Concrete is one of the main building products used in the construction of a house. Depending on where the concrete is used in the construction process, it can become a very critical factor in the overall structural strength of the house. Just because the concrete comes premixed in the concrete truck does not mean that the concrete is always good. One factor to be considered when pouring concrete is the slump. The individual from the testing company will take a sample of concrete in order to determine the slump. The technician will place a plate or board on level ground. He then will place a metal cone on top of the plate and fill the cone with concrete. He would take a rod and move it up and down in the concrete in order to settle the concrete throughout the cone. After doing this, he will screed the top of the cone off with the rod. He will then grab the cone on the both sides and slowly remove the cone upwards. This will allow the concrete to slump. The rod is then placed horizontally on top of the cone and a tape is used to measure the distance from the rod to the top of the concrete. This distance is considered the slump of the concrete The lower the slump the greater the strength but the harder the concrete is to work. The higher the slump the lesser strength but the easier the concrete is to work. When a structural engineer is involved, he might specify that the concrete is to be 3000 psi with a three to five inch slump. If this is specified, it is very important to stay within these limits do not allow anyone to add water to the mix on site without permission from the individual doing the testing. If the concrete is being pumped, there are additives that can be added to the mix in order to allow a higher slump but not jeopardize the strength of the concrete. These additives can also be used in dry and windy climates to allow a wetter mix and hopefully prevent surface cracking due to the fast dehydration of the concrete. If the concrete is tested, the slump might be checked every fifty yards and the cylinders might be taken at the same interval. Concrete cylinders are taken and tested to verify the compressive strength of the cured concrete. The cylinders are compressed and broke at specified intervals. A cylinder broke after 28 days should break at the designed strength or greater.