جستجوی مقالات مرتبط با کلیدواژه "تثبیت با سیمان" در نشریات گروه "عمران"

In this research, the effect of soil stabilization with cement at the same time as its reinforcement with fibers has been studied on the shear strength of sandy soil exposed to freeze-thaw cycles. In order to achieve this goal, laboratory studies were carried out with the help of unconfined compressive strength tests (UCS tests) on different compounds obtained from mixing cement, fibers, and sandy soil. More than 336 cylindrical laboratory models with dimensions including 3.6cm in diameter and 8cm in length have been made. Various modes have been observed during the failure of the samples, including shear, tensile, plastic yielding, and composite failure modes. The fibers used in the present research are waste products of tire factories known as DTY. Percentages of 2, 4, and 6 for cement and 0, 0.5, and 1 for fibers with lengths of 0.5, 1, and 1.5 cm were used relative to the weight of dry sandy soil in making the samples. Uniaxial cylindrical samples were tested for unconfined compressive strength after 7 and 28 days of curing time and under 0, 1, 2, and 3 freeze-thaw cycles. The results show that the act of stabilizing the soil with cement, along with reinforcing it to a certain amount of fibers, improves the uniaxial compressive strength before and after freezing and thawing cycles. This amount depends on the percentage of cement and the curing period. Also, adding cement in a certain curing time increases the unconfined compressive strength before and after applying the cycle, increases stiffness, reduces the ductility and toughness of the sample, and brittle failure when breaking occurs in the soil. Also, the addition of fibers, to some extent, improves the weaknesses caused by soil stabilization, such as reducing the failure axial strain, decreasing the residual strength, and the toughness of the materials in the conditions before and after freezing and thawing.

This paper experimentally examines the effect of geotextile layers on the undrained behavior of cement-stabilized clay specimens using unconfined compressive strength (UCS) tests. Accordingly, the low-plasticity clay specimens were remolded in three different moisture contents, including optimum moisture content and two other ones corresponding to 90% relative compaction. The clay specimens were also stabilized by cement with various percentages equal to 3, 5, and 7% of the dry weight of the soil. The stabilized clay specimens were then cured in 7, 14, and 21 days prior to performing the unconfined compressive tests. In order to investigate the effect of reinforcement type, the stabilized clay specimens were reinforced with two types of non-woven geotextiles with different values of tensile stiffness. Results of experiments showed that reinforcing cemented-clay specimens with geotextile sheets improves the mechanical properties such as maximum compressive strength, residual strength, and rupture strain of reinforced specimens compared to unreinforced ones. The greatest increase in compressive strength occurred in specimens reinforced with three geotextile layers, which had an average 37% increase in strength compared to non-reinforced specimens. The comparison between reinforced specimens with two different geotextiles showed that increasing the tensile strength of the geotextile increases the compressive strength, rupture strain, and residual stress of the reinforced specimens.

Dredged soils are obtained from capital dredging (resulting from the construction of hydraulic structures) or maintenance dredging (from the maintenance of hydraulic structures). Due to the large volume, uselessness and low pollution of these soils; researchers are exploring using these materials as soil alternatives. Poor bearing capacity, fragmentation characteristic, and difficult behavior prediction; are some problems of carbonated soils. Also non-carbonated dredged soils often don’t have proper technical characteristics. The Persian Gulf has coasts covered with carbonated sediments, also forced to dredge. Due to the great importance of this waterway in the world economy and energy supply, as well as the problematic nature of its carbonated soil (for example, creating problems for oil extraction platforms); The Persian Gulf’s carbonated soil, like dredged soil, needs to be improved. One of the most widely used soil improvement methods is stabilization. Besides the use of new materials (such as polymer and fiber), stabilization by cement and lime are still the most common stabilization methods for variety of soils. In addition to economic value, it will also be environmental and technical importance to consider the possibility of using it in engineering structures such as road bodies as base and subbase. Soil improvement is done in various additives and methods. Depending on the type of soil and materials in each area, the appropriate stabilization method varies; therefore, the same prescription for soil stabilization cannot be proposed. This paper focuses on carbonated and dredged soils, their stabilization methods; and reviews some practical experiences of stabilizing them.

Natural soft clay soils due to the lack of sufficient bearing capacity and the high deformation potential require to be improved using either chemical stabilization methods or physical methods such as soil reinforcement or pre- compression. The method used is greatly influenced by technical and the economic considerations as well as the physical characteristics required (Abdi and Zandieh, 2014). Chemical stabilization generally results in increasing the strength and the bearing capacity and reduces the swelling- shrinkage potential of the clayey soil. On the other hand from ancient times humans have used natural fibers to alleviate the weakness of soil in resisting tensile stresses (Abu-Farsakh et al., 2008). Now-a-days due to the technical progress made synthetic materials such as geo-synthetics are used for soil improvement. Use of geo-synthetics such as geogrids and geotextiles have grown rapidly in the construction of soil structures such as embankment dams for reducing the volume of materials needed as well as drainage purposes, increasing bearing capacity in foundation engineering, etc (Alawaji, 2001). These materials are easy to use and environmentally friendly. Coarse grained materials are also employed in construction of reinforced soil structures due to high drainage and shear strength characteristics as well as volume stability due to moisture variations and time (Alawaji, 2001).

Chemical stabilization by cement is among the factors of optimizing the soil performance. Numerous studies have been performed in the field of using cement as a stabilizing material (Naderi Nia- Naeini SA, 2009; Dupas J, Pecker A, 1979). The results of this research show that the addition of cement to the soil increases stiffness and improves soil’s failure behavior and its engineering properties. Improving the engineering properties of the soils stabilized with cement is essentially due to hardening of cement as a result of hydration of cement and forming additional cementitious materials between the hydrated cement and clay particles in the soil (Shihata SA, Baghdadi ZA, 2001). On the other hand, although cement industry has adopted the most modern technologies to reduce pollution, different stages of cement production and transportation have a great share in the environmental pollution. Studies indicate that to produce one ton of cement and clinker in Iran 0.655 and 0.79 tons of CO2 greenhouse gas are emitted respectively (Milika Bildrici 2019). Therefore the cement mix optimization is such that the lowest amount of energy is used to produce it with the least damage to natural resources and finally the best performance possible is provided which is considered as a main goal (Khaleghi, M. H. 1990).

It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on compaction studied as one of pozelan additive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. Compaction poroctor tests were carried out on 24 combination type of cement and zeolite with include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 cement with zeolite. Results show that by replacement cement material by zeolite, the maximum dry density increased 2 to 2.5% in comparison with cemented samples and 14% optimum water content approximately concluded. At the end, a function fits Based on Voltra series presented to relate maximum dry density and zeolite-cement-soil parameters.

The lack of accessibility of high- quality materials and the increased costs associated with the use of these materials will finally necessitate engineers to use local soils. In such cases, ground improvement behaved satisfactorily in many conditions. Ground improvement can be defined as the procedure of increasing shear strength parameters and decreasing the permeability and compressibility of the soil. Different methods can be used to improve the geotechnical properties of the problematic soil, one of which is using additives. Additive stabilization is achieved by the addition of proper percentages of cement, lime, fly ash, bitumen, or combinations of these materials to the soil. The selection of type and determination of the percentage of additive to be used are dependent upon the soil classification and the degree of improvement in desired soil quality. It is known that, when using soil-cement as a compacted layer over low bearing capacity soil, the system failure usually happens under tensile stresses at the base of the improved layer. Then, it would seem more reasonable to use the tensile strength as a direct measure of the soil-cement strength. In this investigation, zeolite and its effect on compaction are studied as one of addictive material to cement. Therefore, Kilinopiolite kind of zeolite, Neka cement type 2, and Babolsar sand are used. 24 combination types of cement and zeolite include different cement percentages: 2, 4, 6, and 8 percent of the total dry weight of samples and replacement percent's of 0, 10, 30, 50, 70, and 90 zeolites with cement. In this article, first, soil mixture and producing samples based on standard compaction test have been done. Results show that by increasing the replacementpercentages of zeolite with cement, decreasing maximum dry density and 14% optimum water content approximately concluded. Also, by replacing 30 percentage of cement by zeolite material, the tensile strength increased up to 40 % in comparison with cemented samples.

The lack of accessibility of high quality materials and the increased costs associated with the use of these materials will finally demand engineers to use local soils. In such cases, ground improvement performed reasonably in many conditions. Ground improvement can be defined as the procedure of increasing shear strength parameters and decreasing the permeability and compressibility of the soil. Different methods can be used to improve the geotechnical properties of the problematic soils such as loose sand that one of them is using additives. The stabilization of soils with cement is an attractive technique due to economic and environmental issues and avoiding the use of borrow materials from elsewhere. Cementation of sand results in increased brittle behavior as peak compression strength increases. The compressive strength of artificially cemented soils has been studied in the past by several investigators.A number of studies have also reported on the influence fiber, glass, fly ash, silica fume and nono particle on the mechanical behavior of cemented sands .However, to the author’s knowledge, there has been a little effort devoted to the research on the use of pozzolans such as natural zeolite as an addictive material to the cemented sands. Natural zeolite, an extender, has been investigated for use as cement and concrete improver by some researchers.
It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on unconfined compression studied as one of addictive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. A total number of 144 unconfined compression tests were carried out on 24 combination type of cement and zeolite include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 zeolite with cement based on 50,70 and 85% relative densities in7 and 28 days curing times. Results show that in 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. At the end, a power function fits presented to relate unconfined compressive strength (UCS) and zeolite-cement-soil parameters (porosity (n) and voids/ polynomial model of cement and zeolite voids).It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on unconfined compression studied as one of addictive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. A total number of 144 unconfined compression tests were carried out on 24 combination type of cement and zeolite include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 zeolite with cement based on 50,70 and 85% relative densities in7 and 28 days curing times. Results show that in 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. At the end, a power function fits presented to relate unconfined compressive strength (UCS) and zeolite-cement-soil parameters (porosity (n) and voids/ polynomial model of cement and zeolite voids).