Exposed aggregate concrete is a material, which resembles marble, or granite and takes its actual look after getting polished. To expose its beauty the contractors uses several methods according to the desired looks and the size of projects. It is generally used in pavement areas or driveways. Where look is the first concern, decorators should pay utmost important to aggregate shape, color, and texture. For making superior quality and good look concrete gravel and crushed stones are used but gravel is the first choice. Aggregates quality must be durable, hard, clean, good color, easily available, economical and most importantly it should be neither too fine nor too dusty which can hamper cement water concentration and lead to a bad result. Basalt, quartz and granite are the most popular among aggregate for decoration purpose but the sometimes-colored glass is also used. The size of aggregate ranges from 3/8 to 2 inches and the depth of exposure by size.
Exposed aggregate concrete gives you a wide range of eye catching looking finishes. Techniques used for exposures: -
- Brushing and Washing: - this technique is used for small size projects. This is the oldest and well-known technique for exposure and is very simple to use. In this, a thin layer is washed by water sprinkling water on the floor and wiping with a broom until and unless the required depth is met with. This technique requires much more labors than compared to others.
- Concrete surface retarder: - often known as a surface de activator. It is less labor prone method. One of the easiest and reliable way which leads to a proper structuring and finishing of a surface. It gives an accurate depth of exposure. It stops the hydration process upon the desired depth which helps in hardening the beneath layer and easy removal of the topmost layer which gives excellent look after high-pressure washing. After one or two weeks, a process of acid washing is done in order to remove white patches from the
- Abrasive blasting: - can also be called as sand blasting or shot blasting. This method is not advisable as it can create gaps between exposed aggregate concrete and doesn’t give a new look.
Determining the Percentage for Concrete Mix:
A good concrete mix is a combination of four materials which should be blended efficiently to produce consistent concrete strength, durability, and finish-ability. The proportion of a good concrete mix is mentioned below:
- Cement –7% to 15%
- Aggregate – 60% to 80%
- Water- 14% to 18 %
- Air – 2% to 8%
Thumb rule for picking good quality aggregate: -
- Presence of durable particles
- Free from chemicals
- Cannot be split easily
- Shouldn’t be porous
Fitness modulus index
It is the measure of fineness of an aggregate, which ranges between 2.3 to 3.1. If the material is extremely fine then it will have a higher demand for water which can make the mix sticky. On the other hand, if the mixture is too rough then it will become difficult to place properly and finishing touch won’t be good.
There are both pros and cons of exposed aggregate concrete. Here are some of them:
- Attractive effects of the surface at an affordable price.
- Very little additional material required.
- Techniques used are very simple.
- Long lasting.
- Different colors shape and size available.
- No maintenance needed.
- Decorative stones can get damaged.
- Repairing any particular part of the floor is very difficult.
- Matching the repaired part with the remaining area is a big headache.
- The heavy object can damage the flooring.
So, we can now easily figure out what is best for exposed aggregate concrete!