by Click the blue word to pay attention to our precast buildings, which are strongly advocated by the state because of their high production efficiency, labor saving and compliance with the “four sections and one environmental protection”.
However, the development of precast buildings in China is still imperfect, the construction technology is not mature, and the construction quality management system is not perfect.
According to the investigation results of the construction site of precast reinforced concrete structure in Shenyang in recent years, this paper expounds its construction process, classifies the common quality problems in the construction process, systematically analyzes the causes of these quality problems, and puts forward the corresponding preventive measures.
The construction process of precast building is mainly divided into three parts: foundation engineering, main structure engineering and decoration engineering.
The basic engineering part and decoration part are basically the same as the cast-in-situ building, mainly describing the main structure part.
The process flow of the main structure includes: industrialized prefabrication, transportation and hoisting of components and accessories; Component support and fixation; Reinforcement connection and sleeve grouting; Binding of reinforcement, formwork erection and installation of embedded parts at post cast parts; Concrete pouring and curing of post pouring parts; Up to the top floor.
Assembly integral building construction process.
01 common quality problems and preventive measures in precast building construction problem 1: plate fabrication and installation problem 1 corner plate is broken, and the corner position of corner plate is easy to break during transportation and hoisting; Deviation of angle between plates during machining; Cracks occur when connecting with cast-in-situ parts.
Corner plate is an important component to maintain the stability of the overall frame of precast buildings.
Because it has the characteristics of thin thickness, large volume and easy to break at the corner, it may cause damage to the corner plate in the process of component transportation and on-site hoisting.
The main causes of damage are that both sides of the corner plate are folded inward during hoisting; Improper maintenance during production is easy to cause angle change at the corner; During construction, partial cast-in-place is required to increase the integrity of precast buildings.
The pre supported formwork can not be well connected with the precast parts, and the formwork expansion and vibration are often incomplete.
2.
The laminated plate is broken.
The plate surface of the laminated plate is often cracked or even broken during transportation and hoisting; During production and processing, the plate surface is often warped, missing corners and broken corners, the truss reinforcement is exposed or the embedded parts fall off.
It is mainly because the span of some laminated plates is too large, the plates are squeezed during transportation, or cracks are generated due to excessive deflection during hoisting, and the cracks extend to the whole plate, resulting in member damage; Improper maintenance of components during production results in warpage of laminated plate surface, uneven painting of release agent during demoulding, less painting and missing painting, resulting in die sticking at the edge of laminated plate; During processing, the operation loophole causes the truss reinforcement on the laminated plate surface to be exposed or the embedded parts to fall off, affecting the follow-up work.
3.
The insulation layer of the external wall panel is broken.
The insulation layer of the precast external wall panel often falls off or breaks.
Generally, the precast exterior wall panels of processing plants are “sandwich” components, which are composed of “exterior decoration finish + thermal insulation layer + structural layer”.
The inconsistent thermal insulation materials in the middle often cause the exterior wall panels of thermal insulation materials to fall off.
02 preventive measures use relevant auxiliary tools (1) corner plate “L-shaped” spreader.
Precast building corner plate is often easy to break during transportation and hoisting.
To solve this problem, it is suggested that “L-shaped” spreader can be used during hoisting to transfer the tension of the corner plate to the “L-shaped” spreader during hoisting, so as to reduce the damage rate of the corner plate.
(2) flat plate “corner protection” the four corners of the flat plate are easy to be damaged during transportation.
It is recommended to make plastic or rubber corner protection according to the thickness and size of the components.
The corner protection can be sleeved into the components during protection or transportation in the component factory, and can be removed and reused before installation, which can greatly reduce the damage of the flat plate.
In addition, the method of “increasing spacing, a few times” can be adopted in the process of flat plate transportation; During the transportation of flat plates, increase the distance between flat plates, choose a flat transportation road as far as possible, and increase the transportation times to ensure that the flat plates are not broken.
Reduce the fabrication span of laminated plates.
Laminated plates often break due to excessive span during hoisting.
In order to solve this problem, we can communicate with the design unit in advance.
It is suggested that the design unit fully consider this problem when designing components, and try to control the span of the laminated plate within the deflection range of the plate, so as to reduce the damage of the laminated plate during on-site hoisting.
It is also a common problem in site construction to lift the embedded parts of the truss reinforcement laminated plate.
It is suggested that the truss reinforcement of the laminated plate can be reinforced around the hoisting embedded parts or directly hoisted, which can not only save the hoisting embedded parts and ensure the hoisting safety of the laminated plate, but also flexibly change the position of the hoisting point according to the site conditions.
Problem 2: connection of precast components problem 1 grouting is not full, and it is difficult to determine the grouting fullness of precast wallboard in longitudinal connection; Grouting holes of precast members are blocked.
It is generally believed that the grouting is completed when the concrete poured from the lower part flows out of the upper hole, but in fact, the internal situation of the grouting pipe is difficult to test and the grouting fullness is difficult to grasp.
At present, it is difficult to overcome this problem technically.
In addition, the grouting hole will be blocked due to the careless operation of the component factory during component production and the unclean cleaning of the grouting hole by the on-site workers.
2 sleeve connection dislocation component when sleeve connection, the position of reinforcement and precast sleeve often has dislocation offset.
This offset can be divided into two types: the first is partial offset, in which case the reinforcement can barely be inserted into the hole; The second, full offset, can only rework components.
The main reason for this phenomenon is that the sleeve aperture itself is small, and the machining position or size is not precise due to machine or human factors in the production of components..
