Understanding Concrete Control Joints

Perfectly placing concrete is a skill that demands attention to detail around structures for long-term durability. While concrete starts as a liquid base, the solution undergoes a great amount of stress during the drying process. Concrete rapidly shrinks in volume as the plastic mass adapts to the environment.

There is nothing better than a concrete surface that looks pristine, but these exteriors are destined to crack through temperature changes, pressure and other factors. What if there was a way to control where concrete splits? This is possible with concrete control joints.

How to Keep Concrete From Cracking

Concrete mainly cracks due to drying shrinkage. However, there are two main strategies for providing proper concrete structural behavior. Professionals can use steel reinforcement or control joints.

Steel reinforcement involves holding small cracks together tightly for interlocking strength across a concrete slab. Using steel underneath surfaces is becoming an outdated process as hairline cracks still shine through the top of concrete structures. Always proceed with steel reinforcement methods with caution.

The optimum method for controlling random cracks is by implementing joints at predetermined locations.

What Are Control Joints?

Control joints are planned cracks to compensate for inevitable changes in temperature and drying shrinkage. These cuts allow for movements in a concrete slab by creating weak spots where solutions can crack in a straight line. Concrete still cracks during the drying phase, but the splitting occurs beneath the surface of the slabs.

Depending on the location of your concrete work, teams can hide control joints under carpeted areas, walls and concealed locations. Installers should set control joints at the time of concrete placement for best results. The longer crews wait to cut control joints, the greater the chances of unwanted cracks occurring before sawing is complete.

It’s crucial to cut joints at least 25% of the depth of a slab. Grooving tools and saws are effective in placing joints at various stages of the drying phase. For most projects, control joints must get cut within six to 18 hours of placing concrete.

Control Joints in Concrete

Control joints in concrete are crucial for pavement jobs large and small. In some cases, concrete joints allow slabs to expand or contract without harming structures around a home or business. Control joints are versatile in several concrete applications and include the following types:

• Contraction joints: Create a weak area for cracks to occur in a straight line. Contraction joints are extremely common in garage flooring, driveways, sidewalks and home slabs.
• Expansion joints: Separate slabs of concrete from other parts of a structure. Expansion joints promote independent movement for thermal stretching. This control joint is essential in projects where soil below concrete is expected to shift, settle or lift upward. This type of control joint keeps two pieces of concrete from rubbing together, which results in chipping.
• Cold joints: Contractors use cold joints for intense pressure on thick layers of concrete. Crews pour concrete to a certain height or point and stop to allow for drying. Crews return and pour a second layer on top for additional strength. Inform buyers of cold joints as they are mistakable as cracks.

It is much easier to treat a control joint than repair random cracks. Inform your customer about control joints while on the job to increase understanding and property owner satisfaction.

Contact Dynamic Concrete Pumping Today

Dynamic Concrete Pumping is proud to provide concrete pumping, placing, and finishing services. Our pumps offer a 360-degree continuous swing boom for placing concrete across multiple locations. With over 30 years of user experience, we want to help your crew take utilization to a new level.

Contact Dynamic Concrete Pumping today for more information about our concrete services.