While concrete is recognized as one of the most ideal materials used in construction, it can at times have its own serious problems. These include improper placement due to the exterior elements, along with cracking and heaving due to various factors. In addition, the interior of the structure can be compromised by moisture penetrating through the concrete, or losing structural integrity due to rust and corrosion of its reinforcing metal.
To ensure a quality pour, it is important that the concrete placement be performed under ideal conditions. Pouring concrete on days that are extremely hot can cause the concrete to set up too quickly, which could affect both the structural integrity and the finish. It is best to avoid pouring concrete on extremely hot days.
Additionally, pouring concrete when it is less than 50°F outside can cause significant issues with the structural integrity of the finished product. The strength and durability of concrete is determined by its ability to chemically react properly, when the cement makes contact with water. The ideal environment is to pour concrete on days when the temperature is 50°F and rising to ensure that the cement and water react properly. This will allow the concrete to cure correctly.
Cracking and Heaving
There are significant factors that can cause concrete to crack including shrinkage, changes in temperature, lack of support, and rusting of its metallic components. The mixture of concrete, aggregate and water mixed with air will naturally be bigger during the pour than when it is completely dried and cured. There will be a significant amount of shrinkage as the water evaporates from the interior of the concrete. Without proper control joints, cracking may occur in undesirable locations instead of inside the joint.
Additionally, a change in temperature can cause the concrete to contract in the cold, and expand during the heat of summer. Often times, major expansion can cause the slab to heave from the ground.
Lack of support is also a major issue that can cause significant problems for the concrete. The position of the concrete slab can shift due to inadequate support of the structure, which could be a result of erosion caused by rain or wind. Additionally, insufficient rebar or reduced structural support can cause catastrophic failure.
Rusting and Spalling
Rusting is also another concrete issue. Any time there is corrosion of metal reinforcements including rebar, wire mesh or steel beams, it can decrease the concrete’s tensile strength. However, there are solutions to stopping the corrosion process when found.
Spalling is a serious condition where the surface of the concrete becomes flaky and rough. This is usually a condition of hundreds of extremely tiny cracks that were first only visible on the concrete surface. Spalling is a typical occurrence that happens when a high level of water was added to the mixture of concrete, or when the surface of the concrete was allowed to dry much faster than the interior.
All of these concrete problems can be addressed through repair or replacement, or by adding sealants to the surface, where applicable.