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RoadPacker Plus

RoadPacker Plus - The Introduction

Substantial World Wide Cost Savings With Alternative Road Construction Methods

Great concern has been expressed for some considerable time in both the public and private sectors of Governments and Municipalities the world over, concerning the deteriorating condition of vital road networks due to the lack of funding availability.

Each year, the declining situation accelerates due to costly preventive maintenance not being carried out. Various interest groups that include special Government appointed committees are continuously examining new or alternative road construction technology to identify more cost-effective construction and maintenance methods, so this trend can be halted and reversed. The use of chemical soil stabilisation is now seriously under consideration and many roads have been built and evaluated during the last ten years with extremely encouraging results.

Several Governments worldwide have instructed their bureau of standards to conduct research into new testing procedures that would provide provincial and private road construction engineers and consultants, with an effective means of assessing in advance the extent to which chemical stabilisation will improve the mechanical properties of their road materials. Once these new testing procedures have been identified and published, there will undoubtedly be a major swing towards the use of chemical stabilisation due to the huge benefits inherent in the possibility of using insitu soils (which would otherwise be unsuitable and require transporting away to waste). Simultaneously, the need to import expensive better gravels to replace unsuitable materials, would be minimised.

Projections show that millions of dollars would be saved annually in terms of reduced maintenance costs not only from a reconstruction point of view, but also from a reduced need for routine grading and watering of gravelled roads. Certain tests carried out over a twelve month period have revealed that the chemically stabilised sections did not require any routine grading, whereas identical but untreated sections of the same roads, required grading at least once or twice per month.

Ionic Soil Stabilisation has been promoted in many third world countries for many years using Sulphonated Petroleum Products ( SPP's) with documented levels of success. It was originally introduced from the United States in the early 1960's to South Africa, South America and many other countries over the next twenty years. Originally it was used on a small number of secondary roads where little or no money was available for proper concrete or asphalt roads. During the past twenty years and in particular the last ten years, ionic soil stabilisation has become accepted as an alternative method of road construction in many countries.

To date, thousands of kilometres of roads throughout the world have been successfully treated, some for private end users, and others for provincial, regional and municipal bodies where the engineers concerned have monitored and kept effective records on performance.

In a project carried out for Pretoria City Council in South Africa and monitored by CSIR, Ionic Soil Stabilisation products were used to treat a totally unacceptable high clay soil with a Plasticity Index (P.I.) of between 25 and 48 and a soaked California Bearing Ratio ( C.B.R. ) of 4. After a period of six months a sample removed from the treated layer was found to have a P.I. of 5 and tests conducted in situ showed the C.B.R. value to be 96. *

Results of both the field and laboratory test, clearly showed that the Ionic Soil Stabilisation products greatly affected the treated materials. The laboratory tests showed that the increase found in layer strength was not only due to compaction, but also due to improvement of material properties such as P.I., grading modules and linear shrinkage.

In recent years, (over the last fifteen or so) Ionic Soil Stabilisation products have been successfully introduced into countries such as Australia, Papua New Guinea, China, The Philippines, Singapore and many other Asian countries together with Europe and South America. It is also being used throughout the U.S.A. and more recently Canada.

Sulphonated Petroleum Products are tried and proven in enough countries in the world and under varying adverse climatic conditions, such as extreme heat and equally extreme cold and frost, to be considered as an alternative cost-effective method of road construction for national highways, secondary and feeder roads.

* These statistics were taken from a technical paper delivered by W.J.vdM Steyn who was a Snr. Engineer with the Division of Roads and Transport Technology CSIR South Africa at the 2nd. African Young Geo Technical Engineers Conference in Stellenbosch South Africa.

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RoadPacker Plus - What is it?

RoadPacker Plus requires only standard design, drainage features and construction methods.


RoadPacker Plus

The Benefits of RoadPacker Plus:

  • Cheaper
  • Faster
  • Greater Performance
  • Reduced Maintenance

RoadPacker Plus Saves Money

RoadPacker Plus by increasing densities, strength and C.B.R. values, significantly gives the user the ability to reduce base depths by more than 50%, saving on quantity of gravel, handling and other associated costs. RoadPacker Plus can increase strengths in local or insitu materials usually considered unsuitable for road construction. Laboratory testing is recommended to confirm suitability. RoadPacker Plus when used in unpaved roads greatly reduces maintenance by minimizing the damaging effects of water and traffic.

AIM:

To blend the required amount of RoadPacker Plus with water through the top 150mm of soil then evenly mix and physically compact into place.

Desirable Construction Equipment:

A Road Grader equipped with scarifiers.
Water Bowser - with known volume.
Rotovator/Disc Harrow/Pulvey Mixer - desirable but not essential if a road grader is available.
Vibratory Compactor/Sheeps Foot/ Steel Drum (12-15 tonne).
Wobbly Wheel/Pneumatic Rollers - for thorough compaction.

Required Equipment:

Drum pump, Measured bucket, Safety Glasses and Gloves.

RoadPacker Plus

To calculate the amount of RoadPacker Plus required; ( Length x Width x 0.03 Litres )

Water: The amount of water required varies depending on the moisture content of the soil at the time of application. Enough water is to be added to bring the moisture content to 1 - 2% above the optimum

N.B. It may be desirable, from a construction point of view, to dry the insitu material prior to calculating the amount of water required, i.e. it is more accurate to apply 2ltrs. per/sq.m than 0.5ltrs per/sq.m.

Important: Once the quantity of RoadPacker Plus required has been calculated, judge approximately how many water trucks will be required to bring the moisture content up to the recommended level. For example: If four water trucks and 80 Litres of RoadPacker Plus are required to treat the road, then add 20 Litres of RoadPacker Plus to each load of water. If after two loads of treated water you only require one additional load, then add the remaining 40 Litres of RoadPacker Plus to the final load of water, this method will ensure the diluted RoadPacker Plus is spread evenly over the area treated and the water content is correct.

Standard Method of Construction

  • 1. Grade and contour road to finished levels and cross fall. Use the grader blade to cut and form drainage channels on both sides of the road to ensure good drainage. Standard road building methods apply.
  • 2. Rip the road with grader's rippers to a depth of 150 mm. Accurate depth is important for calculating product concentrate required. Break up lumps with roller and windrow.
  • 3. Apply diluted RoadPacker Plus with water truck and windrow while applying to ensure product is mixed evenly. Bring moisture content to 1 - 2% above optimum using more water if necessary. Note: All concentrate must be applied at this time.
  • 4. Re-grade and contour road.
  • 5. Compact road using a 15 ton Pads Foot vibrating compactor , followed by the same sized steel drum vibratory compactor. If a rubber wheeled roller is available use it to obtain a final finish.


NB: A fine layer of crusher dust or gravel may be applied to the finished surface of a completed road showing slippery characteristics.

To cure road, apply RoadPacker Plus at a rate of 1:1000 for 2 - 3 days.

Manufacturers Recommendations For Use Of RoadPacker Plus

Suitability Criteria:

  • Linear Shrinkage: Not less than 2%
  • Particle Size: Minimum percentage of clay passing 0.075 sieve 15
  • P.H. of Soil: Less than 8

N.B.These are all very simple laboratory tests. If linear shrinkage is less than 2% this can be corrected by adding poor clayey material.

RoadPacker Plus Dosage:

The dosage of undiluted RoadPacker Plus is a constant for all materials recommended for use, i.e. 200 millilitres per cubic metre of RoadPacker Plus material which, at a base depth of 150 mm, equates to 30 millilitres per square metre of surface area to be treated. One litre of RoadPacker Plus is sufficient to treat 33.3 square metres (150mm base depth).

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RoadPacker Plus - How Does It Work?

To obtain even a most basic understanding of the action of RoadPacker Plus as an effective soil stabiliser, it is necessary to have some knowledge of the nature of clay particles and the interaction of water and clay. This brief explanation touches simplistically on the nature and properties of clay, the attraction of water to it, it's role in road construction, problems of road failure and the stabilising action of RoadPacker Plus soil stabiliser.

Small particles of sand and silt are particles of original rock or small mineral crystals. Of the fine particles in the soil and in a typical road gravel, only clays, unlike sand and silt, have undergone mineralogical change. The mineral structure of clays is typified by octahedra or tetrahedra joined together in a lattice structure. The lattice molecular structure of clays is such, that they exhibit a net electrical charge on the surface of the particles. The charge may be predominantly anionic (--) on the flat surface and cationic (+) on the edges.

Clay particles are called layer silicates as the lattice structures form layers so that many clay particles resemble minute fish scales. As a result some clays have an enormous surface area per gram. The large surface area of the clays combined with the electrostatic attraction between water and clay can result in enormous forces in the process of swelling and shrinkage of clays (up to 10,000 atmospheres of pressure), such that the swelling of clay, can lift buildings off their foundations.

The water molecule is Di-polar, i.e. it has the oxygen at one end and the hydrogen at the other end of the molecule so that there is a net (--) charge at one end of the molecule and a net (+) charge at the other end. It is this characteristic of the water molecule which weakly attracts one molecule to an other and gives water it's surface tension. Water, which is a conductor, is electrostatically attracted to the surface of the clay particles. In fact clay particles are surrounded by a layer of water electrostatically bound to the clay. This layer is called a " diffuse double layer " because the molecules of water and cations close to the clay particle surface are tightly bound while the molecules of water in the outer part of the electrostatically bound water are more weakly held.

It is this affinity (attraction) between water and clay which gives clay its properties of cohesion and plasticity, properties which sand and silt do not possess. Clay is therefore essential in a gravel as its plasticity ( plastic nature when wet ) enables the road to be shaped and compacted, and its cohesion binds all of the rocks, sand and silt together.

The majority of road failures are associated with the action of water ( sometimes the lack of water ), or perhaps more precisely, the interaction between water and the clay particles in the road. Wetting and drying cycles can cause the road to break up through associated swelling and shrinkage of clay in the road . High moisture content can make gravels with high clay content very soft and plastic so they become very boggy in wet weather.

On the other hand, road gravels with insufficient clay or poorly compacted clay, which thus lack cohesion, can become loose dusty and corrugated in dry weather (similar to dry sand on the beach compared to wet sand).

RoadPacker Plus is an advanced chemical soil stabiliser which has an extremely powerful ionizing action in water, which induces cation (+ ions e.g. Ca++, Na+, K+, Mg++, H+ ) exchange at the surface of the clay particles in the gravel. By the process of ionic exchange water that would normally be electrostatically bound to the clay particles, is replaced by ions allowing much of this water to be expelled as free water.

Other processes occur through the use of RoadPacker Plus soil stabiliser, including coagulation and flocculation of clay particles after compaction and some cementing action through formation of insoluble salts.

The result of treating a soil with RoadPacker Plus is that, on compaction, clay particles can be moved much closer together thus reducing voids, and achieving a significant increase in soil density, with better particle interlock and increased agglomeration of the clay. The bearing capacity ( ability to hold up under heavy loads or high traffic volume ) of the road is increased significantly, and road wear is greatly reduced.

The process of ionic exchange induced by RoadPacker Plus at the surface of clay particles is a permanent process. The net charge on an ion is greater than the electrostatic attraction of a water molecule so that after ionic exchange, the net forces of attraction at the surface of the clay particles are largely neutralized.

Treatment with RoadPacker Plus permanently reduces the attraction between water and clay and reduces the swell and shrinkage of the clay. Use of RoadPacker Plus has been shown to increase the bearing capacity of a compacted gravel by as much as 250% according to the California Bearing Ratio (C.B.R.), which is a standard measure of bearing capacity used worldwide.

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