1. Mixing silo of cement and admixtures

1.1 Case 1

A commercial concrete company has just been established and has obtained the corresponding production qualifications. When supplying concrete for beams and slabs of two buildings in a community, the concrete did not solidify after two days of pouring. The construction unit and the supervisor went to the concrete company to negotiate. After investigation, it was found that the collector of the concrete company mistakenly mistook the mineral powder tank for a cement tank, and mistakenly used the ore powder tank as a cement tank. The powder was pumped into the cement tank, so the concrete did not set for two days. After finding the cause, the construction unit knocked out two layers of beams and plates, and then claimed compensation from the concrete company for more than 5 million yuan in formwork, steel bars, labor, loss of construction period, equipment rental, etc. The concrete company, which had been in business for less than three months, was unable to continue operating due to compensation and reputational damage, so it had to be transferred.

1.2 Preventive measures

(1) Each silo in a concrete enterprise should be listed and clearly marked, and the name, origin, model, inspection status, and storage of raw materials should be indicated. Date, etc.;

(2) The closed storage tank in the company should be locked at the pump pipe mouth to prevent unfamiliar drivers from making mistakes. The key should be kept by the company’s full-time material collector, who is responsible for unlocking and warehousing. ;

(3) Regularly train full-time material collectors to strengthen their sense of responsibility, improve their business level, and prevent cementitious materials from being mixed in warehouses.

2. The mix ratio of the mixing floor was entered incorrectly

2.1 Case 2

When a concrete company was supplying the basement foundation of a construction site, due to the mixing floor operator's business The tester wrote down the ratio and gave it to the operator to input. Then he went to the laboratory to play games. The operator mistakenly input cement into fly ash, causing fly ash to be used as cement. When the supply reached more than 500 The cubic concrete silo was discovered only after it was empty of fly ash. As a result, the steel bars were cut off and the concrete was dug up. The construction site and concrete were compensated for more than 2 million yuan in damages.

2.2 Preventive measures

(1) Strengthen the professional knowledge training of testers and operators. Before taking up the job, they must be familiar with the names of the materials stored in each silo and the names in the computer must match;

(2) After the operator inputs the ratio into the computer, it must be reviewed and confirmed by the tester and then signed on the review form before production can be organized. In addition, for the production of the first plate of concrete, the tester must be present to conduct the opening appraisal;

(3) The company must develop a strict management system and proceed in accordance with the quality management system and operation instructions.

3. Overdosage of admixtures

3.1 Case 3

A concrete company’s mixing plant admixture scale. The electronic valve was broken, and the admixtures were directly The water from the weighing cylinder overflowed into the weighing cylinder, but the operator did not notice it. After more than 10 trucks of concrete arrived at the construction site, the construction site found that the slump of the concrete was extremely large. Only when the information was fed back to the concrete company did they know that the admixtures were being used as water, causing the use of None of the parts are solidified, so the mold cannot be removed and can only be knocked off.

Another concrete company had a sloppy operator who input 5.06kg of admixture into 50.6kg when inputting the proportion. As a result, the poured shear wall did not solidify and the formwork could not be removed.

　3.2 Preventive measures

　(1) Strengthen the education of operators’ work responsibility, because temporary negligence in work may lead to the existence of hidden dangers in project quality and bring huge losses to the enterprise;

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(2) Mechanics should strengthen inspections of equipment. Don’t wait for the equipment to break before repairing it. They should do more maintenance and inspect frequently to nip problems in the bud. In addition, there are many types of electronic valves. Don’t be cheap. If you buy poor quality ones, they will have a short service life. You should buy imported ones, which have better quality, good accuracy and sensitivity, and a long service life;

(3) Testers should be diligent Observe, effectively monitor the operator's production process, and control the quality of concrete leaving the factory to prevent substandard products from being delivered to customers.

4. Procurement and use of unqualified materials

4.1 Case 4

At the end of last year, a material clerk of a concrete company received benefits from the supplier and put the test materials into use. A ship (more than 300 tons) of weathered stone returned from the room was privately arranged to be hoisted into the station at night for use. The forklift workers also directly loaded the materials and poured the wall columns and beam slabs of a commercial office building. The strength was C40. After 28 days, the construction site forming test was carried out. The strength of the parts submitted for inspection was 19.8MPa, 22.5MPa, and 25.8MPa. After 35 days, on-site rebound and core testing was commissioned, and there was no increase in strength. For this reason, the supervisor requested that the work be suspended for more than a month, and then reinforced. The reinforcement costs and suspension compensation cost nearly 3 million yuan.

4.2 Preventive measures

(1) The division of responsibilities of the company must be clear, the laboratory should be in charge of quality, and the receiving staff should be in charge of quantity;

(2) The company must have Strict management system strictly prohibits employees from doing things that harm the public and private interests;

(3) Testers should strengthen inspections of raw materials during the production process, report any abnormalities immediately, and take emergency measures.

5. Concrete was delivered to the wrong construction site

5.1 Case 5

A driver from a concrete company worked carelessly at night and transported a truck of C15 concrete to the C35 construction site. It was poured up, and the pouring part was the cafeteria pillar. 28 days later, the quality inspection station conducted a random inspection of the entity during the quality inspection and found that the strength of some C35 pillars was only 13.8MPa and 15.6MPa, so the owner was notified that the owner is Taiwanese and strongly requested The construction unit demolished and rebuilt it, and invited TV stations and construction authorities to witness it on site. However, the upper beams and slabs had already been poured, and there were 17 unqualified wall columns. The construction unit and the concrete company coordinated with the design, supervision, and owner many times for reinforcement, and the owner Strong opposition led to unsuccessful coordination, and the building was eventually forced to be demolished and rebuilt.

5.2 Preventive measures

(1) Strengthen the company’s internal management and strictly prohibit concrete from being sent to the wrong construction site, causing quality hazards;

(2) Production scheduling should strengthen GPS Supervision and management of vehicle operation. If a vehicle is found to be traveling in the wrong direction, it must be stopped and verified immediately.

By elaborating on five major problems that are prone to occur in concrete companies and proposing corresponding preventive measures, the purpose is to hope that the person in charge of concrete companies will not neglect the internal management of production and strengthen the training of professional managers. Develop corresponding management systems and implement them to the letter. The internal production management of the enterprise is in place, which plays a key role in cost management, thereby enhancing the enterprise's market competitiveness.