Why Does Concrete Crack? Causes & Solutions on Concrete Cracking

Concrete is a must-have material at all construction sites. It is famous for its long life and tough nature. All contractors accept its winning features. But they do not know how to prevent and repair if this strong material cracks. It often affects their reputation among customers because concrete cracking causes quality issues. 

Are you a professional contractor worried about concrete cracking? This guide is for all contractors, including you. Here, you will learn about common causes of cracking, major types, prevention strategies, and repairing techniques. You will also get to know how the right tools and accurate scientific systems can help you ace the concrete project. 

Root Causes: Why Concrete Cracking Occurs

As a professional contractor, you understand that the solution starts with the correct identification of the problem. Every crack is different, with specific causative forces involved behind. For different types, you will need to take particular repairing actions in the concrete mix and curing compounds. 

The most common cause behind cracking involves too much drying and resulting shrinkage cracks. When the tensile strength of concrete decreases compared to the external forces or internal tensile stress forces, it leads to the occurrence of cracks. Any crack wider than a standard credit card, or one that runs through the entire slab, requires repair or replacement of the compromised concrete section.

Let’s discuss some of the major causes leading to cracks in concrete slabs.

Plastic Shrinkage

One of the quick-occurring types is plastic shrinkage. These cracks occur, but the concrete slab retains its plastic (wet form of poured concrete) form and does not harden. The reason behind it is the rapid drying of the surface due to supporting environmental conditions. These include the warm climate, increased winds, and low moisture. 

The quick drying will cause excess water to evaporate from the surface. As a result, it will start shrinking and constricting. This process starts before the concrete roots develop enough tensile strength to dominate the internal stress and outside forces.

Prevention Technique: Reduce the amount of water being lost from the root surfaces for several hours after pouring concrete mix into its accurate place.

Drying Shrinkage

Different from the plastic shrinkage, it is severe. These cracks occur due to the decrease in moisture after concrete curing. In this process, the roots will lose extra water within days, weeks, or months. 

The reason involved behind this is the addition of extra water in the mix before pouring, increasing the water-cement ratio. When there is excessive water in the concrete mixture, its roots will constrict as that water evaporates from the concrete. They usually appear on surfaces, like tiny hair. They can accumulate debris and worsen the situation through further water entry. 

Prevention Method: When mixing water in concrete before pouring, always go for the minimum amount to control the water-cement ratio.

Load Stress and Settlement cracks happen

There are two more types of cracks: structural and settlement cracks. Both occur when the forces applied from outward are greater than the resisting capability of the concrete. The causes may include heavy motor vehicles, big industrial equipment, oil and water tanks, and increased wear in the internal system. 

Another reason include the inappropriate positioning and placement of the base. If you do not clean and level the soil beneath properly, it will destabilize the slab. This leads to the formation of structural cracks wider than will affect the toughness of the slab. The stability of concrete structures is directly dependent on the integrity of the ground beneath.

Protection Technique: Make sure that you compact the base beneath the concrete slab. You must follow the advanced features to align with a particular slab design.

Thermal Stress

Another type of cracking is thermal cracking. In this type, concrete slab damages due to temperature fluctuations. Concrete is a material that responds to temperature changes by expansion and contraction. 

When you pour the new concrete and allow it to settle, quick thermal changes occur. For instance, you poured during the day when it was hot and that very night, temperature decreased due to rain or cool breeze. These changes will create increased internal stress greater than the concrete’s tensile strength. When it gains its tough texture, if you restrict movements, you will still face the occurrence of  cracks.

Protection Method: Apply accurate controlled joint system to predetermine the cracking areas to manage them easily in near future.

Identifying Severity: Crazing vs. Structural Cracks

When you pour concrete accurately into the right place and let it settle, now is the time to determine the type of cracks. They are either minor surface cracks or major cracks. Each type requires its own solution. So, understanding these types in detail will allow you to take necessary steps quickly. 

Concrete Crazing

Most contractors get confused about the term crazing in concrete. Concrete crazing refers to tiny, hairline cracks that are less than 1/8 in. in width. They look like a spider web and appear usually on surfaces. The reasons include the inappropriate curing or surface finish methods. The increased water-cement ratio will lead to excessive drying and then constriction of concrete roots. This constriction leads to surface cracks or crazing. 

Crazing vs. Structural Cracks

Here, a question arises: Is crazing that bad in concrete as the structural cracks? 

• Crazing: Overall, crazing doesn’t have severe worse effects. Usually, the reason involves the inappropriate surface finish, regarding the appearance and aesthetic of the concrete. They accumulate dirt and appear bad. It does not affect the strength of the concrete or reduce its resistance against stress forces. They do not spread the cracks in the surroundings as they do not allow the water entry into the roots.
• Structural Cracks: Yes, the structural cracks are bad and have many worse effects on the integrity of the concrete slab. They are large in size with increased depth. They can spread and penetrate onto the whole slab surface. The reasons include the inappropriate positioning of the base, inaccurate reinforcement of steel rebar or wire mesh, and increased stress forces after the concrete shrinks. 

Identifying and Choosing Specific Corrective Action

Being an expert, you must identify different classes of cracks and their particular solutions required on time. 

Type of Crack	Major Reasons	Depth	Solution Required
Crazing	Make up the repair by grinding, polishing, refining, or overlaying.	Concrete surface only (tiny, hairlike).	Make up the repair by grinding, polishing, refining, overlaying.
Structural	Increased water-cement ratio, quick drying, excessive shrinkage, and inaccurate surface finish.	Deep penetration or spread onto the entire slab.	Demands technical evaluation; apply epoxy injection or use repaired mortar; replace the slab if damage is severe.

If you put a dime into the concrete crack, and it fits, identify it as a structural crack. They are wider than normal. So, you will need to consider replacing them with a new one. To achieve its intended structural integrity, the newly poured concrete must be kept wet (cured) for a sufficient period, typically around 21 days, to allow the water-activated cement to bond effectively with the aggregate.

Concrete Cracking Prevention Strategies 

Being a concrete contractor, you must prevent the damage on concrete. It should be your first preference. Though you can not interrupt the natural processes happening, you can avoid cracks. For this prevention approach, you have to follow some strict measures regarding concrete mix and its accurate placement. 

Monitor the Water-Cement Ratio

The easiest, yet practical way to avoid cracking involves the careful monitoring of the amount of water in the concrete sinks mix. If you add excessive water, it will cause the roots to lose their strength and cause excessive drying and constriction. When you pour concrete mix in its accurate placement, make sure you add the minimum amount of water. In short, the correct amount of water will prevent the damage of root cracks. 

Follow Proper Curing Protocols

The curing step is important when you pour the concrete mix in its place. Curing involves monitoring of moisture and temperature in the concrete mix. If both are accurate, they will ensure concrete gets its tough texture and develop its strong features.

• Moist Curing: If you want to avoid excessive drying of roots, apply curing with moist methods. Use wet burlap or plastic sheeting to cover the slab.
• Curing Compounds: Use curing compounds available in liquid solutions. They will restrict the movement of moisture, locking it in the internal side. You will be required to adopt this method especially if you are working in windy or warm or cold weather.

Myth-Buster with Fact-Checking: The moist curing does not prevent the occurrence of cracks completely. If you use them in excess by just spraying over the concrete, they will increase the water-cement ratio. This increased ratio will lead to crazing. So, you need to monitor the moisture for over several days for accurate curing.

Implement Proper Joint Placement

You must place concrete properly, regardless of small surfaces or wide surfaces like garages. You have to know the reasoning involved behind the term “control joints.” You predetermine these places as weak spots with increased chances of developing cracks in the near future. 

You must be careful of the timing and design of the joints. If you want to cut accurately, use diamond saw blades right after the mix settles. Regarding design, you need to identify the size, depth and location. For all these measures, use Johnson Tools’ accurate systems and tools to protect the concrete slab and make a perfect cut through the slab.

Reinforce the Concrete

When you add rebar or wire mesh inside the base of the concrete, it adds to their toughness and strength. 

• Rebar and Wire Mesh: The addition of these materials will increase the resistance against stress occurring after it dries and constricts.
• Fibers: You can add fibers (artificial or steel) into a concrete mix before pouring. It will help you reduce the chances of early cracking during the initial curing stage.

Avoid Excessive Troweling During Surface Finish

When you give a final touch to the concrete surface, carefully conduct this step. If you do too much trowelling or do not follow the proper timeline, it will lead to severe damage. In either case, it will send water and debris to the top layer, causing crazing and hair-like tiny cracks.

Repairing and Preventing Concrete Cracks

Even when you use high-quality concrete mix, pour it carefully, and let it settle with optimal addition of moisture, cracks may still appear. In this situation, you should not panic. Not all cracks warrants an urgent repair. need to be fixed immediately. As a good contractor, you must know several ways to repair the cracks for the long-term. The solution must be according to the situation. 

How to Fix Cracked Concrete

Minor Cracks and Crazing

If you face tiny, hair-like cracks or crazing (surface cracks), you should go for protective solutions to prevent further occurrence and make up the tiny cracks. 

• Minor Cracks: If you measure cracks and they appear to be less than 1/8 in. in width, identify them as unstructural. You can repair them by using compounds like acrylic seams or polyurethane. It will stop the entry of water content into further roots and prevent further damage.
• Surface Crazing: If you face cracks on concrete surfaces, identify them as crazing. You just need to repair the surface. You can use polishing, refining, grinding, or just tap the surface with a thin film of cement or epoxy. It will make up or hide those surface cracks. 

Large Structural Cracks

If you are facing the major cracks (higher than 1/8 in. in width) in the concrete structure, the repair should be to strengthen the concrete slab. For this type of repair, you can follow these steps.

1. Preparation: Clean the cracks to remove debris and germs. If possible, stretch the crack a bit to increase the surface area for the application of curing material.
2. Apply Mortar or Epoxy: Use tough epoxy through injection or apply mortars. Among the two, epoxy is more effective as it re-joins the cracks. As a result, it allows concrete slabs to regain their strength. 
3. Joint Placement: If the crack was random rather than pre-determined, try to seal the cracks at one joint. It will prevent the future damage of these roots.

How to Prevent Concrete Cracks: Control Joints

The best way you can deal with concrete cracks is to prevent their occurrence. This strategy calls for accurate joining of concrete roots.

• JohnsonTools Integration: If you make appropriate, early cuts in new placed concrete, it will lead to cracks in the lines predetermined by you. It will be easy to manage.
• Use Johnson Tools’ diamond-incorporated blades: You will cut the concrete at the exact depth and location. It will minimize cracking the occurrence of the entire surface and internal damage. You will need to perform this preventive step in almost all concrete tasks to ensure the long life of the concrete slabs.

Best Concrete Practices for Contractors

If you want to deliver a remarkable concrete project to your client, you must follow discipline from the first step till the last step, on the site. As a contractor, you should know it is not a single-step procedure. Rather, it is a multi-step procedure with each step having specific requirements. Let’s discuss some of the best practical suggestions you can follow as a contractor. 

Evaluation and Controlling the Environmental Conditions

You might ignore the environmental conditions during the process. They can make and break a project by applying stress inside the material and calling for early settling. It will lead to cracks. 

• Pre-Pour Testing: When you are going to put concrete in its place, check the environmental conditions. These include wind velocity, moisture, and temperature. If you notice dryness, warmth, and increased wind speed, be careful. These are the prerequisite conditions for constriction and early damage. 
• Mitigation: If you have a windy environment with sunlight falling directly on the site, use protectors. You can use wind breaks and moisten the concrete frequently after pouring in its place. It will prevent the chances of early strains. Moreover, you should start preparing the curing material to apply when your concrete mix settles down.

Proper Concrete Joint Placement

If you have not put concrete properly in its place, it is a sign of early damage.

• Design-Specific Placements: You must identify the design of concrete first, including the size, depth, and location. You can use the rule of thumb to determine the depth of the concrete. The rule follows that the thumb should be one-fourth of the slab in thickness. It will allow you to handle cracking at one specific place, pre-determined by you, rather than occurring randomly on the entire slab.
• Follow Regulatory Standards: Understanding and following guidelines related to concrete is mandatory. These include the joint spacing accurate ratios, i.e., 20/30/40 rule. They will determine the strength of the concrete mix against damage. It is a preventive step that you will take to increase its durability.

Staff Training and Elimination of Workmanship Errors

A successful project owes to the hard work of the team. If you have not communicated properly with the team, there are chance that they will make errors. These errors lead to the domination of weak points.

• Consistency and Commitment: Deliver clear instructions to the team to avoid adding too much water to the concrete mix when they settle down. The team should stay committed to the project goals. 
• Compaction: The base under the concrete slab should be proper. If it is reinforced with rebar or steel alloys, workers should place them correctly to increase the strength.

Technical Impacts on Tools such as Diamond Cutting Blades

In older times, there were less accurate blades used in the working of concrete slabs. Today, the requirements for the tools have changed. There is a greater focus on how to strengthen the authenticity of concrete and prevent cracks by using appropriate tools. Diamond-embedded blades must fulfil the modern demands and put joints of concrete in exact places. 

Standard Tools’ Requirements	Modern-day Impact on Tool Technology
Higher Accuracy: Accurate in results, with controlled actions in depth, penetration, velocity, and sizing.	Call for advanced technology in diamond-embedded blades; cut through concrete slabs in one go.
Time-Necessary Cutting: Able to be cut through materials after they have settled primarily, if conditions call for early cutting.	Require protection against early wear, heat buildup, and resistance to bear the strength of the new concrete mix, especially in rebar concrete.
Longevity and Protection: Shorter time-frame with composition of authentic concrete mix; features of resistance and protection.	Longevity and Protection: Shorter time frame with composition of authentic concrete mix; features of resistance and protection.

Johnson Tools’ Response and Services 

If you want to become a successful contractor, you must think ahead of time and adapt your services to clients’ changing demands. For these, you need the right partner who can help you adapt to the modern requirements. At Johnson Tools, we understand what clients require with modern technological advancements. We manufacture such equipment and tools that can prevent cracking.

• Innovation: Our team has made a variety of diamond saw blades. They meet the global regulations regarding accuracy, longevity, and speed.
• Reliable Performance: Our clients’ feedback proves that our tools always give accurate results, regardless of easy or challenging conditions. Clients have applied them in various concrete tasks, such as roads, floors, buildings, and bridges.
• Regulations: Each product fulfils the international regulatory standards, such as CE/EN13236. These regulations give you the liberty to use these products at any site. 

At Johnson Tools, we provide modern services to prevent or reduce the early damage of concrete slabs. Using our tools and systems, you can save a large amount of money that you are going to otherwise spend. 

Final Note 

Concrete cracking is one of the major problems for contractors. But you can easily control it. Though you can not interrupt the processes of their constriction and settling, you can reduce the timeline and severity of the consequences. If you want to ace the concrete project, you must be careful in four steps. These include identification and complete knowledge of cracking types, taking preventive protocols, adopting long-term construction practices, and reducing the early damage possibilities of the roots.  

Visit us at Johnson Tools on our website today and gain deep knowledge about our diamond blades to prevent the occurrence of concrete root cracks. Contact us today!