Soil Stabilization or Rammed Earth has been used for thousands of years as a basic building material. Soil stabilization from the Ancient Pyramids to the Great Wall of China, soil has provided structural solutions that were principally based on the binding properties of clay soils.
Throughout Latin America soil stabilization of sorts was achieved with clay-based soil blocks (rammed earth blocks or earthen blocks) were (are) known as the Adobe Block.
In our rapidly changing and developing world we have needed to find alternatives to dependency clay-based soils for soil stabilizing and soil stabilization.
Unlike portland cement, soil cement with low tensile strength, asphalt, tree resin, ionic stabilizers and others,
- AggreBind’s unique characteristics offer soil stabilization solutions that are readily available from most on-site materials.
- AggreBind offers environmentally friendly solutions.
- AggreBind was developed to meet today’s environmental concerns and today’s specific engineering challenges.
- AggreBind is a cross-linked copolymer that makes it the perfect soil stabilizing product.
- Soil Stabilization with AggreBind does not need clay.
- AggreBind can effectively stabilize a wide range of on-site materials including sub-soils, sands, and waste construction/mine materials. Sieve analysis is highly recommended.
- AggreBind works with stabilizing soil contaminated mining materials and non-organic waste materials.
- Recycled AggreBind roads and blocks are ideal for soil mixing and aerating of fields.
AggreBind is ideal for Specialty Applications and can replace traditional house construction methods and road construction soil stabilization methods such as:
- Soil-cement base (SCB)
- Soil nailing
- Jet grouting and Grout of the soil
- Erosion Blanket and Erosion control for dust control
- Sediment Control and management of mine dumping waste
Soil stabilization products are varied on the market and often mislead the user because they refer to their product as a soil stabilizer. This is a very misused term and unfortunately it misleads the users. In many parts of the world, Indonesia and Malaysia, India, in various countries of Latin America and Africa, there have been stabilized soil projects that failed or did not perform as promised and represented.
- Some of these products simply neutralize the interaction between clay particles to allow the platelets to be compacted with no true binding or soil stabilization action.
- Some soil-binders do not work with non-cohesive materials such as sand.
- Some soil stabilizers improve the CBR by only 2-3 times. (Any conventional soap product can do this.)
- Some products require medium to high clay content for stabilizing, essentially lubricating the clay to bind when compacted. (Sometimes they call this increasing plasticity and to do so they say add clay. In fact, they are actually clay-based soil stabilizers.)
- Some soil stabilizer products are based on tree resins, presenting themselves as “ionic stabilizers” and a “green” alternative to bitumen, etc. This class of resin-based soil stabilizers generally needs a minimum of 15% clay content and an annual maintenance program or topping-up of the surface. (There claim is to be bio-degradable. A bio-degradable road is guaranteed to breakdown rapidly.)
These various alternatives cause confusion and doubt in the marketplace. These assumptions, based on poor experiences with so called soil stabilizers, create misconceptions about AggreBind.
When we compare AggreBind to soil stabilization products supplied by others, we must ask: Do the so-called “competitive products”,
- stabilizing soil only work with cohesive (clay) soils?
AggreBind works with non-cohesive materials.
- stabilizing soil turn non-cohesive desert sand into a structural material?
With AggreBind soil stabilization you can make roads and blocks from desert sand.
- soil stabilizers conform to International standards in terms of being environmentally friendly?
- stabilized soil improve the CBR bearing capacity of the sub-soil?
AggreBind increases the load-bearing capacity by 4-6 times.
- soil stabilization provide a flexible structural layer that does not dry out and cause cracking?
AggreBind through its unique cross-linking properties, enhances tensile strength and offers flexibility to linear construction.
- provide resistance to damage by petrol and oil?
Inherent property characteristics within the AggreBind formulation.
- retain the soils natural color if required?
AggreBind is available in white which ties to the natural color.
- offer colors for the making of roads, blocks, bricks and pavers?
AggreBind is the only true soil stabilization material available in black for stabilizing soil roads that will look like asphalt roads. This is very important to the perception of “roads” in developing countries.
- react in a positive way with virtually all road construction materials?
AggreBind adheres to non-cohesive materials. In Africa, pecan shells were used with AGB to make a road.
- soil stabilization and function on inclines?
AggreBind because of its cross-linking technology, has extremely strong binding properties and tensile strength to achieve functionality on most inclines.
- require a significantly higher dosage rate to achieve the same results as AggreBind?
AggreBind is sold in the highest concentrated form possible to maximize dilution rates and minimize cost per m3 and m2.
AggreBind soil stabilization is the only cross-linked styrene acrylic polymer on the market. We are the only company that offers black and colored polymer for roads and production of blocks, bricks and pavers.
We are different! We are unique! We are AggreBind!
What is Soil Stabilization?
Soil Stabilization: is a term that is used to describe how to improve the load bearing capabilities and water resistance of a wide variety of different soils and aggregates.
There are many different types of soils and these have to be identified and evaluated before preparing a specification for stabilizing soil.
This information is used to prepare a specification for soil stabilizing.
Soil stabilization with AggreBind will basically improve the CBR of all soils by 4 to 6 times.
The basic principles of engineering still apply to soil for use in soil stabilization. A minimum of 35% fines passing through a 200 sieve and no stone larger than 20% of the layer depth being soil stabilized.
AggreBind coats each individual soil particle and the polymer then cross-links them together to form a solid and flexible structure during compaction.
The surface is then sealed with AggreBind to provide a water resistant and durable surface.
1. First identify the soil type.
2. Carry out a sieve analysis to indicate particle and stone size.
3. Determine the residual moisture content of the soil.
4. Carry out a CBR strength test
AggreBind acts as a water repellent after the curing process which is normally within 2 hours after installation at 16°C. Ambient humidity directly affects curing. Make sure the surface is dry to the touch prior to opening the road.
All soil types and a wide variety of waste materials can all be successfully soil stabilized with AggreBind for use in roads, pathways, parking areas, runways, bricks/blocks for housing, dust control.
AggreBind is applied diluted with water ( even sea water) and it is important that the soil moisture level is just over OMC before being compacted.
AggreBind is the totally effective Soil Stabilizer, proven and environmentally safe alternative for Road Construction, Blocks, Bricks, Soil Stabilization, Ground Stabilization, Erosion Control and more
Comparisons between different test methods for soil stabilization: Per Lindh, Torleif Dahlin and Mats Svensson
Geotechnology, Lund University P.O. Box 118, SE-221 00 Lund, Sweden
Soil stabilization is a very useful technique for road construction. To utilize the full advantage of the technique the quality control must be adequate. In this study three main groups of test methods are tested and discussed. The first group deals with methods for determination of bearing capacity e.g. complete surface compaction control, static plate load test and light drop weight tester. The second group of method deals with workability and homogeneity tests e.g. moisture condition value (MCV), core sampler and pulverization test. The third group deals with geophysical methods e.g. spectral analysis of surface waves (SASW) and resistivity.
Shallow soil stabilization has been used in Sweden since the late 50 ́s but during the 80 ́s it was only occasionally applied, due changed regulations. However the soil stabilization method has met a renaissance during the late 90 ́s partly because of the environmental advantages of the method. During the construction of the new connecting road for the Öresund fixed link, soil stabilization has been used to ensure sufficient bearing capacity and homogeneity. In the first phase 300,000 square metres of clay till have been soil stabilized with lime. At three different sites full-scale tests have been performed during the construction of the ring road. At all the sites both conventional testing and geophysics have been used for evaluation. The soil stabilization test methods that have been used are static plate load test (SPLT), light drop weight tester (LDWT), roller-mounted compaction meter, moister condition value (MCV), core sampler, pulverization, spectral analysis of surface waves (SASW) and resistivity measurement.
In 1996 the construction of Yttre Ringvägen, a ring road around Malmö Sweden, was started, see Figure 1. The soil in the area consists of clay till and silty till. This type of soil is very sensitive to variation in water content. At an early stage it was discovered that the bearing capacity of the embankments was too low to meet the requirement in ROAD 94, which is the general technical construction specification for roads from the Swedish National Road Administrations (SNRA). To fulfill the requirements in ROAD 94, either soil stabilization or soil replacement can be used.
REQUIREMENTS FOR THE BEARING CAPACITY OF SUBGRADES
According to ROAD 94, the bearing capacity can be verified in two different ways, both with an inspection area ≤ 4,500 m2. In the first alternative, eight random samples of the inspection area are chosen and a static plate load test is performed at each test point. The modulus of elasticity (Ev2) has to be at least 25 MPa. The second way to verify the soil stabilization bearing capacity is to use a roller-mounted compaction meter and use the obtained information to choose the two areas with lowest response, see Figure 2. In these low response areas static plate load tests are performed. The requirement is a mean modulus of elasticity (Ev2) ≥ 10 MPa for those two points (SNRA). In this study, results before and after stabilization were to be compared, and therefore four test points had to be chosen in advance.
SOIL STABILIZATION TEST FIELD
The soil stabilization test field chosen was an area of twenty by fifteen metres and a part of the ring road. This area was an embankment with a height of two metres and was divided in four squares with a test point in the center of each square, see Figure 2. To test resistivity and SASW, four lines were chosen. These lines went through the test points. Two of the lines were parallel to the highway and the other two were perpendicular to the highway. The soil is clay till with a clay content of approximately 15% and a natural water content of around 13%.
SOIL STABILIZATION METHODS AND RESULTS
Methods for determination of bearing capacity
The complete soil stabilized surface compaction control method is performed with a roller-mounted compaction meter in combination with static plate load tests. Soil stabilization compaction meter values (CMV) obtained at the test area are presented in Figure 2. The surface is relatively homogenous with respect to the CMV. The static plate load tests were performed at the test points and LDWT was also performed.
Results from the soil stabilized static plate load test and light drop weight tester are presented in Figure 3. The values from the light drop weight tester are converted from a dynamic modulus to a static modulus. This conversion is based on unpublished results from the Swedish Road and Transport Research Institute (VTI). The results in Figure 3 show that static plate load test and light drop weight tester gives very similar results on the unstabilized soil.
On the stabilized soil, however, the LDWT gives lower values for three out of four points. The results from CMV shown in Figure 2, indicate that the stabilized soil responds rather uniformly over the test area. In Figure 2, point 2 shows the lowest value, which is contrary to the results in Figure 3 where point 2 gives, the highest value. The contradiction could be explained by the difference in influence depth of the two methods. The soil stabilization CM value depends on the weight of the roller and in this case takes a greater depth than the stabilized layer into account.
Workability and homogeneity tests
The MCV method is developed at Transport and Road Research Laboratory in Great Britain (Parsons, 1976). The method is a field method that rapidly measures the moisture condition of earthwork material. The test is carried out by placing 1500 g sample soil where all material greater than 20 mm has been excluded in a mould with a diameter of 100 mm. On top of the soil a disk with a diameter of 99 mm is placed. A 7 kg rammer, 97 mm in diameter with a falling height of 250 mm, hits the soil until the soil is compacted to maximum bulk density. In other words the moisture condition test gives the minimum compaction work required to produce full or nearly full compaction for soil stabilization. The MCV is then determined for different water contents of the soil. From this, a correlation between MCV and water content can be done. When the relationship between MCV and water content is known the water content can be determined within five minutes at field conditions. Research in England has shown that an upper value for MCV is between 12-14 to ensure compacting on the “wet” side (Perry, et al. 1996).
The core sampler is used to determine the in-situ density and void ratio. For this purpose a core sampler according to British Standard (BS 1924:1990) was manufactured. From earlier tests, nuclear methods have shown to give unsatisfactory results. The same conclusions were drawn in England (Sherwood, 1993). In Figure 4 dry density determined by the core sampler is compared to dry density determined by the MCV samples. The core sample results show both lower dry density and higher water content when compared to the MCV results. One plausible explanation to the lower dry density could be that the embankment below the soil stabilized layer had to high water content too be able to respond to compaction.
The pulverization test was performed according to British Standard (BS 1924:1990). This test is a method to control how the rotovator have managed to break up the soil. Indirectly, it also tests how homogenised the soil-binder blend is. The soil sample, approximately 1 kg, is spread over a 5 mm sieve and gently shaken. Then the weight of the soil that has not passed the 5 mm sieve is determined. All lumps should then be broken until all individual particles finer than 5 mm are separated. Then the sample has to be replaced on the 5 mm sieve and shaken until all the material finer than 5 mm has passed through it. From this the degree of pulverization can be determined (P, in %) see Equation 1.
P = 100(m1-m2)/(m1-m3)
m1 is the total mass of the sample
m2 is the mass of the unbroken material retained on the sieve m3 is the mass of the material finally retained in the sieve
Specifications from Department of Transport requires that at least 90% of the stabilized soil is passing the 28 mm sieve and a minimum of 30% is passing the 5 mm sieve (British Lime Association, 1990). The soil stabilized result from the pulverization test is presented in Figure 5. From Figure 4 it is clear that the P value at the site is > 30% and pass the requirements.
In this study two different geophysical methods were also tested, the SASW method and 2D resistivity. The SASW method was tested to be compared, principally with static plate load test but also with LDWT. The SASW technique (Spectral
Analysis of Surface Waves) is based on the dispersive character of the Rayleigh wave (Svensson, 1998). With two vertical receivers (geophones or accelerometers) and a Spectrum analyzer different velocities and hence different moduli can be determined for different depths when recording the wave field produced by an impulse or vibrating source for soil stabilization. The shear moduli, G, which is the mechanical parameter determined, is most often compared to moduli produced by SPLT, FWD etc. The soil stabilization evaluated moduli are presented in Table 1. The SASW method was able to obtain the increase in stiffness in the soil stabilized layer. Though in the shallowest part of point 2 and 3 at a depth of 0.15 metre the results were disturbed. Another observation is that the G modulus profile had the lowest value at the bottom of the embankment 2 metres below surface. Then the moduli started to increase in the natural soil.
The resistivity method was used to evaluate the method in stabilized soil. The idea was to find out if the method can measure the homogeneity of the soil stabilized layer. The surveying was made as two-dimensional resistivity imaging, also called continuous vertical electrical sounding (CVES), presenting as cross sections of the resistivity of the ground.
The measurements were carried out with the Wenner array, with 12 different electrode separations. The ABEM Lund Imaging System was used for the data acquisition, a computer controlled multi-electrode system. Four electrode cables with 21 take-outs each were laid out on a line using an electrode separation of 0.25 metre (Dahlin, 1996). The data was processed using inverse numerical modelling (inversion), in which a finite difference model of the subsurface resistivities is automatically adjusted to minimize the residuals between the model response and the measured data. The software Res2dinv was used for the inversion (Loke, 1999). The resistivity results before and after soil stabilization is presented in Figure 6. There is a clear difference in resistivity between un-stabilized and stabilized soil. The differences in resistivity before and after soil stabilization depend on some major effects. These effects are change in water content, change in porosity and the change in ion content. In this study there is no possibility to separate these effects.
SOIL STABILIZATION CONCLUSIONS
There are several useful soil stabilization methods to measure bearing capacity, workability and homogeneity. For quality control of the bearing capacity the complete surface compaction control method have a big advantage. This method can be used on all of the passes with the roller measuring the increase in stiffness with a very limited effort in stabilizing soil. This method is the only method that covers the whole area. To calibrate the CM-value at least two static plate load tests have to be performed on each control object (4,500 m ). As an alternative to complete stabilizing soil surface compaction control the SASW method could be used but the technique must be faster and more automatic to be economical. On the workability control the MCV method is very useful and can be performed both at laboratory and on site. The limitations for this method is the grain size of the stabilized soil that is, MCV is developed fine grained soils.
For the homogeneity tests a more flexible method is requested, and the study shows that the resistivity method has a large potential as a complement to traditional testing. The technique could also give a 3-D model of the soil stabilized area. However, there is a need for faster data acquisition, and this could for example be solved with a fast multi-electrode system that could be pulled after a vehicle. There is also a need of a more efficient soil stabilization data processing used in routine applications.
The Swedish National Board for Industrial and Technical Development (NUTEK), Peab (contractor). The authors also gratefully acknowledge the valuable assistance of Per Löwhagen.
British Lime Association (1990) “Lime stabilization manual” British Lime Association
British Standards 1924 (1990) “Part 2. Methods of test for cement-stabilized and lime-stabilized materials”, British Standards Institution.
Dahlin, T. (1996) 2D resistivity surveying for environmental and engineering applications, First Break, vol 14, no 7, p 275-283.
Loke, M.H. (1999) Res2dinv ver 3.4 – Rapid 2D Resistivity and IP inversion using the least squares method, Manual, 81p.
Parsons, A. W. (1976) “The rapid measurement of the moisture condition of earthwork material”, TRRL Laboratory report 750, 1976.
Perry J., Snowdon R. A., Wilson P. E. (1996) “Site investigation for lime stabilization of highway works”, Advances in site investigation practice, Thomas Telford, 85-96.
Svensson M. (1998) “Modern methods for determination of shear modulus – Spectral Analysis of Surfface Waves and Bender element method”, Lic. Thesis, ISBN 91-630-6748-X, Lund University.
Swedish National Road Administration (1996) “ ROAD 94 General Technical Construction Specifications For Roads” Publication. 1994:25E, Vägverket.