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EP-4581213-B1 - PROCESS TO STABILIZE UNPAVED ROADS

EP4581213B1EP 4581213 B1EP4581213 B1EP 4581213B1EP-4581213-B1

Inventors

  • FAN, YI
  • RADLER, MICHAEL J.
  • Levin, Jessica R.
  • THEUERKAUF, Jorg

Dates

Publication Date
20260513
Application Date
20231012

Claims (15)

  1. A process to stabilize a layer of soil or aggregate, called "road material", in an unpaved road, comprising the steps of: a) providing an unpaved road that contains a layer of loose road material, wherein the layer of loose road material further contains (1) a water-soluble nonionic cellulose ether in a quantity of at least 0.05 weight percent, based on the weight of road material in the layer excluding water, and (2) water; b) compacting the layer of loose road material containing the cellulose ether and water.
  2. The process of Claim 1 wherein the water and the water-soluble nonionic cellulose ether are mixed together before adding to the loose road material.
  3. The process of Claim 2 wherein the mixture of water and water-soluble nonionic cellulose ether has a viscosity at 20°C from 1000 cP to 100,000 cP.
  4. The process of Claim 1 wherein the water-soluble nonionic cellulose ether is added to the loose road material separately from the water.
  5. The process of Claim 1 wherein the loose road material comprises primarily soil.
  6. The process of Claim 1 wherein the loose road material comprises primarily aggregate.
  7. The process of Claim 1 wherein the weight ratio of cellulose ether to loose road material (excluding water) is at least 0.1 percent.
  8. The process of Claim 7 wherein the weight ratio of cellulose ether to loose road material (excluding water) is at least 0.2 percent.
  9. The process of Claim 7 wherein the weight ratio of cellulose ether to loose road material (excluding water) is at most 2 percent.
  10. The process of Claim 1 wherein the weight ratio of cellulose ether to water is at least 1 percent.
  11. The process of Claim 10 wherein the weight ratio of cellulose ether to water is at most 15 percent.
  12. The process of Claim 1 wherein the cellulose ether is selected from the group consisting of hydroxyethyl methylcellulose and hydroxypropyl methylcellulose.
  13. The process of Claim 1 wherein after compaction the road material exhibits a yield strength that is at least 10 percent higher than the yield strength of similarly compacted road material without cellulose ether.
  14. The process of Claim 1 wherein after compaction the road material exhibits a linearized internal angle of friction that is less than 35°.
  15. A road comprising a layer of soil or aggregate, called "road material", which contains at least 0.025 weight percent of a water-soluble nonionic cellulose ether, based on the weight of solids in the layer of road material, excluding water.

Description

FIELD This invention relates to the art of road building. INTRODUCTION Roughly half the roads in the US are unpaved, and the proportion of unpaved roads are even higher in other countries. Unpaved roads are typically surfaced with soil or aggregate, which a blend of rock particles of different sizes down to sand. Creation of unpaved roads often involves the steps of: (1) clearing and grading the roadway to create the desired cross-section, and adding ditches and culverts to manage water; (2) applying loose road material (soil or aggregate) in one or more layers; (3) leveling and grading each layer of loose road material after it is applied; and (4) compacting the road material, either at the end or layer by layer. In some cases, the road is constructed in two or more layers of aggregate, with one or more base layers of larger aggregate topped with one or more layers of smaller aggregate at the surface. In some cases, the road is further stabilized by chemical methods, most typically with cement and/or lime. WO 2013/074296 A1 discloses CMC/HEC blends for cement slurries. JP S53 145312 A discloses a bentonite-based ground stabilization liquid containing non-ionic cellulose ether soluble in water. Maintenance of unpaved roads involves similar steps. Ditches and culverts are maintained to ensure adequate water drainage. A fresh surface of loose road material is provided by: (1) scarifying (breaking up and turning up) the existing surface to eliminate ruts, vegetation, and other unevenness; and/or (2) adding a fresh layer of loose road material; (3) leveling and grading each layer of loose road material after it is applied; and (4) compacting the road material, either at the end or layer by layer. Optionally, the road can again be stabilized by chemical methods. Construction and maintenance procedures for unpaved roads are described in many publications, such as "Gravel Roads Construction and Maintenance Guide (August 2015)", FHWA Publication No.: FHWA-OTS- 15-0002 published by the Federal Highway Administration of the US Department of Transportation; and "Dirt and Gravel Road Best Management Practices (2019)" published by the Culpeper Soil and Water Conservation District of Culpeper, VA. Other publications include US 2006/128838 A1 which discloses a process for the stabilization of dusting surfaces. Proper compaction of road material is an important step in construction and maintenance. Compaction stabilizes the road, making the various layers more resistant to vehicle traffic and erosion. Improved stability resulting from compaction also reduces the level of dust produced by traffic on the road. It is known to spray water on loose road material to aid compaction. In addition, various chemical additives can be added to water and sprayed on unpaved roads to assist with stabilization and dust control. Magnesium chloride and calcium chloride draw moisture from the air to keep the road slightly damp. Lignin sulfate, clay, vegetable oils or latex can help particles of road material to adhere to each other, stabilizing them and reducing dust. Portland cement can be mixed into a layer of road material to stabilize it. Alternate methods are needed to improve compacting and therefore ultimately stabilizing the road material using inexpensive and environmentally benign ingredients. SUMMARY One aspect of the present invention is a process to stabilize a layer of soil or aggregate, called "road material", in an unpaved road, comprising the steps of: a)providing an unpaved road that contains a layer of loose road material, wherein the layer of loose road material further contains (1) a water-soluble nonionic cellulose ether in a quantity of at least 0.05 weight percent, based on the weight of road material in the layer excluding water, and (2) water;b)compacting the layer of loose road material containing the cellulose ether and water. A second aspect of the present invention is a road comprising a layer of soil or aggregate, called "road material", which contains at least 0.025 weight percent of a water-soluble nonionic cellulose ether, based on the weight of solids in the layer of road material, excluding water. We have discovered that water-soluble nonionic cellulose ether aids in the compaction of road material, improving their stability. Without intending to be bound, we hypothesize that the cellulose ether temporarily reduces friction between particles of the road material, allowing them to compact better and provide a firmer surface. The cellulose ether is water-soluble and biodegradable, so that later it can wash away and/or be digested by microbes, leaving the particles compacted but no longer lubricated by the cellulose ether. DETAILED DESCRIPTION The present invention begins with an unpaved road that contains a layer of loose road material (soil and/or aggregate), which further contains cellulose ether and water. By "loose" we mean that the layer of road material can be further compacted to substantially stabiliz