Prestressed Precast Walls
Maintenance and Cleaning
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Reinforced Dense Concrete and Precast Concrete
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Maintenance & Cleaning
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Cleaning Frequency
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| Precast walls complying with BS 8110: Parts land 2 or CP 81:1999, with cover to steel complying with Table 3.3 and specified to match the appropriate exposure category selected from Table 3.2. Minimum nominal cover to all reinforcement of 20mm. Minimum cement content 275kg/m³. |
Regular cleaning using pressure-high foaming jet with high foaming alkaline (chlorinated or non-chlorinated). Avoid acidic products Refer to cleaning method |
Once a year is recommended |
| Unclassified, ie walls not complying with BS 8110: Parts 1 and 2 or CP 81:1999. |
Unclassified
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Cleaning Method |
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| Condition of concrete wall | |
| Light soiling | Low-pressure water spray from top down to moisten dirt deposits until they soften. Softened dirt may be removed by hosing down the surfaces. Brushing may be required to supplement the hosing operation |
| Deep soiling and with hard to reach areas | Ultra-high-pressure jetting (5000 to 10,000 psi) with flat-fan pattern nozzle. Water may leak into building.Live steam can clean effectively without damaging the surfaces. Brushes and abrasives may be required to help remove the dirt. Expensive and seldom used. |
| Severe soiling | Chemical cleaning:
Ammonium hydroxide, sodium hypochlorite or hydrogen peroxide can be used. Saturating the surface with water before applying the acid solution and flushing it thoroughly reduces etching by acidic agents. May damage concrete due to build-up of salts in the pores. Mechanical cleaning: Power tools (grinder, buffers, chisels, brushes), steam/ flame cleaners. Some concrete may be removed along with the stain to result in a roughened or uneven surface. Flame cleaner can burn off organic stains that do not respond to solvents. However, the heat can cause the concrete surface to scale off. |
| Walls with efflorescence | Removed by scrubbing with water, or by hosing with water under high pressure. Dilute acids may be useful:
” 1 part hydrochloric acid in 9 to 19 parts water ” 1 part phosphoric acid in 9 parts water ” 1 part phosphoric and 1 part acetic acids in 19 parts water Concrete should be rinsed thoroughly with water after removal of efflorescence. |