Slab strengthening

Project overview

The Islamic Association of Ningxia building, in November 2, 2007 ,the pouring shaft eight layer roof, because the template support system is not stable, so that the section of concrete in the pouring collapsed. The seven layer is cracked. The concrete strength can't meet the design requirements, the crack width range is different, slab crack width exceeds the permissible value of standard 0.3 mm, therefore reinforcement measures for cracks taken.

The construction procedure

1.crack treatment:

1) clean the floating dust and other sundries in the fractured area, and can be constructed after a certain drying degree.

2) for cracks in slab width less than 0.3 mm, base after cleaning, evenly 2~3 modified epoxy resin structural reinforcing glue along the crack extension direction of liquid absorption, low viscosity and good permeability by capillary action in concrete surface, closed fracture channel.

3) for slab width between 0.3 ~ 1 mm static independent cracks, through the cracks of the base, after the treatment, the recoverable crack repair glue with certain pressure will be low viscosity and high strength crack injection, closed fracture channel.

4) for slabs width greater than 1 mm structure through cracks, in a certain period of time, with a high pressure grouting material will repair cracks with the indentation fracture cavity closed fracture channel.

(repair slab crack with HM-120L crack injection adhesive)

2.externally bonded carbon fiber reinfroced polymer(CFRP)

>>The treatment of concrete surface

The cosmetic layer, oil, dirt etc. Of concrete surface should be chiseled off and then rubbed off 1 ~2 mm thick surface layer with the

angle grinder, concrete components should be handled by chamfering on the corner, dust was blew out with compressed air after the

completion Of polishing, and finally the surface was wiped by cotton cloth dipped in acetone, and kept dry for use. If the concrete

needed to strengthen existed cracks, first choose HM-120M perfusion adhesive or HM-120L pouring crack adhesive to perfuse according

to the size of crack, and then strengthen.

>>Primer construction

When construction, two components of primer A and B were weighed according to the stipulated proportion of preparing glue, and

dumped into a clean container and stirred to uniformity (when mixing, best mix along the same direction to avoid the air from forming

air bubbles.) Brush or roller brush was used to evenly brush on the concrete surface, after the glue surface layer dried, it should be

brushed several times depending on the particular circumstances, but the coating thickness did not exceed 0.4 mm, and it should

not be missed out to brush, or have flowing or bubbles, waiting for glue curing (curing time was depended on the site temperature,

it was appropriate when finger felt dry, generally not less than 2 hours), then the next process was proceeded. The glue prepared

every time should be used up one time during the applicable period of the glue.

>>Leveling construction

The pores and defects on concrete surface were filled by leveling adhesive.When depression area was existed, the prepared leveling

adhesive was used to repair and fill through scraper embedding and scraping, the position emerging altitude difference such as the

joint of templates should be filled by leveling adhesive, which tried to minimize the height difference. The treatment of corner was that

it was repaired to smooth arc through leveling adhesive, its radius was not more than 20mm. After the leveling adhesive cured (curing

time was depended on the site temperature, it was appropriate when finger felt dry, generally not less than 2 hours), the next process

should be proceeded further.

>>Paste of carbon fiber cloth

Carbon fiber impregnated adhesive was smeared to the pasted area evenly,the corner site was more smeared appropriately. Paste after

hauling carbon fiber cloth tight and alignment, use a plastic scraper or roller (a paint roller that the villus was removed outside) to roll

repeatedly along the same direction, until the glue compound exuded. And then smear impregnated adhesive to the outside surface

of the carbon fiber cloth evenly, and roll repeatedly, 50 that the impregnated adhesive can immerse the carbon fiber cloth in two ways,

if it is multi-paste, until your fingers touch dry, the next layer of paste can be beginner. If the carbon fiber cloth needs overlapping

>>Curing and conservation

Prevent rain or moisture 24 hours after the completion of construction, and pay attention to protection against a hard Object bumping

into the surface of the construction. When the average air temperature is 20 , 25 ℃ , the curing time is not less than 3 days; when

the average air temperature is 10 ℃, the curing time is not less than 7 days.

（externally bonded carbon fiber reinfroced polymer(CFRP)）

3.epoxy bonded steel plate

1.substrate surface clean

2.scribe line ro setting out

3.anchoring

4.plate surface preparing

5.bonding steel plate with the structural adhesive

6.maintaince

7.checking

8.protection coating

(slab strengthening with epoxy bonded steel plate)