Stabilization of Tropical Fibrous Peat Using Ordinary Portland Cement and Additives

One of the most troublesome of soft and organic soils is fibrous peat due mainly to their high compressibility, and their low shear strength. In this study, fibrous peat has been stabilized with ordinary Portland cement (OPC), as well as OPC and five different types of additives namely; polypropylene fibers, steel fibers, silica fume, blast furnace slag, and fly ash. Shallow and deep stabilizations have been studied to improve strengths, as well as to reduce compressibility of fibrous peat. For shallow stabilization of fibrous peat, strength evaluation tests (un-soaked and soaked) were unconfined compressive strength (UCS), and California bearing ratios (CBR), and for deep stabilizations were, consolidation undrained triaxial (CU), and Rowe cell consolidation tests. Three types of curing technique have been studied for their effectiveness, as well as their ease of applications in the field. Curing techniques were; moist curing, moist curing with surcharge load, and air curing. Curing periods used were continued up to 180 days. Based on the results obtained from various curing techniques, air curing technique was chosen to be used for the entire shallow stabilization process. Optimum dosage rates for polypropylene fibers, silica fume, blast furnace slag, and fly ash as additives to be used in the research either in shallow or deep stabilization was determined through UCS tests. In-order to examine the effectiveness of stabilization method used in the research in the field, fibrous peat with its field moisture contents has been used for stabilized samples. Also, in-order for shallow stabilization process to be more effective, stabilized samples were tested for their strength at their optimum moisture contents (OMC) found from compaction curves. For deep stabilization of fibrous peat deposits, precast stabilized columns were developed and tested for their effects to improve shear strength parameters, as well as reducing compressibility of fibrous peat. The process of making precast stabilized peat columns included mixing fibrous peat with a specified amount of OPC, (with or without additives) at their optimum moisture contents. Each type of mixture was then compacted in to molds and left to dry. When drying was completed, they were taken out of their molds and inserted in the pre-drilled holes within the undisturbed fibrous peat, and tested for their strength as well as their deformation through CU triaxial, and Rowe cell consolidation tests respectively. Precast stabilized peat columns that were made of hemic or sapric peats were also tried for their strengths and deformations evaluations as well. The columns were tested for their load bearing capacities in a larger scale test tank. Untreated fibrous peats as well as six different types of precast stabilized fibrous peat columns were tested in the test tank. As the curing period were increased, more strength obtained by the stabilized peat samples. Among various types of additives used in this research, the most effective dosage rates for polypropylene fibers was found to be 0.15%, and for silica fume 10, and 5% when lower amount of OPC ( 25%) were used respectively. As the amount of steel fibers increased from 2 to 4% in the OPC treated samples, the stabilized samples gained further strength. Joint uses of polypropylene and steel fibers, use of polypropylene fibers, and use of silica fume in OPC treated fibrous peat provide the highest strength during curing period respectively. Use of blast furnace slag and fly ash as chemically active additives to stabilize fibrous peat were positive but the degree of effectiveness was not as effective as when OPC alone was used. Test results in this study indicate that, stabilization procedures used in either shallow (mass), or deep stabilization improve the load bearing capacities of untreated fibrous peat by increasing its load bearing capacity, as well as decreasing its deformations upon imposed loads

Evaluating Negative Environmental Impacts Caused by Dam Construction

Dams are one of the most important structures in the water resources transmission and storage systems. Thus, given the growth and development of dam construction in the world, evaluating environmental consequences of the dam has high importance. Dams leave positive and negative impacts on the environment. The destructive impacts of dam construction include social, economic, hydraulic, biological, health, and atmospheric impacts, etc., leading to change and complexity. Hence, given the importance of the positive impacts of dams, it is essential that negative environmental impacts of the dam to be minimized for sustainable development. The current article evaluates the negative environmental impacts caused by dam construction

Effect of polypropylene fibers on the California bearing ratio of air cured stabilized tropical peat soil

Problem statement: Peat soil is well known to deform and fail under a light surcharge load and is characterized with low shear strength, high compressibility and high water content. With the rising demand from the construction industry, utilization of these soils is required and suitable technique needs to be found out for stabilizing them. Approach: Model study had been carried to stabilize peat soil using cement as binding agent and polypropylene fibers as additive. Due to high natural water content of the peat soil, the stabilized peat soil samples were kept at normal room temperature and relative humidity for air curing for 90 days. The improvement in the mechanical strength of the stabilized samples was studied by California Bearing Ratio (CBR) test for both, unsoaked and soaked samples. The water-cement ratio of the samples was measured for 180 days to study the improvement in strength over time. Results: The results of CBR tests showed an increase by a factor over 22 for unsoaked condition and 15 for the soaked condition of the stabilized samples. With the addition of the polypropylene fibers to the stabilized peat soil with cement not only improved the strength of the stabilized peat soil but also contributed to considerable amount of uniformity and intactness to the stabilized peat soil samples. It was also observed that as the curing time for the stabilized peat soil continued through 180 days the moisture content continued to decrease as well. Thus the water-cement (w/c) ratio reduced and as a result of cement hydration, the strength stabilized peat soil samples increased in hardness and gained strength through the curing period. Conclusion/Recommendations: Cement and polypropylene fibers can be used to improve the mechanical strength of the soft peat soil by adopting air curing technique

RC concrete versus conventional concrete in pavement

This article contains a discussion on roller-compacted concrete(RCC)or zero-slump concrete construction techniques. While discussing the various aspects of RCC, this study introduces the similarities and differences between conventional concrete and RCC for using as pavement. The article also describes the production of concrete, and a list of laboratory and field tests for the quality control of both types of concrete. A general view of what the RCC actually is, followed by the mix-design techniques, performance (strength and durability), handling techniques for concrete in both cold and hot weather, and curing guides for both types of concrete, with more emphasis on RCC, are herein presented. The study ends with an introductory discussion on dam construction using RCC

A behavior of reinforced vibrocompacted stone column in peat

In the literature, several methods of ground improvement have been presented including compacted stone columns. The bearing capacity of the granular column is governed mainly by the lateral confining pressure mobilized in the soft soil to restrain or prevent bulging of the granular column. Therefore, the technique becomes unfeasible in peat that does not provide sufficient lateral confinement. This condition can be overcome by encasing the stone column with geogrid. This paper investigates the performance of the geogrid encased vibrocompacted stone column in peat. This study was carried out using PLAXIS software equipped with unit cell concept. The peat was modelled using soft soil model and the stone column using Mohr-Coulomb soil model, respectively. The geogrid was modelled using the geogrid option and could take only tensile force. The results indicate that the geogrid encased stone column can take much higher load in comparison to ordinary stone columns as the stiffness of the column increases. Meanwhile, the length of encasement also varied and it was observed that it was very effective up to about two times the diameter of the column. It also increased the column stiffness, and therefore led to a significant strain reduction. It was also observed that the columns at a spacing of three times the diameter are very effective. The results presented here can be used by the geotechnical engineers to design the geogrid reinforced stone column based on the strength of the soil, diameter of the column, spacing of the columns and stiffness of the geogrid

Effect of fly ash on the strength values of air cured stabilized tropical peat with cement

This article describes laboratory research done on strength evaluations for stabilized samples made of tropical fibrous peat. The stabilizing agents used were ordinary Portland cement (OPC) as binding agent and flay ash as additive. Stabilized samples were tested for their strength through unconfined compressive strength (UCS) and California bearing ratio (CBR). Different dosage rates of OPC and fly ash were used in trial and error experiments for the most effective combination for stabilized peat samples that were at their natural moisture content. Strength tests used for the trial samples were UCS and they were air cured for 90 days. After detecting the most effective dosage rate in the trial samples, their values were used to prepare CBR samples at their optimum moisture content. CBR samples were then air cured from 1 to 90 days and tested under un-soaked and soaked conditions. The most effective dosage rate for the stabilized peat samples was found to be close to 50% for each. If less than (100 kg/m3) of ordinary Portland cement with the same amount (100 kg/m3) of fly ash are mixed with peat soil and compacted at their optimum moisture content, after 90 days of air curing the soft peat soil having a field CBR of less than unity, will have a CBR of 28 % for un-soaked and 15% for soaked conditions

Stabilising peat soil with cement and silica fume

Stabilising soft, wet and unconsolidated peat soil by using cement as binders and silica fume as additive is often cost-effective compared with other ground improvement methods. This study was carried out by adding 5–50% (by weight) cement to peat soil, and silica fume was added at the rate of 5–10% (by weight) of cement. An air-curing technique was used to cure the samples, as it was found that the water content of the untreated peat soil was very high. The air-cured peat samples were tested for unconfined compressive strength (UCS) and California bearing ratio (CBR) for two conditions: soaked and unsoaked. For the soaked condition the samples were submerged in water for a period of 96 h; the samples after 90 days of air curing were considered as being in the unsoaked condition. From the test results, it was observed that the UCS and CBR increased by a factor as high as 11 and 25 respectively as compared with untreated peat soil. The optimum dose of cement and silica fume was also evaluated. It was observed that the upper layer of in situ peat soil can be stabilised with cement and silica fume to increase the strength of sub-base for the pavement

Cement and Silica Fume Treated Columns to Improve Peat Ground

Peat layers are weak; much weaker and more compressible than inorganic soils, and thus do not provide suitable support for most engineering structures. The usual methods have been either to remove peat and replace it with suitable soil or to pass piles through it to the stronger soil layers below. On the other hand, research has been carried out to discover ways to strengthen peat deposits by deep stabilization. Peat was reinforced with precast columns stabilized with cement and silica fume. Unconfined compressive strength, Rowe cell consolidation test and plate load test were carried out to evaluate the increase in strength. The compression index (C c) of peat samples, upon use of stabilized precast columns, was found to reduce by 36 % using only 5 % cement. Further, when 10 % silica fume was added along with cement, the C c decreased by 42 %. Plate load test results indicated that the bearing capacity of peat can be improved significantly by over 84.6 % when 15 % cement is used, and also the use of silica fume with cement further increased it to 107.7 % compared with untreated peat. The precast stabilized columns (stabilized with cement and silica fume) can be used successfully to improve the engineering behaviour of soft peat deposits and as a result improve its strength and bearing capacity. Finite element analysis was carried out to understand the distribution of stresses in peat as well as in the stabilized column

The prevalence of dental caries in primary molars and its related factors in 6 and 7 years old children in Shemiranat health center

Background and Aims: Healthy People plan that is expressed by WHO stipulated that by 2000 at least 50% of the children and by 2010, 90% of 6-5 year-old children should be with no caries in their primary teeth. The present study investigated the prevalence of teeth decay of D, E and related factors in 6 and 7 years old children.Material and Methods: This cross-sectional study was conducted in 2013 to assess the bases covered by student Shemiranat health center. Study population including 5000 students aged 6 and 7 and the sample size of 450 patients was available in sampling method. Data in a form that was designed for this study were collected and analyzed using Epi data and SPSS software.Results: The index dmft (Decayed Missed Filled Teeth) in primary teeth D and E is equaled to 2.46 and prevalence of dental caries E and D were estimated 63.4%. There is significant relationship between decay of teeth D and E and father education (Pvalue<0.001) and mother education (Pvalue<0.001) children age (Pvalue<0.001) locality of children whether they live in rural or urban regions (Pvalue <0.001) economic condition of families (P value<0.001) and social status (Pvalue<0.001) with number of decay teeth.Conclusion: The results imply on high prevalence of teeth caries among the children molar covered by Shemiranat health center so that the number of teeth without caries is far from the global measures and WHO. Likewise there is a significant relationship between social and economical status with children decay teeth and there is a need to pay more attention to mouth health in poor regions from the social and economical point of views.Key words: Prevalence of carries, D and E teeth, dm

شيوع پوسيدگي دندان هاي آسياي شيري و عوامل مرتبط با آن در كودكان 6 و 7 ساله در شبكه بهداشت و درمان شميرانات

Background and Aims: Healthy People plan that is expressed by WHO stipulated that by 2000 at least 50% of the children and by 2010, 90% of 6-5 year-old children should be with no caries in their primary teeth. The present study investigated the prevalence of teeth decay of D, E and related factors in 6 and 7 years old children.Material and Methods: This cross-sectional study was conducted in 2013 to assess the bases covered by student Shemiranat health center. Study population including 5000 students aged 6 and 7 and the sample size of 450 patients was available in sampling method. Data in a form that was designed for this study were collected and analyzed uBackground and Aims: Healthy People plan that is expressed by WHO stipulated that by 2000 at least 50% of the children and by 2010, 90% of 6-5 year-old children should be with no caries in their primary teeth. The present study investigated the prevalence of teeth decay of D, E and related factors in 6 and 7 years old children.Material and Methods: This cross-sectional study was conducted in 2013 to assess the bases covered by student Shemiranat health center. Study population including 5000 students aged 6 and 7 and the sample size of 450 patients was available in sampling method. Data in a form that was designed for this study were collected and analyzed using Epi data and SPSS software.Results: The index dmft (Decayed Missed Filled Teeth) in primary teeth D and E is equaled to 2.46 and prevalence of dental caries E and D were estimated 63.4%. There is significant relationship between decay of teeth D and E and father education (Pvalue<0.001) and mother education (Pvalue<0.001) children age (Pvalue<0.001) locality of children whether they live in rural or urban regions (Pvalue <0.001) economic condition of families (P value<0.001) and social status (Pvalue<0.001) with number of decay teeth.Conclusion: The results imply on high prevalence of teeth caries among the children molar covered by Shemiranat health center so that the number of teeth without caries is far from the global measures and WHO. Likewise there is a significant relationship between social and economical status with children decay teeth and there is a need to pay more attention to mouth health in poor regions from the social and economical point of views. education (Pvalue<0.001) and mother education (Pvalue<0.001) children age (Pvalue<0.001) locality of children whether they live in rural or urban regions (Pvalue <0.001) economic condition of families (P value<0.001) and social status (Pvalue<0.001) with number of decay teeth.Conclusion: The results imply on high prevalence of teeth caries among the children molar covered by Shemiranat health center so that the number of teeth without caries is far from the global measures and WHO. Likewise there is a significant relationship between social and economical status with children decay teeth and there is a need to pay more attention to mouth health in poor regions from the social and economical point of views.زمینه و اهداف: برنامه مردم سالم که توسط سازمان جهانی بهداشت عنوان شده است تصریح نموده که تا سال2000 میلادی حداقل50% کودکان و تا سال 2010، 90% کودکان 5-6 ساله باید بدون پوسیدگی در دندان شیری باشند. هدف از این مطالعه بررسی شیوع پوسیدگی دندان های D و E و ارتباط آن با وضعیت اقتصادی و اجتماعی در کودکان 6 و 7 سال بدو ورود به مدرسه می باشد. مواد و روش ها: این تحقیق توصیفی مقطعی در سال 1392 و در پایگاه های سنجش دنش آموزی تحت پوشش شبکه بهداشت و درمان شمیرانات انجام شده است. یافته ها: شاخصdmf در دندان های شیری معادل 2/46 درصد برآورد گردید وشیوع پوسیدگب دندان هاE و D 63/4% می باشد. بین متغیرهای پوسیدگی  دندان های D و E میزان تحصیلات پدر و مادر ارتباط معناداری وجود دارد.  همچنین بین سن گودکان وضعیت اقتصادی خانوده ها و نیز محل زندگی کودکان به لحاظ شهری و روستایی بودن با پوسیدگی دندان ها ارتباط  معناداری مشاهده شد. نتیجه گیری: نتایج این مطالعه بر شیوع بالای پوسیدگی در بین کودکان تحت پوشش شبکه بهداشت شمیرانات دلالت دارد. همچنین تعداد کمی از کودکان مورد پژوهش فاقد پوسیدگی بوده که با معیارهای جهانی فاصله زیادی دارد این مزالعه لزم توجه بیشتر به رعایت بهداشت دهان در کودکان را نمایان کرد