Compressibility Behavior Of Tropical Peat Reinforced With Cement Column

One of the most serious problems encountered by civil engineers these days are when it comes to construction on peat soil. Peat soil poses a difficult problem, which has the tendency to subside especially when its moisture content is high. The moisture content may come from rain flooding, leaking from water or sewer lines or from reduction in surface evapo-transpiration when an area is covered by building or pavement. Peat soil causes cracking, settlements and break-up of pavements, railways, highways, embankments, roadways, building foundations, reservoir linings, water lines and sewer line. These entire problems can be solved if the engineering properties of the problem soil are improved to make them suitable for construction. The main objective of this research is to evaluate the effect of cement column on compressibility when installed in peat soil. Apart from that the researcher also found it important to examine the peculiar engineering behaviour of tropical peat with respect to their compressibility characteristics due to variation in fiber content and organic content In addition, the researcher is also interested to identify the influences of other factors like diameter, length, curing time, number of cement columns and amount of cement in cement columns in reducing compressibility. Undisturbed sample of peat soils were taken from Banting, which is situated in the West coast of Peninsular Malaysia. A suitable auger was designed and fabricated to collect undisturbed peat sample of 150 mm diameter and 230 mm in length. Specimens with 45 mm diameter (area ratio = 0.09) and 60 mm diameter (area ratio = 0.16) of cement column were cured for 7, 14 and 28 days, after which they were subjected to Rowe Cell consolidation test. Results are also presented from test conducted on groups of cement columns using four (area ratio = 0.04) and nine (area ratio = 0.09) columns of 15 mm diameter each to investigate the influence of number of cement columns on compressibility of peat soil. Based on the results obtained, it shows that the cement columns can successfully reduce the compressibility of tropical peat. Compression index of fibric sample was reduced by 60% using cement column of 45 mm diameter and 80% with cement column of 60 mm diameter. Hence, it suggests that larger diameter cement column (or high area ratio) has a higher reduction effect in the compression index. The trend is similar in hemic and sapric peat. A group of cement columns had a significant impact in reducing the compressibility parameters compared to a single cement column due to higher surface area. Using 100% amount of cement in columns recorded the best performance. Compressibility parameters (compression index and coefficient of secondary compression) were significantly improved (lowered) with cement column

Strength And Stiffness Improvement Of Bio-Cemented Sydney Sand

This thesis explores the performance of small scale cemented soil columns produced using soil mixing with cement resulting from bacterially mediated reactions that precipitate calcium carbonate, a process often referred to as bio-cementation. Bio-cementation has received considerable research attention over the last decade as it has the potential to complement existing ground improvement techniques and mitigate environmental concerns with currently used materials. Previous research has concentrated on pumping and injection techniques because of concerns that bacteria will be unable to survive the stresses associated with industrial mixing processes, however it has been difficult to create uniform bio-cemented soil masses. In this thesis the ureolytic bacterium, Bacillus Megaterium, not previously reported in bio-cementation studies, has been investigated to determine its viability and efficiency as a microbe for mediating the calcite precipitation. It has been found that the highest hydrolysis rate is recorded when calcium concentrations are double the urea concentrations, and that significant amounts of calcite can be precipitated in a single mixing process. Unconfined compressive strength (UCS) tests and a series of triaxial tests have been conducted to quantify the effects of the bio-cementation on the mechanical response. Bender elements mounted in the triaxial cell have also been used to monitor the shear wave velocity during curing and shearing. The results of mechanical tests on the bio-cemented sand have been compared with tests on gypsum cemented and uncemented specimens. It has been found that bio-cementation by mixing produces homogeneous specimens with similar strengths and stiffnesses to the commonly used flushing or injection technique. To assess the performance of in-situ mixed, 38 mm diameter, bio-cemented sand columns a small scale in-situ mixing technique was used to create the model columns. Foundation tests have been performed at 1-g in a cylindrical tank with diameter of 600 mm. A significant improvement was observed in the response of foundations when placed on bio-cemented columns, and this was similar to the improvement from more conventional gypsum cements. These tests confirmed the feasibility of using an in-situ mixing technique with bio-cementation and provided valuable insight into the factors that must be considered in developing field applications. This thesis also has demonstrated repair strategies and techniques to encourage healing and self-healing should damage occur in foundations. Results from tests performed to investigate the ability of biocement to repair cemented soil columns are reported

Geomechanical Behavior of Bio-Cemented Sand for Foundation Works

Bio-cementation is an innovative green technology that complements existing ground improvement techniques, but it is yet to be proven for large-scale foundation works. Previously attention has been focused on strategies to inject the bacteria and nutrients to produce the cement in the ground. This study looks at the performance of geomechanical response when the bacteria and nutrients are mixed in sand, an approach that is used in producing cemented soil columns. To explore the mechanical response of bio-cemented soil, results from unconfined compressive strength (UCS) tests and triaxial tests have been analyzed to understand the effects of bio-cementation for sand in contrast to alternative cement, gypsum. The stiffness has also been monitored using bender element techniques in triaxial cell. Both the shear wave signals during the cementation phase and the shearing phase were recorded using this technique. The results show that for a given amount of cement, higher resistances are measured for the bio-cemented samples compared to gypsum. The mixing process is shown to produce homogeneous bio-cemented samples with higher strength and stiffness than the technique of flushing or injection commonly used, provided the amount of calcite is less than 4%. The results show that the bio-cement produces similar mechanical behavior to other artificially cemented sands

The effects of bottom ash in coastal sand

In the construction industry, breakage of sand particles is very common especially at the very early stage of the pile driving work. The breakage of sand particles will result in change of size spectrum and alter its engineering properties. In this research, the effectiveness of bottom ash in improving the engineering properties of crushed sandy soil was studied. The bottom ash of 5%, 10%, 15% and 20% was added into the sand and crushed with 500 and 1000 blows under the Automatic Compactor machine. The engineering properties of different proportion of bottom ash mixture before crushing and after crushing with 500 and 1000 blows were tested. The engineering properties which were measured include the coefficient of uniformity, breakage index, fouling index, permeability and bearing capacity. Results show that adding of bottom ash into the crushable sand improved the load bearing capacity. By adding 20% of bottom ash, the bearing capacity of the crushed sandy soil can be improved by 55% meanwhile the permeability of the sandy soil can be improved by 200%

Influences of waste inclusion on impact and crushing force resistance of track ballast

Recently, the incorporation of various waste materials into the ballast is studied in terms of physical and mechanical behavior. However, the inclusion of concrete debris (CD) and bottom ash (BA) waste, which are enlisted as the inventory materials for railway ballast have not been thoroughly examined. Hence, this paper investigates the improvement in damage resistance of waste incorporated conventional ballast (CB) under impact and crushing force using impact hammer and crushing machine. The initial and final particle size distribution (PSD) were obtained to analyze the damages through the Hardin‘s breakage index and fouling index. The results show that the resistance against crushing and impact force is better when the composition is in the ratio of 1:1 of conventional ballast (CB) and concrete debris (CD). Under crushing load, mixture with 50% of CD recorded breakage index with 4% deviation compared to using 100% of CB. However, integrating with 40% of CD and 10% of BA proved that the values are 2.14% lower than the ACV limit and 9.09% higher than the AIV limit set by British Standard. Although the impact and crushing index of 100% CB aggregates are below the allowable limit, mixing the CD and BA also records results which is only slightly different than the threshold limit. This is due to the cushioning effect caused by the waste acting as the buffering material that reduces the time of impact, which saves the angular materials from wearing off. This will reduce the ballast maintenance intervals that indirectly reduce the service cost and promotes sustainable construction. Based on the results from this study, further experiments are recommended to be carried out to relate and understand which waste material plays a major role in damage reduction or causing higher maitenance cost

Innovative ballast replacement material (IBRM) in-line with geo-technology pillar of IR4.0 in construction

To reduce the damages exerted on existing granite ballast, waste materials such as concrete debris from construction and demolition process and bottom ash from coal energy production mixed in different proportion with granite ballast, creating IBRM. IBRM will be scrutinized to replace the track ballast upto to 50% depending on the speed of train and load exerted on the rail

Suitability of conventional ballast mixed with concrete debris and bottom ash waste

The use of waste materials as a substitute for natural aggregate has been widely tested in all areas of the construction industry. Yet, there is a lack of study on the suitability of the physical properties of waste material when used as one of the components in track ballast. This study evaluates the suitability of conventional ballast (CB) incorporated with concrete debris (CD) and bottom ash (BA) as track ballast material. To achieve the objective, sieve analysis, shape analysis, specific gravity test, water absorption test, and permeability test were carried out. Furthermore, microscopic analysis was used to validate the presence of voids. The result shows that the waste mixed ballast has a coefficient of uniformity (Cu) in the range of 1.92 to 12, a coefficient of curvature (Cc) in the range of 0.8 to 1.18, fines less than 14 mm account for 0.1 % to 28 %, and the mean size is in the range of 22.5 mm to 27.5 mm. Furthermore, the flakiness ranged from 7.56% to 22.5%, the void ratio was 0.43 to 0.55, and water absorption was 2.86% to 4%. The specific gravity was found to range from 2.30 to 2.77 when the permeability measurement was in between 30 cm/sec to 61 cm/sec. All these promising values of engineering properties exhibit the confidence of a suitable alternative to track ballast materials. Hence, CD and BA waste materials incorporated into conventional ballast have a high potential to exhibit better performance and reduce the dependency on natural aggregate

Effects of concrete debris and bottom ash usage on the improvement of ballast degradation

Railway track bed degradation happens due to single-particle and angular corner breakage, which is the current research interest. However, there is a lack of study on the effects of certain inventory waste incorporation in reducing the particle damages. This study evaluates the damage that can be reduced by incorporating waste into conventional ballast (CB). The optimum percentage of waste that can be incorporated in order to have an undisrupted ballast function were also evaluated. Concrete debris (CD) waste from construction and demolition works and bottom ash (BA) waste from coal power plants were incorporated with conventional ballast (CB) in twelve different track design mixtures (TDM). These mixtures were studied by conducting Los Angeles Abrasion (LAA) to fasten deterioration and obtaining the initial and final particle size distribution (PSD). The Hardin breakage index (HBI), ballast breakage index (BBI), void contamination index (VCI) and fouling index (FI) were obtained through the PSD of each TDM. Using the data obtained the damage that is reduced and the optimum amount of CD and BA that can be incorporated with conventional ballast were determined. The microscopic image was used to support and validate theoutcomes. When bottom ash and concrete debris were added in various percentage no more than 50% in total, the BBI value within the TDM improved by 22.95%. The HBI, FI, and VCI have all seen improvement of 64.52%, 5.5%, and 18.22%, respectively. This proves that waste incorporation reduces the overall track bed deterioration effectively. As a result, the BBI for wastecontaining ballast fall between 0.34 and 0.6, whereas the HBI was in the range of 0 to 0.61. The fouling index was recorded less than 15.5%, and the VCI was in the range of 33.28% to 62.45%. Therefore, provision of various waste materials into conventional ballast considerably reduces the damages. In conclusion, the usage and the dependency of natural ballast can be reduced which promotes sustainable development in the railway construction industry

Durability of basalt rebars under alkaline environment

Basalt Fibre Reinforced Polymer (BRRP) is a new composite material made from basalt fibre, and resin matrix. It has been introduced to replace steel rebars as the main component of reinforced concrete structures because of their corrosion resistance under aggressive environments. This study investigates the mechanical properties of BFRP and the degradation state exposed to the alkaline environment and compares the corrosion rate with steel rebars. The flexural strength properties are tested as the parameter of mechanical properties. The results show that the flexural strength of BFRP is affected by immersion time (100h, 500h, 1000h) significantly. SEM results show mechanism of corrosion state that cracked resin matrix occurred and EDS results indicate the percentage components especially silicon elements that detected increased after corrosion. This research identifies a current knowledge gap and can be serve as a reference point for further studies on the properties of BFRP bars to replace steel bars for safe and economic reinforced concrete structures in alkaline environments

Suitability of Eugenia oleina in tropical slope as bio-anchorage system

Landslide is a major geological hazard and poses high risk to most countries in the tropical regions. This problem is more severe in places like Malaysia where residual soil is abundant. High temperature and humidity will easily disintegrate soil particles and therefore loosen the bonding between the soil and the root system. The main goal is to elucidate the interaction mechanism of bioinspired soil anchorage system to enhance bonding between residual soil matrix in tropical region. Hence, this research aims to establish correlation between the pattern of root and its tensile strength to reinforce tropical residual slope. Basic soil property tests and classification protocols were carried out in the laboratory. Root tensile test results from the laboratory was correlated with field pull-out test data. Slope stability in the area where the plant roots were introduced have been disturbed. The factor of safety of slope with bio-anchorage system was one third of the slope with grass. The findings provide the best solution from the bioinspired soil anchorage system for tropical slope. Hence, the plant species that works well in residual soil for the purpose of reinforcing tropical slope was identified and recommended. As a result, many serious landslides and slope failures in residual soil could be avoided in the tropical region. Therefore, slope stabilization technique such as the bioinspired soil anchorage system once established can reduce the dependency on conventional concrete wall