Concrete consists of three core ingredients; cement, aggregates and water. Aggregates play a major role in holding the concrete together and adding to the durability of the finished product. Using the right aggregates is important when it comes to the performance of the concrete – they make up between 60% and 80% of concrete, after all.
The main types of aggregate are sand and gravel. These both come in a variety of forms, such as fine river sand, small gravel chips or larger crushed stones. A combination of aggregates can be used to create the perfect concrete texture for your project.
Choosing the right aggregates
The size, weight and moisture content of aggregates will directly affect the quality of the final concrete mix. Aggregate choice can also affect the cost, workability and durability of the concrete, so it is a major factor to consider when starting a construction project.
Aggregates should be clean, hard and strong. Choose aggregates that are free of clay coating, soil impurities, additional chemicals and organic material. Sand and gravel should not contain any mud, seeds or leaves.
Other factors to consider when choosing aggregates
The moisture content of aggregates is also important. It can affect the water-cement ratio in the concrete mix and either cause the concrete to be too dry (by absorbing the water) or too wet (by adding additional moisture to the mix).
Ideally, the aggregates should be in a saturated surface dry (SSD) condition. This means that they are dry on the outside but have internal moisture. In turn, the aggregates will not absorb any moisture from the concrete mix and leave it too dry.
Choosing the right gradation is also important. Aggregates that are too fine will need more water and will result in a sticky concrete mix – such as ultra-fine river sand. Aggregates that are too coarse will make the concrete harsh, hard to work and more difficult to place. The key is to find the right balance with aggregate gradations.
Aggregates make up the majority of concrete and are a vital factor to consider. Depending on the project and the final finish of the concrete, choose the right aggregate for your needs.
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 the Mbeya Region at Songwe in 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.