Sometimes when working with concrete, you might notice water rising to the surface after you pour and level it. This phenomenon is called bleeding in concrete. You might think that it is a minor issue and not take it seriously. However, this is not a minor issue and needs to be addressed as soon as possible. Before that, let’s understand the concrete bleeding definition a little better.
Bleeding in concrete happens when water in the mix rises to the surfaces as heavier particles like cement and aggregates settle down. You can think of it as if the materials within the concrete are separating. Although bleeding is a natural part of the concrete setting process, excessive bleeding can weaken your structure. But there is no need to panic, you can manage it if you know the exact cause of this bleeding.
Bleeding can weaken the surface strength of the concrete. It can create voids and water campuses. And when the water evaporates, it can cause shrinkage. Additionally, the water can also create a thin layer between the reinforcing steel and the concrete, weakening the bond. Bleeding can also make it harder to achieve a smooth and uniform finish. It can even cause discolouration. Over time, the excessive bleeding can lead to poor density and likely deteriorate.
There are many reasons behind the bleeding of concrete. Understanding it will help you rectify the situation properly
1. Excessive Water in the Mix: When you add excess water to the mix, it does not bond properly with the cement and rises to the surface.
2. Low Cement Content: Cement is a binding agent. So if the concrete has less cement than it needs, it reduces the ability of the particles to hold the water, leading it to cause bleeding in the concrete.
3. Poor Aggregate Selection: Aggregate is the stones and sand that are present in concrete. They play a huge role in the mix. If the particles are too large or even poorly graded, they can’t hold the water properly.
4. High Water-Cement Ratio: The water-cement ratio is critical in determining concrete’s properties, and if the ratio is off, there will be more bleeding.
5. Improper Compaction: Concrete tends to trap air during mixing, transportation and placing, which can reduce its strength and lead to weak spots. Compaction is the process of removing air voids trapped in the mix to ensure the concrete becomes dense, strong, and durable. If the compaction doesn’t go well and properly, the particle does not settle evenly and causes water to rise.
6. Slow Setting Time: Sometimes environmental conditions or even certain additives can slow the setting time. When that happens, water has a higher chance of rising to the surface.
It’s not easy to spot bleeding if you know what to look for. If you see the following signs, its time to take action.
1. A shiny or wet layer on the surface of freshly poured concrete.
2. Small puddles on the surface.
3. Weak or powdery areas after the concrete sets.
4. Visible cracks or flakes because of uneven drying.
The good news about bleeding is that you can reduce and even prevent it by being careful about a few simple things.
1. Always make sure you measure the water carefully to maintain the right cement-water ratio.
2. Use well-graded aggregates and high-quality cement.
3. Admixtures like water reducers and accelerators can improve the mix’s properties and reduce bleeding. So keep them in hand and use them when needed.
4. Make sure that compacting is done properly.
5. Trowel the cement only when necessary because excessive trowelling can trap water near the surface.
6. Be aware of the environmental conditions and control them when necessary. High humidity, direct sunlight, or wind can affect how concrete is set.
7. Go for mixes that are designed to reduce permeability because they can retain water better and minimise bleeding.
8. When in doubt, ask an expert.
Although bleeding in concrete might sound like a complicated issue, it is a natural process that can be managed with the right approach. All you need to remember is that proper planning and execution is key. Whether you are a DIY enthusiast or a professional, keep these tips in mind and you are good to go.
