Why is concrete chiseled? If the foundation isn’t done right, it’s useless even if an experienced master comes!

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This post was last edited by HaiChuanLaoYu on 2026-5-3 08:44. The most easily overlooked yet deadliest step on a construction site is definitely concrete texturing; there are countless instances where cracks, leaks, and delamination occur at the joints between old and new concrete. After checking the materials, the pouring process, and the curing procedures, it turns out that the problem lies in inadequate texturing of the concrete. Many people think that roughening the surface just means making a few casual scratches to satisfy the supervisor, but let me tell you: roughening the surface is not a mere formality – it’s crucial for ensuring that the new concrete bonds properly with the existing concrete. If the surface isn’t properly roughened, no matter how standard the pouring process is or how thoroughly the concrete is vibrated, it won’t help; cracks will still appear and parts of the structure will still fall off. Then why must concrete be roughened? To put it simply, there are two objectives, and neither can be omitted: after the concrete is poured, a thin layer of slurry forms on its surface, and this layer must be completely removed. This slurry is loose and contains many pores; its strength is very low. It acts like a barrier layer between the old and new concrete. If it isn’t removed, the newly poured concrete won’t be able to bond with the old concrete, and a gap will always remain between them. This gap will crack under stress and allow water to seep through. It is not enough to simply remove the floating slurry; one must chisel until the hard stone aggregates are exposed. Only in this way can the cement paste of the new concrete bond with the aggregates of the old concrete, just as gears interlock with each other, thus forming a true unified structure. If one only chisels down to the mortar layer, the new and old concrete will still be held together only by the mortar, resulting in insufficient strength – any slight stress will cause the structure to separate. These incorrect methods of roughening the surface are equivalent to wasting 90% of the effort; most surface roughening tasks are done carelessly. ❌ Using a wire brush casually only removes surface dust; the floating slurry isn’t removed at all, nor are any stones exposed. ❌ Roughening is done too superficially, with only a thin layer removed; the underlying slurry remains, making it completely ineffective. ❌ No cleanup is done after roughening; the debris and dust left on the joint surface mean that when new concrete is poured, there is still a layer of dust in between. ❌ Only the center area is roughened while the edges are ignored; the edges are the most prone to cracking, and if they aren’t properly roughened, cracks will definitely occur later. Many people say, “I used to do this too, and nothing went wrong,” but that was just luck. When cracks or leaks appear at the joint later on, trying to fix them means having to chisel away the entire joint surface and pour new concrete, which costs dozens of times more than what was spent on proper roughening initially. To perform proper chiseling, remember these 3 points: chisel deep enough to expose the gravel; the chiseling depth should be at least 5 mm, so that more than 70% of the surface shows the hard gravel aggregate. All debris must be removed completely, with no residue left. After chiseling, use a high-pressure water gun to clean away all mortar, debris, and dust. The joints must be clean and rough. Before pouring new concrete, wet the existing concrete surface thoroughly with water, but ensure there is no standing water, as this ensures the strongest bond. It’s just these three simple steps; if done properly, the old and new concrete can be bonded together to form a single unit that will not crack or leak for decades. Roughening the surface is essential – if this step isn’t done properly, any repairs will be pointless. Stop treating roughening the surface as a trivial task or handling it carelessly. By ensuring this step is done correctly, the subsequent construction processes can proceed smoothly, the supervisor will have no issues to point out, and the quality of the work will be guaranteed.