From 2016 to 2019, the new construction area of precast buildings in China tripled.

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Among them, concrete structures accounted for 65.4% of the newly started precast buildings in 2019.

Based on the analysis of the problems of the components of different engineering projects in the investigated component factories from July to October 2020, including the sorting of customer complaints and customer returns, a total of 75 component quality problem points are counted.

Through analysis, due to tight time, heavy tasks, improper management and other reasons, the production enterprises have quality defects in the finished products of precast components, such as surface honeycomb, pitted surface, missing edges and corners, dimensional deviation, embedded reservation, rough surface, finished product protection and other problems, which affect the overall quality of precast buildings.

In 2016, several opinions on Further Strengthening the management of urban planning and construction proposed that the development goal of building assembly rate of 30% in the country within ten years [1] has become the first year of promoting the policy of precast construction.

Component surface pollution.

Among them, the frequency of appearance quality problems is the most, and the frequency of size deviation and reserved hole problems is also more.

1.1.3 component crack the main cause of component crack is that the concrete strength does not reach the design strength and is lifted too early; The protective measures of components during stacking and transportation are not standardized; Improper hoisting method or spreader selection of precast components, unreasonable reinforcement allocation, resulting in tensile stress exceeding the allowable stress.

1.1.2 the main reasons for missing edges and corners of components are demoulding due to the failure of components to reach the design strength, resulting in the damage of concrete edges and corners with the removal of molds; Improper formwork removal operation, and the edges and corners are damaged by external force; The sundries at the edges and corners of the mold are not cleaned in time, or the release agent is applied unevenly and the retarder is not dry; The finished products of precast components are not protected in place during transportation, storage and transportation, and are damaged by external force or heavy object impact.

1.1.4 the honeycomb, hole and pockmarked surface of components are mainly caused by non dense concrete vibration and missing vibration; The formwork surface is not cleaned or the formwork is not fully coated with isolating agent; Uneven mixing of concrete results in poor cohesion and fluidity of concrete; When the concrete is put into the formwork, the free fall height is large, or the concrete is not poured in layers, resulting in segregation, honeycomb and pitted surface, etc..

Article 9.3.2 of the technical standard for precast concrete buildings (GB / t51231-2016) stipulates that the mold shall have sufficient strength, stiffness and overall stability, and shall comply with the following provisions: the mold shall be kept clean, and the application of release agent and surface retarder shall be uniform, without omission and accumulation, and shall not affect the appearance effect of precast components [3].

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By analyzing the causes of the quality problems of precast components, the author divides the factory production quality control process into three stages, and puts forward the treatment measures for the defects of precast components.

Due to the late development of precast buildings in China, the production level and management level of precast concrete precast component production enterprises are not high, there are few skilled workers, and the industrial supporting facilities are not mature.

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The main reasons for the surface pollution of precast components are that the release agent on the mold surface is not painted evenly, and the mold is rusted after not being used for a long time; The finished products of precast components are not well protected during transportation, storage and transportation, and the surface is polluted by foreign objects.

Through investigation and analysis, the finished products of precast components are prone to appearance quality problems, size deviation problems, reserved hole blockage problems and so on, which affect the overall quality of precast buildings.

Abstract: the production of precast concrete components is an important link of precast buildings, and its product quality directly affects the smooth implementation of precast buildings.

Before the production of precast components, the design depth of precast components shall not only meet the structural performance and functional requirements of components, but also meet the construction requirements of component production, hoisting and transportation, on-site installation, temporary fixation, connection with cast-in-situ structure, formwork, support and so on.

Relying on the 2020 project of young teachers’ enterprise practice project and school level natural science project in Higher Vocational Colleges in Jiangsu Province, the author took a temporary training in a precast concrete component production enterprise in Jiangsu for half a year, and found the problems in the production process through field investigation, Sort out and summarize according to customer complaints and customer returns, and analyze the quality problems and solutions in the production stage of precast concrete components by consulting domestic and foreign literature.

Appearance quality problems 1.1.1.

Article 11.2.3 of the technical standard for precast concrete buildings (GB / t51231-2016) stipulates that the concrete appearance quality of precast components shall not have serious defects, and there shall be no dimensional deviation affecting the structural performance, installation and use function.

Quality problems in the production stage of precast concrete components.

Because the production of precast components is an important link of precast buildings, the quality of its products directly affects the smooth implementation of precast buildings.

Specific analysis of the following problems: 1.1.

There are still some problems in the production and application of precast components [2].

See Table 1 for specific data.