الفهرس 
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NATIVE MATERIALS charACTERIZATIONOnly 14 pages are availabe for public view
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Abstract
Fine grained clay rich soils, particularly those containing clay minerals, may cause problems in the foundations or other infrastructure, because they expand and have a tendency to swell or shrink, when their moisture content changes. They may also degrade with time, loosing strength and deformation resistance. Such characteristics may be attributable to their composition, the nature of their pore fluids, their mineralogy or their fabrics. These soils were responsible for high costs of damage to man-made structures, such as buildings and roads.
The Nile Delta soils have encountered numerous specific construction problems, because of the soils are too weak to support heavy foundations. The soils are generally too fine and/or plastic to be used for pavement construction and this largely accounts for the widespread pavement failures in the areas of study. Soils are unsuitable for use in construction projects; they may have to be altered or improving their properties.
Within the frame work of this thesis, soil materials of some localities in the Nile Delta have been studied in their natural state and after stabilization with kiln dust (KDS) and slag to see, whether sufficient improvement can be achieved and to understand the processes relevant to stabilization process. The disturbed soil samples used for the laboratory study of the present study were collected from five different localities of the Nile Delta. These localities include Menofyia Governorate, Daqahlia Governorate, Gharbyia Governorate and Damietta Governorate (Soil 1, Soil 2a & b, Soil 3, Soil 4a & b, Soil 5a & b). The main objective of the present work is to design an effective and economic method of soil improvement for roadways and the other infrastructure in Egypt. In this thesis, the soil samples in the selected localities have been studied in the natural state and after stabilization.
As shown by X-ray diffraction study, the non-clay mineral of the untreated soil samples are essentially consisting of three main groups: I) Silicate minerals; including quartz and Albite, II) Oxides; including hematite and magnetite, and III) Carbonates and evaporates; consisting of calcite, dolomite and halite. The results of XRD and SEM showed that, montmorillonites and kaolinite are the predominant clay minerals in the soil samples.
Based on the grading data, the untreated soil samples in the Nile Delta are fine-grained, consisting mainly of mud, sandy silt, silty sand, sandy mud and silt. The frequency distributions of the fines (<0.063 mm) showed that, the highest frequencies of fines occur in the most soil types. The highest content of fines (>20%) and the lack of gravels in the soils make them unsuitable for the construction of granular road-base and sub-base courses. However, some soils of some groups with less than 20% fines can be used for sub-base construction. The studied soil samples are classified according to the USCS as CL, CH and MH, which are clay of low to high plasticity. Also the soils are classified according to ASHTOO as A-7-5, A-7-6 and A6. According to the geotechnical characteristics, the liquid limits of the soil samples are more than 37.3 % and less than 145.4 %. The plastic limit ranges from 13.7 % to 44 %. The Plasticity index ranges from 13.6 % to 106%. The free swelling ranges from 10 % to 110 %, while the shrinkage limit ranges from 3.3% to 21.94%. Swelling and shrinkage are often characterized by high liquid limit and plastic limit caused by a variable content of more active clay minerals. The soils under investigation are classified into normal clay soils (0.86) and active clay soils (2.41). Significant correlation is found between the clay fractions, free swelling, liquid limit and plastic limit.
The data obtained from the compaction curves showed that, the soil samples have maximum dry density (MDD) ranging between 1.299 and 1.877 g/cm3 and optimum moisture content (OMC) varying 9.2 and 30.668 %, while the UCS values of the selected soils range from 0.21 to 0.34 Mpa.
The soils in the areas of study are classified according to the indices parameters into four groups: group 1 is characterized by extremely high plasticity, lower compressive strength, and higher optimum moisture content and lower maximum dry density (G1), very high plasticity (G2), high plasticity (G3) and medium plasticity (G4). G4 soil samples have lower clay fraction, liquid limit, plastic limit, plasticity index, swelling, shrinkage, optimum moisture content values than the other three groups, as well as higher values of compressive strength and maximum dry density compared to the other three groups. The highest plasticity and moisture content imply that, they will take longer periods to dry. This creates a serious problem during engineering construction in the Nile Delta, where long dry periods are infrequent. The maximum dry densities achieved in the laboratory indicated that the soil groups can be used for general filling work and the construction of sub-grade and sub-base courses of the major roads. They may even be used for the base course construction of secondary roads. The low density, soft and organic clays have very low strength and can only used bear light loads. For heavy structures, pile foundations may be required for the soil groups, whereas shallow spread footing is adequate for medium to slightly heavy structures built on the soil groups.
Soils with undesired properties can present great problems underlying the pavement and light structures. It is possible to overcome the problems by altering the soil itself or improving the properties of the soils, which can be achieved by stabilization methods. Two soils (I & II) of different locations and properties are selected in this work. Industrial wastes, cement kiln dust (CKD), granulated blast furnace slag (GBFS) and combination of CKD/GBFS are used as stabilizers. The stabilizer quantities are 5, 10 and 20 % in weight) for both cement kiln dust and slag.
All the CKD, GBFS and CKD-GBFS additions to the soil I and II caused increasing in the pH values of soils when compared to the pH values of untreated soils. The two types of soil treated with slag showing a reduction in the liquid limit and plastic limit, the same behaviour was observed by both Wild et al. (1996) and Al-Rawas et al. (2002). In the case of soil-CKD and soil-CKD + slag mixtures, there is an increase in liquid limit for soil I and decrease in soil II. However, increases in the plastic limit are consistently large enough to lower the plasticity index for the two soils. The plasticity index values of the two soils (I & II) treated with CKD, Slag, CKD + slag showed a similar behaviour of decrease in the plasticity index (PI) with increasing the percentage of stabilizers. Reduction in plasticity index indicated as the quality control for soil improvement. The only exception is the soil stabilized with 5% CKD + 5% slag, that reflects an increase in the plasticity index value. This indicated that, higher additions of CKD + slag will be useful in stabilizing the medium plasticity soil G1. Confirming with the previous results, the increasing of 10% CKD +10% slag decreased the plasticity index. Concerning the curing time, the results of the liquid limit (LL), plastic limit (PL) and plasticity index (PI) showed that, these limits increase or decrease with more curing time, but in all cases the plasticity index of the two soils (I & II) are lower than the untreated soils.
The effect of the addition of CKD, slag and CKD-slag mixtures on the compaction characteristics of the soil II increased the maximum dry density and decreased the optimum moisture content with increasing the CKD and CKD - slag mixture. However, the addition of 5% CKD alone and 10 % slag caused the decrease in the maximum dry density of soil II. There is a substantial increase of the optimum moisture content with the addition of slag percent.
It is obvious that, adding CKD, slag and CKD - slag mixture increased the optimum moisture content (OMC) and decreased the maximum dry density for soil I. The increase in the OMC is due to the additional water held with flocculants soil structure resulting from cementitious reaction. Principally, increases in the dry density are an indicator of improvement. But unfortunately, both the CKD and slag reduced the maximum dry density.
For the CKD and slag, increasing the amount of stabilizer did not provide any benefit to certain soil strength. However, the inclusion of five and ten percent slag increased the UCS strength by over 140 percent, when compared to the untreated soil II.
To observe the effect of curing time on the compressive strength, the soils with CKD, slag and CKD + slag mixture are tested in unconfined compressive strength apparatus in 1, 7, 28, 60 and 139 days. The unconfined compressive strength values of soil II containing 5%, 10 %, and 20 % slag and 5% slag + 5% CKD increased in 7 days compared to the untreated soil II.
Significantly, the greater improvement in the strength (536.4, 631.76 and 571 %) is measured in the case of soil I treated with 5 % CKD at 7, 28 and 60 days, also the unconfined compressive strength in soil I increased in 7 and 60 days (121.178 & 684.11). With the higher amount of CKD (10 %), the compressive strength in soil I did not show any increase over time, compared to the untreated soil. But, the mixture of soil I with 5 % slag + 5 % CKD and 10% slag + 10 % CKD, the UCS strength increased at 7 days and 28 days. Soil I gained the maximum strength at 28 days.SEM micrographs of the composite samples prepared with CKD, slag and CKD + slag (0%, 5%, 10% and 20%) after a hydration period of 7 days. In some places, the untreated soil morphology is disappeared and new products are formed. One of the major features of the microstructure of soil I prepared with 5% CKD at 60 days is the presence of elongated shaped particles which are identified by the EDX analysis, as Ca, Si, Al and S. The other features present in the hydrated microstructure of soil I CKD mixture showed cemented elongated particles.
The main constituents of hydrated soil with slag is the calcite, originally present in soil II with 20% slag at 7 days. The CSH gel-like structure is found in the hydrated soil-slag.