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Modification-Stabilization of Clayey Silt Soil Using Small Amounts of Cement
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.ORCID-id: 0000-0002-1365-8552
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.ORCID-id: 0000-0002-6790-2653
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.ORCID-id: 0000-0003-1935-1743
2017 (Engelska)Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 7, nr 3, s. 77-96Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This paper presents the effects of using a small percentage of cement to stabilize clayey silt with a low organic content. Cement was added at percentages of 1, 2, 4 and 7% by dry weight. The physical and mechanical properties of the treated and untreated soil were evaluated by laboratory tests including tests of consistency limits, unconfined compressive strength, soil density, solidification and pH values. These tests have been conducted after 7, 14, 28, 60 and 90 days of curing time. Workability is defined as how easily the soil can be control or to handle physically. Results showed that the engineering properties of the clayey silt were improved. The soil exhibited better workability directly after treatment, and the workability increased with time. Soil density increased, while water content decreased, with increasing cement content and longer curing time. The pH value was immediately raised to 12 after adding 7% cement content, and then it gradually decreased as curing time increased. An increase of unconfined compressive strength and stiffness was observed, while strain at failure decreased. A gradual change in failure mode from ductile behavior to brittle failure was observed. The findings are useful when there is a need for modification and stabilization of clayey silt in order to increase the possibilities for different use which will reduce transportation and excavation.

Ort, förlag, år, upplaga, sidor
ScienPress Ltd , 2017. Vol. 7, nr 3, s. 77-96
Nyckelord [en]
Stabilization, small amounts, cement, secant modulus, workability
Nationell ämneskategori
Teknik och teknologier Geoteknik
Forskningsämne
Geoteknik
Identifikatorer
URN: urn:nbn:se:ltu:diva-63156OAI: oai:DiVA.org:ltu-63156DiVA, id: diva2:1091146
Anmärkning

Validerad; 2017; Nivå 1; 2017-04-28 (andbra)

Tillgänglig från: 2017-04-26 Skapad: 2017-04-26 Senast uppdaterad: 2019-09-04Bibliografiskt granskad
Ingår i avhandling
1. Soil Modification By Adding Small Amounts of Soil Stabilizers: Impact of Portland Cement and the Industrial By-Product Petrit T
Öppna denna publikation i ny flik eller fönster >>Soil Modification By Adding Small Amounts of Soil Stabilizers: Impact of Portland Cement and the Industrial By-Product Petrit T
2017 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This licentiate thesis presents results of laboratory experiments regarding the effectiveness of adding small amounts of binders in order to modify and improve the mechanical performance of low organic clayey silt soil. Two types of binders have been used i.e. cement and an industrial by-product named Petrit T. The study covered both the immediate and longterm effects on the soil material. Binder content was added by soil dry weight, Petrit T at 2, 4 and 7% and cement at 1, 2, 4 and 7%. An experimental program has been carried out, including tests of consistency limits, unconfined compressive strength, density, solidification, grain size distribution (by laser particle size analyzer) and pH. The tests were conducted on the treated soil with varying binder contents and after different curing periods, i.e. after 7, 14, 28, 60 and 90 days. Results show that cement is more effective in improving the physical and engineering properties than Petrit T. Plasticity index decreases after treatment and leads to an immediate increase in workability. This is found directly after treatment and it increases with time. Soil density increased, whilst water content decreased, with increasing binder content and curing time. Particle size distribution of soil is changed toward the granular side by the reduction of the particles in clay size fraction and increasing silt size particles after 28 days of treatment. Both binder types resulted in an immediate effect on the soil pH value. This value increased to 12.3 after adding 7% of the binder and then it gradually decreased as curing time increased. The cement treated soil exhibits a more brittle failure behavior than the soil treated with Petrit T. In this case a more ductile behavior was observed. The findings confirmed that adding small binder contents of cement and by-product Petrit T significantly improved the physical and mechanical properties of soil, which can contribute to reduce the environmental threats and costs that are associated with using high binder contents in various construction projects.

Ort, förlag, år, upplaga, sidor
Luleå University of Technology, 2017
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Nationell ämneskategori
Geoteknik
Forskningsämne
Geoteknik
Identifikatorer
urn:nbn:se:ltu:diva-65813 (URN)978-91-7583-977-6 (ISBN)978-91-7583-978-3 (ISBN)
Presentation
2017-10-30, F1031, Luleå, 10:00 (Engelska)
Tillgänglig från: 2017-09-26 Skapad: 2017-09-25 Senast uppdaterad: 2017-11-24Bibliografiskt granskad
2. Soil Modification by adding small amounts of binders: A laboratory study
Öppna denna publikation i ny flik eller fönster >>Soil Modification by adding small amounts of binders: A laboratory study
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Soil stabilization through addition of a hydraulic binder is a method frequently used to modify and improve engineering properties of soft soils. Additives like cement and lime are typically used as stabilizers. More recently, industrial by-products, such as fly ashes, cement kiln dust, blast furnace slags and other slags have been used. The chemical reaction between the soil and the stabilizer alters the physical and engineering properties of the soil and thus desired strength and durability are obtained. The choice of appropriate type and quantity of stabilizer (binder) depends largely on factors such as soil type, moisture content, organic content, sulfate content, curing conditions (time and temperature) and the desired improvement.

The objective of this thesis is to increase knowledge and understanding of how small amounts of binders change various engineering properties of stabilized soils in short- and longtime perspective. Extensive laboratory and field programs have been carried out. They cover immediate and long-term effects on the engineering properties by adding various binders. Cement, Multicem, and by-products Petrit T and Mesa were used as binders. Binder was added to the soil at various quantities: 1%, 2%, 4%, 7% and 8% of soil dry weight. The field and laboratory investigation included tests of consistency limits, sieving and hydrometer, unconfined compressive strength, density, solidification, grain size distribution using laser particle size analyzer, leaching tests and pH value. The tests were carried out on the treated soil with different binder contents and after different curing times i.e. 7, 14, 28, 60, 90 days for laboratory tests and 7 and 35 days for field investigation.

The unconfined compression tests were used to show the effects of different binders on the enhancement in strength and stiffness over time. Consistency limits were determined to investigate the effects of the binders on the consistency limits, directly after treatment and over time. Laser particle size analyzer tests were conducted to investigate the effects of different binders on the particle size distribution (PSD) before and after treatment. The pH tests were conducted to investigate the effects of different binders on the alkalinity of the soil immediately after treatment and over time. This was used to give an indication of soil-binder reactions. MRM leaching tests were conducted to investigate the acidification potential of soils before and after treatment. Freeze-thaw cycles were conducted to investigate the strength characteristics after freezing and thawing in short- and long-term perspectives. Visual observation and standard dry sieving tests were conducted to optimize the proper mixing times to disintegrate or homogenize the soils by decreasing the size of agglomerated soil particles.

The results show, that the variation in soil strength and stiffness of the treated soils are linked to different chemical reactions. Cement is most effective in improving the physical and engineering properties compared to the other binders studied. The plasticity index of soil decreases after treatment and over time. Liquidity index and the ratio of water content to plastic limit are introduced as new indices to illustrate the improvement in workability of treated soil by measuring the reduction in the liquidity index. This is found directly after treatment and it increases with time when the liquidity index is within the plastic range or when the water/plastic vi limit ratio is more than one. Increase of binder content and using longer curing times result in increase of soil density and decrease of water content. Particle size distribution of soil is changed by reducing the clay size fraction and increasing the silt size particles after treatment. This shows that an aggregation of particles take place resulting in coarser material than the initial. The cement-treated soils exhibit a more brittle failure in the unconfined compression tests compared to soils treated with other binder types where a more ductile behavior is observed. Applying freezing-thawing-cycles reduces the strength and stiffness of the treated soil.

The appropriate length of time to homogenize and disintegrate the natural soil prior to treatment depends on several factors, such as soil type, water content, and plasticity properties of soil. For high plasticity soil, the disintegration time should be kept as short as possible. The homogenizing and disintegration time is less important for low plasticity soils with low water content than for medium to high plasticity soils.

The acidification potential of soils are related to the addition of cementitious binders. The effect is found directly after treatment and over time. The treated soil exhibits higher resistance to decrease in pH value. The strength and stiffness properties found in the field investigation agree in general with those obtained from the laboratory investigation for the same binder type.

Ort, förlag, år, upplaga, sidor
Luleå University of Technology, 2019
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Nationell ämneskategori
Geoteknik
Forskningsämne
Geoteknik
Identifikatorer
urn:nbn:se:ltu:diva-75484 (URN)978-91-7790-417-5 (ISBN)978-91-7790-418-2 (ISBN)
Disputation
2019-09-23, F 1031, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-08-14 Skapad: 2019-08-12 Senast uppdaterad: 2019-09-04Bibliografiskt granskad

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