Concrete admixture material for road base : Flexibility Property

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	Renolith PRODUCT QUALIFICATION
	Flexibility System (FS) - Conventional road - Renolith road
	Water Penetration Protection System (WPPS)
	Water Supply System (WSS)
	Cement Poison Protection System (CPPS)

The Renolith Flexibility System (FS):

For the deep understanding of the FS, we have to take a look on the loads, which are typically

         for road construction. In opposite to the normal usage of concrete, ie. construction of buildings, we have dynamic loads here, which are acting through the asphalt concrete to the road base (see figure 1).

         Idealised, the force F is acting only in one point (the tyre of a vehicle), which is moving by time over the road. If we look at one segment of the road, then for this segment an alternating stress occurs. The segment is deflected under the force F, but if the force F has passed the segment, the deflection has to go back. Than this segment is loaded again, relieved, loaded, and so on.

         Unfortunately, normal concrete is not able to stand this alternating stress for a long period of time. If a load is so high, that the elasticity limit of the concrete is exceeded, a plastic deformation will stay even after the load has passed the segment. But in reality, after every load a small amount of deformation will stay. This effect is well known causing furrows.

Therefore, an ideal concrete for road construction should have the following attributes:

High modulus of elasticity.

High flexibility.

Fig. 1

In the first moment, this two points seems to be similar, but they are not.

The modulus of elasticity is a value which determines, what for a force F is needed to deflect the material. Therefore, higher values for the modulus of elasticity means, that the force F has also to be higher to deflect the material. That means, that the elasticity limit of the concrete then will be raised.

High flexibility for the concrete is needed to compensate the deformation (or deflection) after load to avoid things like furrows, which often also causes cracks in the asphalt concrete.

But it is possible, to have these two attributes within one material? Reinforced concrete is a very good example: It has a higher modulus of elasticity than normal concrete, but is also more flexible.

Of course, no steel is needed for road construction, because Renolith is able to add these attributes to the concrete in the following way (see figure 2).

Between the particles, Renolith adds kinds of ?micro-rubberbands", which are under pressure. This will cause the following effects: The particles are bonded together much stronger than the particles in normal concrete. That means, that a load has to be much higher to deflect Renolith concrete. Test results have shown, that the average modulus of elasticity is 25%-50% raised using Renolith. On the other hand, deflections will be compensated very efficient, because after load, the ?rubberbands" will push the particles back to their original positions. The high flexibility of Renolith concrete can be easily proofed using our styrofoam samples.

Fig. 2

But what does that mean for road construction?

Let us take a look on a Renolith road (see figure 3.1). The first obvious thing is, that only one road base is needed, which can be mixed with in-situ materials. That means, that time and money can be saved up to 50%.
The use of Renolith raise now the modulus of elasticity and the flexibility of the base, so that the following situation occurs:

Fig. 3.1

         Let us look again on our segment, which is loaded by a force F (see figure 3.2). The factor ?a" means, that because of the higher modulus of elasticity, a higher load is needed to force the same deflection as in a normal road (see figure 2). This is the first advantage using Renolith.
          After the load has passed the segment, no deformation will stay, because of the high flexibility of the Renolith base. This is essential, because the segment will be loaded again and again. Therefore, Renolith concrete is able to stand this alternating stress for a long period of time without having severe effects.
          To draw the conclusion, you can say, that a Renolith based road is very resistant regarding the loads, which are typically for normal traffic. Therefore, a Renolith road has a long durability and only needs low maintenance, which is again saving time and money

Fig. 3.2

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New Technology for road constructionsLow maintenance, Save time and Save money

New Technology for road constructions
Low maintenance, Save time and Save money