History & Evolution

Example of an industrial floor with saw cuts

Before 1980

Technology before 1980

Concrete floor slab of 1600m² with 5 meters of saw cuts each = 720 meters of possible jointing problems.

To solve the shrinkage problem, they have broken down the floor by sawing. In fact they 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 changes and wheel impact combined with possible static load vertical movement of the floor slabs. Within a short period of time the floor will be seriously damaged, unsafe and even unusable.

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.

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 concrete floor slab. In this example, the floor slab measures 40x40 metres (1600 m²) with 160 linear metres of armoured joints. The jointing problem is reduced in comparison with saw cuts. At first sight, this looks a good solution. However, the efficacy is strongly dependent on the intensity of forklift traffic and the static loads on the floor.

Expansion joints permit the free horizontal movement of the floor. The shrinkage as a result of the drying process of the concrete is taken up. The crack formation will be avoided and saw cuts are unnecessary.

Once the dilatation process is stabilised, the joint will only 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 concrete 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. However another potential problem regarding 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 concrete 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 and 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. Unfortunately, this is not sufficient for certain forklift traffic. An expansion joint is also used as a day joint. This allows for the finishing of floor sections according to a daily or longer-term deployment schedule or where there are limited concrete pour supplies. It is feasible to continue construction on an abutting section without the risk of cracking or poor attachment of the concrete. A correctly levelled out expansion joint is also an aid to the finishing of the floor.

2007

The Sinus Slide® solution

Despite the advantageous characteristics explained above, traditional expansion joints have one big problem and this is the joint opening. In each logistic centre with forklift traffic, the (hard) wheels will fall into the opening gap. These reoccurring ‘shock’ impacts cause damage to the; floor, joint, handling equipment, transported goods and even to forklift operators.

With harder forklift wheels, higher loads and a faster speed the wheel pressure will have a worsening negative impact on the joint.

There is now a trend in the logistics world for forklift wheels to be smaller and harder and loads and speeds of forklifts increasing. Our Sinus Slide® joint is evolving with this tendency.

Where other producers try to reinforce the joint, HCJ found the solution by eliminating the cause. With the Sinus Slide® solution, there is continuous support between the wheels and the floor in the most effective proportion. It is due to this that the wheels slide noiselessly and vibration and shock-free from one concrete floor slab panel to another. This happens without any change or damage and with a comfort for the operator and machine never before experienced. The Sinus Slide® solution saves thousands of Euro’s annually 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 – Cosinus Slide®”.

2012

The Cosinus floor concept

With the Cosinus Slide® 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 floor itself 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 slide over each other. This technique permits the sliding of the two-floor parts over each other (horizontal dilatation) and realises 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”.

Non-linear computer simulation

2015

Stability verification Cosinus Slide®

However, having invented and introduced this revolutionary jointing solution we decided to go one step further and tackle one of the most dogmatic principles in industrial floor design.

All existing published guidance documents, regarding concrete industrial flooring, explain that the weakest point of a floor is the joint and that load transfer at the joint must be calculated separately.

But now, after demonstrating the excellent load transfer mechanism in several job sites all over the world, HCJ can prove the load transfer potential of Cosinus slide® profiles with calculations based on non-linear simulations and laboratory testing in different concrete grades and slab thicknesses. Using the different load cases that occur on the floor, we are now able to check in detail the load transfer at the joint.

Until now, most of the design engineers made assumptions regarding the load transfer capacity of contraction joint profiles. Today, HCJ can now prove it!… Again a new era in designing in industrial flooring technology has started.