Plastering in Concrete Surfaces
In order to improve the surface’s longevity and structural integrity as well as its cosmetic appeal, lean mortar is applied during the crucial building process of plastering concrete surfaces. We explore the complexities of plastering concrete surfaces in this extensive guide, covering a range of techniques that can be applied to different kinds of concrete compositions. We also cover important safety precautions, which guarantee the accuracy of the work and the participants’ safety.
How to Plaster a Concrete Surface & its Procedure
Concrete surface plastering can be reduced to a methodical sequence of steps:
1. Preparation of Surface
Precise surface preparation is essential before starting any plastering. The surface that has to be plastered needs to be well cleaned in order to guarantee the best possible adhesion between the plaster and the concrete. This include cleaning up any peeling paint, removing any loose pieces of old plaster, and getting rid of pollutants like dust, paint, and oil. The cornerstone of a good plastering endeavor is a spotless surface.
2. Applying Slurry for Treatment
In order to facilitate plaster adherence, the concrete surface needs to be sufficiently rough. It is possible to accomplish this by applying a slurry or dash. Carefully, one part cement to one and a half parts coarse sand is combined with the right amount of water to create a fluid fluidity in this slurry. This initial stage creates a foundation upon which the subsequent plaster layers will rest.
3. Plaster Mixing
The process of making plaster involves precisely combining cement, water, and fine aggregate (sand) to create the right consistency of plaster for the job at hand. For this mixture to be successful and workable, it must be applied within a specific two-hour timetable
4. Plaster Applications
During the application process, a foundation coat of plaster must be applied to the slurry-coated surface using a steel trowel, which requires competence. The appropriate thickness for this plaster layer is between 10 and 15 mm. To ensure uniformity and a flat surface, application is done carefully in short, even strokes. When applying a single layer, the thickness shouldn’t be more than 10 to 15 mm, and the topcoat should be between 5 and 10 mm thick.
5. Plaster Curing
After the plaster has been applied correctly and has gone through the setting and hardening process, curing needs to start and last for at least seven days. This crucial phase is essential to guaranteeing the plastered concrete’s durability and structural integrity. The surface is prepared for paint or wallpaper application after the drying phase.
6. Plaster Thickness
When using Thistle Bond-it or other bonding chemicals, the thickness of the undercoat must follow strict guidelines: wall undercoats cannot be thicker than 11 mm, and soffit undercoats must be thicker than 8 mm. The final coat that is put on top of the undercoat needs to be exactly 2 mm in size. When a higher thickness is required, plastering over expanded metal lathing that is mechanically fastened becomes an alternative, albeit a more expensive one.
Applying Plaster on Various Concrete Surfaces
Concrete Plastering in Dense
Particular care is needed to address the special problems that dense concrete surfaces—which are smooth and have minimal porosity—present. In such cases, reference is made to Section 4 of BS 5492: 1990, which suggests the use of bonding techniques to facilitate proper adhesion of plaster. The plaster’s grip can be improved by mechanically modifying the surface using techniques like shot blasting or scrabbling. But plastering cannot be done until the concrete has sufficiently dried after the shutters are removed. Moreover, plastering should not start if there is any free water left on the surface of the concrete. Plastering mechanically secured expanded metal lathing provides a dependable, albeit pricy, method for best outcomes, especially on new construction projects where time is of the essence.
Pouring Concrete Using No-Fines and Lightweight
The unique challenges of plastering on fully compacted lightweight aggregate concrete stem from variations in surface qualities and thermal properties. Certain precautions may be required due to the dusty surface and strong suction that this kind of concrete may demonstrate. These difficulties can be successfully reduced by using bonding treatments like Thistle Gyp Prime or PVAC bonding solutions. Especially thistle Gyp Prime keeps undercoat plaster from drying out quickly on backgrounds with strong suction. To ensure full absorption without leaving a glossy layer, Thistle GypPrime must be diluted with water before application. It is best to start plastering just when the surface has completely dried. Conversely, because it has a lot of voids, which act as an effective key for plaster adherence, no-fines concrete makes an excellent substrate for plastering.
Plastering Works on Mixed Concrete Surfaces
Strategies to reduce cracking from differential movements are crucial when plastering over varied backgrounds:
- Expanded Metal Fixation: By installing expanded metal across the intersection of two distinct backgrounds, the chance of cracks forming as a result of disparate material movements can be significantly decreased.
- Isolation Measures: Completely spanning the column with expanded metal over building paper can isolate the plaster from differential movement in narrow widths where a concrete column divides brick panels. An ugly, uneven cracking can be avoided by making a straight knife cut through the plaster along the connection line.
Crucial Things to Keep in Mind When Plastering Concrete
Plastering projects require exacting attention to detail in order to be successful:
- Avoid Plastering Concrete: Look into alternate construction techniques that might be used to avoid plastering concrete surfaces.
- Concrete Mixes with Flint Aggregate: To improve surface quality in areas intended for plastering, use concrete mixes that contain flint aggregate.
- Chemical Release Agents: Use of a thin coating of chemical release agents should take precedence over conventional mould oils.
- Contamination Inspection: Carefully check the surface of the concrete for impurities, and if needed, take the necessary corrective action.
- Surface Dust Removal: It is essential to remove surface dust from hard concrete surfaces. It is advisable to think about using exclusive bonding solutions like Thistle Bond-it. Thistle GypPrime works quite well on backdrops that absorb.
- Plaster Application: Use firm pressure when applying the plaster, and once it hardens, carefully check the building during the first heating period to make sure no hollow spots have developed in the plaster.
- Gradual Heating: To avoid sudden temperature changes, use a gradual temperature increase approach while heating the building for the first time.
Individual Defense in Plastering
The first concern is the safety of the workers doing plastering procedures. It is essential to follow personal safety precautions to the letter:
- Sufficient Ventilation: Make sure the workspace has enough ventilation. When controlling dust is difficult, wear a half-face mask that complies with EN 149 Class FFP1.
- Impermeable Protective Gear: To reduce the chance of prolonged or recurrent wet contact, dress in impermeable gloves, protective dungarees and safety boots.
- Application of Barrier lotion: To further protect your hands from skin contact with plaster, apply a barrier lotion to them.
- Eye Protection: When plaster powder or splashes are expected during the plastering process, wear safety goggles that meet BS EN 166 type 2A5 criteria.
You may do concrete surface plastering with the utmost expertise and accuracy and produce visually pleasing and structurally sound results by following these detailed instructions and safety precautions.