Concrete is full with water when it is still in its plastic condition (before hardening). When the water gradually evaporates from the slab, it creates enormous holes between the solid particles. Because concrete cannot shrink around a corner, tension will cause the concrete to crack at that point. The more intense the heat during drying, the faster the hole will appear and the sooner the slab will crack.
The best way to avoid this problem is to allow the concrete to dry slowly in the air. Don't use a dehumidifier because it will pull moisture out of the concrete, causing other problems such as mold growth. Also, don't pour concrete into an already-dry area or one where there is already standing water because that water will be trapped inside the slab and cause cracking too. Finally, keep children and pets away from freshly poured concrete because they will be tempted to play in it!
If you must pour concrete while it's still wet, then add 1/4 inch of sand to the mix to prevent cracking. The sand will also make the slab easier to clean off tools and vehicles before it fully cures.
For outside surfaces, like patio decks, allow the concrete to cure for at least 24 hours before washing it with a hose. If it gets wet, let it dry completely before rewetting areas of standing water. Cracked concrete can be repaired by using a concrete resurfacing material called spackling putty.
These voids weaken the concrete and make it more prone to breaking. Cracks can be caused by many factors such as freezing/thawing cycles, excessive heat, mechanical stress, etc.
The most effective way to repair concrete cracks is to fill them with a colored resin. The crack will not show once it has been filled. You can find information about how to select a resin and how to apply it here: How do I choose a concrete repair material?
If you want to avoid using resins, there are other options available for repairing concrete cracks. The best option depends on how much damage there is to the concrete and what type of surface it has. For example, if the crack goes all the way through then it should be filled before it gets any deeper. Otherwise, you might end up having to replace the entire piece of concrete.
Concrete cracking can be caused by a variety of circumstances. Concrete fractures can be caused by a variety of events, including: Drying Shrinkage: As concrete cures and the chemical interaction between the water and cement particles takes place, it begins to "dry." This process leads to internal stresses that can cause cracks when the concrete dries enough for these stresses to be released.
Dry Rot: When bacteria from outside the concrete structure get into the surface of the concrete and start to eat it from the inside out, this activity can result in small holes or "hols" forming in the concrete. These holes can allow moisture to reach the inner portion of the concrete, causing more rapid drying and subsequent shrinkage. This is called "dry rott".
Hydrostatic Pressure: As water evaporates, less pressure is exerted on the concrete slab. If it is not replaced, the reduced pressure will cause cracks to form in the concrete.
Nuclear Radiation: Nuclear radiation can cause an array of harmful effects to living organisms. It can also have an impact on the performance and durability of building materials. Irradiated concrete may appear normal during construction, but after it has set up it may fail prematurely due to radiation damage to the steel reinforcement within it.
Preventing Cracks: There are several ways to prevent cracks from forming in the first place.
When shrinkage forces exceed the strength of the concrete, cracking develops. This is also true for non-deformable concrete pieces. Deformation cannot occur during shrinking. When the tension exceeds the strength of the concrete, these conditions cause internal stress, which leads to cracking. The overall effect is similar to the effect of external loads on deformable concrete.
The two main causes of failure are deep cracks and open joints. Deep cracks go all the way through the concrete while open joints are gaps between the concrete blocks or pavers. Both types of damage can be seen as defects in the concrete surface. They must be repaired before the concrete can be restored. Repairing deep cracks requires special tools and expertise. An expert contractor should be hired for this job because it is difficult work that can cause serious injuries if done incorrectly.
Open joints are much easier to repair. Any type of mortar can be used to fill open joints in concrete. The choice of material depends on how long you expect to keep the concrete surface intact. If you plan to protect the concrete for only a few years, then simple colored mortar will do. For longer service periods, more expensive materials such as epoxy resin or stone dust should be used instead.
In conclusion, reinforced concrete cracks because of internal stresses caused by contraction and deformation. Open joints and deep cracks can both be repaired easily without using tools.
Cracking is a natural propensity of concrete. Concrete is a liquid when it is initially poured. It solidifies into a solid over a few of days, shrinking as it does so. Within the first few days after installation, this initial shrinkage frequently results in hairline cracking. As the concrete continues to cure, it will continue to harden and shrink, causing further cracking.
Concrete cracks can be caused by many things such as poor mixing, water content, temperature changes, etc. Sometimes they are an indication that there is something wrong with your concrete floor; for example, if there is moisture beneath the flooring material, then you should investigate this matter before it gets worse. Other times they are not important at all; for example, when used as a parking lot surface, cracking can be expected and even desirable. But most often they are due to damage done during construction.
When placing concrete down, it is important to allow for any settling prior to pouring more concrete. This is true whether you are building up a slab or repairing damaged concrete. If you don't, you may have to bring in fill dirt or other materials to reach your desired finished height. The same thing goes for windows and doors which require blocking off part of the area for preparation before pouring the concrete into that space.
Finally, make sure that you clean up all debris from around the site prior to pouring the concrete.