Cement stabilisation of crude-oil-contaminated soil

© 2016, Thomas Telford Services Ltd. All rights reserved. Crude-oil-contaminated soils are usually considered unsuitable construction materials for earthworks. This paper presents an experimental investigation of the effects of applying Portland cement on the plasticity, strength and permeability of a crude-oil-contaminated soil in order to ascertain its suitability for use as an earthworks construction material. Series of specific gravity, Atterberg limits, compaction, strength and permeability characteristics were determined for a natural soil, the soil after being artificially contaminated with crude oil and the contaminated soil with varying proportions of added cement. It was found that the geotechnical properties of the soil became less desirable after contamination with crude oil, but the application of cement to the contaminated soil improved its properties by way of cation exchange, agglomeration and cementation. Cement stabilisation of crude-oil-contaminated soil provides a stable supporting structure, as well as a capping layer, that prevents the crude oil from interacting with the construction materials above. Thus, instead of disposing of contaminated soils, creating unnecessary waste and incurring costs, stabilisation with cement – which is practically feasible to undertake on site – makes such soils useful for supporting structural foundations or road pavement structures

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Experimental insights of using waste marble fines to modify the geotechnical properties of a Lateritic soil

Marble spoil waste is an environmental nuisance. The effects of adding waste marble fines (WMF) on the plasticity, strength and permeability of a lateritic clay have been investigated for its potential use as a soil modifier or stabilizer of road pavement layer materials or earth-building materials. The chemical compositions of the WMF and soil were determined using X-ray fluorescence and atomic absorption spectrometry, respectively. The specific gravity, Atterberg limits, compaction, strength and permeability characteristics of the soil were determined for varying proportions of the soil-WMF blends. The properties of the natural soil–classified as clay of low plasticity (CL) and A-7-6(7), according to unified soil classification and AASHTO classification systems, respectively–were improved after the addition of 10% WMF such that it behaves like a silt of low plasticity. Therefore, WMF is recommended as a low-cost soil modifier or stabilizer for lateritic soil and well-suited for road construction application

Engineering properties of tropical clay and bentonite modified with sawdust

Construction engineers typically avoid the use of expansive soils as construction materials because they are usually difficult to work on and can cause structural failure. This research work investigates how the application of sawdust to tropical clay and bentonite influences their geotechnical properties in order to determine their suitability for use as landfill-liner materials for the effective containment of toxic substances from landfills. X-ray diffractometry, X-ray fluorescence spectroscopy and scanning electron microscopy were used to determine the mineralogical composition, oxide composition and microstructure, respectively, of the clay and the bentonite. A series of laboratory tests were conducted to determine the specific gravity, Atterberg limits, compaction, unconfined compressive strength and permeability characteristics of the clay and the bentonite for varying proportions of sawdust application. Generally, increasing the percentage of sawdust caused a reduction in its specific gravity, maximum dry unit weight and unconfined compressive strength, while it caused an increase in the optimum moisture content and permeability of the modified clay and bentonite. The clay and bentonite both have a sufficiently low permeability that satisfies the hydraulic conductivity requirement for use as clay liners. Eight percent sawdust application to a clay having similar properties as that in this study is recommended as an economic way of modifying it – with the potential of improving its adsorbent property – for use in landfill-liner systems in order to prevent the toxic substances leaching from the landfills, thereby protecting the environment and public health

A short review of CO2 responsive polymeric adsorbents and membranes for water quality control

Separation processes using adsorbents and membranes can be regulated by incorporating stimuli-responsive materials. A wide range of polymers demonstrates changes in characteristics and performance reacted to an external stimulus including pH, temperature, gases, or pressure. Among the stimuli, CO2 is a nontoxic and abundant stimulus that can also be easily added or removed from the separation processes. In this paper, the progress of CO2 responsive adsorbents and membranes was studied. The tertiary amine or amidine groups of the CO2-responsive polymers could be easily protonated by CO2 bubbling, causing characteristic changes to regulate the separation. The synthesis, characteristics, and separation performance were examined. Poly(diethyl-amino-ethyl methacrylate) (PDEAEMA) modified microparticles were used to adsorb protein, but protein recovery remained unclear. The grafting of PDEAAMA and poly(2-(di-methylamino)ethyl methacrylate) (PDMAEMA) on microparticles allowed the adsorption of heavy metals, but higher recovery was attained by PDMAEMA modified microparticles under CO2 bubbling. The CO2- responsive polymeric microparticles were successfully applied in forward osmosis, producing water from salt solution without high temperature or pressure. PDEAEMA modified membranes were extensively studied in the separation of oil and water mixture due to their switchable surface hydrophilicity. PDEAEMA and PDMAEMA modified membranes were also tested in nanofiltration since they exhibited changes in pore size and zeta potential to control pollutant rejection. Nevertheless, CO2-responsive membranes could be cleaned under CO2/N2 bubbling

Strength and microstructure of eco-concrete produced using waste glass as partial and complete replacement for sand

The sustainable benefits of waste glass usage in concrete include the possibility of reducing solid waste and greenhouse gas emission and preservation of raw materials. This current study examines the effect of recycled waste glass as a partial and complete substitute for natural sand in producing eco-friendly concrete. The recycled waste glass was proportioned in levels of 25, 50, 75 and 100% by weight to substitute sand in the concrete using a mix ratio of 1:2:4 (cement:sand:gravel) at a W/C ratio of 0.5 targeting 20 MPa strength at 28 days. Tests, which include X-ray fluorescence (XRF), were conducted on the waste glass and cement materials; slump test was performed on the freshly prepare concrete at different percentage glass content. Compressive and tensile strength tests were performed on 60 specimens after 3, 7, 28 and 90 days of curing. The concrete microstructure was examined using the scanning electron microscope (SEM). Results showed that workability and the mechanical strength of the concrete produced decreased with increasing waste glass content. However, concrete containing 25% and 50% waste glass contents showed significant enhancement in strength, but it is recommended that the optimum glass content should be 25% for the production of sustainable eco-concrete

Lignin modified PVDF membrane with antifouling properties for oil filtration

Lignin is a sustainable chemical that can be extracted from a wide range of lignocellulosic biowaste. It was blended into polymeric membranes to improve membrane morphology for filtration. Lignin dissolved in NaOH solution can be coated on different substrates to improve the surface hydrophilicity. In this work, the polyvinylidene fluoride (PVDF) membrane was coated with lignin to improve the filtration of oily water. Lignin was dissolved in NaOH solution with varied alkaline concentration (0.25–1.50 wt%) and lignin concentration (0.25–1.00 wt%). The PVDF membrane degraded in the highly alkaline solution, but the increasing lignin content reduced the membrane pore size for the effective rejection of oil emulsion. The PVDF membrane modified with 0.75 wt% of lignin in 0.5 wt% of NaOH solution attained a permeate flux about 70 L⋅m-2⋅h-1, but a slightly lower permeate flux of 55 L⋅m-2⋅h-1 was recorded after immersed in alkaline solution 12 h. The lignin modified membrane rejected up to 99.30% of oil, while the neat PVDF membrane only rejected 83.30% of oil. The lignin modified membrane showed slightly lower but stable flux than the neat PVDF membrane due to the reduction of membrane fouling

Causality between challenges, motivations, and extent of use of water recycling systems in residential properties

The paper examines the challenges and extent of the use of water recycling systems in residential properties in five case studies: Malaysia, Mexico, Nigeria, Panama, and South Africa. Based on a review of related literature and a survey of households was conducted, the micro-social, economic, and technical challenges in households and the level of adoption and willingness to use water recycling systems by the homeowners have been identified. The study found that the lack of space, no clear savings on water payment and lack of information/awareness are the most micro-challenges on implementation of water recycling in residential properties. The study deduces that the negative impacts of micro-challenges on implementing water recycling systems will be significantly reduced by improving water recycling systems' efficiency. Moreover, the study concludes that the extent of the use of recycled water in residential properties will increase with public awareness and educating homeowners. The acquisition of the basic environmental and technical knowledge associated with water recycling and the government incentive for implementing water recycling systems in residential properties were recommended in the study. The findings of this study assist in developing a data-driven decision-making framework to build capacity for the analysis of new water reuse intervention strategies commensurate with the capabilities and resources of urban authorities and communities

Causality between challenges, motivations, and extent of use of water recycling systems in residential properties

The paper examines the challenges and extent of the use of water recycling systems in residential properties in five case studies: Malaysia, Mexico, Nigeria, Panama, and South Africa. Based on a review of related literature and a survey of households was conducted, the micro-social, economic, and technical challenges in households and the level of adoption and willingness to use water recycling systems by the homeowners have been identified. The study found that the lack of space, no clear savings on water payment and lack of information/awareness are the most micro-challenges on implementation of water recycling in residential properties. The study deduces that the negative impacts of micro-challenges on implementing water recycling systems will be significantly reduced by improving water recycling systems' efficiency. Moreover, the study concludes that the extent of the use of recycled water in residential properties will increase with public awareness and educating homeowners. The acquisition of the basic environmental and technical knowledge associated with water recycling and the government incentive for implementing water recycling systems in residential properties were recommended in the study. The findings of this study assist in developing a data-driven decision-making framework to build capacity for the analysis of new water reuse intervention strategies commensurate with the capabilities and resources of urban authorities and communities