الفهرس 
LITERATURE REVIEW
The Composition of Soils and Clay MineralogyOnly 14 pages are availabe for public view
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Abstract
Swelling soil is a soil or soft bedrock that increase in volume by
wetting and shrink by drying. They are also commonly known as
bentonite, expansive soil. They contain a high percentage of certain kinds
of clay particles that are capable of absorbing large quantities of water;
the clay mineral responsible generally for swelling is montmorillonite. A
sample of pure montmorillonite may swell up to 15 times its original
volume. Over 250,000 new homes are built on expansive soils each year.
A natural expansive soil, present in area in Upper Egypt south of Aswan
city which named as Toshka area in the new valley and in modern urban
areas as 6 October city. More water they absorb more their volume
increases. Change in volume can exert enough force on a building or
other structure to cause damage more than twice the damage from floods,
hurricanes, tornadoes, and earthquakes.
Currently there are large volumes of materials considered as wastes
or by-products produced by industrial activities. In most cases, these
wastes have no possibility of reuse or may be of low economic value for
the companies that generate them. One of these waste products is
Phosphogypsum (PG), which is a by-product in the wet process for
manufacture of phosphoric acid by reaction of sulphuric acid on the rock
phosphate during the production of ammonium phosphate fertilizer.
Also another one of these waste products is the cement kiln dust
(CKD), which is a by-product of Portland cement manufacturing process.
It is generated from burning the raw materials in a rotary kiln to produce
clinker. Generally, for each one ton of clinker, a typical kiln generates
around 0.06 - 0.07 ton of cement kiln dust.The utilization of solid wastes in civil engineering applications has
undergone drastic development over the past. In recent years, use of
various waste products in ground construction has gained considerable
attention worldwide in view of increasing costs of waste disposal, and
environmental constraints. The utilization of phosphogypsum and cement
kiln dust they used as construction materials and the environmental
impact of such methods have been studied for many years.
This research aims the study of utilizing the industrial wastes (solid
wastes as phosphogypsum and cement kiln dust) for the improvement
and stabilization of engineering properties of swelling clayey soil.
Hence, a series of laboratory tests included chemical analysis (to
determine some predominant chemical characteristics, e.g. used in
examining the chemical analysis (to determine some predominant
chemical characteristics, e.g. T.D.S, pH, Cl-, SO3, SiO2, R2O3, CaO,
MgO, L.O.I); The Geotechnical tests used to identify properties of
swelling soils and include: (free swell tests, Atterberg Limits (liquid
limit, plastic limit and plasticity index), in addition to the analytical
technique (x- ray diffraction). These tests were conducted to investigate
and assess the chemical and geotechnical behavior of swelling soil after
treatment process for uses in construction purposes.
The results obtained show that stabilization by the addition of solid
waste products and NaCl salt changes the physico-chemical
characteristics of soil and the results are quite satisfactory in significantly
reducing the phenomenon of swelling, as regards the effect of salt on the
swelling pressure it varies from additive to another and concentration to
another.
The conclusions, study implications developed from this
experimental study, and Recommendations for future research are
presented in this chapter.The following main conclusions are offered:
from the results it is clear that a change of the expansive soil
texture takes place.
It was noticed that the free swelling of the swelling soil has been
reduced with the addition of phosphogypsum, cement kiln dust
and NaCl, which resulted in an improvement of swelling soil for
engineering properties.
For all additives used in the tests, the free swelling of bentonite
generally decreased when the additive percentages increased.
All the mixtures cannot have the same type of influence over the
swelling soil; the swelling rate of bentonite decreases strongly
with increasing the percentages of NaCl and It is also observed
that group B (PG + NaCl + B) is more effective additive than the
others.
Chloride Cl- in NaCl and Ca ++ are causing decreasing the
repulsive forces between clay particles imparting flocculated
structure with some cementation or binding that should have
been responsible for decreasing free swell. The reason of such
tendency might be the reduction in diffuse double layer thickness
due to ion exchange causing flocculation as showed in figure
(5.1). Bentonite converted from dispersed structure clay particles
joined (face-to-face) to needle like interlocking metal line
structure clay particles joined (edge-to-face).When phosphogypsum, cement kiln dust & NaCl are mixed with
the bentonite, the Liquid limit, plastic limit of bentonite is also
decreased with the increase of percentages of the chemical
wastes and NaCl, while the plasticity index for these mixtures is
decrease, after that slightly increased when the concentration of
the chemical wastes and NaCl percentages increased, which also
resulted in an improvement of swelling soil engineering
properties.
Salinity effect on soil physical properties by causing fine
particles to bind together into aggregates, it has a positive effect
on soil aggregation and stabilization.
The higher the power of hydrogen ion concentration “pH” of
samples therefore the lower the free swell.
Increasing in pH is responsible for separation of silica causing
cementation. Increasing of sio2% enable formation of a strong
inter particle bond that enhances the stability and cause
improvement
All the examined samples consisted mainly of SiO2, Al2O3 and
Fe2O3 (R2O3) and CaO in a descending order of abundance. A
minor to trace amounts of MgO were also detected indicated the
presence of kaolinite clay.
Low loss on ignition (LOI) as in appendix and alkalinity (high
pH) improve the swelling properties and reduce the plasticity
index (PI).
For analytical technique (x- ray diffraction) that was used to
identify the reaction products of PG, CKD and NaCl with
bentonite showed that montmorillonite was approximately
transformed to a non-swelling clay mineral commonly Kaolinite
and Microcline; Kaolinite has higher ratio than montmorillonite.
from the results of the present study, Additives PG, CKD and
NaCl can be used to be good stabilizer for expansive clay soil.Further Research Recommendations
The recommendations summarized here below have been single
out based on the results of visual observations and field and
laboratory investigations:
1. Construction on this type of problematic expansive soil needs
special requirement recommendations due to the hazard effect of
this swelling/shrinking soil with any change of their moisture
content.
2. Improve the expansive soils by stabilization: Soil stabilization
can improve the properties of swelling soil considerably.
Possible materials for the stabilization could include PG, CKD
and NaCl. The choice of a material or a combination of materials
depends on the size and importance of the building (risk/damage
acceptable) and economic consideration of the client. However,
the need to strike a proper balance between quality and cost
should not be overlooked.
3. A more detailed study of possible treatment techniques to reduce
the swelling behavior of bentonite using PG, CKD and NaCl as a
resource for construction purposes is highly recommended.
4. In the field PG, CKD and NaCl as solutions were mixed with the
upper layer on the surface of the swelling soil.
5. Soil stabilization based on additive. As additives increased in the
mixture specially NaCl the mixture will be more stabilized.
6. Put insulating layer between the construction and the treated soil
to prevent the erosion of concrete by chlorine.
7. Also we can use other chemicals such as KCl, Na2Co3 salts we
expected that they will give good results.
8. More study regarding (CEC and SEM) tests for mixtures are
required.9. Wear the appropriate personal protective equipment, such as
gloves, boots, and sand filter respirators to minimize inhalation
of cement kiln dust.
10. Use soap and water to wash off dust to avoid skin damage.
11. Eat and drink only in dust-free areas to avoid ingesting cement
kiln dust or phosphogypsum.
12. Avoid exposure to cement kiln dust to prevent bronchitis and
silicosis.
13. Prevent burns and skin and eye irritation by avoiding skin
contact and eye contact with cement kiln dust or
phosphogypsum.
14. Good knowledge must be given to the factories through
promoting system on how to protect or reduced pollution of the
environment.