Bridge deck blasting
Construction technology of shot blasting on bridge deck
1. Construction preparation
(1) the quality of the bridge panel shall meet the specification or design requirements.
(2) the bridge deck (including the protection wall root) shall be flat, clean and dry, and shall not be free of drums, looseness, honeycomb, pockmarks, floating ballast, floating soil, mold release agent and oil stains;
The surface strength meets the specified requirements.
(3) raw materials have been sampled and tested to be qualified.

2. The shot blasting

(1) shot blasting technology is adopted for the treatment of waterproof layer base of bridge, that is, shot blasting machine is used to remove floating slurry on the surface of beam.
The surface treated by shot blasting is rough and even;
It will not damage the original base surface structure and flatness, and can completely remove the floating pulp and sand, 100% "wound", revealing;
But at the same time, it will not cause the loosening and micro-crack of aggregate, so as to enhance the adhesion of waterproof material on the surface and provide a certain penetration effect.
The basic treatment equipment adopts the equipment with synchronous removal of floating slurry and dust absorption function, and the self-recycling shot blasting equipment with driving walking system to treat the concrete base of bridge deck.
(2) large area shot blasting should be carried out before the shot blasting process test, to determine the best shot specification, shot flow is the best motor load, shot blasting machine speed and other key process parameters.
After the shot blasting process parameters are determined, large area shot blasting is carried out, and attention is paid to cleaning after the treatment is completed.
(3) the shot blasting process should be carried out continuously. If the shot blasting machine is stopped due to special reasons, the machine should be set back about 30cm before the next re-casting, and then the shot blasting should be started again. After the machine walks past, the quality of the shot blasting in the lap joint area should be checked in time, and if there is any omission, the shot blasting should be made up.
(4) when leveling local concrete at the base of bridge deck and protective wall, Angle grinder can be used to avoid obvious concave and convex groove marks, so as to make the edge face flat and ensure effective bonding of waterproof layer.
(5) roughness of shot blasting treatment shall conform to the provisions.
If the roughness is too large, it will bring a lot of work to the bottom coating and repair, and is not conducive to bond strength;
If the rough base is too small, it will cause insufficient adhesion.
Shot blasting control standard is based on visual measurement of no floating slurry, and roughness control at SP3 is appropriate.
(6) there are slopes at the end and side of the beam, the shot blasting machine is easy to leak the shot material, and the loss is very serious. In order to save costs, it is necessary to do a good job in recovering the shot material. The work of recovering the shot material requires the shot blasting team to collect well, and the loss of the shot material is required to be within 10% to 20%.
On the premise of not leaking the shot material, try to press the edge and shot blasting, which can greatly reduce the polishing process in the next process and save time and material loss.

Repair putty

(1) after shot blasting, the defects of the base layer are fully exposed and numerous holes are formed in the concrete bridge deck.
Moisture or air in the hole will cause pinholes on the surface of the coating and affect the apparent quality of the coating.
In order to ensure the construction quality, the roughness of the base layer can be controlled by adjusting the walking speed of the shot blasting machine for the parts that have been processed in the acceptance process of beam surface, so as to avoid the phenomenon of over-throwing and bring inconvenience to the subsequent construction.
Check the base surface, and repair putty repair, generally use epoxy mortar repair putty scraping coating 2-3 times.
The first full scratch, the use of mortar epoxy resin repair material (epoxy resin + quartz sand), to deal with large holes, cracks and drainage holes, Yin Angle details defects.
For the second local treatment, the mortar epoxy resin is used to repair the large holes, air holes and uneven places (if there is no such time, it can be omitted).
For the third full scratch, putty epoxy resin repair material (epoxy resin + talcum powder) is used to seal fine pores.

(2) the basic repair is all manually operated.
Repair completed, careful inspection, so that the surface of the base layer without visible defects.
(3) when the crack width is greater than 0.2mm, epoxy mortar shall be used to repair separately.
(4) try to close all pinholes, pits and other defects.
(5) repair putty should be uniform, flat, as far as possible thin scraping, to avoid the impact of adhesion and waste of materials.
Be bored with child thickness should not exceed 0.5mm, in scraping besmearing process, personnel division of labor is clear, scraping besmearing area is radius with the body, into arc distribution, scraping besmearing should be rapid, avoid because of slurry cure, cause working face to stay hang and Pilate.
(6) professional blower blowing and cleaning.
Be sure to keep it clean and dry.


Key words: bridge surface shot blasting bridge shot blasting construction bridge bearing replacement