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Linyi City, Shandong Province, China – November 9, 2026

Concrete blocks can develop cracks shortly after demolding or within a few hours of being manufactured. For a block production company, this problem can lead to material losses, slow down production, and affect the quality of finished products.

But why do concrete slabs crack? The problem isn’t always due to the concrete mixer. The quality of the raw materials, the amount of water, the compaction, demolding, and curing conditions can also play a role.

Before modifying your production process, it’s important to identify when the cracks begin to appear.

1. Identifying the moment when cracks begin to appear

The appearance and timing of cracks can help in identifying their cause.

• Cracks appearing shortly after demolding: check the consistency of the concrete, compaction, demolding process, and machine settings.
• Initial checks: assess moisture content, stability of newly manufactured blocks, and drying conditions.
• Cracks that appear during the curing process or after storage: check the curing conditions, handling of the blocks, and how they are stacked.

These observations provide clues, but they are not always sufficient to determine the exact cause. Several factors can be present simultaneously.

2. Verify the cement, sand, and aggregate dosages.

An imbalanced mixture can reduce the strength of the blocks and increase the risk of cracking.

If the amount of cement is insufficient compared to the other components, the blocks may lack strength. Conversely, simply adding more cement without adjusting the entire mix is not necessarily the best solution.

The quality and particle size distribution of sand and gravel are also important. Inconsistent raw materials or significant variations between batches can make production less consistent.

What should I do?

• Regularly measure the raw materials.
• Maintain consistent proportions across different batches.
• Check the quality and grain size of the sand and gravel.
• To better understand the effect of each change, avoid modifying multiple settings at the same time.

The appropriate dosage depends on the available raw materials, the type of concrete, and the desired performance characteristics. It should be determined through testing, rather than being chosen arbitrarily.

3. Controlling the amount of water in the mixture

The amount of water is a crucial factor in concrete block production. A mix that is too dry can be difficult to compact properly. Conversely, a mix that is too wet can result in blocks that are unstable after demolding, depending on the formulation and the machine used.

It is also important to consider the moisture content of the sand: if this changes, the amount of water already present in the mixture also changes.

What should I do?

• Regularly monitor the moisture levels of raw materials.
• Measure the amount of water added, rather than simply pouring it by eye.
• Observe whether the mixture remains homogeneous.
• Ensure that the molded parts retain their shape after demolding.

The goal is not simply to add more or less water, but to obtain a mixture that is suitable for the manufacturing process being used.

4. Check the compaction and settings of the concrete mixer.

Even with high-quality raw materials, uneven compaction can affect the density and cohesion of the blocks.

If cracks primarily appear at the machine’s exit, it’s important to check the equipment’s operation, specifically vibration, compaction, mold filling, and demolding.

Some key points to check:

• Is the mold clean and properly installed?
• Is the mold filling evenly?
• Do the vibrations and compaction match the recommended settings?
• Are the molds released without causing any damage or deformation?
• Does the mold show any visible wear and tear or mechanical issues?

Do not change the settings randomly. Consult the machine’s manual or contact the manufacturer if cracks persist after basic checks.

5. Don’t neglect the care of the fenders.

After being manufactured, concrete blocks require specific curing conditions to develop their strength. Allowing them to dry too quickly, especially in direct sunlight or a hot, windy environment, can increase the risk of cracking.

The solution doesn’t simply involve leaving the blocks exposed to the elements. It must prevent excessive moisture loss while also taking into account the type of concrete and local conditions.

Best practices:

• Place the chilled blocks on a stable, suitable surface.
• Protect them from direct sunlight and excessive wind during the initial period, based on the specific site conditions.
• Maintain appropriate curing conditions for the specific formulation being used.
• Avoid forceful handling and premature stacking.
• Please adhere to the recommended treatment duration before transport or use.

The specific conditions depend on the formulation, climate, and product requirements. If there is any doubt, please request a curing procedure tailored to your production process.

6. What should I do if the window sills continue to crack?

If the problem persists, avoid immediately changing all production settings. Instead, proceed in stages:

1. Note when the cracks begin to appear.
2. Examine several blocks and compare their appearance.
3. Check the proportions of raw materials and the amount of water.
4. Control the compaction, molding, and demolding processes.
5. Examine the conditions for storage and handling.
6. Perform controlled tests before implementing a new setting.

If the cracks are significant or the blocks are intended for load-bearing applications, do not assume they are still usable. Have them inspected to ensure they meet the applicable requirements before putting them into service.

7. Consistent production starts with a well-controlled process.

To produce consistently high-quality concrete, it’s not enough to simply have a good machine. Regular and reliable raw materials, careful mixing, appropriate settings, and an appropriate curing method are also essential.

A well-calibrated concrete block production machine can contribute to more consistent production, but it cannot compensate for an unsuitable mix or poor curing process on its own.

Shunya Machinery offers equipment for concrete block manufacturing and customized production solutions to suit various needs. When selecting a brick machine, mold, or production configuration, it is helpful to specify the types of blocks desired, the desired production capacity, and the conditions of your site.

Contact our team to discuss your project and the equipment that best suits your needs.

FAQ: Cracks in concrete blocks after manufacturingWhy do bread molds crack immediately after being removed from the mold?

Possible causes include an unsuitable mix, uneven compaction, incorrect machine settings, or demolding that warps the blocks. It is important to examine the process before selecting a corrective measure.

Can an excess of water cause cracks?

An inappropriate amount of water can affect the stability and performance of the blocks. However, cracks are not always caused by an excess of water; the formulation, compaction, and curing process should also be considered.

How can we prevent cracking during the curing process?

It is important to avoid excessive drying, protect fresh blocks from unfavorable weather conditions, and follow a curing procedure that is appropriate for the mix and the production environment.

Does an automatic concrete mixer prevent cracking?

Not necessarily. An automated machine can improve the consistency of the process when properly adjusted, but the final quality also depends on the raw materials, the mix, the compaction, and the curing process.

When can concrete be transported or used?

The timeframe depends on the mix, curing conditions, and the required strength of the product. Do not rely solely on the appearance of the blocks; always follow the recommended technical guidelines and applicable requirements before transport or use.

About us

Shandong Shunya Machinery Co., Ltd. specializes in the design, manufacture, and supply of block making machines, concrete mixers, concrete pole molds, concrete pipe molds, and other concrete production equipment.

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Company Name: Shandong Shunya Machinery Co., Ltd.
Contact Person: Media Relations
Email: Send Email
Country: China
Website: https://www.shunyamachine.com/