Shrinkage

• Two types of shrinkage can cause cracks in cement. If too much water is added to the cement mixture, drying shrinkage will occur, causing noticeable cracks in the cement upon dying. Usually if there is a restraint in the form of physical structure connected to the new cement, it will cause the cement to pull away from the restraint. The result will be that the cement dries too quickly and creates this type of crack. Other types of shrinkage cracks can occur with plastic shrinkage cracking. Cracking occurs when water on the surface of the cement evaporates quicker than the surface water used to smooth it out. While these cracks are not as deep as drying shrinkage cracks, they are unsightly.
  
  

Crazing

• Crazing occurs on most cement services over time. This type of cracking is not a threat to the cement and it is only a cosmetic issue. Crazing does not penetrate below into the depth of the cement. Some people enjoying the visual appeal of crazing, as it creates an antique or vintage look to the cement.
  
  

Weak Cement

• Concrete mixtures come in a wide variety of strengths. Many homeowners pour concrete themselves. Prior to pouring concrete, it is important to speak with an experienced contractor in your area to ensure the proper strength of cement is being used for your project. Additionally, don't forget to add control joints to your cement pouring project. Control joints will help your concrete to crack in the places you want it to crack. Where you place your control joints depends on the thickness of the cement you are pouring. According to Concrete Network, 4-inch cement should have joints approximately 8 to 12 inches apart.
  
  

Weather-Related Cracking

• D-cracking and thermal cracking, are both related to weather conditions. D-cracking normally happens on cement driveways or other large cement slabs. D-cracking normally starts near the joint, and is due to the freezing and thawing cycles of the weather. Thermal cracking is similar, in that it is affected by the temperature outside. Thermal cracking happens more often due to excessive heat. Warm weather expands and contrasts the concrete, allowing for excess stress on the concrete that eventually creates cracks.
  
  

Corrosion

• Corrosion cracks occur when embedded metals, like steel or iron, begin to corrode inside the cement, which creates stress on the cement and causes cracks around the embedded metals.