Example of an industrial floor with saw cuts
Some problems after application
To solve the shrinkage problem, they have broken down the floor by the sawing. In fact they have created a new big jointing problem. In the case of forklift traffic, saw cuts are always the wrong decision because of missing load transfer and edge protection. The edges will crumble off due to dynamic charges and wheel impact and together with static loads vertical movement of the floor slabs is possible. On very short term the floor will be damaged seriously, unsafe and even unusable.
2 – 1980 – Using expansion joints to take up the shrinkage of the concrete
The saw cuts are replaced by expansion joints at the edges of the floor slab. In this example, the floor slab measures 40x40 metres (1600 m²) with 160 linear metres expansion joints. The jointing problem is reduced with 78% in comparison with saw cuts. At first sight, this looks a good solution. However, the effectivity is strongly dependent on the intensity of forklift traffic and the types (hardness) of wheels. (see infra/below)
Example of a joint-free floor slab with expansion joints. Beside the reduction of the jointing problems with +/- 75%, expansion joints still generates several other advantageous characteristics.
Expansion joints permits the free horizontal movement of the floor. The shrinkage as a result of the drying process of the concrete is taken up.Crack formationwill be avoided and saw cuts are unnecessary. Once the dilatation process is stabilised the joint only will expand or retract slightly by extreme fluctuating temperatures. However, this phenomenon will only occur in outside floors. So, the existing opening gap of the expansion is the result of the shrinkage process and the size of the gap depends on the dimensions of the floor slab. The bigger the joint free slabs, the bigger the opening gap of the expansion joint. The crimping of a floor slab is strongly dependent on a number of thermal variables like climatic circumstances, type of reinforcement as well as the quality and wetness of the concrete. The average shrinkage varies between 0,3 to 0,5 mm/meter. Joint free floor slabs of 30x30 metres will create a gap opening from 0,9 up to 1,5 cm. So the shrinkage problem of the concrete is controlled by the expansion joint but another potential problem (in case off forklift traffic) that should not be underestimated is created. That problem is the joint opening. (see infra/below) - An expansion joint realises load transfer and prevents vertical movement of the floor slab. The construction of the expansion joint ensures the floor slab panels are connected and entwined with each other thus preventing any vertical movement of the floor. In addition, the expansion joints realise load transfer from one slab to another that extends the life span of the floor. The more solid and continuous the connection of the expansion joint, the more efficient and effective the load transfer. Because of this, continuous joints have much better performance than discontinuous joints. - An expansion joint protects the edges of the floor slabs. This unfortunately is not sufficient for certain fork lift traffic. - An expansion joint is also used as a day joint. This allows the finishing of floor sections according to a daily or longer term deployment schedule or where there is limited concrete pour supplies. It is feasible to continue construction on an abutting section without the risk of cracking of poor attaching of the concrete. A correctly leveled out expansion joint is also an aid to the finishing of the floor.
3 – 2007 – The Sinus slide® solution
Technology from 2007
Despite the above explained advantageous characteristics, traditional linear joints have one big problem which is the joint opening. In each logistic centre with forklift traffic the (hard) wheels will fall in the opening gap. These always returning shock impacts cause damage on floor, joint, handling equipment, transported goods and even on forklift operators.
The harder the forklift wheel, the higher the loads, the higher the speed, results in a higher wheel pressure and the harder the shock impact. There is a tendency in the logistic world that forklift wheels are coming smaller and harder and that loads and speeds of forklifts are increasing. Our Sinus Slide® joint is evolving together with this tendency. Whereas other producers try to reinforce the joint, HCJ found the solution in eliminating the cause. With the Sinus Slide® solution (patent pending) there is continuous support between wheels and floor in the most effective proportion. Because of this, wheels are sliding noiseless and vibration- and shock free from one floor slab panel to another without any change on damage and with previously unknown comfort for operator and machine. The Sinus Slide® solution saves yearly dozens of thousand euro’s in maintenance costs and contributes to a safe and comfortable working environment. For more detailed information concerning the Sinus Slide® solution we refer to the page “products – HC-Omega Sinus Slide®”.
4 – 2012 The Cosinus Floor Concept
Technologie from 2012
With the Cosinus flooring concept HCJ go one step further. In the search to develop the perfect expansion joint a new technology (patent pending) is introduced to the market that realises load transfer in the most efficient way. With actual law of nature, better is simply not possible.
With the Cosinus floor concept , the ideal characteristics of the Sinus Slide® solution are preserved but without the traditional dowel and anchoring system. Load transfer is realised by the flooritself and not by dowel connections. When taking up the shrinkage process the Cosinus floor concept creates vertical columns simultaneously on both sides in the floor which slides over each other. This technique permits the sliding of the two floor parts over each other (horizontal dilatation) and realise at the same time an optimal connection and limits the vertical movement of the 2 parts. The floor has taken over the load transfer function of the joint. That’s why we say “the joint is the floor – the floor is the joint”.
With this, we think the final stage in dilatation technology for industrial floors is achieved. Better is simply not possible with actual law of nature and mathematic knowledge. However, innovation is the keyword in our company philosophy. The never ending search for solutions and new ideas is our challenge. Who knows, maybe one day we come with a sequel on this overview.
1. A test that includes substrate reveals more about the strength and firmness of the substrate
than about the joint.
2. Since the nature of substrate varies, it is never consistent.
3. Preperation of the substrate is not always ideal.
4. After some time substrate can be expected to settle or subside.
5. Other factors such as seeping water, corrosion, etc. must be considered.
1. TESTING UNDER COMPARABLE CONCRETE QUALITY CONDITIONS
Testing with inferior quality concrete could be employed to indicate an expansion joint is not the weakest element. This approach is not realistic and that is why our testing is carried out using regular strength concrete. We use the same concrete that is used daily in the construction of industrial floors.
In order to perform testing on 150 mm floor thicknesses, we prefer to use non reinforced concrete such as the type used on a daily basis to lay industrial floors of that stature. When concrete elements from 200 mm and upwards are being tested, steel fibre cement
reinforcing is used to represent the material of heavily loaded industrial floors or lload bearing posts. After being poured, the concrete is left to dry for at least 28 days before any testing is performed. While the concrete has not yet reached its optimal strength at that time, it would normally be carrying 100% loading after this period in practice.
2. TEST LENGTH OF 1 METRE
We opt for a test length of 1 m. Since our continuous profiles also distribute their load over the length of the profiles due to their rigidity, this relatively short length is in favour of discontinued profiles. However we accept these challenges nonetheless.
3. THE TEST SETUP
The test setup shown alongside was developed in collaboration with the Magnel Laboratory for Concrete Research at Ghent University. We attempted to create an objective base for comparison as far as possible to strongly simulate external conditions in a realistic way. The attained results are therefore scientifically substantiable and very reliable and representative.
The test results not only served as valuable information about our expansion joints’ mutual force and load relationships, but also about other profiles and systems on the market. All profiles were tested in equivalent circumstances.
Thanks to these tests and the attained results, we are able to prove the quality of our joints in comparison with the other products being offered on the market. If you would like more information about our test results, don’t hesitate to contact us. We would gladly help you reach a clear understanding of the strengths of the various profiles. That will aid you in selecting the most suitable profile for your own industrial floor.