How To Cover, Harden or Dry Up Mud in your Backyard, Paddock or Construction Site with Soil Stabilization Techniques
Mud presents a problem not only in your home yard, but also in other environments such as farm paddocks, construction sites, dirt roads, alluvial plains by the river, undeveloped rural areas, cultivated land and just about any place with bare ground, exposed to soil erosion and deposits. On your residential backyard, muddy ground makes the yard look unsightly. It’s not comfortable to walk on mud since it messes up your shoes. Kids and dogs can bring mud inside the house, messing up the floor, walls and furniture. Even more serious, body exposure to mud or wet soil can put you at risk of contracting infections caused by soil and water borne pathogens such as Aeromonas Hydrophilia, Novovirus, Leptospira, C.Coli and E.Coli.
If you live on a farm or ranch, your greatest concern will be protecting your livestock against numerous health hazards caused by mud in your animal pens, paddocks, feed pads and drinking bays. Disease causing bacteria, viruses, fungi and parasites found in these muddy places can infect your livestock. Taking measures to cover up or dry mud on your livestock farm will reduce visits by your veterinary inspector, and help you in saving costs associated with veterinary services such as diagnosis, treatment and quarantine.
What Causes Muddy Conditions on Your Backyard? Why Does Dirt Turn into Mud?
Muddy soil and swampy land can be dried, dehydrated or hardened using various soil stabilization techniques to achieve solidification of the wet soil mass. Before we delve into these techniques, we have to look at situations which cause muddy conditions.
Mud is a mixture of soil and water, but it’s not all soils that cause mud. More specifically, mud is created when certain types of soil containing a high percentage of fine and cohesive particles are mixed with water. These are soils like clay, loam and silt. These three types of soils have high water retention capabilities and low permeability, with clay possessing extreme characteristics. However, loam soil and silt have the highest permeability among the three, which means that they drain water quite well.
Non-cohesive soils also known as granular soils (e.g. sand and gravel) have poor water retention qualities and high permeability, which means that they drain water extremely well, much better than cohesive and semi-cohesive soils such as clay, loam and silt. As you can see, if you have a granular soil bed on your yard or site, you won’t have mud problems unless the granular layer is too thin and exposed to mixing with subgrade soil containing a high amount of clay or loam. With time, soil erosion may remove the granular layer, exposing the clayey subgrade to wetting by surface rainwater and runoff.
Highly trafficked areas with bare ground, such as pathways, playgrounds, dirt roads, livestock pens and paddocks, are more exposed to soil degradation caused by human and animal traffic. Topsoil will disintegrate and loosen up in these areas, and at the same the subgrade (subsurface soil) will be compacted by the impact of traffic activity. During a rainfall, water will mix with this loose topsoil to create mud. Considering that the subsoil has been compacted over time by the impact of traffic, it will be highly impermeable and resistant to water percolation. Thus, mud pools and puddles will form on the surface.
Looking at the situations mentioned above, it can be deduced that a muddy backyard or lot is caused by:
- Soils with high water absorption properties
- Soils with low permeability (high resistance to water percolation)
- Soils with high amounts of fine and cohesive particles (clay)
- Soils with poor drainage qualities
- Degradation of topsoil on bare ground caused by traffic and soil erosion
- Subsoil compaction caused by traffic, leading to reduced permeability and formation of mud puddles and pools
- Lack of natural and manmade ground cover
- Poor choice of ground cover and bad installation
- Lack of surface and sub-surface drainage systems on the site
- Poor site drainage systems
The location of your home and landscape design is very critical in preventing muddy situations. Homes located in valleys and alluvial plains close to rivers, lakes and the sea are more likely to suffer from muddy situations caused by sediments deposited by water and floods on the shore and inlands. In such circumstances, the only way to prevent swamps and mud is building on elevated ground, on a firm and sturdy base of natural rock.
How To Cover Up or Dry Up Mud in Your Backyard Using Soil Solidification Techniques
How do you dry muddy soil? How do you make wet ground firm and hard? There are many tried and tested ways to firm up or harden muddy ground in civil engineering earthworks. The method you choose depends on the ground conditions on your site or yard, for example, the soil profile, sub-surface water table, soil type, strength, cohesiveness, permeability and the degree of subsoil compaction. The soil stabilization technique you choose also depends on the local climate, land use, sub-lot zoning, costs, its efficiency, availability of stabilizing agents and binders in your area, social acceptance, size of your yard, environmental hazards, urgency and job complexity.
The following are stabilizing agents, binders or additives that you can use in drying and hardening muddy soil. Soil stabilizers come in various forms. They can be classified according to physical state i.e. liquid, viscous fluids, powder, fibre, resin and crystals. The most commonly used soil stabilization techniques fall into five main categories – chemical, biological, mechanical, thermal and combined methods.
Chemical Stabilization of Muddy Soil
Chemical stabilization of soil can be achieved using organic and inorganic solidifying agents. Generally, the difference between organic and inorganic compounds is that organic compounds are the building blocks and/or products of all living organisms, and inorganic compounds are associated with non-living things. The presence of carbon-hydrogen bonds is the main feature of organic compounds, and the absence of carbon-hydrogen bonds in inorganic compounds is the main distinguishing feature.
However, in a suitable environment, both organic and inorganic compounds will chemically react with other compounds.
Organic Stabilizers for Solidifying Wet Soil
Organic soil stabilizers are can be injected into or mixed with soil, they can also be sprayed or used as screed layers on soil. When introduced into soil, the organic reaction will convert the hydrophilic soil particles into hydrophobic soil which is resistant to water absorption. An organic stabilizer also reinforces and strengthens the soil, effectively changing the soil structure through polymerization enabled by a catalyst.
Examples of organic solidifying agents are listed below:
Sodium Silicate – The other name for this compound is water glass. It’s a cheap stabilizing agent that you can mix with soil to give it water-resistant qualities. The compound to soil mixing ratio is 5% by weight. To get good results, sodium silicate works well on soils with high sand content (fine aggregates), for example sand, sandy loam, sandy silt, sandy clay, sandy clay loam and loamy sand.
Lignin – This is an organic polymer found in plant tissues and cells. It functions as a natural glue or adhesive that binds fibres in vascular plant cells, wood, bark and algae. Research has shown that silty soils mixed with Lignin in a ratio of 12% by weight has much better mechanical properties than soil stabilized with 8% quicklime. Lignin stabilizes silty soil through precipitation and cementation which binds soil particles and fills pores, thereby improving its structure. Lignin is a bio-based organic by-product of wood pulp processing mills.
Epoxy Resin – This is an organic polymer used as a soil stabilizer. It occurs as both as a natural substance, extracted and processed from plants, and as a synthesized material obtained from industrial processes and chemical engineering. Manufactured / synthetic thermosetting resin is produced in liquid or solid state. It is widely used in paints, adhesives, coatings, joint fillers, water pipes, plastics, floor topping, varnishes and other applications. There are more than 20 types of epoxy resin, all which are specially formulated for a particular use.
The stabilizer is applied as two-part system consisting of a hardener and curing agent. Bisphenol A/Epichlorohydrin is a type of epoxy resin that is used as a hardener. It is a yellow highly viscous liquid, slightly soluble and stable. However, it can react with acids, strong minerals and oxidizing agents to produce a great amount of heat. To prevent this hazard, quantities are decreased below a certain threshold, less than or equal to 4% during application or as low as 0.25%. The curing agent in the epoxy resin system is a tan-coloured viscous liquid that is insoluble in water. The compound can react with oxidizing agents to produce carbon monoxide, nitrogen oxides and polyamides which are all hazardous. To prevent this from happening during application, a protective surface coating is done.
In stabilization of soils, not more than 4% of epoxy resin should be applied. A range of epoxy resin stabilizers will harden within 20 minutes to 3 hours, and during the curing process, they will gain up to 16,000 and 8,000 psi of compressive and tensile strength within 24 hours respectively. As a solidifying agent, the action of epoxy resin on soil is non-reactive or chemical. The epoxy resin binds the soil particles together like a glue, forming a hardened mass of soil. The resin has been tried on poorly graded river sand, silty soil and clay-silt. Another advantage of epoxy resin is its ability to deliver the same strength (CBR load bearing ratio) at a lower fractional weight, 0.166 to 0.04 less than that of widely used stabilizers like cement and pulverized coal ash.
The strength of an epoxy resin system depends on the degree of mixing. Thorough mixing is good for molecular cross-linking reaction and increase in strength of mixture. Proper curing of epoxy resins is essential in attaining compressive, tensile and flexural strength which is exceedingly higher than traditional stabilizing agents such as cement, asphalt and lime.
The downside of epoxy resin is its high cost. Most traditional binding agents like cement, lime and fly ash are very cheap at only $0.04 per pound, while epoxy resin is 44 times more expensive at $1.76 per pound. The installation also requires thoughtful design to prevent toxic hazards.
Ultra-High-Molecular Weight Polymers (UHMWP) – High molecular weight polymers both synthetic and natural (biopolymers) are used in soil stabilization as binders. Scientific research has shown that polymers have a binding effect on soil which binds soil particles together like a glue. This does not only bind soil particles together, but it also improves the mechanical structure of soil, as well as eliminating dust.
Examples of synthetic polymers are Polypropylene and Polyethylene. Examples of biopolymers include Polysaccharides such as cellulose, starch and chitin. Polysaccharides are more effective soil binding agents than protein-based biopolymers (polynucleotides, polypeptides etc.). However, protein-based biopolymers are highly resistant to water. The disadvantage of some polysaccharides is that their cohesiveness may decrease due to dilution by increased soil water, but this disadvantage is offset by the increased compressive strength which is greater than normal soil with no binding agent.
Inorganic Stabilizers for Solidifying Wet Soil
Inorganic stabilizers or binders are made from naturally occurring minerals and materials such as silica, shells, limestone, marl, chalk, slate, shale, clay, iron ore and sand. Natural and synthetic pozzolana (waste and by-products of industrial processes) can be added to the mix to achieve a specific formulation with improved properties or unique attributes. The materials are processed in a production plant where they are crushed into a powder. Almost all inorganic binders are available in powder form, packed in 5, 10, 20, 25 or 50kg bags. A commercial inorganic binder like cement is usually a combination of different minerals and materials, but there are singular stabilizers like quicklime and slacked lime (hydrated lime) which can provide binding capabilities on their own when exposed to a reagent or reactive substance.
Inorganic binders work via a chemical reaction known as hydration or hydrolysis. The inorganic solidifying agent reacts with water in wet soil to produce heat, calcium hydroxide and hydrates of calcium carbonate (calcium silicates) which are responsible for strength development. Some stabilizers will need the assistance of pozzolana to start the reaction with water.
Cement contains a compound known as Tricalcium Silicate. The hydration equation for Tricalcium Silicate is:
Tricalcium Silicate + Water >> Calcium Hydroxide + Calcium Silicate Hydrates + Energy (Heat)
The hydrolysis reaction starts immediately when cement is mixed with water. When the energy (hydration heat) produced by the reaction starts to decrease, the calcium hydroxide and calcium silicate hydrates will undergo crystallization.
Inorganic compounds will stabilize the soil through the following processes:
- Drying the soil through the heat of hydration (dissipation of heat).
- Strengthening or stiffening the soil through crystallization of hydrates.
- Cementation/adhesion – bonding soil particles together like a glue.
- Filling voids and pores in soil.
- Soil structure modification through ion exchange. Transformation of soil particle shape to achieve interlocking (stable structure).
There are many kinds of cement but Portland cement is the most common. Soil that is stabilized with cement is known as soilcrete. The cement is mixed with soil in a 1:10 ratio to form a weak concrete mixture (about 7 to 15MPA strength) that will set and harden, binding the soil particles together in the process. Many types of soil can be stabilized with cement, especially soils that are deficient in clay. The structure of the soil remains the same during the hardening of cement, but the soil gains increased compressive strength imparted by the cement mortar, pores and voids are filled, cementation takes place and the crystallization of hydrates reinforces the soil. A cement soil mixture should be compacted with a rammer to eliminate as much voids (bubbles) as possible. Compaction also improves the final hardened strength of soilcrete. Soilcrete has high resistance to volume expansion and contraction (swelling and shrinkage). The stabilized soil is also resistant to water absorption.
Lime is a stabilizing agent that dries wet soil by producing heat of hydration, i.e. when quicklime (CaO) reacts with water. Quicklime is a by-product of limestone combustion and it is the most concentrated and strongest type of lime. This type of lime is also known as burnt or unslacked lime. Its chemical name is Calcium Oxide (CaO).
The production of quicklime is represented by the following formula:
Limestone + Heat >> Calcium Oxide (Quicklime) + Carbon Dioxide (CO2)
Quicklime or Calcium Oxide can be used in its state as a soil stabilizer. When mixed with wet soil, it absorbs the water (up to 32% of its own weight). The reaction between the quicklime and soil water produces Calcium Hydroxide (CaOH2) and heat, as shown in the formula below:
Quicklime (CaO) + Water (H2O) >> CaOH2 + Heat.
The heat of hydration (65kj per mole) will evaporate the water causing the soil to dry up. In the presence of wet clay, pozzolana, soluble siliceous and alumina materials, lime will further react with these materials to form cementitious hydrates which bind soil particles together like a glue.
Calcium Hydroxide is known as Hydrated Lime or Slaked Lime. Hydrated lime is available in powder, liquid and viscous fluid form. Hydrated lime can be mixed with water in a suitable ratio to form lime slurry. About 10 to 300 grams of hydrated lime is mixed with 1000ml of water in a mixing agitator tank to form lime slurry.
Lime is only suitable for stabilizing soils with a high clay content (40% and above). If the soil is deficient in clay, mix the lime with pozzolana to enable a chemical reaction that will form a soil binding material.
The lime to soil mixing ratio depends on the amount of clay in the soil. More lime is required for more clay content. About 3 to 14% of lime is required to stabilize soil, adjusted proportionally to the clay content.
Organic Fibres and Matter
Organic fibres and matter are widely used traditional methods of stabilizing weak soil via the reinforcement effect which prevents cracks caused by volume changes in clay (drying and wetting). Fibre-reinforced soil contains natural fibres which are spread, mixed with and embedded between soil layers.
It should be noted that soil reinforced with natural fibres is highly water absorbent and retaining, which is not good for mud prevention. To prevent mud, you have to use the organic fibres as ground cover. A thick layer of ground cover (4 to 6 inches / 100 to 150mm) will be required. A wide range of fruit, seed, leaf and stalk fibres are used in covering up muddy ground. These include wheat, barley, rye, rice, straw, coconut fibre, bagasse, hemp, sisal, elephant grass, banana and pineapple leaf fibre.
Other types of organic matter that can be used to stabilize soil are plant juices, vegetable oils and fat, seed oil, burnt hardwood ashes and organic colloids such as animal glue made from collagen (bones, hides, horns etc). The problem with hardwood ashes is that they don’t reduce water absorption and may be toxic to soil. However, ashes increase the compressive strength of soil.
Molasses is another organic stabilizing agent that is effective in improving soil properties such as reduced water absorption and increased compressive strength. Mix the soil with 5% molasses to achieve the desired results. Molasses has produced good results on sandy and silty soil. To stabilize clay, mix the molasses with small amounts of lime.
Fly ash, a by-product from a coal processing plant obtained by burning pulverized coal has been tested and found to be effective in the hardening of muddy soil. If your construction site or backyard is muddy, this might be a suitable hardening additive to use to achieve increased soil strength and stability. The effectiveness of fly ash as a hardening agent depends on its quality and environment in which it’s stored.
Drying Wet Soil Using Thermal / Heat Treatment
A mud dryer also known as a soil dryer is a driven machine that can dry mud or wet soil on a piece of land. The equipment consisting of a heating unit (propane burner and fans) and scarifying unit or tiller is pulled by a tractor across the ground. The burner and fan can produce 6 million BTU of hot air which can evaporate and reduce the moisture content of soil from 26% to 15% depending on the type of soil. The mud dryer can evaporate water on topsoil, clay and clayey silt. Up to 6 passes are required for clay and topsoil at a scarifying depth of 6 inches (152mm). Three passes are enough to dry clayey silts and clayey sands.
If you need to dry muddy ground in your yard within a few hours, heat treatment of soil using a mud drying machine may be the answer for you. The equipment (including the driver) can be hired and dispatched on your yard, construction site or field.
After scarifying and drying the soil, you should compact the soil to the required AASHTO Density to achieve a firm and stable ground.