Aggregate is necessary for the production of concrete. However, the type you select is the most important factor. The most preferable aggregate is coarse aggregate. The best concrete will always use coarse aggregate because it forms the strongest bond with cement paste. All aggregate used for the production of concrete should be rough. Broken stone and gravel pieces should have a non-glassy texture. Aggregate must be cleaned before use in concrete paste because any dirt coatings or organic substances will weaken its bonding effect. Almost all aggregate suppliers will confirm aggregate is 20mm or less in diameter
How to Select the Absolute Best Aggregate for Your Concrete
When searching for the best aggregate for your concrete paste, there are a few signs to look out for. These markers will help you determine whether or not the aggregate will be strong and durable. Engineers and aggregate suppliers pay close attention to these signs to make the process easier and more efficient.
- The ideal diameter for coarse aggregate is between 4.75mm and 18mm.
- The best bond will be formed with a non-glassy texture.
- Gravel and broken stone should be rough in texture.
- All aggregate must be non-porous, chemically inert and strong.
- All organic substances and/or dirt on the surface will weaken the bond.
- When submerged in water for 24 hours, aggregate should not absorb any more than 10% of its weight.
- In the event the aggregate does absorb more than 10% of its weight, it is too porous for concrete production.
- Flaky and/or elongated pieces are not ideal.
- Angular and cubical aggregate pieces are the most ideal for concrete production.
- Stacking aggregate sizes is a great method for efficiency in concrete production.
Another major consideration when selecting aggregate is the quality of each piece. Field observations and various tests are conducted in order to verify the quality of each piece. The most ideal aggregate will be rough in texture and have a clean surface that is non-glassy. Furthermore, the aggregate should not have any coating on it. Crushed stone and gravel are the best for high-quality concrete.
The Importance of Proper Aggregate in Mixture
During the production of concrete, it is very important the right type of aggregate is chosen for strong and durable bonds. Most people view aggregate as inert filler. The larger the pieces of aggregate, the lower the cost of concrete mix. The most costly ingredient during concrete production is the concrete mix.
In many cases, aggregate can be as high as 60% to 80% of the total mixture. While aggregate accounts for 60% to 80%, the other portions are made up of cement, water and air. Any aggregate which is susceptible to breaking or splitting should not be used. Aggregate with porous and soft material should not be used either. Due to the fact aggregate is a naturally-occurring material it may have small amounts of unstable particles. The allowance level for this is based upon each aggregate supplier and specific limits set by ASTM International.