Concrete is a highly versatile building material. It can be tailor-made to suit the specific requirements of the contractor, simply by adding certain chemicals. These admixtures can speed up the setting of concrete, trap more air or absorb the water inside the concrete structure.
Admixtures can help to improve the workability and performance of concrete, depending on the type of structure being built and its environment. This improves the versatility of this popular building material. Admixtures offer many benefits for contractors, so researchers are always looking at new types of admixtures that will improve concrete mixes.
What are researchers looking to improve?
In particular, researchers are exploring ways to make concrete more sustainable by sourcing local materials. This reduces the carbon emissions needed for transport of the raw materials. Admixtures help this local sourcing to be a viable solution for cement manufacturers and suppliers.
Research and development teams have studied the properties of concrete that give it strength and durability. The aim is to see how these molecules behave and how they can be manipulated by admixtures to improve performance, especially when it comes to harsh environmental conditions such as floods and earthquakes.
These international research teams are examining how admixtures, such as volcanic ash, can enhance the frictional forces between cement particles. Using local admixtures can further improve the suitability of concrete to local environmental conditions.
The most common admixtures
It is common for contractors to use admixtures in concrete batches. Each additive has a different effect on the concrete. Here are five of the most common admixtures and what they do to concrete mixes:
1. Accelerating admixtures
Accelerating admixtures speed up the early strength development of the concrete batch. This reduces the curing time and accelerates the time for construction. Accelerating admixtures are useful in winter when the cold weather slows down the time for setting and curing of concrete.
2. Retarding admixtures
Retarding admixtures are the opposite of accelerating ones – they slow down the rate of setting and curing of concrete. This makes concrete more workable in hot weather, where the heat makes the concrete set quickly.
3. Air-entrainment admixtures
Air-entrainment admixtures help to trap air in the concrete. This improves the workability of concrete and helps to reduce water-bleeding and segregation. The microscopic air bubbles also help to prevent internal cracking that sometimes occurs when the water in the concrete freezes in cold temperatures.
4. Water-reducing admixtures
Water-reducing admixtures reduce the amount of water needed for a concrete mix. This additive will lower the water-to-cement ratio, which makes the concrete batch more economical in water-scarce regions. These admixtures also enable contractors to increase the strength of concrete without the need for more cement, making it more affordable.
Superplasticisers, also known as high-range water reducers, drastically reduce the water content of a concrete batch – more than water-reducing admixtures. Superplasticisers create a high-slump, flowing concrete batch which improves workability and reduces the need for compaction.
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.