How to understand the honeycomb surface mentioned in construction engineering and concrete structure

The phenomenon of honeycomb is that the concrete structure is partially scattered and has no strength. The phenomenon of hemp surface is that there is a lack of slurry and many small pits and pittings on the local surface of the concrete, forming a rough surface, but there is no exposed steel bar.

Causes:

1. The air content of concrete is too large, and the quality of air-entraining agent is not good. At present, the amount of pumped concrete is large, and in order to ensure the pumpability of pumped concrete, an appropriate amount of air-entraining agent is often added to the pumped concrete. Because there is a large difference in the performance of various air-entraining agents, the state presented in the concrete is not the same, some air-entraining agents can form larger bubbles in the concrete, and the surface energy is low, it is easy to form a large bubble of connectivity, if the vibration is unreasonable, the large bubble can not be completely discharged, and it will definitely cause a honeycomb surface to the surface of the hardened concrete structure.

2. The concrete mix ratio is improper, the concrete is too viscous, and it is difficult to discharge the bubbles when vibrating. Due to the improper mix ratio of concrete, such as more cementing material, larger sand rate, too small water consumption, unreasonable thickening components in admixtures, etc., will lead to too viscous new concrete, so that the concrete will be wrapped in a large number of bubbles when mixing, even if the vibration is reasonable, the bubbles are also very difficult to discharge in the viscous concrete, so that the surface of the hardened concrete structure appears honeycomb surface.

3. Due to the poor workability of concrete, segregation and water secretion are produced. In order to prevent concrete delamination, the concrete does not dare to fully vibrate after entering the mold, and a large number of air bubbles cannot be discharged, which will also lead to the appearance of honeycomb surface on the surface of the hardened concrete structure. In order to increase the fineness of cement, improve the early strength of cement, and consider saving electricity, some grinding aids are often added when grinding, such as wood calcium, diethylene glycol, triethanolamine, propylene glycol (and other substances, because some of these grinding aids have air entrainment, and the introduced bubbles are uneven and large, which will also cause honeycomb surface to the surface of hardened concrete structures.

Solution: 1. Choose to use high-quality air-entraining agent. The diameter of the high-quality air-entraining agent in the concrete should be 10-200 microns, the surface energy of the bubbles is relatively high, and the bubbles are evenly distributed in the concrete (the average spacing is not more than millimeters).

2. Reduce the viscosity of concrete. Appropriately adjust the water-cement ratio, sand ratio, amount of cementing material and the composition of admixtures to improve the viscosity of concrete, and also improve the quality of the window layer of the concrete structure;

3. Control the workability of freshly mixed concrete. If the concrete is segregated and leaked, the vibration time is strictly controlled, and the vibration must be revived in a timely manner;

4. If the cement contains air-entraining components, a defoamer should be added to it when mixing concrete. For example, the addition of the right amount of tributyl phosphate, silicone defoamers, polyether defoamers and many additives with a surface tension of less than 30 dyne centimeters can eliminate air bubbles.

It is that the concrete surface is pitted, and it is generally smoothed with mortar.

It can only be smoothed with mortar, and the best way to control it is to use a concrete vibrator to pour and compact.

The explanation upstairs was very detailed.

The main reason for the formation of concrete hemp surface is due to the unclean air removal after pouring, or the leakage of concrete slurry. There are concave pits on the surface of the concrete and the surface is not smooth and uneven, which is called concrete hemp surface. For honeycomb surface repair, materials with high bonding strength should be selected, and the aggregate should be delicate, so as to achieve an aesthetic effect.

1.The reason for the honeycomb is that the concrete is too thick at one time, the vibration is not solid or the vibration leakage, the template has a gap to make the cement slurry lose, the steel bar is dense and the concrete slump is too small or the stone is too large, and the wall root template has a gap, so that the mortar in the concrete gushes out from the lower part.

2.The so-called hemp surface refers to the local lack of grout on the surface of the concrete component, and the occurrence of countless small pits is mainly caused by:

1) The wood formwork is not fully watered and moistened or not wet enough before pouring concrete;

2) The surface of the template is not cleaned;

3) The separator on the template is unevenly brushed or missed;

4) The joints of the formwork are not tight, and the gaps leak when the concrete is poured;

5) The concrete vibration is not compact, and the bubbles in the concrete are not discharged.

The phenomenon of honeycomb is that the concrete structure is partially scattered and has no strength. The phenomenon of hemp surface is the lack of slurry and many small pits and pitting on the local surface of concrete, forming a rough surface.

The control measures are as follows:

1. Strictly control the concrete mix ratio, the concrete is mixed evenly, and the slump is suitable; 2. Control the height of concrete blanking, and set up a string drum or chute if it exceeds 2m; 3. The watering should be layered and vibrated to prevent vibration leakage; 4. The formwork joint should be tightly blocked to prevent slurry leakage; 5. The formwork surface is cleaned up, and there shall be no dry and hard cement mortar and other sundries, before pouring concrete, the formwork should be watered and fully moistened, and the formwork gaps should be blocked with linoleum paper and putty, and the mold wrench isolating agent should be selected for a long time, evenly brushed, and shall not be missed; (If the surface is painted, it can not be treated).

1.Honeycomb: The original bai is that the concrete is too thick at one time, the vibration is not solid or leakage, and the formwork has gaps.

DAO causes the cement slurry to be lost, the steel bar is dense, the concrete slump is too small or the stone is too large, and there are gaps in the wall root formwork, so that the mortar in the concrete gushes out from the lower part.

2.The so-called hemp surface refers to the rough local lack of slurry on the surface of the concrete component, and countless small pits. The main reasons for its occurrence are:

1) The wood formwork is not fully watered and moistened or not wet enough before pouring concrete; 2) The surface of the template is not cleaned; 3) The separator on the template is unevenly brushed or missed; 4) The joints of the formwork are not tight, and the gaps leak when the concrete is poured; 5) The concrete vibration is not compact, and the bubbles in the concrete are not discharged.

The main reason for the honeycomb surface of concrete is that the vibration is not compact, there is excess air in the concrete, and the honeycomb and hemp surface will be produced after the concrete is condensed;

Prevention and control measures: mainly for the vibrator workers to strengthen the training and sense of responsibility education before the shooting, concrete vibration is completely manual work wisdom industry, one to rely on the long-term vibration of the feeling, the other to rely on the sense of responsibility of workers;

Of course, it is impossible to completely avoid honeycomb and hemp surfaces, but it can be minimized, especially in large areas;

In addition, in the concrete pouring process, you can send a special person to knock on the outside of the formwork, which can reduce the generation of honeycomb and hemp surface, and at the same time can check out the possible holes, and guide the vibrating rod personnel to strengthen the vibration of the part.

Reason: Improper concrete mix ratio or inaccurate material measurement, resulting in less mortar and more stones;

The mixing time is insufficient, the mixing is not good, the workability is poor, and the vibration is not compact;

The cutting height is too high, resulting in concrete segregation;

Unlayered blanking, false vibration, leakage vibration or insufficient vibration time;

The gap of the formwork is not blocked tightly, and the cement slurry is lost;

The steel bar is dense, and the particle size of the stone used is too large or the slump is too small.

Preventive measures: strictly control the mix ratio, strict measurement, and frequent inspection;

The concrete should be fully mixed evenly, and the slump should meet the requirements;

When the height of the blank material exceeds 2m, a string drum or chute should be used. Before pouring concrete, the roots of the vertical components should be watered with stone mortar in the same proportion (30 50mm is appropriate).

When pouring concrete, it should be cut and compacted in layers to prevent vibration leakage;

Strictly plug the cracks of the formwork, and check and correct the leakage phenomenon at any time during the pouring process;

Treatment measures: For small honeycombs, after cleaning, level and compact with 1:2 or cement mortar;

For larger honeycombs, chisel away the weaker loose particles, clean the formwork, and carefully fill with fine stone concrete of a higher strength grade;

Deep honeycomb can be buried inside the grouting pipe and exhaust pipe, and the surface can be plastered with mortar or poured concrete for cement grouting.

Several treatment methods for concrete hemp surface treatment:1. Strengthen the concrete vibration during pouring.

2. Clean the template in time and oil the template.

3. The formwork is tightly blocked to prevent slurry leakage.

Common Problems with Concrete:

a) Commercial concrete and workability are not good.

1.Reason analysis: Improper selection of cement dosage, loose mixture and clumping phenomenon; Improper selection of sand rate, which is manifested as insufficient cohesion or not easy to compact; The water-cement ratio is not selected properly, and delamination and segregation occur; Improper selection of cement varieties is more likely to cause water leakage and segregation; Inaccurate mixing ratio, inaccurate measurement, insufficient mixing time, and lax management will have a direct impact on the uniformity of the mixture and the ease of living.

2.Preventive measures: Correctly carry out the design and test of the mix ratio of pavement commercial concrete, and strictly implement the requirements of the "Cement Pavement Construction and Acceptance Specifications". The water-cement ratio and slump of commercial concrete should be reasonably selected according to the nature of the road, the use requirements and the construction conditions.

The honeycomb surface area of concrete is greater than how much, and the honeycomb and hemp surface area shall not exceed the surface area, and the non-stressed cracks on the concrete surface shall not exceed the construction quality requirements of the pipe culvert. (2) Ensure that the concrete surface is smooth, the ridge line is straight, and there is no serious edge gnawing and corner loss. (3) If the area of honeycomb and hemp surface shall not exceed the surface area, the non-stressed cracks on the concrete surface shall not be exceeded.

4) The caulking of the plate should be flat and compact. (5) During the construction process, it is strictly forbidden to use chutes to transport concrete. For low-lying construction sections in mountainous areas, if necessary, pump trucks are used to transport concrete, and long chutes are not allowed.

The main reason for the honeycomb surface of concrete is that the vibration is not compact, there is excess air in the concrete, and the honeycomb and hemp surface will be produced after the concrete is condensed;

Prevention and control measures: mainly for the vibrating rod workers to strengthen the training and sense of responsibility education, concrete vibration is completely manual work, one to rely on the long-term vibration feeling, two to rely on the sense of responsibility of workers;

Of course, it is impossible to completely avoid honeycomb and hemp surfaces, but it can be minimized, especially in large areas;

In addition, in the process of concrete pouring, a special person can be sent to knock on the outside of the formwork, which can reduce the generation of honeycomb and hemp surface, and at the same time can check out the possible hole generation, and guide the person holding the vibrating rod to strengthen the vibration of the part.