December 25, 2024

Common quality problems and countermeasures of prefabricated components in prefabricated buildings

The manufacturing problems of prefabricated components mainly include missing edges and corners, irregular edges and corners, warping unevenness, flying out of ribs, etc; Pitted surface, peeling, sanding, contamination, honeycomb, holes, etc.

on the surface of components.

Most of these problems are caused by formwork leakage, insufficient or excessive vibration, serious slurry leakage, and inadequate production and acceptance.

In addition, the slab surface of prefabricated members often cracks or even breaks during transportation and hoisting.

The reason is that the span of some prefabricated slabs 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 slab, resulting in component damage; Improper production and maintenance caused the warping of the precast slab surface, uneven painting of the release agent, insufficient painting, missing painting, etc.

during the demoulding caused the formwork sticking on the edge of the precast slab; The processing operation loophole causes the truss reinforcement of the laminated plate surface to be exposed or the embedded parts to fall off.

The construction quality of the joint leakage waterproofing project directly affects the improvement of the future use function of the building.

The waterproof treatment of traditional prefabricated large wall panel building adopts the construction method of pressure balance horizontal joint and pressure balance vertical joint, that is, the horizontal joint adopts the high and low joint, and the vertical joint adopts the comprehensive waterproof scheme combining cavity drainage.

Although the structural waterproofing scheme is also adopted, the problem of joint waterproofing is ignored, so joint leakage often occurs.

It can be seen that the waterproof of slab joints must be considered together with the problems of structure, heat preservation, heat insulation, construction and installation.

Only through reasonable design can the ideal effect of waterproof be truly achieved.

Before the hoisting of prefabricated components, if the targeted hoisting construction scheme is not formulated according to the single piece quality, shape, installation height and site conditions of prefabricated components, it will inevitably cause problems in the verticality and flatness of prefabricated components.

The embedded pipeline installation of prefabricated components The embedded pipeline is blocked, fallen off, the position is offset, and there are obstacles when threading at the construction site, all of which are due to the embedded pipeline is not well connected during the production of components, part of the concrete enters the embedded pipe during the vibration, which causes the pipeline to be blocked, or the pipeline and components are not well fixed, and the pipeline falls off or deviates during the vibration process.

In addition, after the water and electricity pipelines are embedded in the processing plant, the radian problems such as corners are not considered in the field assembly process, resulting in 90 ° right angles of the embedded wire pipes, which makes it difficult to thread on site.

The stacking time of finished product protection components is too long.

If the protection and storage are improper, the component damage is inevitable.

Countermeasures to solve the quality problems of prefabricated components 1.

The quality of prefabricated components in the production stage determines the overall safety performance of the engineering structure.

In the preparation stage of prefabricated components, in order to ensure that the quality and overall dimensions of the components meet the requirements, it is necessary to inspect the reinforcement, cement, sand, stone and other materials used in the production of the components.

The molds used in production shall have sufficient strength, rigidity, overall stability and accuracy.

The installation and fixation of the mould shall be straight, tight, not inclined and accurate in size.

During the processing of prefabricated components, the size of the reinforcement cage should be accurate, the bound reinforcement cage should be hoisted according to the specifications, and the position of the reinforcement and embedded parts should be corrected before the concrete pouring.

The concrete protective layer of reinforcement shall use special plastic cushion blocks or washers to ensure accurate dimensions.

The connectors and reserved holes in the prefabricated wall panel shall be accurately positioned in the prefabricated components.

The quality control requirements for the pouring and curing of prefabricated components are roughly the same as those for cast-in-place structures.

As the section size of some prefabricated members of plate type is small, small vibrating rods shall be selected to assist the vibration, densify the vibration points, and properly extend the vibration time.

After the component is formed, the appearance quality and size of the component shall be inspected, and the defective component shall be treated in time to ensure the service performance of the component by controlling the appearance quality of the component.

Common appearance defects include loose extension reinforcement, appearance defects, exposed reinforcement, etc.

The dimension deviation inspection focuses on the length, width and height of the component and the thickness of the protective layer of the main reinforcement.

2.

In the design stage, 2.1 Control the span of prefabricated members To solve the problem that prefabricated slabs often break due to excessive span during lifting, it is recommended that the span of prefabricated slabs be controlled within the deflection range of slabs as far as possible during design to reduce damage during on-site lifting.

2.2 In the design of waterproof measures, the wallboard joint can be designed as a groove shape with high inside and low outside, and combined with a certain decompression cavity setting to prevent water from entering the room through the pores.

The lower part is provided with shims to solve the problem of component leveling.

After the installation of the prefabricated external hanging plate, connect the plate to the plate through the transverse connecting piece on the inner side of the external wall plate, and then install the inner diagonal brace to ensure the verticality of the prefabricated external hanging plate.

In order to prevent water from flowing out through the assembly joint, waterproof adhesive tape shall be pasted between the plates.

In order to solve the common leakage problem of exterior wall door and window frame in structural construction, the window frame is placed into the component for one-time pouring when the component is processed in the factory.

▲ Leakage node profile 3.

Construction stage 3.1 Component hoisting positioning Before hoisting prefabricated components, the mechanical model and supporting lifting appliance shall be determined according to the single piece quality, shape, installation height and hoisting site conditions of prefabricated components.

For the hoisting of prefabricated components, the operation sequence of “hoisting, positioning and preliminary correction” can be adopted, and the method of “first extensive, then fine adjustment” can be implemented.

After the prefabricated wallboard is hoisted, the level, access and perpendicularity of the prefabricated components shall be adjusted to ensure the flatness of the facade after the components are assembled.

After the wallboard is hoisted in place, first determine the position and perpendicularity of the wall inside and outside according to the preset floor control line, then align the left and right wall column reinforcement with the elevation line snapped on the prefabricated component, adjust the elevation and adjust the clamp to make it at the same height.

In the side movement direction of the prefabricated wall, use a crowbar to push the wall at the side of the out-of-way direction, and determine the position of the component in the side direction according to the lateral positioning line snapped on the floor and the component.

After the upper and lower openings of the wall are basically adjusted, the diagonal brace is used for fine adjustment.
.