pouring the concrete will ensure a solid foundation, but there should also be steps taken to manage drainage and other aspects of wear and tear in order to limit any excessive exposure if possible. By limiting the amount of moisture that will be able to affect the concrete the impact that the moisture can have will also be limited.
Al Manaratain Concrete pH Quality Control
The quality control team at Al Manaratain has designed an experimental program to observe the effects of major variables; such as the type of cement being used and the water/cement ratio. We also conduct a number of tests for other variables; including waiting time, sample gradation, and temperature.
The testing of water plays an important role in controlling the quality of cement and the concrete it goes on to produce. Systematic testing of the water helps to achieve higher efficiency of concrete and greater assurance of the performance in regard to both strength and durability.
At Al Manaratain, we use an extremely sensitive pH probe with a detailed digital meter to test our cement and concrete on a daily basis.