What Are The Preventive Measures For Common Concrete Quality Problems?

The concrete structure is partially loose, with less mortar, more gravel, and gaps between the gravel, similar to honeycomb holes.

1) The main reasons for its occurrence are:
1. Improper concrete mix ratio or inaccurate measurement of water addition to sand, gravel, and cement materials, resulting in less mortar and more gravel;
2. Insufficient concrete mixing time, uneven mixing, poor workability, and poor vibration;
3. Improper material feeding or too high material feeding, no connection to concentrate the gravel, resulting in segregation of gravel mortar; 4. Concrete is not layered, vibration is not solid, or leakage, or insufficient vibration time;
5. The gaps in the template are not blocked tightly, and cement slurry is lost;
6. The steel bars are dense, the stone particle size used is too large or the slump is too small;
7. The foundation, column, and wall roots are poured with the upper layer of concrete without a slight break.
2) Prevention and control measures:
 Carefully design and strictly control the concrete mix ratio, check frequently to ensure accurate measurement, uniform concrete mixing, and appropriate slump; if the concrete feeding height exceeds 2m, a string tube or chute should be set; pouring should be layered and vibrated to prevent leakage: the template joints should be tightly blocked, and the template support should be checked at any time during pouring to prevent leakage; the foundation, column, and wall roots should be poured for 1-1.5 hours after the lower part is poured, and then the upper concrete should be poured after it settles.

There is a lack of mortar and many small pits and pits on the local surface of the concrete, forming a rough surface, but there is no leakage of steel bars.

1) The main reasons for its occurrence are:
1. The template surface is rough or adhered to cement slurry and other debris that are not cleaned up, and the concrete surface is damaged when the template is removed;
2. The template is not wetted or not wet enough, and the moisture of the concrete on the surface of the component is absorbed, causing the concrete to lose too much water and appear rough:
3. The template joints are not tight, and the slurry leaks locally;
4. The template isolation agent is not evenly applied, or it is partially missed or ineffective, and pitting forms on the concrete surface.

2) Prevention and control measures 1. The template surface should be cleaned and should not be adhered to dry and hard cement mortar and other debris. Before pouring concrete, the template should be fully wetted with water. The gaps in the template should be sealed with linoleum paper, putty, etc. The template isolation agent should be long-lasting and evenly applied without missing any. The concrete should be vibrated and compacted in layers until the bubbles are eliminated; 2. If the surface is painted, it can be left untreated. If the surface is not painted, the rough surface should be fully wetted with water, and then the original concrete mix ratio of stone-removing mortar should be used to smooth and polish the rough surface.

The main reinforcement, secondary reinforcement or stirrups inside the concrete are partially exposed on the surface of the structural member.

I) The main reasons for its occurrence are:
1. When pouring concrete, the pads of the steel bar protection layer are displaced or there are too few pads or they are omitted, causing the steel bar to leak out close to the formwork;
2. The cross-section of the structural member is small, the steel bars are too dense, and the stones are stuck on the steel bars, so that the cement mortar cannot fill the area around the steel bars, causing leakage of reinforcement
3. Improper concrete mix ratio, segregation, lack of mortar near the formwork or leakage of mortar in the formwork
4. The concrete protection layer is too small or the concrete at the protection layer is not vibrated properly; or the vibrating rod hits the steel bar or steps on the steel bar, causing the steel bar to move, causing leakage;
5. The wooden formwork is not watered and moistened, and it absorbs water and sticks or is demolded too early, and the edges and corners are missing when the formwork is removed, resulting in leakage
2) Prevention and control measures
1. When pouring concrete, the position of the steel bars and the thickness of the protective layer should be correct, and inspection should be strengthened. When the steel bars are dense, stones of appropriate particle size should be selected to ensure the accuracy of the concrete mix ratio and good workability; when the pouring height exceeds 2m, the material should be discharged by a string tube or chute to prevent segregation; the formwork should be fully moistened and the gaps should be carefully blocked; it is strictly forbidden to hit the steel bars when vibrating the concrete. During operation, avoid stepping on the steel bars. If there is bending or disengagement, adjust the straightness in time; the protective layer concrete should be vibrated and compacted; correctly grasp the demoulding time to prevent premature demoulding and damage to the edges and corners.
2. If the surface leaks reinforcement, brush it clean, apply 1:2 or 1:2.5 cement mortar on the surface, and smooth the part that is full of leaking reinforcement; if the leaking reinforcement is deep, chisel off the weak concrete and protruding particles, wash it clean, and fill and compact it with fine stone concrete one level higher than the original one. The above are common problems in high-rise concrete construction. If you encounter the above problems during construction, you can refer to the above items, which can well prevent some common problems of concrete quality.