Analysis and control of common quality problems of reinforced concrete piles
1. Cause analysis of common column quality problems
(1) concrete strength is low, poor uniformity, lower than the same grade of concrete beam and plate, the main reason is the same grade of concrete beam and plate, the main reason is to arbitrarily change the mix ratio, large water-cement ratio, large slump;Stir inadequately and evenly;Uneven vibration;Premature mold removal, not in place maintenance, early dehydration surface loose.
(2) the phenomenon of "soft top" of the concrete column, with more mortar on the top of the column, less stones, loose surface and cracks.The main reason is: concrete water cement ratio, slump, pouring ramming speed is too fast, did not remove water layer, to the top did not remove water and second pouring ramming.
(3) Concrete honeycomb and holes.The main reason is incorrect mix ratio.Concrete mixing time is short, not even mixing, too much material at one time, vibration and compaction;No layered pouring, concrete segregation, template pores are not well blocked, or formwork support is not firm, vibration, template displacement and leakage of pulp.
(4) concrete bars exposed, the main reason is that when the concrete is poured and vibrated, the reinforcing steel pad shifts, or the pad guide blocks are too few, or even leakage, the steel bars close to the formwork, resulting in the steel bars exposed after the mold is removed;The section of reinforced concrete structure is small, the steel is too dense, the big stone is stuck on the steel, the cement slurry cannot fill around the steel, and the steel is exposed.Due to the concrete mix ratio is not accurate, pouring improper method, concrete segregation;Pouring and ramming site lack of pulp or template serious leakage of pulp, resulting in gluten;The formwork is not wet enough, the concrete surface loses too much water, or the concrete lacks edge and loses Angle when the formwork is removed, resulting in the emergence of tendons.
(5) Concrete pitted surface, missing edge off Angle.The main reason is that the surface of the template is rough or not clean.The front wooden formwork of pouring reinforced concrete is not wet or not wet enough;Poor maintenance;Vibration and compaction of concrete;Premature mold removal, by external force impact or protection is not good, edges and corners are knocked off.
2. Control measures
main control measures for low strength and poor uniformity of concrete
1. Ensure the quality of concrete raw materials, check and accept the materials on site according to the quality standards, and conduct sampling and retesting according to the provisions.
2. Strictly control the mix ratio of concrete, ensure accurate measurement, according to the mix ratio determined by the laboratory and adjust the construction mix ratio, and correctly control the amount of added water and additives.Strengthen the propaganda and education to the construction personnel, emphasize the importance of the standard operation of the concrete pile structure, change the wrong idea that the column concrete has a large water-cement ratio, easy to operate and easy to compact.
3. Concrete should be mixed fully and evenly, and concrete slump value can be smaller than beam and slab concrete. Water reducer should be mixed to increase the workability of concrete and reduce water consumption.
4. Vibration should be uniform and compact. For the column with small section area and high height, the hole should be opened on the side of the large column mold and poured in sections.
5. Need to change the traditional bad habits of premature demolition and no maintenance of column mold;Change the concrete column water loss too fast, loose performance, strength reduction.
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