Conventional Sand Cement Plaster v/s Ready Mix Plaster

Saint-Gobain Weber India

Introduction

In today’s construction world, New innovations and breakthroughs in construction materials have enhanced the life of new upcoming constructions. As expected, new materials and new practices may seem costlier in the beginning during purchase as compared to existing material and practices. But if new products and practices are seen in an overall perspective of ease of application, performance, features and facilities; these new material and practices become a more economical choice. Cementitious plaster is also one such critical product in construction.

In every construction, plastering is the process after which one can start identifying the exact look and appearance of the structure. It is the process after which mostly decorative and interiors’ works start. Plastering is not a new innovation, it is known to mankind since ages. You must have seen houses where mud is applied on walls. That was one of those earliest forms of plastering.

 

Key Function of Plastering

The key functions of plastering are to provide the following

  1. Appearance- It provides a smooth, regular, clean and even surface which is suitable for decorative applications like painting, tiling etc.
  2. Protection- Plastering on external masonry surfaces is done to protect the structure from atmospheric conditions and on internal masonry surfaces to protect from dust.
  3. Concealing defects- Plastering helps in concealing defects in structure due to alignment like levelling, cracks etc.

Today, in the traditional method of plastering which is prevalent, contractors buy sand and cement from the market and store it on construction site. When required, they mix sand and cement in a fixed proportion along with water to prepare mix which is then applied to the wall to create a plastered surface.

Though it appears very simple, each ingredient has its own importance in terms of requirement and contribution to quality.

Let’s discuss first the role of sand.

Role of Sand in Plastering

Sand is one of the key ingredients which decides the texture, smoothness and compactness of plasters. In geographies like India and current scenario of bans for sand, it is very difficult to obtain the same sand quality during the entire project duration. With the change of source, sand appearance changes. Also, the sand which reaches the market has organic material and silt content in it which impacts the quality of plaster heavily. In the conventional method of plastering, this key aspect of sand is ignored. In general, people ignore if the sand is silt free or organic content free.

For consistent and good quality, sand used during plastering must be free from silt and organic content. Also, the same sand shall be used during the entire project.

Also, one key quality of plaster which provides strength is its compactness. Compactness is directly associated with perfect packing of particles which impacts the strength of plaster significantly. The compactness of plaster is dependent on the right mix of different sizes of a particle in the sand so that it can achieve the maximum compactness. Graded sand plays a key role here. If sand is not graded, the desired compactness of plasters cannot be achieved which will reduce plaster strength significantly.

In Conventional plaster, applicator generally doesn’t go for grading of sand. It finally results in lots of quality issues like cracks, debonding, uneven surfaces.

In India, there are so many different varieties of sand and there is no reliability that same quality of sand will be available in the near future. In general, construction of a house goes for a year and even a few years in case of big projects. Under such a big range of time, maintaining consistent sand quality and type is impractical. Due to storage space constraint at project sites, one cannot buy a complete amount of sand at one time. So to obtain a consistent quality, sourcing of plastering material shall be kept the same to avoid inconsistencies.

Polymerized

Plaster needs to play an important role in providing protection from external weather conditions like raining etc. Excellent weather resistance can add many years to structure’s life. A mix of only sand and cement has limitations in providing a long life to the structure. Advantage of new innovations shall be taken. Special additives and polymers are available in the market which can enhance weather resistance of plasters by enhancing their water resistance capabilities and can add many more years in the life of a structure. These polymerized plasters are more durable than ordinary plasters which directly impacts the maintenance cost in future.

Not only the above ingredients, but there are other factors related to the handling of material and application which also plays a key role in the cost of the project.

Storage and material handling

Once bought sand has to be stored on construction. But storage of loose material invites more requirement of storage due to its conical storage and wastage due to spillage. Also, it is exposed to contamination of foreign particles which are in abundance on a construction site. High storage space requirements, wastage of sand due to spillage and contamination can hamper the quality of the project.

In such cases, packed material protects against contamination and spillage and also can be stacked in forms which attract less storage space than loose material.

Application -

During comparison in terms of performance, application becomes one of most critical element of evaluation. Application involves many aspects of performance like time of application, ease of application, ease of adaptation to new practices etc. Lets discuss them one by one.

During plastering- one person needs to bring sand and cement on-site and has to mix it thoroughly, then the application starts. This part is much more time consuming than simply bringing bags to site and applying after mixing with water.

Sand Cleaning on Site- For sand cleaning on site, one manpower is required always during conventional method of plastering. While in case of ready mix plaster, material is already premixed. Also ready mix material’s sand grading is far superior quality then what is done manually on site which ultimately results in really compact and smooth plaster.

Application Time- In ready mix plaster, polymer content has higher adhesion tendency on the substrate than normal sand cement mix. Due to this, the high retention rate of the material is obtained in each delivery on the substrate by applicator while using a ready mix plaster. It saves time during application. Also, rebound losses are less. In general practice in the market, these rebound losses are remixed in the material which also increases the time of mixing. So ineffective, time of mixing and application are both high in case of the conventional method of plastering as compared to ready mix plaster.

Curing Time- Polymeric content of ready mix plaster provides high water retention which reduces the need for long curing periods unlike in conventional method of plastering. In a conventional method, applicators cure the plastered surface for a week-long time. In the case of ready mix plaster, the same can be achieved in 3-4 days’ time. It saves lots of time and a very valuable resource i.e. water.

Mix Quality- Ready mix plaster is a machine mixed material which ensured thorough mixing of material. In the case of manual mixing on-site in conventional plaster, it is hard to achieve quality of mixing of sand and cement equivalent to ready mix plaster.

Comparison of Conventional Method Of Plastering & Ready Mix Plasters

Below is the summary of a comparison of the conventional method of plastering and using ready-mix plasters.

 

Attribute

Conventional Method

Ready Mix plasters

Graded Sand- for compactness

NO

YES

Silt free & organic content free Sand- For good quality

NO

YES

Same sand Source- Consistencies

Not always

YES

Polymers – for enhanced weather  resistance and workability

NO

YES

Storage space requirement- For sand and cement

High

Low

Manpower Requirement During Application

Normal

Low- due to premixed content, only water to be added on site

Sand – Cement Mix Ratio

Inconsistent

Consistent and optimized for best results

Wastage- due to sand spillage or on-site

Yes

Negligible

Time of application- Mixing & Application

High

Low

 

From the above factors, it is evident that ready-mix plasters provide much better plaster surfaces which are durable and have very low maintenance issues and associated costs than conventional plasters.

Also, quality issues in conventional plaster bring the additional cost of repainting, putty filling, or even re plastering.

So to summarize, the immediate benefits like manpower savings, fast application, storage space-saving, are also accompanied by long term benefits like adding additional years in the life of structure which attract very low maintenance issue due to its strong, compact and weather-resistant properties, in case of ready-mix plasters. This ultimately makes ready mix plasters (Weberwall Premium plaster) an economical choice compared to the conventional method of plaster