A new way for Co2 reduced Soil compaction

01. Sustainable soil compaction

General information about the product.

Underbold is not a product in the true sense of the term, but a process technology. The new system Underbold, a wax emulsion, works with and enables existing soil to be converted into a frost-resistant base layer for the permanent way by using a cold recycling milling machine. This is so simple and advantageous because the system does not require any additional equipment. Conventional methods are different: Heavy equipment is needed here. But we will come to the advantages of the new technology later. What exactly is this product?

Ultimately, the soil is compacted by a wax emulsion that is worked into the soil. This wax emulsion binds and is water-repellent. After processing it is frost and heat resistant. This makes the substructure very durable. The emulsion firmly encloses each individual grain of soil after incorporation, so that a homogeneous mass is formed. Pressure compresses the soil with the binding agent, creating a permanently stable bond. The material is now highly resistant to pressure, which is advantageous in cases of high pavement loads and even prevents rutting.

The process is based on the ZTVE-StB 2009, optionally our company has introduced an additive to the market. The patented additive PR-Plast prevents the formation of ruts and is suitable for the production of PMA for bituminous asphalt layers. It is therefore not worked into the substrate, but complements the particularly stable substrate in a sensible way. With a grain size of around 3 millimetres, it improves the properties of bituminous mixes for surface courses and binder courses. The polymer-modified asphalt prevents rutting even at high temperatures and improves the asphalt’s e-modulus by around 25 percent. The additive does not require a PMP manufacturing plant, as it is easy to use and is added directly in the mixer.

02. Benefits and Comparison with Underbold

With all conventional methods of soil compaction, it is difficult to extract the material used from the soil again. It cannot be recycled. However, our company has also solved this problem with Underbold: The worked soil can be loosened up again with a rotary tiller. The wax emulsion can remain in the soil and the soil regenerates over time - because the binder as well as the wax emulsion are environmentally friendly. If the road is to be renewed rather than destroyed, the material can simply be reused. This means that the soil can be worked and compacted again after the upper layers have been removed.

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Cost saving

On average, our customers save 33% in the procurement of raw materials for soil compaction over the entire project period.

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Time and resource saving

Underbold can save up to 80% time and up to 66% manpower.

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Ecological & Sustainable

An ecologically appropriate construction method through environmentally and climate-friendly technology.

03. Underbold technology

Preparations for the implementation of Underbold

Before Underbold can be used for soil compaction, the soil must be prepared. This preparation begins with the taking of soil samples: the analysis of soil weight and soil moisture helps to determine the exact composition of the subsoil. These data are important to determine the mixing and quantity ratio of the wax emulsion. If the soil has organic vegetation, about five to fifteen centimeters of the upper soil layer must be removed. All organic parts, such as roots and other plant parts, must be removed before the emulsion is worked in. The soil may contain a maximum of three percent organic substances, and the subsoil should not contain more than this.

Often roads are simply renewed or a new road is built on a so-called dirt road. In this case preparation is not necessary. This is because it can be assumed that the composition of the soil is known and that there is less than three percent organic material in it.

Underbold implementation

Whereas conventional methods require several working steps with sometimes quite special, heavy equipment, Underbold, the wax emulsion, is mixed into the soil with the milling machine in a single working step. A homogeneous mixture is produced immediately. The tiller not only opens up the soil and picks up the soil, but also mixes in the wax emulsion and returns the homogeneously mixed mass to the ground.

Compaction of the soil

In the next work step, the loosely applied mixture of soil and wax emulsion is pre-compacted. The soil is thus returned to its original level. And above all, the soil is now so firm that the following construction machines can drive on it safely – they do not sink in. This enables even working at the required depth. Levelling and pre-compaction is therefore combined into one work step. In the next step, a hydraulic binding agent is distributed by a spreading vehicle. The STREUMASTER, for instance, is suitable for this purpose. The soil under the construction vehicles now shows three different layers: At the very bottom is still natural, unworked soil. Above this, there is a compacted layer of soil to which a wax emulsion has been added. Both are water-permeable and moist. A layer of binding agent has been applied on top of this in the final work step.

Final soil compaction

Binding material is mixed into the soil with a rotary tiller.

During this phase, the milling machine comes into use once again: The binding agent applied by the gritting vehicle is mixed into the pre-compacted layer of the base material by a milling machine. Only a small quantity of binding agent is required, Underbold has already been incorporated into the soil. The soil needs to be levelled and compacted again after this operation as well. This is the only way to make the ground stable. However, this is already final compaction: The soil is compressed in such a way that Underbold can develop its optimum effect.

04. Frost Protection of Roads and Railways

This study is a part of a larger research project on frost protection of roads and railways at Norwegian University of Science and Technology.

Another challenge we are facing now is climate change, which leads to increasing winter temperatures and precipitation. And as a result, the areas, which before were enjoying stable winter conditions, now are facing frequent freeze-thaw cycles during winter months, which lead to severe frost heave problems. Frost action mainly develops in the frost-susceptible subgrade soils, leading to ice lens formation, surface heave, and to pavement deterioration (Konrad and Lemieux 2005). Frost action in the subbase granular layers, especially in the frost protection layer, is often ignored, because these materials are usually not considered to be frost susceptible. This may not necessarily be the case because the presence of fines can modify their frost susceptibility and cause severe degradations...

Norwegian University of Science and Technology

05. High density and stable layers

A new hydraulic additive for resource-saving and ecologically sustainable compaction of floor surfaces and building substrates.

The Underbold method achieves the very high density. This is because the air pockets in the soil are still filled with the nanoparticles even in the micro range. They do not remain empty. And this is exactly what provides the desired stability. In comparison, conventional methods only achieve a lower density. This is because the air inclusions in the soil remain even after compaction. They remain empty or occasionally fill with water – and this causes movement in the material particles. The subsoil is therefore not stable, but mobile. And that in turn can lead to damage to the asphalt surface over time as weather conditions change.

Our company’s new technology also scores points in terms of resistance to temperature changes: the soil layers are not permeable to water. On the contrary, they are extremely impermeable to water due to their dense structure without air pockets. If the temperatures change between day and night or between summer and winter, no cracks will form in the soil. Because the soil is always equally dense, it does not change its volume. This is different with the conventional method: The soil remains permeable to water, the soil works with changes in temperature, and this leads to cracks in the asphalt surface.

The mixture of soil and wax emulsion can be adjusted as required using cement admixtures. Ultimately, therefore, there is no limit to the bearing capacity. This also distinguishes this method from conventional construction. Up to now, the bearing capacity has always been dependent on the existing soil material. The bearing capacity could only be increased by laying a thicker asphalt layer. This is far less economical than increasing the bearing capacity by adjusting the mixing ratio.

06. Efficient use of resources

Less equipment, shorter construction phase, economic advantages

Our company has found a reliable method here that reduces the construction phase for one kilometre of road with a width of ten metres to two days. With conventional construction methods, ten days are required for such a section, as the base course can only be applied after the binder course. Incidentally, our company’s wax emulsion can be used for all types of soil. If old roads are to be rehabilitated, the existing asphalt layers are simply worked into the subgrade. This is also more economical than conventional methods: Previously, existing soil and asphalt layers had to be removed at a cost, they could not be used any further, and it was not possible to work them into the soil. Disposal and the procurement of new material increases costs and prolongs the construction time – which means a further increase in costs.

07. Conclusion

Underbold is sustainable and ecological, yet economical

The advantages of our developed process technology over conventional technologies are obvious. It is an ecologically as well as economically very sensible product – in several respects. Not only does the shortened construction time have a positive effect on environmental and climate protection and financing, but also the reusability of existing materials. As a result, the cost of materials can be reduced just as much as the costs incurred by a (previously) fairly long construction period. If the PR-Plast additive is used together with the new compaction method, further advantages are created. In short, the new method of soil compaction offers.

It is clear that ecologically responsible construction using environmentally and climate-friendly technologies does not conflict with economic interests. With the wax emulsion and its processing, our company has found a simple and sustainable way to make the substructure of roads even more durable and stable

  • A considerable time saving due to a shorter construction time
  • Better adaptation of the bonded superstructure to the traffic load and thus a reduction in the number of layers,
  • More efficient use of cement through the above-mentioned better adaptation
  • Longer shelf life
  • Reduced maintenance costs
  • Avoidance of ground movements outside the gradient adjustments,
  • Elimination of fees for landfill and disposal outside the gradient adjustments
  • Reduced construction time less influence on flowing traffic
  • Higher loading capacity
  • Higher modulus of rigidity
  • Increased elasticity
  • Shorter setting time outside the processing period
  • Less tendency to shrink
  • No cracking
  • No load input from the setting reactions to the layers superimposed on them
  • Reduction of the penetration depth of water
  • Hydrophobic setting

We will gladly advise you on further procedures and Undebold