Exploring the potential of natural resin-based air entrainment in dry-mix repair mortars
Repair mortar manufacturers face a constant challenge: achieving the right balance between workability, adhesion, mechanical strength, dimensional stability, and durability.
Selecting the right combination of additives is essential to achieving the desired performance. As the construction chemicals industry continues to explore more sustainable raw materials and innovative formulation approaches, natural resin-based technologies offer new possibilities for mortar development.
At Polytrade Brasil, we are exploring the potential of CARBOFEN NCX, our powdered, natural resin-based air-entraining additive, for dry-mix repair mortar applications.
But how can controlled air entrainment contribute to repair mortar formulations, and what should manufacturers consider when evaluating this type of additive?
- Understanding Air Entrainment in Repair Mortars
Air-entraining additives introduce and stabilize small air bubbles within cement-based formulations. When properly controlled, this air-void system can influence several fresh and hardened mortar properties.
In repair mortar formulations, the objective is not simply to increase air content. Instead, formulators must identify an appropriate balance between air incorporation and the performance requirements of the finished product.
Depending on the formulation, air entrainment may influence:
- Workability: the presence of uniformly distributed air bubbles can contribute to improved handling and application characteristics.
- Fresh density: entrained air can reduce the density of the fresh mortar.
- Consistency: air content may influence the rheological behavior and application feel of the mixture.
- Hardened performance: excessive air incorporation can reduce compressive strength and may affect other mechanical properties.
For repair mortars, these factors must be evaluated together. A formulation that offers improved workability but compromises adhesion or mechanical strength may not meet the application’s requirements.
- Introducing CARBOFEN NCX
CARBOFEN NCX is a powdered air-entraining additive based on modified natural pine resins.
Produced through a neutralization process followed by spray drying, CARBOFEN NCX is a water-soluble powder designed for use in cement-based formulations.
Its main characteristics include:
- Natural resin-based technology.
- Powder form, suitable for dry-mix applications.
- Water-soluble composition.
- No organic solvents.
- Compatibility evaluation in different cement-based formulations.
The powder format allows CARBOFEN NCX to be incorporated directly into dry-mix formulations, offering flexibility for manufacturers developing premixed mortars.
Its potential use in repair mortars should be evaluated according to the specific formulation, raw materials, application requirements, and target performance.
- Why Evaluate CARBOFEN NCX in Dry-Mix Repair Mortars?
The performance of a repair mortar depends on the interaction between cement, aggregates, polymers, cellulose ethers, and other functional additives.
Introducing an air-entraining additive such as CARBOFEN NCX may provide formulators with another tool to adjust fresh mortar properties.
However, repair mortars have specific performance requirements. Depending on the intended application, manufacturers may need to control:
- Fresh and hardened density.
- Workability and application consistency.
- Water retention.
- Adhesion to concrete substrates.
- Compressive and flexural strength.
- Shrinkage and dimensional stability.
- Water absorption and durability.
For this reason, CARBOFEN NCX should be evaluated as part of the complete formulation rather than as an isolated ingredient.
The objective is to identify whether controlled air entrainment can contribute to the desired application properties without compromising the technical requirements of the finished repair mortar.
- Preliminary Dosage Levels for Laboratory Evaluation
Dosage selection is one of the most important stages when introducing an air-entraining additive into a new formulation.
For initial laboratory screening in dry-mix repair mortars, the following dosage levels can be considered as exploratory starting points:
| CARBOFEN NCX dosage | Quantity per 1 kg of cement |
| 0.000% | Control formulation |
| 0.005% | 0.05 g |
| 0.010% | 0.10 g |
| 0.020% | 0.20 g |
Dosage expressed as a percentage by weight of cement.
These levels are intended to support preliminary laboratory trials. They are not validated commercial dosage recommendations for repair mortar applications.
The appropriate dosage will depend on the cement type, aggregate characteristics, other additives, water content, mixing procedure, and target performance of the final formulation.
Reference Data from Previous Mortar Evaluations
Previous Polytrade mortar evaluations have demonstrated that CARBOFEN NCX can influence air content at relatively low dosage levels.
The following results illustrate the relationship between dosage and air content in a specific mortar formulation:
| NCX dosage (% by cement mass) | Measured air content |
| 0.00% | 1.3% |
| 0.01% | 7.4% |
| 0.02% | 11.7% |
| 0.04% | 15.9% |
| 0.08% | 22.9% |
| 0.12% | 25.2% |
These results are provided as technical reference data from a previous mortar study. They should not be interpreted as predicted performance or validated dosage levels for repair mortar formulations.
Each repair mortar system requires its own laboratory evaluation.
- Recommended Mixing Procedure for Dry-Mix Formulations
For initial laboratory trials, CARBOFEN NCX can be incorporated directly into the dry components of the repair mortar.
To improve dosage accuracy and distribution, particularly at low addition levels, the following procedure is recommended:
Step 1. Accurate weighing
Weigh CARBOFEN NCX according to the selected dosage. Use a precision balance to ensure accurate measurement.
Step 2. Pre-blending
For low dosage levels, pre-blend CARBOFEN NCX with a measured portion of fine filler or dry sand before adding it to the complete formulation. This helps promote more uniform distribution.
Step 3. Dry mixing
Incorporate the pre-blend into the remaining dry components and mix until a homogeneous dry mixture is obtained.
Step 4. Water addition
Add the specified mixing water gradually, following the normal preparation procedure for the repair mortar. Keep the water content and mixing conditions consistent across the trials.
Step 5. Performance evaluation
Evaluate the fresh mortar properties and compare the results against the control formulation.
For reliable comparisons, maintain consistent mixing time, equipment, temperature, water content, and testing conditions.
- Which Tests Should Be Included in the Evaluation?
A structured testing program is essential to determine whether CARBOFEN NCX is suitable for a specific repair mortar formulation.
We recommend evaluating both fresh and hardened properties.
Fresh mortar testing
- Air content.
- Fresh density.
- Flow or consistency.
- Workability and application characteristics.
- Workability retention, where relevant.
Hardened mortar testing
- Compressive strength.
- Flexural strength, where applicable.
- Adhesion or bond strength to the substrate.
- Shrinkage and dimensional stability.
- Water absorption and other relevant durability properties.
The results should be compared with the control formulation and the manufacturer’s target specifications.
For repair mortars intended for structural applications, the complete finished formulation must be evaluated against the applicable performance requirements. The additive alone does not establish compliance with a repair mortar classification or standard.
- Formulation Compatibility: Evaluating the Complete Additive System
CARBOFEN NCX should be evaluated in combination with the other components of the repair mortar.
Depending on the formulation, other additives may include:
- HPMC or HEMC: used to adjust water retention and rheological properties.
- Redispersible polymer powders (RDP): used to contribute to adhesion, cohesion, and flexibility.
- Polycarboxylate-based superplasticizers (PCE): used to adjust water demand and flow properties.
- Fibers: used to modify crack-control and mechanical behavior.
- Accelerators or retarders: used to adjust setting characteristics.
- Defoamers: may reduce air incorporation and should be considered when evaluating air-entraining additives.
The interaction between these materials can significantly influence the final performance. Therefore, compatibility and dosage optimization should be assessed through controlled laboratory trials.
- Developing New Formulation Possibilities with Polytrade Brasil
The development of high-performance repair mortars requires a careful balance between raw materials, additive selection, and application-specific performance requirements.
At Polytrade Brasil, we work with natural resin-based technologies to support the development of construction chemical formulations.
CARBOFEN NCX represents an opportunity for manufacturers to explore natural resin-based air entrainment in dry-mix repair mortars and evaluate new formulation possibilities.
Our technical approach focuses on understanding each application, establishing suitable laboratory screening conditions, and identifying the dosage that best meets the performance requirements of the finished product.
Are you developing or manufacturing dry-mix repair mortars?
Contact the Polytrade team to discuss your formulation requirements and explore the potential of CARBOFEN NCX in your applications.
Technical Note
The dosage levels proposed in this article are preliminary starting points for laboratory evaluation in repair mortar formulations. They are not validated commercial recommendations.
The appropriate dosage should be selected based on the performance of the complete formulation and internal testing conducted by Polytrade. These initial evaluations are intended to help customers assess CARBOFEN NCX and adapt its dosage to the specific requirements of their own formulations.
Final dosage selection and product suitability must be confirmed through the customer’s own laboratory testing and performance validation.