Admixtures are chemicals that are mixed in with the cement, aggregate and water in a concrete batch. These chemicals have various effects on concrete; some make it waterproof, others make it more workable. Calcium chloride is an admixture that speeds up the hydration process and makes the concrete set quicker with high initial strength.
This can have various benefits. By speeding up the initial setting time, building projects can progress at a more rapid pace. It also allows contractors to build on top of new concrete within a number of days. This is ideal for load-bearing structures, such as columns and beams.
How to add calcium chloride to concrete
Calcium chloride can be purchased as flakes, pellets, granules or as a liquid. All forms of this chemical are soluble; they can dissolve in water, so it is recommended to use the liquid form. No more than two percent of a concrete batch should be calcium chloride.
The chemical reacts directly with cement, not the other ingredients in a concrete batch, so it cannot come into direct contact with cement until a concrete batch is being mixed. Contractors should dilute the calcium chloride in the water for the concrete batch and then mix it with the sand and crushed stone. The cement can then be added to the mix.
Effects of calcium chloride on concrete
As mentioned before, calcium chloride speeds up the setting time of concrete and allows it to develop high initial strength. This admixture can be used in low-temperature conditions where concrete would normally take a few days to set. When using calcium chloride, contractors need to make sure that the concrete does not set before they have finished working with it.
Calcium chloride does not affect the water ratio required for a concrete batch. However, it can cause the mix to become stiff, so contractors may need to add a bit more water to keep the mix workable. This admixture also reduces bleeding in concrete once it has been poured, which can sometimes increase drying shrinkage. Contractors need to keep the surface of the concrete damp to prevent it from cracking.
In some cases, calcium chloride can cause a white deposit to form on the surface of the cured concrete. This efflorescence does not happen in every case, but it is not the same as salt damage – contractors do not need to be concerned. These white deposits cannot be washed away with water, so contractors must dilute hydrochloric acid with water and pour it over the surface of the concrete. Brush the diluted acid away with a broom and always wear rubber gloves.
Advantages of using calcium chloride in concrete
- Development of high initial strength.
- Reduced initial and final setting time.
- Reduced bleeding.
- Improved workability in cold conditions.
- Fast work turnaround.
LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges.
LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.
At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.