Are you planning on laying an expansive concrete floor – or paving? Have you heard that you need expansion joints in concrete but are not sure of what they are, their purpose and how to install them?
When it comes to concrete floors or paving, movements of the earth’s surface and expansion and contraction of the concrete itself can lead to the formation of unsightly and damaging cracks in the newly laid floor, over time.
Continue reading for a detailed definition of concrete expansion joints, their importance and a few tips for using concrete sawing to install them in your next project.
What Are Expansion Joints?
In the simplest of words, expansion joints are exactly what they sound like; they are joints that allow for expansion. Designed as a break between the concrete slab and other parts of a structure, or a division in a large section of concrete, expansion joints allow the concrete to expand and contract during temperature changes. By allowing for expansion and contraction, these joints eliminate the stress that can lead to cracking.
Concrete joints are normally used in concrete driveways and large slabs like foundations and flooring.
The Importance Of Concrete Expansion Joints
Concrete can crack due to a number of reasons. For starters, changes in temperature and humidity levels can lead to expansion and contraction of the concrete; thus causing cracks. Seismic movements in the earth’s crust – no matter how small – can cause concrete to crack. Last but not least, concrete surfaces can crack due to the placement of huge loads on the concrete surface by stationary or mobile objects/machinery.
Concrete cracks normally appear as zigzag lines of any length or size, in any direction. These cracks can seriously affect the longevity and structural integrity of the concrete as well as the overlying structure as a whole.
Expansion joints are strategically positioned in the concrete, in a way that allows the concrete to expand and contract without developing any unsightly and damaging cracks. After being poured, concrete normally contracts as it dries. Once it is set, the concrete expands and contracts according to the air temperature. For any concrete surface exceeding 6 square metres, concrete expansion joints help facilitate the movement of the concrete without any cracking.
It is important to have concrete joints along areas where the concrete borders buildings, walls or objects such as manholes. These joints are also important in areas where concrete has been poured a number of consecutive times. It is recommended that you have a structural engineer design and specify expansion joints, in case several of them are needed on the same project.
How To Properly Place Expansion Joints
To ensure that all your expansion joints are properly placed, follow the tips outlined below.
- Don’t wait too long if you intend to cut joints after pouring concrete. Expansion joints should be cut within 12 hours of pouring concrete; otherwise, the concrete might start cracking.
- To ensure effectiveness without affecting the structural integrity of concrete slabs, all joints should be separated by a distance that is 30 times the thickness of the slab. As such, for a 10cm thick slab, joints should be about 3 meters apart.
- The depth of the joints should be no less than a quarter of the slab thickness. As such, joints should be at least 2.5cm deep for a slab that is 10cm thick.
- To keep these joints hidden, it is recommended that you place them under walls.
- For the best outcome, it is recommended that you enlist the services of an expert when it comes to properly space expansion joints in concrete.
Expansion joints play an important part in ensuring the longevity and structural integrity of expansive concrete slabs and driveways. If you are looking for professional assistance in placing and making expansion joints contact the pros over at Sydney Sawing & Drilling today!