Total Weight Of Mixture Research Articles

Glass fiber waste as a potential bitumen modifier and stabilizing agent in asphalt mixture.

The deterioration of Malaysia's flexible road pavements due to rutting and moisture damage presents a critical problem. Meanwhile, disposing of glass fiber wastes from manufacturing process further worsens environmental concerns. This research explores the feasibility of using glass fiber wastes as bitumen modifiers and stabilizers in stone mastic asphalt (SMA). The performance of SMA14 incorporating glass fiber waste using wet method and dry method were compared in this study. Bitumen 60/70 PEN was modified with varying percentages of glass fiber waste namely, 0.5%, 1.0%, 1.5%, and 2.0% by weight of bitumen. The SMA14 mixture was modified with glass fiber waste at 0.3% by the weight of total mixture. The physical and rheological characteristic of modified bitumen binder were assessed using penetration, softening point, storage stability, viscosity, and dynamic shear rheometer (DSR) tests. The Marshall properties and performance of the SMA14 mixture incorporating glass fiber waste were evaluated. The findings demonstrate that glass fiber waste-modified bitumen exhibits enhanced penetration, softening point, viscosity, and rutting resistance compared to the unmodified sample. Adding glass fiber waste using dry method shows significant resistance to abrasion and rutting and demonstrates higher indirect tensile strength and TSR value.

Modified asphalt by coffee cup Fibres: An optimum mix design using response surface method

Asphalt mixtures with high binder content, such as Stone Mastic Asphalt (SMA), have difficulties retaining the binder in the mix. To prevent the draindown of the binder, natural cellulose fibres (made from wood) are usually added to these asphalt mixes. This study investigates the suitability of recycled coffee cups as an alternative source of natural cellulose fibres. Around 16 billion coffee cups are used worldwide every year, leading to the logging of approximately 6.5 million trees. Since coffee cups are hard to recycle due to the inner side of the cups being lined with plastic, around one billion coffee cups are landfilled annually in Australia. In this research, coffee cups of up to 0.6% of the total weight of the asphalt mixture are used in fourteen different mix designs. The mixes are optimised by the response surface methodology using the Design-Expert software. Models are created based on Marshall and draindown test results. It has been found that shredded coffee cups effectively reduce the draindown and the flow of the asphalt mixture and increase the stability and the air voids. The optimum amount of shredded coffee cups are measured to be 0.4% by the total weight of the mixture. Also, the plastic liners in the coffee cups slightly increased the viscosity and the softening point of the asphalt binder and dropped its penetration value. Overall, the asphalt mixture containing 4% coffee cups (by total weight of the mixture) met all specifications in Australian Standards and performed similarly to the commercial cellulose fibre.

Environmental assessment of asphalt mixtures modified with polymer coated rubber from scrap tires

Polymer coated rubber (PCR) is an engineered crumb rubber developed to address the drawbacks of regular crumb rubber in asphalt mixtures, such as the absorption of asphalt binder and premature cracking. Assessing the use of PCR using life cycle assessment (LCA) is important to evaluate whether its use lowers the environmental impact of asphalt mixtures. In LCA, the choice of allocation procedure significantly impacts the results. The cut-off method is often used in LCA studies of products containing recycled materials. The objectives of this work were to evaluate: i) if asphalt mixtures modified with PCR had lower environmental impact than mixtures modified with synthetic polymers, ii) if using more PCR decreased the environmental impact of the asphalt mixtures, iii) if the results changed by using different allocations methods, and finally, iv) if the environmental impact of asphalt mixtures changed when considering the long-term mechanical performance of the blends. In this work, the global warming potential (GWP), fossil depletion, and cumulative energy demand of one ton of asphalt mixture were calculated using the cut-off method, economic allocation, and system expansion. For the system expansion, the recovery energy in cement kilns from scrap tires was compared to burning petroleum coke or natural gas. The LCA of asphalt mixtures modified with two amounts of PCR (0.5% and 1% by weight of total mixture) compared to the synthetic polymer styrene-butadiene-styrene (SBS) was performed by including results of the experimental investigation (asphalt mixture design and mechanical testing conducted in the asphalt laboratory at Michigan State University). Results were different based on the allocation method considered. Overall, the GWP of PCR 0.5% and PCR 1% mixtures was lower than the SBS mixture, except in one case. The GWP of PCR 1% was 2% higher than the SBS mix when petroleum coke was used in the system expansion. Adding more PCR did not necessarily increase the environmental benefits. PCR 1% had a higher GWP than PCR 0.5% (2.6%, 2.7%, and 6.3% by using cut-off, economic allocation, and system expansion, respectively), except for the system expansion using natural gas as a replacement, which was 3.7% lower than the PCR 0.5%. However, the system expansion with natural gas had the lowest GWP compared to the other methods. On the contrary, the system expansion considering petroleum coke had the highest CO2eq emissions among all the methods used. The GWP of PCR 0.5% and PCR 1% was similar by using cut-off and economic allocation. As the cement industry transition to low-carbon energy, the carbon footprint associated with using scrap tires in pavements will decrease when using system expansion, while it will remain the same with the cut-off method. Considering the mechanical performance of the mixtures, the GWP for the pavement with 0.5% PCR was 8.04% lower over its service life than the synthetic polymer blend.

Plasticity-Based Method for the Design and Analysis of Cold Recycled Pavement Layers

Abstract Asphalt cold recycling technologies allow the use of up to 100 % reclaimed asphalt pavement (RAP) from an existing asphalt pavement to construct new base layers and new subbase layers. Bituminous stabilized materials (BSM), obtained from cold recycling technologies, are susceptible to traffic-induced accumulation of permanent deformation. In the current design methods, BSM pavement layers are typically assumed to have a linear elastic response under traffic loading application, and this does not account for plasticity initiation and accumulation in the material. This research study provides insight on how to integrate plasticity behavior in numerical simulations of rehabilitated pavement structures with BSM. A BSM mixture prepared with 1.5 % cement by weight of total mixture and 1.5 % foamed asphalt binder content by weight of dry aggregates is characterized in the laboratory. Subsequently, a three-dimensional elastic-perfectly plastic finite element model is developed for the simulation of triaxial shear strength tests. Lab measured force-displacement curves are matched with the numerical simulations at different confining pressures. The calibrated mechanical properties are then used as input parameters in multilayer pavement models for pavement evaluation. Different pavement structures with and without BSM layers are compared in terms of a maximum allowable number of loading repetitions before reaching a 20-mm rut depth on the surface of the pavement. The results indicate that structures with BSM and traditional granular base layers yield comparable results in terms of rutting potential. In addition, the study presents a framework for the design and analysis of cold recycled pavement layers and a method to integrate the plasticity behavior of partially-bonded and unbounded layers for pavement evaluation.

Performance Characterization of Stone Mastic Asphalt using Steel Fiber

Stone Mastic Asphalt (SMA) is a gap-graded hot mixture designed to provide higher resistance towards permanent deformation and rutting potential by 30% to 40% more than dense-graded asphalt, due to its stable aggregate skeleton structure. However, compared to other types of hot mix asphalt, SMA unfortunately has some shortcomings in term of its susceptibility towards moisture-induced damage due to its structure and excessive bitumen content in the composition. This research aims to assess the performance of a SMA mixture with steel fiber by enhancing overall stability, abrasion resistance, and, most importantly, moisture susceptibility. This study involved the incorporation of various steel fiber proportions of 0%, 0.3%, 0.5% and 0.7% by the total weight of mixture. The steel fiber modified SMA was made up of 6.0% PEN 60/70 bitumen content. The performance of SMA were evaluated through Marshall stability and flow test, Cantabro loss test and indirect tensile strength test. The results obtained from the testing showed that the incorporation of steel fiber is significantly effective to enhance the resistance towards moisture damage, while increasing the stability and reducing the abrasion loss of SMA mixture, compared to conventional mixture. Overall, it can be concluded that the addition of steel fiber in asphalt mixture specifically SMA, has improved the mechanical performance in the application of asphalt pavement with the optimum steel fiber proportion of 0.3% by the weight of mixture. The developed models between the independent variables and responses demonstrated high levels of correlation. The study found that Response Surface Methodology (RSM) is an effective statistical method for providing an appropriate empirical model for relating parameters and predicting the optimum performance of an asphaltic mixture to reduce flexible pavement failure.

Evaluating the impact of fiber type and dosage rate on laboratory performance of Fiber-Reinforced asphalt mixtures

The purpose of this study was to evaluate the impact of fiber types, binder content, and their dosage rates on the volumetric properties and laboratory performance of asphalt mixtures. One asphalt mixture (control) and three fiber types (Basalt, Fiberglass, and Carbon) were used. Two different fiber dosage rates were considered 0.15% (recommended dosage rate) and 0.30% by total mixture weight. Furthermore, a novel experimental methodology was developed and implemented consisting of a volumetric mixture design and performance testing—Indirect Tensile Asphalt Cracking Test (IDEAL-CT) and Asphalt Pavement Analyzer (APA)—to isolate the effects of fiber types and dosage rates from the effect of binder content. Statistical analysis was also used to further evaluate the impact of fibers on mixture performance. Results showed that 0.15% dosage rate had little to no impact on optimum binder content, whereas 0.30% dosage rate required an increase in binder content of 0.6%, 0.6%, and 0.8% for basalt, fiberglass, and carbon fibers, respectively, to meet the volumetric requirements. This study showed that the need for additional binder content at 0.30% dosage rate could be due to an increase in specimen volume (referred to as rebounding height) that occurred after 24 h of specimen cooling at room temperature. Performance testing showed that 0.15% (regardless of fiber type) had no impact on cracking and rutting performance. At 0.30% dosage rate, only carbon fiber improved cracking performance without the use of additional binder. Overall, the study highlighted laboratory performance benefits and challenges of using fiber-reinforced reinforced asphalt mixtures.

Laboratory Assessment of Epoxy Asphalt Mixture Incorporating Tire Rubber Waste

The use of epoxy asphalt in road paving is one of the promising solutions for long-life road pavements in service with minimal maintenance. However, the high cost still stands as an obstacle to the widespread use of this high-performance material. The use of tire rubber waste (TRW) is one of the solutions in order to reduce costs, improve the environment, and improve the performance of epoxy asphalt mixtures, in addition to alleviating the brittle behaviour that epoxy asphalt tends to. This study proposes to add TRW in improving epoxy asphalt produced in local laboratories by using phenol Novolac resin as an epoxy curing agent of the epoxy base inside asphalt binder to produce and evaluate improved epoxy asphalt. The percentage of epoxy base used was 25% of the asphalt binder mixed with a 1:1 ratio of epoxy to Novolac using potassium hydroxide (KOH) as a catalyst. Whereas the proportions of added TRW were (1%, 2%, and 3%) of the total mixture weight by using the dry mixing method. The results showed, at its best values at 2% of TRW, that there was an increase in Marshall stability by 10%, and Marshall flow remained within specification limits with a decrease in the value of air voids at the highest bulk density, and a slight decrease in indirect tensile strength by 2%, with remaining excellent resistance to moisture sensitivity at 94%, and improvement in resistance to permanent deformation (rutting) by 14%. This indicates an improvement in the improved epoxy asphalt mixtures by the addition of TRW compared to the reference epoxy asphalt mixtures.

Determining optimum fly ash content for Stabilized subbase materials in road pavements

ABSTRACT The investigation of fly ash content for stabilized subbase materials in road pavements was presented in this study. The effects of partial replacement of cement by 17%, 33%, 50% of fly ash contents by total weight of mixture were investigated to evaluate mechanical properties of stabilized subbase materials using the unconfined compressive strength (UCS) test, indirect tensile (IDT) test, and resilient modulus test. It was found that the replacement of cement by 33% of fly ash can use for stabilized subbase material. In addition, a strong relationship between IDT and UCS strength, and resilient modulus and UCS is given which is the coefficient of determination of developed correlation to be 0.9 and 0.82, respectively. It was suggested that the IDT strength or the resilient modulus can be estimated from a UCS test. Finally, the performance of cement replacement with fly ash was evaluated using mechanistic empirical pavement design guide (MEPDG) program. Based on the results of the study, it can be concluded that the cement replacement with 33% fly ash can enhance the performance life significantly and the construction cost reduction can be around 23%, compared to using conventional subbase material.

Modification of cementitious composites with graphene oxide and carbon nanotubes

Both graphene oxide (GO) and carbon nanotubes (CNTs) are carbon-based nanomaterials. Due to their favorable dispersibility in water and excellent mechanical properties, they are potential additives for use as reinforcements in cementitious composites. In this laboratory study, GO and CNTs were simultaneously used as additives to improve the mechanical properties (e.g., compressive strength) and durability (e.g., frost resistance, water impermeability) of cementitious composites. To maintain and optimize the mortar fluidity, fly ash (20% by the mass of the cementitious materials) was also added into the cementitious composite. Based on the laboratory test results, the compressive strength of the cementitious composite was maximized to 43.50 MPa with an optimal dosage of 0.08% GO, by weight of the total mixture. Addition of 0.04% GO (by total mixture weight) and higher dosages of up to 0.08% exhibited a strengthening effect on the cement composites due to the simultaneous bridging effect of 0.15% CNTs and the nucleation effect of GO. Furthermore, the addition of GO and CNTs contributed to improving the freeze–thawing resistance and impermeability of the cementitious composites. Overall, the study results indicated that the addition of GO and CNTs could potentially improve the mechanical properties and durability of cementitious composites, which could be very beneficial for various industrial applications such as concrete roads or building constructions.

Matrix solid-phase dispersion extraction method for HPLC determination of flavonoids from buckwheat sprouts

Herein, we report the development of a matrix solid-phase dispersion (MSPD) extraction method for determining flavonoids (orientin, isoorientin, vitexin, isovitexin, quercetin-3-O-robinobioside, and rutin) from common buckwheat sprouts (CBS) and Tartary buckwheat sprouts (TBS) by high-performance liquid chromatography (HPLC-PDA). Key parameters, including sorbent type, sorbent-to-sample ratio, extraction solvent (type, concentration, and volume), and extraction time were optimized. The optimized MSPD extraction conditions include a C18-sorbent/sample ratio of 2:1 (w/w) [total mixture weight = 100 mg] and 10 min of static extraction with 5 mL of 80% ethanol. The optimized MSPD extraction method was satisfactorily validated for all target flavonoids from both CBS and TBS. The validated method was also more effective and efficient compared to ultrasound- and homogenate-assisted extraction techniques. The overall results show that the MSPD extraction method developed in this study is a simple, effective, and efficient technique for the HPLC analysis of flavonoids in CBS and TBS.

Assessment of the Impact of Fiber Types on the Performance of Fiber-Reinforced Hot Mix Asphalt

This study aims to evaluate the impact of fiber types on the performance of hot mix asphalt (HMA) mixtures. Specifically, the impacts of fiber type on HMA mix design and laboratory performance are investigated. Four types of fiber (fiberglass, basalt, carbon, and polyolefin/aramid blend) were used to produce four fiber-reinforced HMA mixes, and a control mix without fibers was also prepared. The fiber dosage rates used in this study were 0.16% (fiberglass, basalt, and carbon) and 0.05% (polyolefin/aramid) by total mixture weight, based on manufacturer recommendations. Two mixing procedures for introducing fibers into HMA were also evaluated: dry and 15-s dispersion methods. The dry method involved mixing the fibers with aggregates before the addition of asphalt binder while the 15-s dispersion method involved adding the fibers into the mix every 15 seconds (as aggregates were coated by asphalt binder during the mixing process). All the HMA mixtures (unreinforced and fiber-reinforced) were then subjected to several different laboratory performance tests: dynamic complex modulus, Cantabro durability, asphalt pavement analyzer, flow number, and indirect tensile strength. Analysis of variance was conducted to evaluate statistically the impact of fibers on mix performance. Results showed that fibers affected the volumetric properties, mix durability, and rutting resistance of HMA mixes. It was also found that the process for introducing fibers into the mix (i.e., mixing method) affected the consistency of fiber-reinforced HMA samples. Overall, the results of this study showed that the use of fibers improved the rutting and durability performance of asphalt mixtures in the laboratory.

Optimization of biodegradable plastic production using response surface methodology

Optimization is a searching technique for variable values considered optimum, effective and efficient, in order to reach the desirable results. An experiment was carried out to see the relationship between response variable and the independent variable. Several comparison tests can be obtained to gain the level that will create optimal response. The aim of this research is to apply the Response Surface methodology in order to obtain the optimum condition for the process variable in producing biodegradable plastic with lemongrass as antioxidant. Fixed variables in this research are tapioca starch, 69-79°C gelatinization temperature and the total mixture weight that consists of starch, poly(NIPAM) chitosan, lemongrass oil, acetic acid and water. The response variables are tensile strength and break of elongation of each biodegradable plastic that is produced. The application of response surface methodology on each biodegradable plastic can be used to obtain the independent variable that makes the optimal response variable. The predicted result of the optimum value for tensile strength and elongation of break lies on the composition treatment of Poly(NIPAM)-chitosan 0.35 grams, glycerol 3.5 grams and 36,55% lemongrass oil with tensile strength result of 3.98 MPa and elongation of break of 36.55%.

Effect of Density and Total Weight on Flow Depth, Velocity, and Stresses in Loess Debris Flows

Debris flows that involve loess material produce important damage around the world. However, the kinematics of such processes are poorly understood. To better understand these kinematics, we used a flume to measure the kinematics of debris flows with different mixture densities and weights. We used sensors to measure pore fluid pressure and total normal stress. We measured flow patterns, velocities, and depths using a high-speed camera and laser range finder to identify the temporal evolution of the flow behavior and the corresponding peaks. We constructed fitting functions for the relationships between the maximum values of the experimental parameters. The hydrographs of the debris flows could be divided into four phases: increase to a first minor peak, a subsequent smooth increase to a second peak, fluctuation until a third major peak, and a final continuous decrease. The flow depth, velocity, total normal stress, and pore fluid pressure were strongly related to the mixture density and total mixture weight. We defined the corresponding relationships between the flow parameters and mixture kinematics. Linear and exponential relationships described the maximum flow depth and the mixture weight and density, respectively. The flow velocity was linearly related to the weight and density. The pore fluid pressure and total normal stress were linearly related to the weight, but logarithmically related to the density. The regression goodness of fit for all functions was >0.93. Therefore, these functions are accurate and could be used to predict the consequences of loess debris flows. Our results provide an improved understanding of the effects of mixture density and weight on the kinematics of debris flows in loess areas, and can help landscape managers prevent and design improved engineering solutions.

Creep behavior of nylon fiber-reinforced asphalt concrete

This study aims to investigate the permanent deformation behavior of asphalt concrete reinforced by nylon fibers. Nylon fibers (12 mm length) have been added to a typical asphalt concrete at different percentages of 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3% (based on total weight of mixture), and the permanent deformation behavior of the mixtures have been investigated by dynamic creep tests at different stress levels of 200 and 400 kPa, and different temperatures of 40, 50, and 60 °C on the mixtures. A three-stage model (developed by Zhou et al.) has been used for modeling the creep curve of the mixtures and determining the flow number and creep strain slope of the mixtures, which are used to describe the permanent deformation of asphaltic mixtures. The parameters of the models were determined in MATLAB using an algorithm established by Zhou et al. The results showed that the mixture reinforced by 0.1% of nylon fibers has the highest resistance to permanent deformation. The three-stage model was well fitted with the dynamic creep test results of the mixtures. The results also showed that the mixture containing 0.1% of nylon fibers has the lowest creep strain slope and the highest flow number, indicating that this mixture has the highest resistance to permanent deformation.

Investigating the Effects of Nanoclay and Nylon Fibers on the Mechanical Properties of Asphalt Concrete

This paper describes the effects of reinforcement by randomly distributed nylon fibers and addition of nanoclay on some engineering properties of a typical asphalt concrete. The properties of asphalt concrete reinforced by different percentages of 25 mm nylon fibers have been compared with those of the mixtures containing different percentages of nanoclay and those in which both the fibers and nanoclay have been included. Engineering properties, including Marshall stability, resilient modulus, dynamic creep and fatigue life have been studied. Nylon fibers have been used in different percentages of 0.1, 0.2, 0.3 and 0.4% (by the weight of total mixture), and nanoclay has been used in 2, 4 and 7% (by the weight of bitumen). It is found that the addition of fibers is more effective than the nanoclay for increasing the resistance against fatigue cracking. However, nanoclay improves the resistance of the mixture against permanent deformation better than the nylon fibers. The results also show that the mixture reinforced by 0.4% of nylon fibers and containing 7% of nanoclay has the highest resilient modulus, Marshall stability and fatigue life. However, the mixture containing only 7% of nanoclay has the highest resistance against permanent deformation.

INVESTIGATING THE PROPERTIES OF ASPHALT CONCRETE CONTAINING GLASS FIBERS AND NANOCLAY

The performance of asphaltic pavements during their service life is highly dependent on the mechanical properties of the asphaltic layers. Therefore, in order to extend their service life, scientists and engineers are constantly trying to improve the mechanical properties of the asphaltic mixtures. One common method of improving the performance of asphaltic mixtures is using different types of additives. This research investigated the effects of reinforcement by randomly distributed glass fibers and the simultaneous addition of nanoclayon some engineering properties of asphalt concrete have been investigated. The properties of a typical asphalt concrete reinforced by different percentages of glass fibers were compared with those containing both the fibers and nanoclay. Engineering properties, including Marshall stability, flow, Marshall quotient, volumetric properties and indirect tensile strength were studied. Glass fibers were used in different percentages of 0.2, 0.4 and 0.6% (by weight of total mixture), and nanoclay was used in 2, 4 and 6% (by the weight of bitumen). It was found that the addition of fibers proved to be more effective than the nanoclay in increasing the indirect tensile strength. However, nanoclay improved the resistance of the mixture against permanent deformation better than the glass fibers. The results also showed that the mixture reinforced by 0.2% of glass fiber and containing 6% nanoclay possessed the highest Marshall quotient, and the mixture containing 0.6% glass fibers and 2% nanoclay possessedthe highest indirect tensile strength.

Superpave evaluation of higher RAP contents using WMA technologies

In this study, the objective was to conduct an investigation of Superpave mix design characteristics of WMA technologies in terms of various high percentages of reclaimed asphalt pavements (RAPs). One PG 58-28 binder, two PG 64-22 binders, and two RAP sources were selected from South Carolina. In addition, three mix technologies (e.g. hot mix asphalt (HMA), foaming technology, and Evotherm additive) were employed to produce the mixtures. Meanwhile, four RAP contents of 20%, 30%, 40%, and 50% (by weight of total mixture) were utilized to blend with virgin materials. 36 Superpave mix designs were conducted to explore the volumetric characteristics of various mixtures. In this study, the results indicated that, all mixtures have an optimum asphalt content (OAC) less than 5.0%, and most of these values are close to a minimum OAC value of 4.5% set by South Carolina Department of Transportation (SCDOT). No noticeable increases at the mixing and compaction temperatures for these mixtures containing a higher percentage of RAP (i.e., over 40%) were found in this study. In addition, the voids in mineral aggregate (VMA), voids filled with asphalt (VFA), dust/asphalt ratios, and moisture susceptibility meet the requirements of SCDOT’s specifications. Therefore, these specific mix designs could be used as the guidelines for developing a set of specifications for a higher percentage of RAP in terms of warm mix asphalt technology.

A comprehensive evaluation of the fatigue behaviour of plant-produced RAP mixtures

In this study, the fatigue performance of 12 plant-produced mixtures from New Hampshire and Vermont that contain reclaimed asphalt pavement (RAP) contents of 0–40% by total weight of mixture was evaluated. The mixture tests included dynamic modulus, uniaxial fatigue, beam fatigue, and overlay tests. Also, the simplified viscoelastic continuum damage (S-VECD) model failure criterion, called the GR method, was applied and input to the linear viscoelastic pavement analysis for critical distresses (LVECD) programme to predict the fatigue behaviour of the tested mixtures on thin and thick asphalt pavement structures. In order to explain the observed fatigue behaviour, the performance grades (PGs) of the binders that were extracted and recovered from the mixtures were determined. In general, the addition of RAP resulted in an increase in the stiffness of the materials. The magnitude of the impact of higher RAP percentages varied with each set of mixtures. The S-VECD model and beam fatigue test data showed a loss of fatigue resistance for high-percentage RAP mixtures in most of the cases. The overlay tester results showed clear drops in performance at higher RAP contents. The impact of lowering the PG of the virgin binder to compensate for higher levels of RAP also was studied. Lowering the PG led to improvement in the fatigue properties and was found to be a convenient practice. The changes in the measured properties also appeared to be a function of mix design variables that included the stiffness of the RAP, asphalt content, and production parameters such as silo storage times. In some cases, the effects of these factors outweighed the impact of the RAP level or PG of the virgin binder in the mixtures.

Towards a commercially potential process: Enzymatic recovery of phytosterols from plant oil deodoriser distillates mixture

In order to examine the industrial potential to indirectly isolate phytosterols from deodoriser distillates (DODs), enzymatic transesterification of an industrial rapeseed and soybean oil DOD mixture with bioethanol was investigated using commercial lipases and a few newly immobilised preparations of lipases. The lipases from different sources and differing preparation forms were evaluated, in terms of thermostability, enzyme efficiency, and toleration of ethanol. Lipozyme 435 and Lipozyme NS-40044 TLL were found to be most effective biocatalysts in catalysing ethanolysis of glycerides and steryl esters from DODs. The optimum conditions are 10% enzyme load (wt% of DODs), ethanol/DODs of 3.0:1.0 (mol/mol), water content 0.125% (based on the weight of total mixture), and reaction at 30°C for 5h. The results demonstrated that >95% sterols can be recovered as free form (>85% sterol esters were liberated as free sterols within 4h). With this process, the system was simplified as fatty acid ethyl esters and free sterol as major components, where free sterols can be recovered via solvent extraction or molecular distillation. Furthermore, a reuse study of enzyme in consecutive batch reactions demonstrated an excellent operation stability and reusability of Lipozyme 435 and Lipozyme NS-40044 TLL with the developed process. This work indicated that the industrially refined waste DODs can be directly subjected to an enzymatic process for high efficacy recovery of phytosterol without any pre-process, driven by robust lipase preparations.

INFLUENCE OF AMBIENT TEMPERATURE ON STIFFNESS OF ASPHALT PAVING MATERIALS

Asphalt pavement properties in Iraq are highly affected by elevated summer air temperatures. One of these properties is stiffness (resilient modulus). To explain the effect of air temperatures on stiffness of asphalt concrete, it is necessary to determine the distribution of temperatures through the pavement asphalt concrete layers. In this study, the distribution of pavement temperatures at three depths (2cm,7cm, 10cm) below the pavement surface is determined by using the temperature data logger instrument. A relationship for determining pavement temperature as related to depth and air temperature has been suggested. To achieve the objective of this thesis, the prepared specimens have been tested for indirect tension in accordance with ASTM D4123, using the pnuematic repeated load apparatus, in order to determine the values of resilient modulus at three different temperatures (10, 25, 40) °C. From results of testing, it is observed that the resilient modulus decreases with increase in test temperature by a rate of 8.78×10 Psi/C' for asphalt concrete wearing courses. An increase in optimum asphalt content by 0.1% (by weight of total mixture) causes a decrease in resilient modulus by 22% at a temperature of 40C". A statistical model for the prediction of resilient modulus has been developed depending on mixture variables of: asphalt content, asphalt hinder viscosity, surface area of combined aggregates, air voids of compacted mixture and test temperature.