Case 1
- Introduction
- Causes of Defects
- Good Practices
- Standards
- Maintenance and Diagnostics
- Remedial
- Similar Cases
- References
Maintenance and Diagnostics
Maintenance
Masonry requires periodic maintenance to ensure its continued successful performance.
Although the brick units are quite durable over time, other materials in the wall system will require periodic repair and/or replacement.
Typical maintenance items which should be addressed are repairing of cracks in masonry, cleaning clogged weep holes, removing stains and efflorescence, repainting steel, replacing caps or copings, repointing mortar joints (tuckpointing), replacing deteriorated sealants and caulking, and cleaning the masonry.
Cleaning New Masonry
Cleaning of new masonry wall regularly can reduce the formation of fungi on surfaces.
Few methods:
- Bucket and Brush Hand Cleaning
- Pressurized Water Cleaning
- Sandblasting
| Brick Category | Cleaning Method | Remarks |
| Red and Red Flashed | Bucket and Brush Hand Cleaning Pressurized Water Sandblasting | Proprietary compounds, hydrochloric acid solutions, and emulsifying agents may be used. Smooth Texture: Mortar stains and smears are generally easier to remove; less surface area exposed; easier to presoak and rinse; unbroken surface, thus more likely to display poor rinsing, acid staining, poor removal of mortar smears. Rough Texture: Mortar and dirt tend to penetrate deep into textures; additional area for water and acid absorption essential to use pressurized water during rinsing. |
| Red Body with Sand Finish or Surface Coating | Bucket and Brush Hand Cleaning | Clean with plain water and scrub brush using light pressure. Excessive mortar stains may require use of cleaning solution. Sandblasting is not recommended. Cleaning may affect appearance. |
| Light Coloured Units: White, Tan, Buff, Gray, Specks, Pink, Brown and Black | Bucket and Brush Hand Cleaning Pressurized Water Sandblasting | Do not use muriatic acid!!! Clean with plain water, detergents, emulsifying agents, or suitable proprietary compounds. Manganese coloured brick units tend to react to muriatic acid solutions and stain. light coloured brick and more susceptible to “acid burn” and stains, compared to darker units. |
| Light Coloured Units with Sand Finish or Surface Coating | Bucket and Brush Hand Cleaning | See notes for Red Body with Sand Finish or Surface Coating and Light Coloured Units: etc. Sandblasting is not recommended. |
| Glazed Brick | Bucket and Brush Hand Cleaning Pressurized Water | Wipe glazed surface with soft cloth within a few minutes of laying units. Use of soft sponge or brush plus ample water supply for final washing. Use detergents where necessary and acid solutions only for very difficult mortar stain. Do not use acid on salt glazed or metallic glazed brick. Do not use abrasive powders. Do not use metal cleaning tools or brushes. |
| Coloured Mortars | Method is generally controlled by the brick unit. | Many manufacturers of coloured mortars do not recommend chemical cleaning solutions. Most acid tend to bleach coloured mortars. Mild detergent solutions are generally recommended. |
Cleaning Existing Masonry
There are four cleaning techniques for existing masonry [9].
Brick masonry can generally be cleaned with chemical solutions in conjunction with water rinsing. Acidic cleaners containing dilute mineral acids such as hydrochloric, hydrofluoric, phosphoric and/ or organic acids such as acetic and citric are used to remove heavy soiling from most brick masonry.
The cleaning process involves applying the diluted cleaner to the pre-wetted surface and allowing a short dwell period. Chemical and soiling residues are removed by pressure water rinsing.
Great care should be used to avoid damage to mortar, which can be attacked by acids. Sometimes alkaline cleaners are used to remove soiling on brick surfaces, but the type of chemical cleaner should be selected with care, then tested in small areas before it is applied in whole to the walls.
Certain chemicals cause staining of some types of bricks, and soft brick are particularly vulnerable to damage from aggressive cleaning methods (Table 1).
| Condition of Brick wall | Cleaning method |
| Dirt on brick Smooth textured bricksModerately rough texture Very rough texture Walls with coloured mortar joints | Scouring powder and a stiff brush. Where budget allows, high pressure steam (< 60 psi) with detergent allows faster cleaning. Scrubbing with an oxalic acid-ammonium biflouride solution Pressurized water cleaning (< 700 psi) Mild detergent solutions. Acids may bleach coloured mortar. |
| Biological stain | Apply sulpharnate or weed killer. |
| Green Stains from Vanadium salts | Flush brickwall with water followed by solution of potassium or sodium hydroxide. Allow it to stand for 3 days. Hose off remaining white salt on the brickwall from the hydroxide. |
| Paint on wall | Chemicals and high-pressure steam or scrubbing with steel. wool. |
| Walls with efflorescence | Generally disappear with normal weathering. Can be removed by dry brushing or with clear water and a stiff brush. Heavy accumulation requires proprietary cleaner. |
| Grayish- white haze (White scum) | Masking by solutions of paraffin oil and Varsol, or linseed oil and Varsol, applied by brush to the affected brick units. |
Table 1: Cleaning method for different types of stains.
Diagnostics of Defect (see also NDT)
Visual Inspection
Conduct a comprehensive visual inspection.
Age is not necessarily a main contributing factor to algae attack. More importantly determinants are the amount of exposure, susceptibility to attacks and surface treatments. A building that is orientated towards the North is most prone to biological attacks. Surfaces facing the morning sun are less prone to attack since surface temperature of the finish is raised above that suitable for algae growth.
Visual inspection of the building is sufficient to identify the affected areas.
The following tests can be used to assist with the diagnosis:
Hygrometer
Hygrometer can be used to measure the RH of the surrounding.
Thermography can be used to identify the position of cracks. A range of crack widths, representing mechanical damage, has been induced under controlled laboratory conditions. The method is based on the characteristics of heat flow phenomenon, in a conductive medium of specific geometry, which is intended to model predetermined boundary conditions.
