Air

• All concrete has to be mixed, either by hand or with a machine. The cement, sand and water mixture will include air due to the natural mixing process, but too much air can lead to cosmetic issues down the road with finish concrete surfaces. While air is necessary for the curing of concrete, too much leads to bubbles that slowly rise to the top and pop over time during curing.
  
  

Water

• The ratio of cement to water and sand is important to ensure the proper consistency and the bond between the sand and cement particles. Too much water results in particles that do not bond well; these leave behind voids that eventually rise to the surface and pop after the concrete mixture has been poured.
  
  

Mixing Method

• Slow mixing results in the best type of concrete and will reduce pinholes. If the mixture is turned together slowly, it gives it time to blend properly with the weight of the materials naturally pushing any pinholes out toward the top of the mixing container. Mixing mud rapidly introduces more air into the mixture.
  
  

Signs of Troubles

• Normal pinholes are of no concern because they are nothing more than cosmetic. Crumbling, on the other hand, can be a sign of problems to come. If your pinholes are accompanied by crumbling cement and sand, you need to check the surrounding slab to see if it is a topical, cosmetic issue or if the water mixture was off and the entire slab is regressing to powder form.