Mixing sand and cement for plastering involves combining the materials in a specific ratio, typically expressed as Cement: Sand. This ratio dictates the strength and workability of the plaster mix.
Understanding the Plastering Mix Ratio
The fundamental principle for mixing sand and cement for plastering is using defined proportions or 'parts' of each material. As stated in the reference Calculating Cement and Sand Ratio for Plastering, Cement: Sand = 1:5 refers to 1 part of cement and 5 parts of sand in a mortar mix. These parts can be measured by volume, using buckets or containers of the same size. For instance, one bucket of cement would be mixed with five buckets of sand.
Different ratios are used depending on the specific application and the coat of plastering. A common starting point, often referenced in guidelines for general plastering, is the 1:5 ratio mentioned in the reference. Stronger mixes (with less sand relative to cement) might be used for the base coat, while weaker mixes might be used for the finish coat.
Applying the Mix: Coats and Thickness
Proper plastering is often applied in multiple layers to achieve the desired thickness and finish. According to the reference, the plasterwork should be done in two coats or layers. This multi-layer approach helps in achieving a smooth, level surface and provides better adhesion and crack resistance compared to applying a single thick layer.
Furthermore, the reference specifies a target thickness for the completed plasterwork: The overall thickness of plastering should be 20mm minimum, including two coats. The chosen sand-cement ratio is crucial for creating a mix that is strong enough to build up this thickness and durable once cured.
General Mixing Process
Once the correct ratio (e.g., 1:5 or other suitable ratio for the specific coat) is determined:
- Measure: Accurately measure the required parts of cement and sand based on your chosen ratio.
- Dry Mix: Thoroughly mix the dry sand and cement together on a clean, hard surface or in a mechanical mixer until the color is uniform.
- Add Water: Gradually add clean water while continuously mixing. Add just enough water to create a workable paste – wet enough to be applied smoothly but not so wet that it runs or slumps excessively.
- Mix Thoroughly: Continue mixing until the mortar is consistent in texture and color, free of lumps.
Proper mixing ensures that the cement is evenly distributed, allowing it to effectively bind the sand particles together for a strong plaster layer.
