Proper precautions taken during the construction stage can easily prevent plaster defects. These measures range from adequate preparation and cleaning of the wall surface to selecting suitable materials and following standard construction procedures.
To ensure good bonding on a plaster-wall interface and prevent delamination of the plasterwork, it is essential to have a clean and properly prepared wall surface. Exposure of the plaster to wind and sunlight must also be avoided to prevent plastic cracks. A curing regime of at least ten days is necessary to achieve adequate strength and prevent shrinkage crack development.
Plastering work can be plagued by various types of defects such as blistering, cracks, efflorescence, flaking, peeling, popping, softness, and uneven surfaces. These problems not only affect the structural integrity of the building but also its aesthetic appearance.
How to Prevent Plaster Defects in Construction Phase?
Proper plastering techniques are essential to prevent the development of cracks and ensure a durable and attractive finish. Using well-graded sand can help prevent the formation of crazing cracks, which are shallow and have hexagonal patterns. Additionally, it is important to remove loose material and clean the surface from dust and oil to avoid plaster debonding.
Improving bonding and reducing the possibility of debonding or delamination can be achieved by using a cement slurry or spatterdash coat before plastering. It is recommended to avoid using pure cement for the finishing coat and to use a mix ratio of one part cement to four parts sand, depending on the type of sand. Fly ash blended cement is also a good option as it releases low hydration heat and has a lower possibility of crack development compared to ordinary Portland cement.
Before beginning the plastering work, it is crucial to wet the masonry wall with enough water to prevent water absorption in the mortar mix by the brick wall. Water absorption by the brick wall can increase the loss of moisture in the mortar mix, leading to the development of plastic shrinkage cracks. Overworking the cement finishes should also be avoided.
Proper curing is crucial to prevent crack development. Curing should begin as soon as possible, especially in hot and windy conditions. The plaster should be adequately cured for at least ten days. Grinning, which is the appearance of masonry joints through plasterwork, can be prevented by providing an undercoat plastering and applying two coats of plaster on a firm surface.
Plaster thickness should be limited to 1.5 cm or less. Plaster with a thickness of more than 2 cm is likely to suffer from drying shrinkage cracks and may lead to debonding and delamination. If a higher plaster thickness is needed, applying two plaster layers with a gap of around three days is recommended. Each layer should have a thickness of about 1.2 cm.
The selection of construction materials can also affect the quality of the plaster finish. A sand with a fineness modulus ranging from 2.4 to 2.6 is recommended, while sand with a fineness modulus less than 2.2 is likely to result in drying shrinkage cracks. The plaster surface may suffer from popping if it contains substances such as seeds and dead burnt lime.
Efflorescence is a whitish crystalline substance that can appear on the plaster surface due to the presence of salt in construction materials like bricks, water, and sand. To remove efflorescence, brush wash the plaster surface with a mix of one part hydrochloric acid or sulfuric acid and five parts water. After washing, dry the affected area. Finally, rust stains may appear on the surface of plaster if it is applied on a metal background.
FAQs
What is plastering in civil engineering?
Plastering refers to the application of a thin layer of mortar over the walls or uneven surfaces of buildings. This process involves covering the masonry surface with plaster, which serves as a damp-proof coat over the brick masonry work. Apart from its practical function, plastering also adds a finishing touch to the masonry, resulting in a smooth and firm appearance that enhances the building’s overall aesthetic appeal.
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What are the common defects observed in plaster?
Plastering work is vulnerable to various types of defects that can compromise the aesthetic appeal of a building. Some of the common defects observed in plastering work include blistering, cracks, efflorescence, flaking, peeling, popping, softness, and uneven surfaces. These defects can manifest in different forms and affect the quality of the plastering work.
One of the most common defects in plastering work is blistering. This occurs when the plaster loses adhesion with the substrate, resulting in the formation of small or large blisters on the surface. Cracks are another type of defect that can occur due to various reasons, such as poor workmanship, inadequate curing, or structural movement.
Efflorescence is a type of defect that can occur when soluble salts are brought to the surface of the plaster due to moisture. This can result in the formation of white or grayish deposits on the surface, which can be unsightly. Flaking, peeling, and popping are defects that can occur due to poor adhesion between the plaster and the substrate, which can be caused by inadequate surface preparation or the use of low-quality materials.
Softness is a defect that can occur when the plaster is not cured properly, leading to a soft and powdery surface. This can compromise the durability of the plaster and make it more susceptible to damage. Uneven surfaces are another type of defect that can occur due to poor workmanship or inadequate leveling of the substrate.
Overall, these defects can have a significant impact on the appearance and quality of plastering work. It is important to identify and address these issues promptly to ensure that the plastering work meets the required standards and provides a durable and aesthetically pleasing finish.
How to prevent plastering defects?
Proper preparation and cleaning of the wall surface, selecting suitable materials, and following standard construction procedures are crucial preventive measures in plasterwork. These measures ensure good bonding on the plaster-wall interface and prevent the delamination of the plasterwork. A clean and suitably prepared wall surface is a key factor in achieving a strong bond between the plaster and the wall.
Preventing exposure of the plaster to wind and sunlight is also essential to avoid plastic cracks. Plastic cracks can occur when the plaster is exposed to these elements, leading to a weakened structure. Proper protection against these elements can prevent the development of such cracks.
Furthermore, it is essential to follow a proper curing regime for a minimum of ten days after plastering. This process guarantees adequate strength achievement and hinders shrinkage crack development. Failure to follow a suitable curing regime can result in weakened plasterwork and the development of cracks.
In conclusion, taking preventive measures in plasterwork can ensure the durability and longevity of the plastered surface. These measures include proper preparation and cleaning of the wall surface, selecting suitable materials, preventing exposure to wind and sunlight, and following a proper curing regime. By implementing these measures, the chances of delamination, plastic cracks, and shrinkage crack development can be significantly reduced.
Why does plaster crack as it dries?
Drying shrinkage cracks are a common occurrence in plaster, and they usually develop due to the rapid loss of moisture that takes place after the plaster has hardened. The excessive shrinkage that results from this phenomenon can create tensile stresses that exceed the plaster’s tensile strength. Typically, thicker plaster is more prone to drying shrinkage cracks, as it is more likely to experience greater levels of shrinkage. Therefore, it is important to take measures to prevent drying shrinkage cracks in plaster, especially in applications where thicker plaster is used.