In the first part of this article (https://www.dhirubhai.net/pulse/joints-concrete-floors-part-1-construction-ramon-planas-masip/)we talk about the constructive joints. In this second part we will focus attention on the contraction joints.
A sawcut joint is one that divides the pavement with the basic function of marking the concrete where it should be opened, generating straight joints instead cracks of uncontrollable geometry. There are several considerations to bear in mind initially:
- As a general rule, they are joints that exist in the greatest amount in the pavement.
- These joints are generated by cutting the surface with a disc, usually 3mm with a recommended depth of 1/3 of the thickness and in the first 24 hours after the concrete is poured.
- Its spacing depends on several aspects, type and amount of reinforcement, shrinkage of the concrete, and the thickness of the slab. With a good combination of the first two, they can be eliminated, something very recommended for traffic with a small and hard wheel.
There are basically 2 ways to design this type of joints:
- Joint with dowels supported in baskets centered on the cuts: Although from a theorical viewpoint it is the perfect solution to guarantee a correct transmission of loads, the put in work is so complex that in almost all the cases they are misplaced and are a factor of union between slabs, and therefore of impediments to the movement of the slab.
- Joint without dowels, is the most common and is executed with the simple cut, the transmission of the loads is minimally guaranteed with the continuity of the armed and friction of the 2/3 not cut.
The sawn joints have two basic problems:
- The difficulty to guarantee the transmission of loads, as we have seen in the previous section.
- Deprotection of the concrete edges on each side of the cut. Unlike construction joints, we can not put a reinforcement, and if there is a lot of traffic a hard wheel, sooner or later they will strip the edges of the joint, leading to high maintenance costs.
To avoid this, we have 2 solutions:
- Seal the joints with an elastic seal during the first year of the life of the pavement, to change it after that period, when the retraction is practically non-existent, by a more rigid seal. In this way, we will minimize the impact of the wheels and, with good maintenance, we will lengthen the life of the slab.
- Use the solutions that the market has to eliminate the sawcut joints. Undoubtedly the best quality / cost option taking into account the reduction of investment in maintenance that this solution implies. One of the most modern systems to eliminate joints is the use of linkEVR, which I mentioned earlier in an article about curling:
