Potential of scrap tire rubber as lightweight aggregate in flowable fill

Flowable fill is a self-leveling and self-compacting material that is rapidly gaining acceptance and application in construction, particularly in transportation and utility earthworks. When mixed with concrete sand, standard flowable fill produces a mass density ranging from 1.8 to 2.3 g/cm(3) (115-145 pcf). Scrap tires can be granulated to produce crumb rubber, which has a granular texture and ranges in size from very fine powder to coarse sand-sized particles. Due to its low specific gravity, crumb rubber can be considered a lightweight aggregate. This paper describes an experimental study on replacing sand with crumb rubber in flowable fill to produce a lightweight material. To assess the technical feasibility of using crumb rubber, the fluid- and hardened-state properties of nine flowable fill mixtures were measured. Mixture proportions were varied to investigate the effects of water-to-cement ratio and crumb rubber content on fill properties. Experimental results indicate that crumb rubber can be successfully used to produce a lightweight flowable fill (1.2-1.6 g/cm(3) [73-98 pcf]) with excavatable 28-day compressive strengths ranging from 269 to 1194 kPa (39-173 psi). Using a lightweight fill reduces the applied stress on underlying soils, thereby reducing the potential for bearing capacity failure and minimizing soil settlement. Based on these results, a crumb rubber-based flowable fill can be used in a substantial number of construction applications, such as bridge abutment fills, trench fills, and foundation support fills.     

Reuse of thermosetting plastic waste for lightweight concrete

This paper presents the utilization of thermosetting plastic as an admixture in the mix proportion of lightweight concrete. Since this type of plastic cannot be melted in the recycling process, its waste is expected to be more valuable by using as an admixture for the production of non-structural lightweight concrete. Experimental tests for the variation of mix proportion were carried out to determine the suitable proportion to achieve the required properties of lightweight concrete, which are: low dry density and acceptable compressive strength. The mix design in this research is the proportion of plastic, sand, water-cement ratio, aluminum powder, and lignite fly ash. The experimental results show that the plastic not only leads to a low dry density concrete, but also a low strength. It was found that the ratio of cement, sand, fly ash, and plastic equal to 1.0:0.8:0.3:0.9 is an appropriate mix proportion. The results of compressive strength and dry density are 4.14N/mm(2) and 1395kg/m(3), respectively. This type of concrete meets most of the requirements for non-load-bearing lightweight concrete according to ASTM C129 Type II standard.     

全废砖再生轻骨料混凝土试验研究

将废粘土砖加工成粗细骨料,用于配制全废砖再生轻骨料混凝土.检测结果表明：所用废砖粗细骨料属轻骨料范畴,但其吸水率较大,且细骨料级配不良.试验表明：本试验配合比体系中,净水灰比为0.42,体积砂率为50％时最佳;以全废砖配制的再生砖轻骨料混凝土的强度发展规律与普通轻骨料混凝土类似,均有随水泥用量提高而强度提高的趋势,但随着所配制的混凝土强度等级的提高,再生轻骨料混凝土的强度提高趋势下降.以全废砖为骨料适合配制强度等级LC30及以下的再生轻骨料混凝土.     

Bentonite liners for isolation of waste disposal sites

The applicability of bentonite as a lining material for isolation of waste disposal sites was investigated on laboratory and field scale. The permeability of sand-bentonite mixtures depends on the type of bentonite, the bentonite content in the mixture and the dry bulk density. In laboratory experiments the saturated conductivity decreased at low hydraulic head gradients, indicating that water flow in these mixtures does not obey Darcy's law. The swelling of the bentonite, which is responsible for the low permeability, is a time-dependent process. The permeability decreased with time and even after two months the permeability had not reached a constant level. In sand-bentonite mixtures with 5% (w/w) bentonite, the saturated conductivity ultimately reached a level below 1 × 10⁻¹⁰ m s⁻¹, which is sufficiently low for surface capping of waste disposal sites. The sand-bentonite mixtures were 10–100 times more permeable for landfill leachate than for clean water. Bottom liners should, therefore, contain considerably more bentonite to prevent infiltration of leachate in the subsoil. Water-balance studies on experimental fields showed that there was no leakage at all through bentonite liners used for surface capping of a waste disposal site over a two-year period.     

用膨润土处理油田污水的研究进展

介绍了膨润土的基本特性及其存油田污水处理中的研究情况。天然膨润土经改性后,可吸附去除油田污水中的油、烃类衍生物、注聚残留聚合物及表面活性剂;负载金属氧化物的改性膨润土可对光催化氧化产生协同效应,提高光催化氧化油田污水中有机物的能力;在高压下将膨润土制成薄膜,对油田污水中的无机离了有一定的截留去除作用。     

An investigation on the use of shredded waste PET bottles as aggregate in lightweight concrete

In this work, the utilization of shredded waste Poly-ethylene Terephthalate (PET) bottle granules as a lightweight aggregate in mortar was investigated. Investigation was carried out on two groups of mortar samples, one made with only PET aggregates and, second made with PET and sand aggregates together. Additionally, blast-furnace slag was also used as the replacement of cement on mass basis at the replacement ratio of 50% to reduce the amount of cement used and provide savings. The water–binder (w/b) ratio and PET–binder (PET/b) ratio used in the mixtures were 0.45 and 0.50, respectively. The size of shredded PET granules used in the preparation of mortar mixtures were between 0 and 4 mm. The results of the laboratory study and testing carried out showed that mortar containing only PET aggregate, mortar containing PET and sand aggregate, and mortars modified with slag as cement replacement can be drop into structural lightweight concrete category in terms of unit weight and strength properties. Therefore, it was concluded that there is a potential for the use of shredded waste PET granules as aggregate in the production of structural lightweight concrete. The use of shredded waste PET granules due to its low unit weight reduces the unit weight of concrete which results in a reduction in the death weight of a structural concrete member of a building. Reduction in the death weight of a building will help to reduce the seismic risk of the building since the earthquake forces linearly dependant on the dead-weight. Furthermore, it was also concluded that the use of industrial wastes such as PET granules and blast-furnace slag in concrete provides some advantages, i.e., reduction in the use of natural resources, disposal of wastes, prevention of environmental pollution, and energy saving.     

Feasibility study of a soil-based rubberized CLSM

The development of beneficial uses of recycled scrap tires is always in great demand around the world. The disposal of on-site surplus excavated soil and the production of standard engineering aggregates have also been facing increasing environmental and ecological challenges in congested islands, such as Taiwan. This paper presents an experimental study using recycled crumb rubber and native silty sand to produce a lightweight, soil-based, rubberized controlled low strength material (CLSM) for a bridge approach repair. To assess the technical feasibility of this material, the effects of weight ratios of cement-to-water (C/W) and water-to-solid (W/S), and of rubber content on the engineering properties for different mixtures were investigated. The presented test results include flowability, unit weight, strength, settlement potential, and bearing capacity. Based on the findings, we conclude that a soil-based rubberized CLSM with 40% sand by weight and an optimal design ratio of 0.7 for C/W and 0.35 for W/S can be used for the proposed bridge approach repair. Such a mixture has demonstrated acceptable flowability, strength, and bearing capacity. Its lower unit weight, negligible compressibility, and hydrocollapse potential also help ensure that detrimental settlement is unlikely to occur. The results illustrate a novel scheme of CLSM production, and suggest a beneficial alternative for the reduction of scrap tires as well as conservation of resources and environment.     

Experimental research on compressibility characteristics of recycled concrete aggregate: recycled tire waste mixtures

The utilization of processed rubber and construction waste in lieu of soil as a substrate could improve significantly seismic performance, while addressing the pressing environmental issue of how to reutilize and dispose of, i.e., automotive tires and demolition by-products. In this study, a series of laboratory tests explore the influence of recycled tire waste (RTW) and recycled concrete aggregate (RCA) fine particles on the compressibility parameters of RCA–RTW mixtures. The results revealed that the addition of rubber waste to RCA causes an increase in its compressibility and consolidation index (c_v) while prompting a power law decrease in the associated void ratio. It is found that all RCA–RTW mixtures are characterized by higher values of the compression (C_C) and swelling (C_S) indexes when compared to the pure RCA specimens while presenting a primary and secondary constrained modulus of fewer than 42 MPa and 96 MPa, respectively.

     

A field trial of a bentonite landfill liner

Field and laboratory trials were carried out for a bentonite amended weathered granite landfill liner. The trials were undertaken to gain experience in the installation method, and to establish the appropriate mixing techniques and mix design. It was established that a bentonite-amended weathered granite liner could be constructed on steep slopes. This paper presents the results of the trials, which included both field and laboratory permeability testing. It was found that the success of a soil bentonite liner is critically dependent on the mixture having the right moisture content at the time of compaction.     

阳离子聚丙烯酰胺复配钠基膨润土处理模拟苯酚废水

将阳离子聚丙烯酰胺与钠基膨润土进行复配,制备出复合吸附剂,并将其用于模拟苯酚废水的处理。采用XRD和FTIR技术对复配前后的钠基膨润土进行了表征。表征结果显示:阳离子聚丙烯酰胺附着在钠基膨润土的表面,对钠基膨润土的表面具有改性作用,使其由亲水性变为疏水性。实验结果表明:在阳离子聚丙烯酰胺与钠基膨润土的复配比例为200 mg/g、反应时间为40 min、复合吸附剂投加量为6 g/L、废水p H为11的最佳条件下,于25℃处理苯酚质量浓度为50 mg/L的模拟苯酚废水,苯酚去除率达89.5%。     

A Novel Packaging Film from Cassava Starch and Natural Rubber

Currently, there is an environmental pollution problem generated in part by packaging materials produced from non-biodegradable synthetic polymers made from petroleum. However, these can be replaced with biodegradable materials made from cassava starch (CS) and natural rubber (NR). In the work described, a novel biopolymer film was obtained from the CS and NR using glycerol (GE) as a plasticizer in a water-based system. The physical properties of an 95/5 CS/NR blend films with the addition of NR and with varying GE contents were studied based on their swelling ratio, moisture content, moisture absorption, mechanical properties and biodegradability in soil. The results showed that the moisture content and moisture absorption tended to be directly proportional to the GE content, while the moisture content and moisture absorption of the sample decreased as a function of the NR content. The swelling ratio of the 95/5 CS/NR blend slightly decreased as a function of the NR and GE content. Surprisingly, the best swelling ratio of 350% was found at 10% NR. The elongation at break of the CS/NR blend was improved by the addition of GE. The contact angle of the 95/5 CS/NR blend decreased as a function of the GE. With increased NR in the composite, an increasing, trend in the contact angle was found. Further, the 95/5 CS/NR blend exhibited good transparency when it was applied as a coating to delay the ripening of bananas, the results were positive. Moreover, the film showed decomposition well in natural soil.     

Migration of inorganic ions from the leachate of the Rio das Ostras landfill: A comparison of three different configurations of protective barriers

Batch tests and diffusion tests were performed to analyze the efficiency of a protective barrier in a landfill consisting of compacted soil with 10% bentonite compared to the results obtained for only compacted soil and for compacted soil covered with a 1-mm-thick HDPE geomembrane; the soil and leachate were collected from the Rio das Ostras Landfill in Rio de Janeiro, Brazil. The diffusion tests were performed for periods of 3, 10 and 60 days. After the test period, the soil pore water was analyzed and the profiles for chloride, potassium and ammonium were determined along a 6-cm soil depth. The results of the batch tests performed to define sorption parameters were used to adjust the profiles obtained in the diffusion cell experiment by applying an ion transfer model between the interstitial solution and the soil particles. The MPHMTP model (Multi Phase Heat and Mass Transfer Program), which is based upon the solution of the transport equations of the ionic contaminants, was used to solve the inverse problem of simultaneously determining the effective diffusion coefficients. The results of the experimental tests and of the model simulation confirmed that the compacted soil with 10% bentonite was moderately efficient in the retention of chloride, potassium and ammonium ions compared to the configurations of compacted soil with a geomembrane and compacted soil alone, representing a solution that is technically feasible and requires potentially lower costs for implementation in landfills.     

Properties of lightweight aggregate concrete prepared with PVC granules derived from scraped PVC pipes

This paper aims to investigate the fresh and hardened properties of lightweight aggregate concretes that are prepared with the use of recycled plastic waste sourced from scraped PVC pipes to replace river sand as fine aggregates. A number of laboratory prepared concrete mixes were tested, in which river sand was partially replaced by PVC plastic waste granules in percentages of 0%, 5%, 15%, 30% and 45% by volume. Two major findings are identified. The positive side shows that the concrete prepared with a partial replacement by PVC was lighter (lower density), was more ductile (greater Poisson's ratios and reduced modulus of elasticity), and had lower drying shrinkage and higher resistance to chloride ion penetration. The negative side reveals that the workability, compressive strength and tensile splitting strength of the concretes were reduced. The results gathered would form a part of useful information for recycling PVC plastic waste in lightweight concrete mixes.     

Soil reinforcement with recycled carpet wastes.

A root or fibre-reinforced soil behaves as a composite material in which fibres of relatively high tensile strength are embedded in a matrix of relatively plastic soil. Shear stresses in the soil mobilize tensile resistance in the fibres, which in turn impart greater strength to the soil. A research project has been undertaken to study the influence of synthetic fibrous materials for improving the strength characteristics of a fine sandy soil. One of the main objectives of the project is to explore the conversion of fibrous carpet waste into a value-added product for soil reinforcement. Drained triaxial tests were conducted on specimens, which were prepared in a cylindrical mould and compacted at their optimum water contents. The main test variables included the aspect ratio and the weight percentage of the fibrous strips. The results clearly show that fibrous inclusions derived from carpet wastes improve the shear strength of silty sands. A model developed to simulate the effect of the fibrous inclusions accurately predicts the influence of strip content, aspect ratio and confining pressure on the shear strength of reinforced sand.     

An alternative method for the treatment of waste produced at a dye and a metal-plating industry using natural and/or waste materials.

The aim of this study was to develop cost-effective, appropriate solidification technologies for treating hazardous industrial wastes that are currently disposed of in ways that may threaten the quality of local groundwater. One major objective was to use materials other than cement, and preferably materials that are themselves wastes, as the solidification additives, namely using wastes to treat wastes or locally available natural material. This research examines the cement-based and lime-based stabilization/solidification (S/S) techniques applied for waste generated at a metal-plating industry and a dye industry. For the lime-based S/S process the following binder mixtures were used: cement kiln dust/ lime, bentonite/lime and gypsum/lime. For the cement-based S/S process three binder mixtures were used: cement kiln dust/cement, bentonite/cement and gypsum/cement. The leachability of the wastes was evaluated using the toxicity characteristic leaching procedure. The applicability and optimum weight ratio of the binder mixtures were estimated using the unconfined compressive strength test. The optimum ratio mixtures were mixed with waste samples in different ratios and cured for 28 days in order to find the S/S products with the highest strength and lowest leachability at the same time. The results of this work showed that the cement-and lime-based S/S process, using cement kiln dust and bentonite as additives can be effectively used in order to treat industrial waste.     

Modeling Acidification Recovery on Threatened Ecosystems: Application to the Evaluation of the Gothenburg Protocol in France

To evaluate the acid deposition reduction negotiated for 2010 within the UNECE LRTAP Gothenburg Protocol, sulphur and nitrogen deposition time-series (1880–2100) were compared to critical loads of acidity on five French ecosystems: Massif Central basalt (site 1) and granite (2); Paris Bassin tertiary sands (3); Vosges mountains sandstone (4) and Landes eolian sands (5). The SAFE model was used to estimate the response of soil solution pH and ratio to the deposition scenario. Among the five sites, critical loads were exceeded in the past at sites 3, 4 and 5. Sites 3 and 4 were still expected to exceed in 2010, the Protocol year. Further reduction of atmospheric deposition, mainly nitrogen, would be needed to achieve recovery on these ecosystems. At sites 3, 4 and 5, the delay between the critical load exceedance and the violation of the critical chemical criterion was estimated to be 10 to 30 years in the top soil and 50 to 90 years in the deeper soil. At site 5, a recovery was expected in the top soil in 2010 with a time lag of 10 years. Unexpectedly, soil pH continued to decrease after 1980 in the deeper soil at sites 2 and 5. This time lag indicated that acidification moved down the soil profile as a consequence of slow base cation depletion by ion exchange. This delayed response of the soil solution was the result of the combination of weathering rates and vegetation uptake but also of the relative ratio between base cation deposition and acid compounds.     

Aluminium: The Need for a Re-Evaluation of Its Toxicity and Solubility in Mature Forest Stands

Aluminium (Al) is a key element in critical loadcalculations for forest. Here, we argue for re-evaluating theimportance of Al. Effects of two levels of enhanced Alconcentrations and lowered Ca:Al ratios in the soil solutionin a field manipulation experiment in a mature spruce stand(1996–1999) on tree vitality parameters were tested. Inaddition, Al solubility controls were tested. Various loads ofAl were added to forest plots by means of an irrigationsystem. Potentially toxic Al concentrations and criticalratios of Ca to inorganic Al were established. The ratio of Cato total Al was not a suitable indicator for unfavourableconditions for plant growth. No significant effects on crowncondition, tree growth and fine root production were observedafter three years of treatment. In 1999, foliar Mg content inthe highest Al addition treatment had declined significantly.This agreed with the known response to Al stress of seedlingsin nutrient solution experiments. No support was found forusing the chemical criterion Ca:Al ratio in soil solution,foliar and root tissue as an indicator for forest damage dueto acidification. Al solubility was considerably lower thanimplied by the assumption of equilibrium with gibbsite,particularly in the root zone. The gibbsite equilibrium iscommonly used in critical load models. Substitution of thegibbsite equilibrium with an Al-organic matter complexationmodel to describe Al solubility in soil water may have largeconsequences for calculation of critical loads. The resultsindicate that critical load maps for forests should bereconsidered.     

Effects of calcium hydroxide and calcium chloride addition to bentonite in iron ore pelletization.

Pyrite ash is created as waste from the roasting of pyrite ores during the production of sulphuric acid. These processes generate great amounts of pyrite ash waste that is generally land filled. This creates serious environmental pollution due to the release of acids and toxic substances. Pyrite ash waste can be utilized in the iron production industry as a blast furnace feed to process this waste and prevent environmental pollution. The essential parameters affecting the pelletization process of pyrite ash were studied using bentonite as a binder. Experiments were then carried out using bentonite and a mixture of bentonite with calcium hydroxide and calcium chloride in order to make the bentonite more effective. The metallurgical properties of pyrite ash, bentonite, calcium hydroxide, calcium chloride, a mixture of these and sintered pellets were studied using X-ray analysis. The crushing strength tests were carried out to investigate the strength of pyrite ash waste pellets. The results of these analyses showed that pyrite ash can be agglomerated to pellets and used in the iron production industry as a blast furnace feed. The crushing strength of the pellets containing calcium hydroxide and calcium chloride in addition to bentonite was better than the strength of pellets prepared using only bentonite binder.     

Transdermal Delivery of Nicotine Using Pectin Isolated from Durian Fruit-Hulls-Based Polymer Blends as a Matrix Layer

Many natural polymers with various chemical structures are used to prepare transdermal patches. Pectin is a one interesting type of polymer because it can control drug release when used in transdermal patches. In Thailand, the waste from durian fruit-hulls is a major problem for the environment. However, the pectin from it can be isolated under acid conditions and used to prepare transdermal patches for nicotine delivery which has not yet been reported. As the isolated pectin is a natural polymer, the film made from isolated pectin is a brittle; therefore, adding a low protein natural rubber latex (LPNRL) polymer was needed to increase its flexibility. The transdermal patches were amorphous and had T_g values ranging from 81.0 to 93.3 °C. Moisture uptake, swelling ratio, and erosion values of the patches were significantly decreased after addition of LPNRL, which resulted in low hydrophilicity. The in vitro release and permeation of nicotine depends on the hydrophilicity of the patches. The kinetic models for in vitro release and permeation of nicotine were Higuchi model and zero order, respectively. In conclusion, pectin isolated from fruit-hulls of Mon Thong durians is an effective polymer to control the release of nicotine. It also is an option that could solve the environmental problems caused by durian fruit-hulls waste.     

Instrumentation and monitoring of a bentonite landfill liner

A landfill site in northern Wales which lies only a few metres above the local water table was lined with a mixture of locally available sand and imported bentonite. To test the permeability and leachate attenuation capacity of this liner special test chambers lined with high-density polyethylene (HDPE) were constructed underneath the sand-bentonite liner and instrumented to collect samples of any infiltrating water. Over an 18-month period there has been less than 1 mm of infiltration from a completed section of the landfill into the test chambers. No evidence of contamination of the groundwater by the landfill has been detected in test wells. The sampling continues.