how much plasticiser to use in mortar

1. Introduction

2. Understanding Plasticisers in Mortar

3. The Importance of Proper Plasticiser Usage

4. Types of Plasticisers

5. Recommended Dosage Levels for Mortar Plasticisers

6. Testing and Adjustment for Optimal Results

7. Conclusion

Introduction

When it comes to achieving the desired characteristics in mortar, the proper use of plasticisers plays a crucial role. Plasticisers are chemical additives that enhance the workability and performance of mortar. They help to improve the flow, cohesion, and adhesion properties of the mixture. However, using the right quantity of plasticiser is essential to avoid any negative effects on mortar performance, such as reduced strength or durability. In this article, we will discuss the significance of plasticisers in mortar and explore the recommended dosage levels for optimal results.

Understanding Plasticisers in Mortar

Plasticisers are a type of water-reducing admixture that increases the workability of cementitious materials. They achieve this by reducing the water content required to achieve the desired consistency, without compromising the strength or durability of the mortar. This makes plasticisers invaluable in achieving various properties, such as improved slump, better pumping characteristics, and enhanced finishability.

The Importance of Proper Plasticiser Usage

While plasticisers offer numerous advantages in mortar production, their misuse or overuse can lead to detrimental effects on the final product. It is crucial to understand and follow the recommended guidelines for plasticiser usage to prevent any negative impacts. Overdosing plasticisers can result in excessive air entrainment, decreased compressive strength, and prolonged setting times. On the other hand, underdosing can lead to inadequate workability, making mortar difficult to handle and apply.

Types of Plasticisers

There are several types of plasticisers available for mortar formulation, each with its own unique properties. Here are three common categories:

1. Lignosulfonates: Derived from wood pulp, lignosulfonate-based plasticisers are cost-effective and widely used in the construction industry. They excel in enhancing workability and reducing water demand in mortar mixtures.

2. Polycarboxylates: These plasticisers have gained popularity due to their high water-reducing efficiency. Polycarboxylates provide excellent workability and ensure superior strength development in mortar compositions.

3. Melamine-based Superplasticisers: Melamine-based plasticisers are known for their superior water reduction capabilities. They enable the production of high-strength, high-flow mortars suitable for complex construction applications.

Recommended Dosage Levels for Mortar Plasticisers

Achieving the desired workability and performance requires adding the right amount of plasticiser to mortar mixtures. Determining the optimal dosage depends on various factors, including cement type, aggregate grading, water-to-cement ratio, and ambient conditions. Below are some general guidelines for dosing plasticisers:

1. Lignosulfonates: Typically, lignosulfonate-based plasticisers are used at dosage levels of 0.2% to 2.0% by weight of cementitious material. However, it is crucial to refer to the manufacturer's recommendations and conduct site-specific trials to ensure the best results.

2. Polycarboxylates: The dosage range for polycarboxylate-based plasticisers can vary between 0.1% and 1.0% by weight of cementitious material. It is essential to adjust the dosage according to specific project requirements and conduct slump flow or flow table tests to monitor workability.

3. Melamine-based Superplasticisers: Melamine-based plasticisers are dosed at lower levels compared to other plasticisers, typically ranging from 0.1% to 0.6% by weight of cementitious material. However, it is essential to consider the desired flow and strength development when determining the ideal dosage.

Testing and Adjustment for Optimal Results

To achieve the ideal plasticiser dosage for mortar, it is essential to conduct trials and perform tests. The trials should account for material variations, site conditions, and project-specific requirements. The following steps can help in finding the correct dosage:

1. Start with a baseline mixture using the recommended plasticiser dosage.

2. Evaluate the workability, consistency, and flow properties of the mortar.

3. Adjust the dosage gradually, increasing or decreasing in small increments.

4. Perform slump flow or flow table tests after each adjustment.

5. Monitor the compressive strength development and the impact on curing times.

6. Repeat the process until the desired properties are achieved.

Conclusion

Proper plasticiser usage is integral to obtaining the desired workability and performance in mortar. Choosing the appropriate type of plasticiser and following the recommended dosage levels helps in achieving optimal results. By understanding the significance of plasticisers and conducting appropriate tests and adjustments, construction professionals can ensure the successful implementation of mortar in various projects, leading to improved efficiency, quality, and durability.