Treatment of cracks in reinforced concrete floor and carbon fiber fabric reinforcement

The floor is simplified to a simply supported slab, and the floor is reinforced with carbon fiber fabric from the bottom of the floor.

Engineering survey

A residential building is a masonry structure with a building area of about 1517 m 2, the main body of the house is 5 stories, and a garage on the ground floor is added. The total height of the structure is 18.3 M. The foundation of this project is deep mixing pile to reinforce composite foundation, and the strength grade of foundation concrete is C20. The wall is made of 240mm thick load-bearing clay porous brick with the strength of MU10, the wall below 5.15M is made of M10 mixed mortar, and the wall above 5.15M is made of M5 mixed mortar. The design thickness of cast-in-place concrete slab is 110, 90 and 70mm respectively. The strength grade of structural floor and Liang Hezhu concrete is C20. The residential building started in August 2001 and completed in May 2002. Since the end of June 2002, the floor cracks of different floors of the residential building have been varying degrees. In order to ensure the safe use of the residential building, it is necessary to conduct comprehensive appraisal and analysis of the housing structure, and reinforce it according to the appraisal conclusion.


Cracking of floor slab

The cracking phenomenon of structural floor is serious. Most of the floors of buildings are cracked at different degrees. The floor cracks of the residential building can be divided into slant cracks at the corner of the floor, circular cracks around the floor and slant cracks along the middle of the floor. Most of the inclined cracks at the corner of the floor and the circular cracks around the floor belong to through cracks, and the crack width is about 1 mm.

cracks

Cause analysis of floor cracking

1) design reason

In terms of design, it is mainly due to the small design area of the upper reinforcement (negative reinforcement) and the short length of the upper reinforcement at the corner of the floor.


2) construction reasons

In construction, the main reasons are: 1) the thickness of floor slab is thin; 2) the steel bar on the upper floor sinks, so that the steel bar staggers and the thickness of protective layer is too large; 3) uneven concrete placement, resulting in local concrete strength does not meet the design requirements and other reasons.


In the construction process of this residential building, due to blindly pursuing the construction progress, there are some deformation cracks in concrete caused by premature demolition of formwork and improper maintenance, resulting in the change of environmental humidity around the concrete and excessive temperature difference between the inside and outside.


Reinforcement scheme

The floor is simplified to a simply supported slab, and the floor is reinforced with carbon fiber fabric from the bottom of the floor.

reinforced with carbon fiber fabric

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