Description

The invention pertains to a system for constructing a pavement on a soil, preferably a weak soil, to a pavement design and to a method for constructing such a pavement on a soil.

Background

There are different technologies for constructing a pavement on a soil. One technology is to provide chemical stabilization of a top soil layer. The top soil layer may be chemically stabilized (consolidated) in-situ by mixing a chemical composition with the top soil layer forming a pavement on which traffic can move from one location to another. An example of such a method is disclosed in EP1349819.

The present inventors have found that when the soil is very weak, for example due to high ground water levels and/or low bearing capacity soils, the technology of providing a chemical stabilization of a top soil layer can be improved upon, for example by applying a larger amount of cement and chemical additive and/or applying a thicker layer, which might be cumbersome and costly. Due to increasing urbanization, there is an increasing demand for building and paving on weak soil.

It is an object of the present invention to provide a pavement construction, especially suitable for weak soils, that is easy and fast to apply and cost effective.

Summary

The object may be solved by the system for constructing a pavement on a soil according to claim 1 .

Detailed description

Definitions

"soil" as used in the present descriptions means: the layer of soil upon which the pavement construction of the present teachings is to be applied. "sub soil" as used in the present descriptions means: the layer of soil beneath the surface (top) soil; optionally overlying bedrock.

"top soil" as used in the present descriptions means: the surface layer of soil that is removed prior to application of the pavement construction of the present teachings.

"extra soil" as used in the present descriptions means: an additional layer of soil that is added to the top soil prior to application of the pavement construction of the present teachings.

"weak soil" as used in the present descriptions means: a soil having a California Bearing Ratio (CBR) of 2.5% or less as measured according to ISO 1377 part 9, or a soil having a Deformation Modulus (E _v2 ) of 12 MPa or less as measured according to EN 1997-2:2007.

"geosynthetic material" as used in the present descriptions means: a material comprised of one or more component materials that is used in contact with soil to stabilize the soil. A geosynthetic material may for example be a geotextile or a geogrid.

"geotextile" as used in the present descriptions means: a planar, permeable, textile material, which may be nonwoven, knitted or woven (also called woven fabric) prepared from a plurality of strips or yarns of one or more component materials (in accordance with ISO 10318:2015).

"geogrid" as used in the present descriptions means: a planar structure consisting of a regular open network of integrally connected, tensile elements of one or more component materials, which may be linked by extrusion, bonding or interlacing, whose openings are larger than the constituents, (in accordance with ISO 10318:2015). It may for example be a rigid biaxial geogrid of oriented extruded strips or yarns.

"geocomposite material" as used in the present descriptions means: a combination of a geosynthetic material and at least one further material which further material is connected to the geosynthetic material. "component materials" as used in the present descriptions means: components of the geosynthetic material. The component materials may be polymeric or inorganic.

"base layer" as used in the present descriptions means: a granular layer that is applied on top of the geosynthetic material. Said base layer - when compacted - forms in conjunction with a geosynthetic material a mechanically stabilized layer.

"top layer" as used in the present descriptions means: a layer on top of the base layer. The top layer is prepared of several components, being cement, the chemical composition, water and a soil composition. When this mixture of components is hardened it forms a solid layer that forms a chemically stabilized layer.

"pavement" as used in the present description means: a construction comprising several layers that is applied to a soil of a terrain/area and that is intended to sustain (vehicular) traffic. Examples of pavements are roads, bike paths, airports, harbor areas, and piling maps. The pavement is meant to transfer the load induced by traffic via the mechanically and chemically stabilized layers, e.g. by means of granular interlock and/or friction.

"preloading layer" as used in the present description means: a layer of granular material that is used to density the soil, and to minimize the settling during the lifetime of the construction, by means of the weight of said preloading layer.

"surface layer" as used in the present description means: an upper layer that may be applied on top of the pavement construction and that is suitable for trafficking, for example asphalt or concrete/stone pavement parts.

"with a substantial equal thickness (over the axial direction) of the soil" as used in the present description means: with a substantial equal thickness of the soil, preferably with a substantial equal thickness over the axial direction of the soil.

"over the axial direction" as used in the present description means: over the width of the soil and over the width of the pavement construction. In other words, perpendicular to the length of the pavement construction. "primary settling" as used in the present description means: the settling of the pavement construction occurring during the consolidation and construction phase.

"secondary settling" as used in the present description means: the settling of the pavement construction occurring during the service life of the pavement construction.

"silica" as used in the present description means: synthetic and/or purified silica, for example amorphous silica. Silica is not meant to include clay or sand.

"zeolite" as used in the present description means: a widespread group of silicate crystals of, inter alia, hydrated alkali metal and alkaline earth metal aluminosilicates.

"apatite" as used in the present description means: a group of phosphate minerals comprising high concentrations of hydroxyl ions (hydroxylapatite), fluorine ions (fluoroapatite) or chlorine ions (chloroapatite), and e.g. high concentrations of strontium, barium or calcium (respectively strontium halophosphate, barium halophosphate or calcium halophosphate). The halogen ion of halophosphate being a chloride or fluoride, but which may also be substituted by a hydroxyl group.

"cement" as used in the present description means: a salt hydrate consisting of a fine- ground material which, after mixing with water, forms a more or less plastic mass, which hardens both under water and in the outside air and which is capable of bonding materials suitable for that purpose to form a mass that is stable also in water.

Short description of drawings

Figure 1 shows the method for constructing a pavement in an embodiment.

Figure 2 shows the method for constructing a pavement in another embodiment.

Figure 3 shows the method for constructing a pavement in another embodiment.

Summary of aspects and embodiments

The present invention relates in an aspect to a system for constructing a pavement on a soil, said system comprising a geosynthetic material and a chemical composition, said chemical composition comprising: a) one or more components selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride and ammonium chloride, and

b) aluminum chloride, and;

c) one or more components selected from the group consisting of silica, zeolite and apatite.

In an embodiment of said aspect, the geosynthetic material is selected from the group consisting of a geotextile, preferably a woven or knitted fabric, and/or a geogrid, preferably a rigid biaxial geogrid or a composite of a geogrid, preferably having a high stiffness, with a nonwoven. In this embodiment, with high stiffness is meant a secant modulus of at least 200 kN/m at 3% strain, as determined in accordance with test method EN ISO 10319:2015.

In another embodiment of said aspect, the geosynthetic material has a secant modulus at 3% strain of at least 200 kN/m, or at least 300 kN/m, preferably at least 500 kN/m, more preferably at least 1000 kN/m, most preferably at least 2000 kN/m, as determined in accordance with test method EN ISO 10319:2015.

In another embodiment of said aspect, the geosynthetic material comprises a plurality of strips or yarn made from one or materials having a modulus of at least 10 GPa, preferably at least 30 GPa, more preferably at least 50 GPa, as determined according to test method ASTM D2256/D2256M - 10(2015).

In another embodiment of said aspect, the geosynthetic material is a geocomposite material comprised of a geotextile and/or a geogrid and at least one further material, preferably a perforated film or a nonwoven material, which further material is connected to the geotextile and/or the geogrid.

In another embodiment of said aspect, the chemical composition comprises 45 to 90% by weight of one or more of the components of group a), 1 to 10% by weight of the component of group b), and 1 to 10% by weight of one or more of the components of group c) based on the weight of groups a)+b)+c). In another embodiment of said aspect, the chemical composition further comprises one or more components of the group comprising magnesium oxide and calcium oxide.

In another embodiment of said aspect, the chemical composition further comprises one or more components of the group comprising magnesium hydrogen phosphate, magnesium sulfate, and sodium carbonate.

The system for constructing a pavement on a soil allows that the soil onto which the geosynthetic material is to be applied is not stabilization by addition of a stabilizing composition. In particular, the soil onto which the geosynthetic material is to be applied does not comprise a chemical composition for stabilization of the soil.

The present invention relates in an aspect to a pavement construction comprising at least a soil (1 ), a geosynthetic material (5) applied on the soil (1 ), a base layer (6) applied on the geosynthetic material (5), and a top layer (9,1 1 ,12) comprising a soil composition, a cement, and a chemical composition, the chemical composition comprising

a) one or more components, selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride and ammonium chloride, and

b) aluminum chloride, and

c) one or more components, selected from the group consisting of silica, zeolite and apatite.

In an embodiment, the top layer (9) is formed by mixing a cement and a chemical composition with an upper part of the base layer, said upper part of the base layer being the soil composition; said top layer (9) forming the upper part of the base layer (6).

In another embodiment, the top layer (1 1 ) is formed by mixing a cement, a chemical composition with a soil composition; said top layer (1 1 ) being applied on the base layer

(6).

In another embodiment, the top layer (12) is formed by mixing a cement, a chemical composition, and water with a soil composition; said top layer (12) being applied on the base layer (6). In an embodiment of said aspect, the geosynthetic material is selected from the group consisting of a geotextile, preferably a woven or knitted fabric, and/or a geogrid, preferably a rigid biaxial geogrid or a composite of a geogrid, preferably having a high stiffness with a nonwoven. In this embodiment, with high stiffness is meant a secant modulus of at least 200 kN/m at 3% strain, as determined in accordance with test method EN ISO 10319:2015. In another embodiment of said aspect, the geosynthetic material has a secant modulus of at least 200 kN/m, or at least 300 kN/m, preferably at least 500 kN/m, more preferably at least 1000 kN/m, most preferably at least 2000 kN/m at 3% strain, as determined in accordance with test method EN ISO 1031 9:201 5. In another embodiment of said aspect, the geosynthetic material comprises a plurality of strips or yarn made from one or materials having a modulus of at least 10 GPa, preferably at least 30 GPa, more preferably at least 50 GPa, as determined according to test method ASTM D2256/D2256M - 10(2015). In another embodiment of said aspect, the geosynthetic material is a geocomposite material comprised of a geotextile and/or a geogrid and at least one further material, preferably a perforated film or a nonwoven material, which further material is connected to the geotextile and/or the geogrid. In another embodiment of said aspect, the chemical composition comprises 45 to 90% by weight of one or more of the components of group a), 1 to 10% by weight of the component of group b), and 1 to 10% by weight of one or more of the components of group c) based on the weight of groups a)+b)+c). In another embodiment of said aspect, the chemical composition further comprises one or more components of the group comprising magnesium oxide and calcium oxide. In another embodiment of said aspect, the chemical composition further comprises one or more components of the group comprising magnesium hydrogen phosphate, magnesium sulfate, and sodium carbonate.

In an embodiment, the soil of the pavement construction onto which the geosynthetic material is applied does not comprise a stabilizing composition. In particular, the soil of the pavement construction onto which the geosynthetic material is applied does not comprise a chemical composition for stabilization of the soil.

The present invention relates in an aspect to a method for constructing a pavement on a soil comprising the steps of:

i) applying a geosynthetic material (5) on a soil (1 ); ii) applying a layer of a base material on the geosynthetic material (5) to form a base layer (6);

iii) applying a preloading layer (7) to the base layer (6) for preloading the base layer;

iv) removing the preloading layer (7) from the base layer (6);

v) apply a top layer (9,1 1 ,12) comprising a soil composition, a cement and a chemical composition, said chemical composition comprising

a) one or more components, selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride and ammonium chloride, and

b) aluminum chloride, and

c) one or more components, selected from the group consisting of silica, zeolite and apatite,

vi) allowing the top layer (9,1 1 ) to harden by chemical stabilization;

vii) optionally applying a surface layer (10) to said top layer (9,1 1 ,12) and allowing said surface layer to harden or hardening said surface layer (10);

to form a pavement construction on a soil (1 ).

In an embodiment, the method comprises a step o) prior to step i), said step o) comprising providing a soil, said step o) comprising one of the following sub steps:

oa) starting with a soil comprising a top soil (3) and a sub soil (2) and removing the top soil (3) from sub soil (2) to provide soil (1 ) thereby reducing the existing level of the soil and optionally leveling the soil (1 );

ob) starting with a soil comprising a top soil (3) and a sub soil (2) and optionally leveling said top soil (3) to provide soil (1 ) thereby keeping the existing level of the soil; or oc) starting with a soil comprising a top soil (3) and a sub soil (2) and adding extra soil (4) to the top soil (3) and optionally leveling said extra soil (4) to provide soil (1 ) thereby increasing the existing level of the soil.

It is also possible to add another layer on top of the soil prior to the application of the geosynthetic material. It is also possible to apply a vertical drainage, prior to the application of the geosynthetic material.

In another embodiment, step iii) comprises the following sub steps of: iiia) applying a preloading layer (7) to the base layer (6) with a substantial equal thickness (over the axial direction) of the soil (1 );

iiib) allowing the preloading (7) to density and settle the soil (1 ) and create settling for a certain amount of time;

iiic) redistributing the preloading layer (7) on the base layer (6) with an uneven thickness (over the axial direction) of the soil (1 ), preferably with a larger thickness in the center of the base layer (6);

iiid) allowing the preloading (7) to density the soil (1 ) for a certain amount of time and tensioning the geosynthetic material due to the non-homogeneous densification of the soil (1 ).

Preferably, the tension on the geosynthetic material after preloading is at least 2 kN/m, more preferably at least 4 kN/m, even more preferably at least 10 kN/m.

In another embodiment, step iii) comprises the following sub steps:

iiic') applying a preloading layer (7) to the base layer (6) with an uneven thickness (over the axial direction) of the soil (1 ), preferably with a larger thickness in the center of the base layer (6);

iiid) allowing the preloading (7) to density the soil (1 ) for a certain amount of time and tensioning the geosynthetic material due to the non-homogeneous densification of the soil (1 ).

In another embodiment, steps v) and vi) of applying a top layer (9) comprises the following (sub) steps:

va) applying a cement and a chemical composition (8) or a mixture thereof on base layer (6);

vb) mixing the cement and the chemical composition (8) with the soil material to form an mixed upper part of the base layer (9a);

vc) applying water to the mixed upper part of the base layer (9a) to form a wetted upper part of the base layer (9b); and

vi) allowing the wetted upper part of the base layer (9b) to harden by chemical stabilization to form top layer (9). In another embodiment, steps v) and vi) of applying a top layer (1 1 ) comprises the following (sub) steps:

vd) applying a mixture (1 1 a) for forming a top layer said mixture comprising a cement, a chemical composition and a soil composition;

ve) applying water to the mixture (1 1 a) to form a wetted mixture (1 1 b) for forming a top layer; and

vi) allowing the wetted mixture (1 1 b) to harden by chemical stabilization to form top layer (1 1 ).

Step vb) of mixing the cement and the chemical composition (8) with the soil material to form an mixed upper part of the base layer (9a) preferably comprises first mixing the chemical composition (8) with the soil material and subsequently mixing the cement with the soil material - already including the chemical composition.

In another embodiment, wherein steps v) and vi) of applying a top layer (12) comprises the following (sub) steps:

vf) applying a complete mixture (12a) for forming a top layer said mixture comprising a cement, a chemical composition, water and a soil composition;

vi) allowing the complete mixture (12a) to harden by chemical stabilization to form top layer (12).

In an embodiment of said aspect, the geosynthetic material is selected from the group consisting of a geotextile, preferably a woven or knitted fabric, and/or a geogrid, preferably a rigid biaxial geogrid or a composite of a geogrid, preferably having a high stiffness with a nonwoven. In this embodiment, with high stiffness is meant a secant modulus of at least 200 kN/m at 3% strain, as determined in accordance with test method EN ISO 1031 9:201 5. In another embodiment of said aspect, the geosynthetic material has a secant modulus of at least 200 kN/m, or at least 300 kN/m, preferably at least 500 kN/m, more preferably at least 1000 kN/m, most preferably at least 2000 kN/m at 3% strain, as determined in accordance with test method EN ISO 1031 9:201 5. In another embodiment of said aspect, the geosynthetic material comprises a plurality of strips or yarn made from one or materials having a modulus of at least 10 GPa, preferably at least 30 GPa, more preferably at least 50 GPa, as determined according to test method ASTM D2256/D2256M - 10(2015). In another embodiment of said aspect, the geosynthetic material is a geocomposite material comprised of a geotextile and/or a geogrid and at least one further material, preferably a perforated film or a nonwoven material, which further material is connected to the geotextile and/or the geogrid. In another embodiment of said aspect, the chemical composition comprises 45 to 90% by weight of one or more of the components of group a), 1 to 10% by weight of the component of group b), and 1 to 10% by weight of one or more of the components of group c) based on the weight of groups a)+b)+c). In another embodiment of said aspect, the chemical composition further comprises one or more components of the group comprising magnesium oxide and calcium oxide. In another embodiment of said aspect, the chemical composition further comprises one or more components of the group comprising magnesium hydrogen phosphate, magnesium sulfate, and sodium carbonate.

The method for constructing a pavement on a soil does not require stabilization of the soil onto which the geosynthetic material is applied.

In an embodiment, the method for constructing a pavement on a soil does not include a step of applying a stabilizing composition to the soil onto which the geosynthetic material is applied. In particular, the method for constructing a pavement on a soil does not include a step of applying a chemical composition to the soil onto which the geosynthetic material is applied.

Detailed description of aspects and embodiments

First aspect - system

The first aspect of the present teaching relates to a system for constructing a pavement on a soil. The present system comprising at least two components that are to be used in the construction of the pavement. The first component being a geosynthetic material. The second component being a chemical composition, comprising: a) one or more components selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride and ammonium chloride, and b) aluminum chloride, and; c) one or more components selected from the group consisting of silica, zeolite and apatite. The system according to the present teachings may be considered a kit of parts. In another words, this aspect relates to a system for constructing a pavement on a soil, said system comprising a geosynthetic material and a chemical composition, said chemical composition comprising a) one or more components, selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride and ammonium chloride, and b) aluminum chloride, and; c) one or more components, selected from the group consisting silica, zeolite and apatite, wherein said geosynthetic material is to be applied on a soil and beneath a base layer for increasing the stiffness of said base layer, and wherein said chemical composition is used together with a cement composition for hardening / chemical stabilization of a top layer and wherein said pavement comprises the combination of a geosynthetic material, a mechanically stabilized base layer and a chemically stabilized top layer.

By in-situ chemical stabilization of the top layer with the chemical composition comprised in the system according to the invention, the in-situ stabilized top layer enables to distribute the load applied by traffic over a relative thin pavement construction. The load applied by traffic is distributed to the soil in such a way that it prevents, or at least reduces, deformation of the pavement and/or prevents, or at least reduces, the formation of structural cracks in the pavement.

The thickness of the top layer is reduced due to presence of a geosynthetic material on the soil, reducing the secondary settling during a prolonged period of time and preventing, or at least reducing, the deformation of the pavement and/or the formation of structural longitudinal cracks in the pavement. The inventive system for constructing a pavement on a soil thereby provides the possibility to develop areas with a weak soil, for example for urbanization.

Geosynthetic material

The geosynthetic material comprised in the present system for constructing a pavement on a soil increases the stiffness of the base layer before providing in-situ chemical stabilization of the top layer, which allows for a reduction in thickness of the top layer to be hardened, thereby providing a synergistic effect with the chemical composition comprised in the inventive system for constructing a pavement on a soil thereby significantly reducing the time required for hardening due to accelerated hardening of the top layer. Moreover, the geosynthetic material decreases and distributes tensions in the base layer and therefore decreases the chance of cracks occurring in the pavement.

Preferably, the tension on the geosynthetic material after preloading is at least 2 kN/m, more preferably at least 4 kN/m, even more preferably at least 10 kN/m.

The geosynthetic material comprised in the system for constructing a pavement on a soil may be any suitable geosynthetic material, but preferably is a geotextile (for example a woven fabric) or a geogrid (for example a rigid biaxial geogrid of oriented extruded strips or yarns). In case the geosynthetic material is a geotextile, the geotextile preferably is a woven fabric as woven fabrics can be manufactured having a high modulus.

Component materials for the strips or yarns making up the geotextile may be e.g. polymeric or inorganic. Examples of polymeric component materials are polymers, such as polyester, aramid, such as for example Twaron ^® or Kevlar ^® , UHMWPE (Ultra High Molecular Weight PolyEthylene), such as for example Dyneema ^® , and PVA (polyvinylalcohol). Examples of inorganic component materials are inorganics, such as glass, e.g. E-glass ((alumino-borosilicate (fiber) glass), and basalt.

For example a polyester yarn may be used having a modulus of between 10 and 30 GPa. An aramid yarn may be used having a modulus of between 60 and 120 GPa. An UHMWPE may be used having a modulus of between 50 and 140 GPa. An E-Glass may be used having a modulus of between 70 and 80 GPa. PVA (PolyVinylAlcohol) may be used having a modulus of between 25 and 50 GPa. Basalt may be used having a modulus of between 80 and 100 GPa. One or more combinations may also be used.

The geosynthetic material preferably has a secant modulus at 3% strain, as determined in accordance with test method EN ISO 10319:2015, preferably at least 200 kN/m, most preferably at least 300 kN/m, preferably at least 500 kN/m, more preferably at least 1000 kN/m, most preferably at least 2000 kN/m to enable an effective stiffening of the soil.

These component materials may be used in the form of strips or yarns or may be used in another suitable form. The number of strips or yarns comprised in the geotextile or in the geogrid may vary depending on the selected material for the strips or yarns, the fineness of the strips or yarns and/or the desired modulus of the geotextile or the geogrid, but preferably the number of strips or yarns in longitudinal direction of the geotextile or the geogrid is at least 1 per 10 cm to 150 per 10 cm. The fineness of the strips or yarns may vary, but preferably ranges from 100 to 24,000 dtex. The unit dtex defines the fineness of the strips or yarns in grams per 10000 meter.

The strips or yarns may have a modulus of at least 10 GPa, preferably at least 30 GPa, more preferably at least 50 GPa, as determined according to test method ASTM D2256/D2256M - 10(2015).

The geosynthetic material may be a geocomposite material comprised of a geotextile and/or a geogrid and at least one further material, preferably a perforated film or a nonwoven material, which further material is connected to the geotextile and/or the geogrid. The connection may be carried out by known means, for example thermal bonding, adhesive bonding and/or mechanical bonding. The at least one further material may prevent distortion of the geotextile and/or the geogrid during handling and/or installation.

The geosynthetic material preferably is water permeable to allow drainage of for example rain water through the geosynthetic material.

The geosynthetic material preferably has a weight in the range of 50 to 2000 g/m ² , more preferably in the range of 100 to 1750 g/m ² . The thickness of the geosynthetic material depends on the desired use but is preferably at least 1 millimeter.

Chemical composition

The chemical composition comprised in the present system for constructing a pavement on a soil exhibits accelerated in-situ hardening over other prior art chemical compositions for in-situ hardening of top layers. The chemical composition hardens the cement and top layer. Furthermore, without being bound by theory it is believed that the chemical composition comprised in the present system for constructing a pavement on a soil forms crystalline structures in the top layer providing increased stiffness, reduction of shrinkage, improved fatigue properties, increased compressive strength and/or increased tensile strength in the top layer. The crystalline structures are well bonded together and are homogeneously distributed, in between the cement and soil particles, and thereby bind the cement particles. Hardened cement/soil which is prepared without this binder or with known binders has a relatively open structure when viewed on a microscopic scale, with crystalline agglomerations which are not homogeneously distributed and poor. The crystalline compounds which are formed by the present chemical composition results in an optimum strength and stability. The water in the cement is bound in and to the crystalline structures. Consequently, there are no local concentrations of water, and therefore the formation of potential weak spots is avoided. By the use of said chemical composition the thickness of the upper part of the base layer to be hardened may be reduced thereby requiring a lower amount of chemical composition and cement and reducing the time required for hardening compared to the use of only cement of prior art chemical compositions. The time required for hardening is firstly reduced because the thickness is reduced and secondly due to accelerated hardening by the chemical process involved.

Due to the reduced thickness of the pavement construction and the reduced weight of the material of the pavement construction, the amount of primary settling in the consolidation phase of pavement construction is reduced significantly as compared with traditional pavement constructions on a soil, in particular on a weak soil. Furthermore, secondary settling due to loading over a prolonged period of time is reduced as the total weight of the pavement providing a load on the soil is reduced. The application of the geosynthetic material on the soil enables that the thickness of the top layer which has to be chemically stabilized can be reduced and/or that lifetime of the pavement is increased due to an increased resistance against secondary consolidation during the structural life time of the pavement construction.

In an embodiment, the chemical composition comprises 45 to 90% by weight of one or more of the components of group a), 1 to 10% by weight of the component of group b), and 1 to 10% by weight of one or more of the components of group c) based on the weight of groups a)+b)+c).

In an embodiment of the chemical composition, the total quantity of components from group a) is approx. 80 to 98% by weight, the total quantity of components from group b) is approx. 1 to 10% by weight, and the total quantity of components from group c) is approximately 1 to 10% by weight, based on the total weight of a) + b) + c).

The different components of the chemical compositions are disclosed in more detail below. More information regarding this chemical composition is to be found EP1349819 which information is incorporated by reference.

Group a. of components in the chemical composition comprised in the system for constructing a pavement on a soil preferably comprises a combination of sodium chloride and calcium chloride. In particular, the composition according to the invention comprises a combination of sodium chloride, potassium chloride, magnesium chloride, calcium chloride and ammonium chloride.

Group c. of components in the chemical composition comprised in the system for constructing a pavement on a soil preferably comprises zeolite based on a combination of aluminum and silica. The silica is preferably amorphous silica. Preferably, the zeolite is a composite comprising natural zeolite (45%), alkali feldspar (32%), agriniaugite (10%), wollastonite (9%), calcite (1 %), gotzenite (1 %), melanite, apatite, titanite (2%).

In an embodiment, the chemical composition further comprises one or more components of the group comprising magnesium oxide and calcium oxide.

In an embodiment, the chemical composition further comprises one or more components of the group comprising magnesium hydrogen phosphate, magnesium sulfate, and sodium carbonate.

A preferred composition comprises at least sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, aluminum chloride, magnesium oxide, silica and/or zeolite. The overall chemical composition advantageously contains a combination of components comprising:

a. sodium chloride, potassium chloride, ammonium chloride, magnesium chloride and calcium chloride;

b. aluminum chloride

c. silica

d. magnesium oxide

e. magnesium monohydrogen phosphate

f. magnesium sulfate and sodium carbonate.

Specific embodiments are disclosed in EP1349819, especially paragraphs [0016] and [0017] which are incorporated by reference into this application.

The chemical composition may be prepared by combining the required components of groups a), b), c), and optionally others and dry-mixing them. The composition according to the invention is preferably assembled from the abovementioned components in pure form (> 97%). If appropriate, salts including bound water of crystallization, are incorporated to facilitate processing.

As hydraulic cement (a water-hardening cement) according to the cement standards may be used. The cement standards according to European standard NEN-EN-197-1 are as follows: CEM I is Portland cement; CEM II is composite Portland cement; CEM III is blast furnace slag cement; CEM IV is puzzolane cement and CEM V is composite cement. Preferably, CEM III is used.

The amount of chemical composition mixed in the top layer may vary depending on the desired stiffness, compressive strength and/or tensile strength in the top layer, but preferably the amount of chemical composition the top layer ranges from 0.5 to 2.5 kg per m ³ of the upper part of the base layer. The cement composition is preferably used in an amount of between 60 and 200 kg of cement per m ³ of the upper part of the base layer that is to be hardened. It should be noted that the amount (in m ³ ) of upper part of the base layer is determined by the thickness of the upper part of the base layer (in other words the depth to which the chemical composition and cement compositions are mixed in). Second aspect - pavement construction

A second aspect of the present teachings is related to a pavement construction on a soil. The pavement construction comprising - from the bottom/ground up - a soil (1 ), a geosynthetic material (5), a base layer (6), a top layer (9,1 1 ,12), and optionally a surface layer (10). The top layer (9,1 1 ,12) comprises a soil composition, the cement disclosed in the first aspect, and the chemical composition disclosed in the first aspect.

Soil

The system for constructing a pavement on a soil according to the invention is especially useful for application on a weak soil, e.g. having a California Bearing Ratio (CBR) of 2.5% or less, or a Deformation Modulus (E _v2 ) of 12 MPa or less. The system is in particular useful for paving a soil having a CBR of 1 % or less, of a E _v2 of 10 MPa or less. The California Bearing Ratio is determined according to test method ISO 1377 part 9. The Deformation Modulus (Ev2) is determined by a plate loading test (PLT), this test method is included in Eurocode 1997-2 and also in preceding ISO 1377 part 9.

Base layer

The base layer is a layer of a granular material, preferably a soil material. The layer of base material applied on top of the geosynthetic material may comprise a range of different materials, but preferably comprises sand and/or gravel (both considered to be soil materials). The base layer - when compacted - forms in conjunction with a geosynthetic material a mechanically stabilized layer. The thickness of the base layer - after densification - depends on the desired use and the method used. When the method according to the present invention is used wherein the chemical composition and cement are mixed into the upper part of the base layer, the thickness of the upper part of the base layer into which these components are mixed (and which will form the top layer) preferably is between 20 and 55 cm depending on use of the payment. In this case the total thickness of the base layer is between 30 and 100 cm, preferably at least 10 to 20 cm more than the thickness of the upper part. In other words, there preferably is a separation between the geosynthetic material and the stabilizing top layer of at least 10 to 20 cm. Preferably, there is a substantial constant thickness of the base layer in axial directly and preferably also in longitudinal direction. Preloading layer

The thickness of the preloading layer depends on the desired settling that needs to be achieved prior to constructing the stabilization layer and can be determined by the person skilled in the art on the stability/weakness of the subsoil, the thickness and type of base layer and the type of preloading material.

Top layer

The top layer always comprises a soil composition, cement and a chemical composition and water for hardening. There are several ways the top layer may be added, depending on the circumstances. Three of these are disclosed below in more detail.

In an embodiment, the top layer (9) is formed by mixing a cement and a chemical composition with an upper part of the base layer. No additional soil is added, the cement and chemical composition are applied on the base layer and mixed in with upper part thereof. Said top layer (9) forming the upper part of the base layer (6).

In another embodiment, the top layer (1 1 ) is formed by mixing a cement, a chemical composition with a soil composition; said top layer (1 1 ) being applied on the base layer (6). In this case additional soil is added increasing the thickness of the final pavement. A dry mix is applied on the base layer and water is applied in a second step.

In another embodiment, the top layer (12) is formed by mixing a cement, a chemical composition, and water with a soil composition; said top layer (12) being applied on the base layer (6). In this case additional soil is added increasing the thickness of the final pavement. A wet - ready to use - mix is applied on the base layer which can be hardened directly.

The thickness of the top layer may vary depending on expected intensity of traffic, but preferably ranges from 20 to 55 cm.

Surface layer

On top of the top layer optionally a surface layer may be applied, for example in the form of an asphalt layer, a layer of gravel or a layer of cobble stones. The thickness of the surface layer may vary depending on expected intensity of traffic, but preferably ranges from 4 and 20 cm.

Third aspect - method

In a third aspect the present teachings relate to a method for constructing a pavement on a soil. This method comprises several steps that are carried out in consecutive order. Each of these steps is discussed in more detail below.

The construction time for forming the pavement can be reduced as the combination of the geosynthetic material on the soil and the chemical composition mixed in the top layer provides a synergistic effect with results such that the thickness of the top layer can be significantly reduced, thereby reducing the hardening time and reducing the time required for primary settling of the pavement construction. Alternatively, the amount of base material applied on the soil for primary settling can be reduced and/or the preloading time can be reduced considerably, thus requiring a lower amount of truck movements during construction.

Step o) providing a soil

This step comprises the provision of a soil which is to be used to construct the pavement. In an embodiment, it is a terrain having a certain width and length, e.g. a width of several (tens of) meters and a length of several hundreds of meters to several (tens or hundreds) kilometers. This step is an optional step, the soil may be already be present when the pavement is to be constructed. The soil may or may not require leveling prior to the construction of a pavement. Said leveling may be carried out by methods known by a person skilled in the art using known equipment. This step o) is carried out prior to step i).

In a first embodiment of step o) which is called step oa) the provision of soil entails the following. Step oa) starting with a soil comprising a top soil (3) and a sub soil (2) and removing the top soil (3) from sub soil (2) to provide soil (1 ) thereby reducing the existing level of the soil and optionally leveling the soil (1 ). This step may be carried out when the level of soil is too high or whether the top soil is such that it cannot be used as base for a pavement construction. This might lead to raised pavement, a level pavement or a deepened pavement depending on the depth of excavation and the thickness of the optional layer of base material and the thickness of the top layer. In a second embodiment of step o) which is called step ob) the provision of soil entails the following. Step ob) starting with a soil comprising a top soil (3) and a sub soil (2) and optionally leveling said top soil (3) to provide soil (1 ) thereby keeping the existing level of the soil. This step does not require any action other than optionally the leveling in case required.

In a third embodiment of step o) which is called step oc) the provision of soil entails the following. Step oc) starting with a soil comprising a top soil (3) and a sub soil (2) and adding extra soil (4) to the top soil (3) and optionally leveling said extra soil (4) to provide soil (1 ) thereby increasing the existing level of the soil. This step may be carried out when the level of soil is too low or whether the top soil is such that it cannot be used as base for a pavement construction and hence another additional layer of soil is added. This will lead to a raised pavement. The soil that is added as extra soil may be any type of soil but is preferably sand.

Step i) : applying a geosynthetic material on a soil

This step relates to applying a geosynthetic material onto the soil. The geosynthetic material may also be provided in the form of rolls. This is particular suitable for covering larger areas. More information about the application of the geosynthetic material can be found in the Handbook of Geosynthetic Engineering; Sanjay Kumar Shukla, second revised edition 201 1 (ISBN13 9780727741752).

Step ii) applying a layer of a base material on the geosynthetic material to form a base layer

In this step a base layer is applied on top of the geosynthetic material. The base layer may be selected according to the several aspects of said base layer and base layer material that are disclosed above. The base layer may be applied and compacted by equipment known to a person skilled in the art.

Step iii) applying a preloading layer to the base layer for preloading the base layer

In this step a layer of preloading material is provided on top of the base layer. The reason for this is that it compacts/densities the soil as well as the base layer; this is also called consolidation. This densification allows a more stable/solid underground to apply the top layer. This also allows for a better diversion of forces from the traffic that is to use the pavement construction.

The layer of preloading material also pre-loads or tensions the geosynthetic material. Preloading of the geosynthetic material instantly increases the stiffness of the system comprising an interacting base layer and geosynthetic material by means of lateral restraint of the soil particles in the base layer, and as a result the bearing capacity and the serviceability/durability of the pavement construction is improved.

Preferably, the tension on the geosynthetic material after preloading is at least 2 kN/m, more preferably at least 4 kN/m, even more preferably at least 10 kN/m.

Consolidation is a process that takes a certain amount of time. The present invention allows this time to be significantly reduced since due to the synergetic combination of mechanical stabilization using the geosynthetic material below the base layer and chemical stabilization using cement and the chemical composition above the base layer, the base layer can have reduced thickness compared to prior art base layers. When the thickness of the base layer is reduced, the time needed for preloading is also decreased. This is clear advantage of the present invention. The preloading layer may be applied by equipment known to a person skilled in the art.

In order to obtain maximum benefit of the geosynthetic material it needs to be brought to tension. When the geosynthetic material is applied/laid on the soil and the base layer is applied on top of the geosynthetic material, there is no significant tension in the geosynthetic material because of the substantial uniform axial thickness of the base layer. In order to assert increased tension on the geosynthetic material, an uneven preload is required. When for example the center of the soil (in axial direction), which for example will be the centerline of the road formed, is provided with a larger preload, the soil in this area will density more than the soil on the respective edges. A central trough occurs which is clearly shown in the drawings (see below). This allows the tensioning of the geosynthetic material.

This step iii) of preloading may be carried out in several manners, two specific embodiments of which are discussed below. In a first embodiment, step iii) comprises the following sub steps of:

iiia) applying a preloading layer (7) to the base layer (6) with a substantial equal thickness over the axial direction of the soil (1 );

iiib) allowing the preloading (7) to density the soil (1 ) for a certain amount of time; iiic) redistributing the preloading layer (7) on the base layer (6) with an uneven thickness over the axial direction of the soil (1 ), preferably with a larger thickness in the center of the base layer (6);

iiid) allowing the preloading (7) to density the soil (1 ) for a certain amount of time and tensioning the geosynthetic due to the non-homogeneous densification of the soil (1 ).

Preferably, the tension on the geosynthetic material after preloading is at least 2 kN/m, more preferably at least 4 kN/m, even more preferably at least 10 kN/m.

This embodiment firstly has a uniform densification and in a second step a non-uniform densification.

In a second embodiment, step iii) comprises the following sub steps:

iiic') applying a preloading layer (7) to the base layer (6) with an uneven thickness over the axial direction of the soil (1 ), preferably with a larger thickness in the center of the base layer (6);

iiid) allowing the preloading (7) to density the soil (1 ) for a certain amount of time and tensioning the geosynthetic material due to the non- homogeneous densification of the soil (1 ).

This embodiment only has a non-uniform densification. Step iv) removing the preloading layer from the base layer

In this step the preloading layer is removed when sufficient densification and tensioning of the geosynthetic material has taken place. The preloading layer may be removed by equipment known to a person skilled in the art. Preferably, the tension on the geosynthetic material is maintained after removing the preloading layer from the base layer. Maintaining the tension on the geosynthetic material after removing the preloading layer from the base layer can be achieved by granular material comprised in the base layer. By properly selecting the type of granular material and/or the dimensions of the granular material, movement of the geosynthetic material leading to a reduction of the tension on the geosynthetic material can be prevented, or at least reduced, by means of granular interlock and/or friction between the granular material and the geosynthetic material.

The granular material comprised in the layer of base material applied on top of the geosynthetic material may comprise a range of different materials, but preferably comprises sand and/or gravel.

Step v) apply a top layer comprising a soil composition, a cement and a chemical composition

In this step a top layer is applied to the densified base layer. The top layer comprises of a soil composition, a cement and a chemical composition and requires water for hardening. There are several embodiments for this step that are each discussed in more detail below.

The chemical composition can be mixed in-situ with the cement composition and applied to the base layer or the separate components (chemical composition, cement composition etc.) may be applied separately to the base layer. After the application of the (mixture) of materials the materials are mixed with an upper part of the base layer, e.g. by mechanical means. The thickness of the upper part of the base layer that is mixed with the materials depends on the desired use and the weight of the traffic is preferably between 20 and 55 centimeters. This is the thickness that will ultimately be the top layer. For example for a piling map or airport the thickness should be higher than for a bike path or road.

In the embodiment, wherein in step vb) first the chemical composition is mixed with the soil material of the upper part of the base layer and subsequently the cement is mixed with the soil material already including the chemical composition is carried out the following is observed. When the thickness of the upper part of the base layer into which the components are to be mixed is considered to be 100%, the chemical composition may be mixed into the soil for between 50 and 100%, preferably between 70 and 85%, of the thickness of the upper layer and the cement is mixed in to 100%. In other words, the chemical composition may be mixed in to a somewhat lower depth than the cement. Water is required in order for the chemical composition and the cement to form a top layer. Water may be added after the chemical composition and cement have been added to and mixed with the upper part of the base layer. Otherwise, water may be added anywhere during the addition of the different materials to the upper part of the base layer and mixing. Fresh water or salt (sea) water or brine water may be used.

The chemical composition may also be added as a suspension, e.g. after the cement composition has firstly been applied. Or firstly a suspension of the chemical composition is added and mixed in (cut) to the desired depth after which cement in dry form is added and cut to the desired depth. Preferably, after all components have been added and mixed, the upper part of the base layer is compacted using e.g. a suitable roller and optionally profiled using a grader after which the hardening will commence. During the hardening it may be required to add additional water to prevent cracking.

The present system of geosynthetic material an chemical composition is suitable for all these different applications.

In a first embodiment, step v) comprises the following sub steps:

va) applying a cement and a chemical composition (8) or a mixture thereof on base layer (6);

vb) mixing the cement and the chemical composition (8) with the soil material to form an mixed upper part of the base layer (9a);

vc) applying water to the mixed upper part of the base layer (9a) to form a wetted upper part of the base layer (9b).

In this embodiment, the cement and the chemical composition (both of which have been described in detail above) are applied on top of the base layer, e.g. by sprinkling or by other means, either manually or by equipment known to a person skilled in the art. The cement and chemical composition may be applied separately or pre-mixed.

After the component have been applied, the upper part of the base layer (which is considered to be the soil composition in this embodiment) is mixed with these components. Mixing can be carried out with equipment known to a person skilled in the art. Next, water is applied, e.g. by spraying, to activate the cement and chemical composition to start the hardening process.

In a second embodiment, step v) comprises the following sub steps:

vd) applying a mixture (1 1 a) for forming a top layer said mixture comprising a cement, a chemical composition and a soil composition;

ve) applying water to the mixture (1 1 a) to form a wetted mixture (1 1 b) for forming a top layer; and

The difference with the first embodiment is that in this case the soil composition is added and not taken as the upper part of the base layer. In this embodiment an extra layer is applied which is pre-mixed soil, cement and chemical composition. The following step of applying water is the same as in the first embodiment. A forced mixer may be used which first mixes the components into a homogenous mixture and said mixture is then e.g. transferred via a conveyor belt to a suitable means of transport, such as a lorry. This means of transport transports the ready mix to the location line which is to be stabilized or immobilized. At the location line, the mixture is distributed over a suitable thickness.

In a third embodiment, step v) comprises the following sub step:

vf) applying a complete mixture (12a) for forming a top layer said mixture comprising a cement, a chemical composition, water and a soil composition;

This step is in fact a modification of the second embodiment where water is added to the mixture including soil, cement and chemical composition prior to the application on the base layer.

Step vi) allowing the top layer to harden by chemical stabilization;

This step relates to the chemical hardening of the cement and chemical composition under the influence of water. This step takes a certain period of time. The time is considerable reduced compared to prior art road construction using only chemical stabilization. Due to the synergistic combination of mechanical and chemical stabilization, the thickness of the top layer may be reduced which in turn leads to a reduction in the hardening time of the top layer. The hardening of the top layer usually takes a number of days to about a month, for example 7 to 28 days, and depends on the thickness and type of material that is used for the base layer. For example, if sand is used as the material of the base layer, a hardening period of about 7 days will suffice, whereas a hardening period of up to 28 days may be required in the case of the presence of, for example, organic material. In addition to that, the amount of water plays a part in connection with the hardening period, with the hardening time increasing as the amount of water increases.

Step vii) applying a surface layer to the top layer

In this optional step an additional layer of e.g. concrete, stone or asphalt may be applied on top of the top layer for added strength or appearance.

Detailed description of drawings

Figures 1 -3 show several embodiments of the construction of a pavement according to the present invention. It should be noted that these are example embodiments and the invention is not limited to the embodiments disclosed in the description.

In figure 1 , the following is observed. Figure 1 b shows a soil 1 on which the pavement construction according to the present teachings is to be applied. The soil 1 is shown in cross section and may be a stretch of land for a road. The soil 1 may be obtained by either removing a top soil 3 from a subsoil 2 in order to decrease the level prior to application of the pavement construction (see step oa) in Figure 1 a). In another embodiment soil 1 is a combination of a subsoil 2 and a top soil 3 as is present on the site. No additional pre-work is needed; (see step Ob) in Figure 1 a). In another embodiment it may be required to increase the level and in this case extra soil 4 may be applied on top of the subsoil 2 and top soil 3 in order to arrive at soil 1 that is the basis for the pavement construction (see step 0c) in figure 1 a).

After the soil 1 has been optionally leveled the first step of the present method is step i) of applying a geosynthetic material 5 (Figure 1 c). This geosynthetic material is laid on top of the soil 1 .

The next step in the present method is step ii) applying a layer of base material on the geosynthetic material 5 to form a base layer 6 (Figure 1 d). Subsequently, in step iiia) a preloading layer is applied (Figure 1 e) with a uniform thickness in axial direction. After a certain predetermined period of time passes which allows the preloading layer to density the soil and base layer (Figure 1 f), the preloading layer is redistributed so that the thickness thereof is uneven (Figure 1 g). An embodiment thereof shown in Figure 1 g, wherein the thickness of the preloading layer in the center of the base layer is higher than on both edges thereof. However other embodiments are also possible, e.g. were the thickness of the preloading layer is higher or one of the edges or both of the edges. After a certain predetermined period of time passes which allows the preloading layer to further density/consolidate the soil (figure 1 h) a "trough" may be observed in the soil 1 and the geosynthetic material 5. This is due to the difference in weight in the center of the base layer and on the edges as a result of which the soil is compressed more in the center which stretches the geosynthetic material and allows the geosynthetic material to be tensioned ensuring sufficient stiffness. It should be noted that the drawings are not to scale and the tensioning of the geosynthetic material which is shown by a sagging of the geosynthetic material into the soil is exaggerated. The top of the base layer is substantially even. In another embodiment it may be considered to skip the steps shown in Figures 1 d and 1 c and apply the preloading layer directly with an uneven preloading.

After the preloading is sufficient, the preloading layer is removed (step iv Figure 1 i). Then, a top layer is applied according to a first embodiment. In this embodiment a mixture of at least cement and the chemical composition 8 is applied (e.g. sprinkled) on top of the base layer (Figure 1 i). The cement and chemical composition are mixed with the upper part of the base layer to form a mixed upper part of the base layer 9a (Figure 1 k). The cement and chemical composition are then activated by the addition (e.g. spraying) of water which is shown in Figure 1 1. This addition of water may for example be carried out by spraying to form the wetted upper part 9b being a mixture of the material of the base layer, cement, chemical composition and water.

The next step is the hardening of the wetted layer 9a to form top layer 9 (figure 1 m). A pavement construction is formed, consisting of a geosynthetic material, a base layer, and a top layer.

Optionally an additional surface layer is added on top of said hardened upper part of the base layer which optional surface layer 10 is shown in Figure 1 n. In another embodiment of the application of a top layer is shown in Figure 2. Figure 2a corresponds to Figure 1 h, being soil 1 with the tensioned geosynthetic material 5 and base layer 6. On top of the base layer 6 a dry mixture 1 1 a of a soil composition, cement and chemical composition is added (Figure 2b) which layer is wetted by application of water to form a wetted layer 1 1 b (Figure 2c). This wetted layer is then hardened to form top layer 1 1 (Figure 2d) after which optionally a surface layer 10 may be added (Figure 2e).

In yet another embodiment of the application of a top layer is shown in Figure 3. Figure 3a corresponds to Figure 1 h, being soil 1 with the tensioned geosynthetic material 5 and base layer 6. On top of the base layer 6 a wet -ready to use mixture 12a of a soil composition, water, cement and chemical composition is added (Figure 3b). This layer is then hardened to form top layer 12 (Figure 2c) after which optionally a surface layer 10 may be added (Figure 2d).

The invention is as defined in the claims.

Soil

Subsoil

Topsoil

Extra soil

Geosynthetic material

Base layer

Preloading layer

Cement & chemical composition

Top layer

a mixed upper part of base layerb Wetted upper part of base layer

0 Surface layer

1 Top layer

1 a mixture for forming top layer

1 b wetted mixture for forming top layer 2 Top layer

2a complete mixture for forming top layer