What to do when using non-shrink mortar but still cracks?

Non-shrink mortar is considered an ideal solution for construction projects that require high stability and minimize shrinkage. However, many people still encounter cracking even though they have used this type of mortar, affecting the aesthetics and quality of the project. So what is the cause, how to fix and prevent it? Let's find out the details with LEMAN in the article below to ensure that your project is always durable and beautiful over time.

Why does non-shrink mortar still crack?

1. Why does non-shrink mortar still crack?

Although non-shrink grout is designed to minimize shrinkage, cracks still occur in some cases. Here are some common causes of this:

• Failure to follow the mixing ratio: Failure to mix the grout with the correct ratio of water and materials according to the manufacturer's instructions is the leading cause of cracking. If there is too much water, the grout can shrink sharply when dry. Conversely, if there is too little water, the mixture will not achieve the necessary plasticity and adhesion, reducing its load-bearing capacity.
• Unsuitable environmental conditions: When working in high temperature or strong wind conditions, the water in the grout evaporates too quickly, causing sudden shrinkage and cracks. An overly dry working environment reduces the curing ability of the grout, making the surface susceptible to cracking.
• Improper maintenance: After construction, if the mortar is not maintained such as covered or sprayed with water to keep it moist, the surface will quickly lose water, leading to cracking. Skipping this important maintenance step is a common mistake in construction projects.

Incorrect mixing ratio is the cause of non-shrink grout cracking.

• Substandard mortar quality: Using poor quality or unknown origin non-shrink mortar will directly affect the durability and efficiency of use. Substandard products often have uneven composition, leading to cracking.
• Uneven or excessive load: If the construction is subjected to uneven loads or exceeds the load-bearing capacity of the mortar, cracks will appear on the surface. This often happens with construction works that are not carefully calculated.
• Unsatisfactory construction surface: The construction surface is not thoroughly cleaned, still has dirt or grease, which can reduce the adhesion of the mortar, making the construction susceptible to cracking when subjected to force.
• Structural design errors: Improper structural design, lack of expansion joints or use of different materials in the same area can cause uneven stress, leading to cracking.

The structure cracked despite using non-shrink mortar.

2. How to fix cracked construction

When cracks appear in a construction despite the use of non-shrink mortar, timely remedial measures must be taken to ensure safety and prolong the life of the construction. Below are detailed solutions:

2.1. Assess the severity of the crack

• Small cracks (less than 2mm): Usually just a surface problem, not affecting the structure. Can be handled by filling.

• Large cracks (over 2mm): May be related to the structure of the building. Need to check carefully to determine the cause and find a suitable solution.

2.2. Fix small cracks

• Clean the crack: Use a wire brush or vacuum cleaner to clean the dirt and debris inside the crack.

• Use epoxy glue or specialized mortar: Mix and pump epoxy glue into the crack to increase durability. For mortar, it is necessary to choose a non-shrink mortar that meets the technical requirements of the project.

• Smooth the surface: After filling the crack, use a putty knife to smooth it and wait for it to dry completely before repainting.

2.3. Handling large cracks

• Structural inspection: Hire an engineer or inspector to determine the cause. If the crack is due to a structural defect, recalculate the load-bearing capacity and have a reinforcement plan.

• Reinforce with steel bars or reinforced materials: In case the crack weakens the structure, steel bars or reinforced materials can be added.

• Replace damaged mortar: If the cracked area is too severe, the old mortar layer must be chiseled out and re-constructed with high-quality non-shrink mortar.

2.4. Adjust construction conditions

• Moisture control: Spray water or cover the surface with anti-evaporation material to maintain the necessary moisture for the mortar to set.

• Limit construction in harsh conditions: Avoid construction during times of intense sunlight, strong winds or extremely low temperatures.

2.5. Enhanced maintenance after construction

• Cover the surface: Use wet sacks or plastic film to cover and keep it moist for 7–14 days after construction.

• Spray water to keep it moist periodically: If not covered, spray water to keep it moist at least twice a day, especially in the first days after completion.

2.6. Use additional materials to increase durability

• Use anti-shrinkage additives: Add additives to non-shrinkage mortar to increase crack resistance, improve adhesion and reduce shrinkage.

• Waterproofing layer: Apply a waterproofing layer to the surface after finishing to prevent water and moisture from penetrating, reducing the risk of environmental cracking.

Ways to fix cracked construction

3. Measures to prevent cracking

To avoid future cracking, you should take the following precautions:

• Follow the correct mixing ratio: Mix according to the manufacturer's instructions to ensure the mixture meets the standards.
• Control environmental conditions: Work in an environment with stable temperature and humidity, avoid working in extremely hot or windy conditions.
• Perform thorough maintenance: Maintain moisture on the mortar surface during the hardening process.
• Use additives: Add anti-shrinkage additives to increase the anti-cracking ability of the project.

Follow the correct mortar mixing ratio to prevent cracking.

4. Factors affecting the durability of non-shrink mortar

To ensure the project achieves optimal durability when using non-shrink mortar, the following factors should be noted:

• Material quality: Use non-shrink mortar from reputable brands with clear quality certifications such as high-quality mortar products from the LEMAN brand.
• Construction techniques: The construction process directly determines the stability and durability of the project.
• Maintenance: This is an indispensable step to ensure that the mortar achieves long-term bearing capacity and durability.
• Construction conditions: Weather, temperature, and humidity factors during construction can greatly affect the quality of the mortar.

High strength non-shrink mortar products of LEMAN brand

Using non-shrink mortar is the ideal solution to ensure that the construction does not shrink or crack. However, to maintain long-term effectiveness, you need to understand the causes and apply the correct construction techniques. To choose high-quality non-shrink mortar products and limit cracking, please contact LEMAN for free and quick advice.