Mineral Filler Content Research Articles

EFFECTS OF ZEOLITE INCORPORATION AND INERT FILLERS ON THE CURING OF CEMENT MORTARS

One of the main approaches to reducing the environmental impacts of the construction industry is the use of mineral additives reducing the use of cement in mortars and concretes for construction. The objects of this research are different cement composites with high content of inert mineral fillers (marble and quartz sand), the influence of zeolite incorporation on the microstructure, and low water-cement ratio, obtained after the hydration of white portland cement.In this study, the evolution of the curing processes and the crystal formation during up to 120 days of water-curing are investigated. Moreover, the effects of replacing up to 10 wt. % of white cement with natural zeolite are studied. Attention was focused on the general microstructural development during curing with special attention on the evolution and morphology of pore space and the observed calcium silicate hydrates (C–S–H), portlandite, and carbonate-containing phases.The phase composition (newly formed phases as well as the formation of C-S-H gel) is defined by using powder X-Ray diffraction and SEM. The experimental data shows that the cement composites with the inert marble filler as an additive lead to the creation of carbo-aluminates. The incorporation of up to 10 percent of clinoptilolite in concrete mixtures by mass of the total cementitious components is more efficient when used in lower strength mixes. A significant reduction in the workability of the fresh mortars is not observed, but the high surface area of zeolite reduces bleeding and accelerates setting without any strong effects on the other physical and technological properties of fresh mortars.

The dependence of the abrasive wear resistance of ultra-high-molecular-weight polyethylene on the content of mineral fillers with needle-like structure

The dependence of the abrasive wear resistance of ultra-high-molecular-weight polyethylene on the content of mineral fillers with needle-like structure

STUDY OF WATER ABSORPTION OF GEOPOLYMER MATERIALS BASED ON IRON ORE ENRICHMENT TAILINGS

As you know, the problem of environmental safety is important in the process of mining and processing of ore and non-metallic minerals. In the process of primary processing of ore minerals, the so-called enrichment tailings or production wastes are formed. The resulting waste accumulates in huge quantities, contributing to changes in the landscape and worsening the hydrogeological and sanitary conditions of the environment. In addition, rainfall and meltwater contribute to the constant leaching of heavy metals from waste dumps, which eventually leads to the pollution of groundwater, rivers and lakes. Therefore, the important ecological task of rational disposal of mining tailings is very relevant around the world. Research aimed at developing and obtaining new materials on the basis of this waste is of the greatest interest. One of such directions is the utilization (immobilization) of mining tailings when obtaining of geopolymer materials, which eliminates the leaching of heavy metals from the volume of the obtained material. Over the past 60 years, millions of tons of enrichment tailings have accumulated at the Dashkesan iron ore deposit, which are waiting to be disposed of. For this reason, the tailings of Dashkesan iron ore enrichment were used as a mineral filler for producing geopolymer material. Mineralogical and chemical compositions of enrichment tailings were studied using X-ray phase and X-ray fluorescence methods. Water absorption of the obtained specimens of geopolymer material was researched in accordance with the known methodology. It was revealed that with the increase of mineral filler content from 60 to 90%wt. the value of water absorption of geopolymer material specimens in the first five minutes of exposure increased from 1 to 10,2%, respectively. With the increase of mineral filler content from 60 to 90%wt. the maximum value of water absorption increases from 2,6 to 10,2%, respectively. Keywords: geopolymer, water absorption, enrichment tailings, iron ore.

Mixture design and performance characterization of asphalt mixtures prepared using paving-heavy crude oils for low-traffic volume roads

Low-volume road development, a fundamental part of national economic infrastructure, requires further advances in identifying alternative materials for their construction. One of these alternative materials is paving-heavy crude oil (PHCO), defined as natural liquid asphalt. However, research on these materials is scarce, and no standards or specifications currently exist for preparing asphalt mixtures using PHCO (AM-PHCO). This paper assesses the feasibility of (i) designing AM-PHCO through the Modified Marshall Method for Cutback Asphalt-Aggregate Cold Mixture Design, with optimum filler content determined via energy parameters, and (ii) evaluating and differentiating moisture-damage and fracture resistances of AM-PHCO through conventional- and unconventional-testing. After characterizing the asphalt products, the mix design was performed for ten asphalt mixtures. Then, the performance of these mixtures was assessed through Marshall stability, indirect tensile strength, Fenix, and semicircular bending tests. The study included two neat and two nano-modified PHCOs and a couple of mineral fillers to produce AM-PHCO compared to control mixtures fabricated with a penetration asphalt binder. Results support the conclusions that (i) the mix design method used applies to AM-PHCO, providing new technical criteria to improve them through mix design standardization, (ii) mineral filler content optimization for AM-PHCO can use energy parameters computed from surface free energy, and (iii) testing employed in this study can differentiate AM-PHCO moisture damage resistance and fracture resistance. However, additional research can evaluate the suitability of adjusting conditioning protocols and current specifications for retained Marshall stability (75%) and retained tensile strength (80%) in characterizing AM-PHCO. Lastly, further research could explore PHCO aging effects on AM-PHCO performance and complementary performance parameters, including fatigue life, rutting resistance, and stiffness.

Mechanical and morphometric characterization of custom-made trabecular bone surrogates

Synthetic bones for biomechanical testing and surgeon training have become more important due to their numerous advantages compared to human bones. Several bone models are already available on the market, but most of them do not reflect the full range of versatile properties that characterize human bone like population-level influences, size, stiffness, bone-implant-interface or morphometry. Thus, the objectives of this study were to develop synthetic trabecular bone surrogates from polyurethane and varying additives and to determine their elastic and plastic mechanical compressive and additionally morphometric properties. Another aim was to investigate the influence of varying additives on aforementioned properties and finally compare the results with published data from human trabecular bone. Additives used were blowing agents to create a porous structure, mineral fillers to manipulate the basic polyurethane resin, and cell stabilizers to achieve an open porous composition. Mechanical properties were obtained from static compression tests until failure while morphometric analysis was carried out using microcomputed tomography. Thereby, the blowing agent showed the strongest influence on mechanical and morphometric properties with mean Young’s moduli ranging from 627 ± 37 MPa (0% blowing agent) to 154 ± 15 MPa (0.25% blowing agent) while the variation of mineral filler content resulted in small standard deviations of approximately 10–20 MPa with a constant proportion of blowing agent. The achieved mechanical properties of the developed synthetic bones, such as the Young’s modulus, ultimate stress and yield stress were in accordance with human trabecular bone, while yield strain for all groups was noticeably higher compared to human trabecular bone. Additionally, morphometric analysis showed results indicating similar morphometry of the custom-made synthetic bone and human cancellous bone. Although recreating bone structures in physiological conditions is not simple, the results of the current study show the possibility of developing synthetic bone materials with characteristics like human trabecular bone.

Composite polypropylene polymer materials that work in contact with raw cotton

Physicomechanical and tribotechnical properties of structural composite materials based on thermoplastic polymer and organomineral ingredients operating under friction and wear conditions during contact with pulp (raw cotton) have been investigated. The regularities of changes in the physical, mechanical and tribotechnical properties of structural composite materials during contact interaction with raw cotton were determined, the dependence of their properties on the type and content of graphite, mineral and fibrous fillers in structural composite materials was studied. It has been established that the nature and structure of fillers has a certain effect on the physical and mechanical properties of composite materials based on polypropylene. At the same time, fiber-filled compositions have the highest mechanical strength. It was also found that when mineral fillers are introduced into composite polymer materials, their coefficient of friction with raw cotton increases significantly, while the wear rate decreases, except for fillers with a plate structure (kaolin, talc), when used, a decrease in the coefficient of friction is observed. The introduction of carbon-graphite fillers into the composition of composite materials leads to a significant decrease in the coefficient of friction, temperature and static electricity charge in the friction zone with raw cotton. The introduction of fillers with a fibrous structure leads to a significant decrease in the rate of wear of the composites. It provides high strength and resistance of the material under thermomechanical action. Effective compositions of structural composite materials for work under conditions of contact interaction with fibrous mass have been developed, and their physical, mechanical and tribotechnical properties have been investigated.

Cellular Polyolefin Composites as Piezoelectric Materials: Properties and Applications.

Piezoelectric polymers characterized by flexibility are sought for applications in microelectronics, medicine, telecommunications, and everyday devices. The objective of this work was to obtain piezoelectric polymeric composites with a cellular structure and to evaluate their usefulness in practice. Composites based on polyolefins (isotactic-polypropylene and polyethylene) with the addition of aluminosilicate fillers were manufactured by extrusion, and then polarized in a constant electric field at 100 V/µm. The content of mineral fillers up to 10 wt% in the polymer matrix enhances its electric stability and mechanical strength. The value of the piezoelectric coefficient d33 attained ~150 pC/N in the range of lower stresses and ~80 pC/N in the range of higher stresses, i.e., at ~120 kPa. The materials exhibited high durability in time, therefore, they can be used as transducers of mechanical energy of the human motion into electric energy. It was demonstrated that one shoe insert generates an energy of 1.1 mJ after a person walks for 300 s. The miniaturized integrated circuits based on polyolefin composites may be applied for the power supply of portable electronics. Due to their high sensitivity, they can be recommended for measuring the blood pulse.

Novel Gradation Design of Porous Asphalt Concrete with Balanced Functional and Structural Performances

To improve the permeability of porous asphalt concrete (PAC) with a small nominal maximum aggregate size (NMAS) of 10 mm (PAC10), a novel gradation design by excluding the 0.075–3 mm aggregate was developed. This study aims to evaluate the functional and structural performances of the novel PAC10 with various mineral filler contents, using the conventional PAC10 and 13 mm NMAS PAC (PAC13) as reference, and develop the optimum gradation of the novel PAC10. The performance properties evaluated include moisture susceptibility, durability, high-temperature stability, low-temperature cracking resistance and permeability. The results indicated that for the two conventional PACs with the same fine aggregate and mineral filler content, PAC10 had worse permeability and rutting resistance, similar moisture susceptibility and durability, and better low-temperature cracking resistance, compared with the PAC13. The novel PAC10 showed better permeability than the conventional PAC10. With the increase of the mineral filler content, the structural performance of the novel PAC10 is improved, but its permeability is decreased. With a mineral filler content of 6%, the novel PAC10 can have balanced functional and structural performances, which are equivalent to those of the conventional PAC13.

Reliability of Microsurfacing Mix Subjected to Variation in Aggregate Gradation

Reliability analysis describes the probability of the pavement satisfying the performance criteria throughout its design life. Assigning reliability during the design stage is vital for the proper planning of maintenance and rehabilitation activities. In this respect, this study evaluates the reliability of microsurfacing mix subjected to variations in aggregate gradation. A total of 10 different combinations of aggregate gradation were selected where the initial five combinations were based on the specification limits and the other five were randomly generated using Monte Carlo simulation. The performance was assessed in relation to cohesion, abrasion loss, rutting, and bleeding. Results indicated a significant variation in test results even when the aggregate gradation was varied within tolerance limits. The primary factors contributing to the variability were the total surface area of aggregates and the mineral filler content in the mix. Reliability analysis of the test parameters was conducted through the specified limits of each test. It was found that the reliability of each test parameter was more than 90%. However, the overall reliability, including all the test parameters, was 73%. The reliability of the microsurfacing mix meeting all the performance requirements increased to 90% when the aggregate gradation tending to a lower specification limit was excluded. Further, the individual reliability of each test parameter was more than 95%. Thus, to ensure higher reliability, microsurfacing mix with a lower total surface area and a lower mineral filler content should be avoided during the production stage of microsurfacing mix.

Characteristics and Mechanisms of Asphalt-Filler Interactions from a Multi-Scale Perspective.

Asphalt mastic plays an important role in asphalt mixtures for pavement engineering. Understanding the asphalt–filler interaction behavior is essential to improve the pavement performance of asphalt mastics. The objective of this paper was to evaluate the asphalt–filler interaction ability based on macro-rheological measurements and to investigate the asphalt–filler interaction mechanism associated with microstructural characteristics of asphalt mastics. First, the asphalt–filler interaction was characterized using macro-rheological features of asphalt mastics based on dynamic shear rheometer (DSR) tests. Second, the physico-chemical interaction between the asphalt and filler was qualitatively evaluated using a Fourier transform infrared (FTIR) spectrometer. Third, the asphalt–filler interaction behavior was investigated in terms of the micro-morphological properties of mineral fillers and asphalt mastics by conducting scanning electron microscopy (SEM) and atomic force microscope (AFM) tests. Finally, the grey relational analysis (GRA) was employed to identify the correlation between the properties of mineral fillers and the macro–micro performances of asphalt mastics. The results show that a higher content of alkaline mineral filler within the critical volume fraction range produced a greater interaction ability between the asphalt and filler. The asphalt–filler interaction is mainly a physical action since no obvious new adsorption peaks appeared in the FTIR spectrum. The micro-morphological characteristics of asphalt mastic mainly depended on the adsorption effect of mineral fillers on polar fractions and the dispersion effect of mineral fillers on wax crystals in the asphalt binder. Based on the results of the GRA, the acidity and content of mineral fillers exhibited a great influence on the micro-morphological and macro-rheological characteristics of asphalt mastics, and the specific surface area of the mineral filler exerted a significant influence on the asphalt–filler interaction ability. Furthermore, the K-B- index was more appropriate for evaluating the asphalt–filler interaction ability.

Influence of a Mineral Filler on the Fire Behaviour and Mechanical Properties of a Wood Waste Composite Material Stabilized with Expanded Polystyrene

The use of vegetable fibers composites in structures sometimes presents significant fires risks because of their high flammability. This work aims to study the impact of the addition of mineral filler (clay) on the fire behaviour of wood-polystyrene composites and their mechanical properties. Thus, composites containing 25% of expanded polystyrene binder have been produced. On this base material, proportions of clay ranging from 0% to 15% were gradually added. These samples were elaborated by compaction and for some them, submitted to thermoforming after drying. Both kinds of sample were subjected to flame persistence test; flexural strength and compressive strength test were also measured. The results show that composites without mineral filler ignite continuously until the total consumption and when the mineral filler content increases the combustion time decreases. The addition of the mineral filler allows these composites to pass from class M3 of moderately flammable combustible materials to class M2 of hardly flammable materials, according to the M classification of construction and furnishing materials. The measurement of the mechanical properties shows that the strengths increase when the filler content goes from 0% to 10% and then decrease. This leads to set the optimum content of mineral filler around 10%.

Analysis of Influence of the Dolomite Inactive Mineral Filler Quantity on Properties of Deep Cold Recycled Mixtures with Foamed Bitumen

The subject of research presented in article was an assessment of the impact of inactive mineral filler content, i.e. dolomite dust, on the recycled cold mix properties with foamed bitumen. The analysis of the impact of dolomite mineral dust was made on the basis of the experiment design type 33. It consisted of three levels of foamed bitumen factor in the range from 1.2% to 3.6% with a 1.2% step and the amount of mineral dust factor in range from 5% to 20% with a 7.5% step. Dolomite dust is a waste material derived from aggregate mining. Foamed bitumen was obtained from foaming process of the neat bitumen 50/70 at water temperature of 25ºC and its amount of 2.7%. In order to increase the cohesion of the recycled cold mix with foamed bitumen, Portland cement CEM I 32.5 R in amount of 2.0% was used. The assessment of the impact of quantitative variables was carried out in accordance with the adopted plan of the experiment that assumed the determination of physical and mechanical properties such as: resistance to climatic factors, dynamic modulus (E*) and phase angle. Analysis of the test results shown that factors quantity affects the variability of analysed features. In the entire scope of experiment plan, the obtained free space values met the requirements in required guidelines. The highest sealing of the recycled mixture was observed for the entire dolomite dust dosage but at maximum amount of foamed bitumen amounted to 3.6%. It was also observed that the maximum water resistance (TSR) was obtained for mixtures with a minimum amount of mineral dust (5%) as well as the maximum amount of dust in the recycled cold mix (20%). However, it was depended of the amount of foamed asphalt in a recycled mixture composition. The study also was considered the influence of the amount of dolomite mineral dust on the change in stiffness modulus tested by means of IT-CY and DTC-CY procedure. It was shown that either stiffness modulus measured by IT-CY or DTC-CY are foam bitumen and dust amount dependent. To assess the rheological properties, the direct compression-compression test (DTC-CY) was used. All samples were subjected to a cyclic sinusoidal constant strain with an amplitude of εo <25με. The tests were carried out in the temperature range (-7ºC, 5ºC, 13ºC, 25ºC, 40ºC) and loading time (0.1 Hz, 0.3 Hz, 1 Hz, 3 Hz, 10 Hz, 20 Hz). It was found a significant variability of recycled base stiffness depending on loading time and temperature.

Influence of gradations on performance of emulsified asphalt cold recycled mixture produced using vertical vibration compaction method

In this study, the effects of virgin aggregate content, such as mineral filler, machine-made sand, and coarse aggregate, on the performance of emulsified asphalt cold recycled mixtures (ECRMs) produced using the vertical vibration compaction method (VVCM) are evaluated. The optimum virgin aggregate contents are proposed based on the results. The results show that with increasing mineral filler content (mass fraction <5%), the mechanical strength, rutting resistance and crack resistance of the ECRMs gradually increase, whereas the moisture sensitivity increases initially but gradually decreases, and 3% mineral filler demonstrates the optimum moisture sensitivity compared to reclaimed asphalt mixtures. Further, as machine-made sand content increases, the mechanical strength, rutting resistance, crack resistance and moisture sensitivity of the ECRMs increase initially and decrease gradually, and the aforementioned performance of the ECRMs reaches the peak values when 20% machine-made sand is added, compared to mixtures without the machine-made sand. The mechanical strength, rutting resistance, crack resistance and moisture sensitivity of the ECRMs initially increase and then gradually decrease with the addition of the coarse aggregate. When the coarse aggregate content is 10%–30%, the ECRMs show a good performance, compared to mixtures without the coarse aggregate. To effectively improve the engineering properties of the ECRMs, the proposed optimum content of the mineral filler, machine-made sand and coarse aggregate are 3%, 20% and 10–30%, respectively.

Исследование физико-механичес- ких и рентгенозащитных свойств деревокомпозиционного слоистого материала «Фанотрен Б»

Physical and mechanical and x-ray protection properties of new wood-based composite material “Fanotren B”, which consist of alternating layers of peeled birch veneer and reinforcing x-ray protective layers, are studied. The x-ray protective layer is nonwoven fabric – sintepon impregnated with x-ray protective composition; consist of barium sulfate, adhesive based on polyvinyl acetate dispersion and water. The material is recommended to be used in construction and decoration of premises in the areas with high radiation background. A distinctive feature of the developed material is the absence of lead and materials based on it. We had the following research objectives: to study the stress strain behavior of the material; to determine the balanced formulation of saturating composition for the x-ray protective layer; to evaluate its physical and mechanical properties. The stress – strain ratio of the ma-terial was simulated by the finite element method, the physical and mechanical properties were evaluated by the standard methods, the protective properties of the x-ray protective layer were measured by the lead equivalent of the image transparency on the radiograph with the use of lux meter. Theoretical studies have shown that the behavior of metal faced plywood under external load is described by the Sophie Germain’s equation with acceptable accuracy. The modeling was carried out on a solid model, which took into account mechani-cal properties of the materials included in the design and scheme of laying out the veneer layers. The developed model of the stress strain behavior has showed that the decrease of the protective layer thickness leads to the increase of deflections and stresses in it. Computer simulation revealed the stress increase in the areas of bonding the material protective layer and outer side of veneer. The impregnating composition was determined experimentally: mineral filler content is 51 %, binder content is 26 %, and water content is 23 %. The technological modes of composite laminated material formation were determined: binder consumption is 176 g/m2; pressing temperature is 50 oС; gluing time is 8 min. The material with the thickness of 9.5 mm has density of 1600 kg/m3; a lead equivalent is 0.54 mm Pb/mm; cross-breaking strength along the outer layers is 39 MPa; shear strength along the adhesive layer is 1.34 MPa; tensile strength along the fibers is 53 MPa.For citation: Yatsun I.V., Gorokhovskiy A.G., Odintseva S.A. Study of Physical and Mechani-cal and X-Ray Protection Properties of Wood-Based Composite Laminated Material “Fanotren B”. Lesnoy Zhurnal [Forestry Journal], 2019, no. 3, pp. 110–120. DOI: 10.17238/ issn0536-1036.2019.3.110

Use of Rice Husk Ash and Domestic Plastic Wastes in Bituminous Concrete (BC)

This paper presents the experimental results on the utilization of Rice Hush Ash (RHA) and Domestic Plastic Wastes as a replacement for mineral filler and Optimum binder content (OBC) in bituminous concrete mixes. Bituminous concrete mixes containing Rice Husk Ash and Domestic Plastic Wastes at different amounts and control specimens were prepared in accordance to Marshall Mix design, and their performance on stability, flow and bulk density were evaluated. Optimum binder content (OBC) and voids analysis were also conducted to compare performance of Rice Husk Ash and Domestic Plastic Wastes at different contents. Results reveal that all Rice Husk Ash and Domestic Plastic Wastes mixes have satisfied the Public Works Department (PWD) specification and MORTH specification on wearing course in regard with Marshall Stability and Flow. This material is potentially to be used as partial or full substitution of mineral filler (stone dust) and Optimum binder content (OBC) in pavement construction. Modified bituminous mixes are expected to give higher life of surfacing depending upon degree of modification and type of additives used. The present study aims at developing bituminous mixes for the Bituminous Concrete (BC) Grade 1 incorporating the plastic wastes, waste tyre tubes and rice husk ash as partial replacement of the bitumen content. In this study, the Stability-Flow analysis for the various BC Grade 1 mixtures with modified binders and with different percentage replacement of bitumen with plastic wastes, waste tyre tubes and rice husk ash are reported.

Fire-Resisting Composites Based on Polymer Matrix

In the present work we have studied the thermal stability, flammability, fume evolution of epoxy matrix composites with different types and amounts of hardeners, fillers, plasticizers and fire retardants. It is shown that chemical composition of fillers has little effect on the flammability of epoxy composites when the content of mineral fillers is less than 45% by mass. Smoke formation decreases linearly with increasing the degree of filling. It is shown that to obtain low-combustible materials the oxygen index should exceed 31%. It was found that the optimal concentration of industrial brominated fire retardants is 8-10% by mass. To reduce the flammability of epoxy composites, additive brominated fire retardants in the form of a solution in N,N-dimethyl-2,4,6-tribromoaniline have been proposed. The high efficiency of acetyl-and α-hydroxyethyl ferrocene as a smoke suppressor of epoxy composites is shown.

Fire-Resiting Composites Based on Polymer Matrix

In the present work we have studied the thermal stability, flammability, fume evolution of epoxy matrix composites with different types and amounts of hardeners, fillers, plasticizers and fire retardants. It is shown that chemical composition of fillers has little effect on the flammability of epoxy composites when the content of mineral fillers is less than 45% by mass. Smoke formation decreases linearly with increasing the degree of filling. It is shown that to obtain low-combustible materials the oxygen index should exceed 31%. It was found that the optimal concentration of industrial brominated fire retardants is 8-10% by mass. To reduce the flammability of epoxy composites, additive brominated fire retardants in the form of a solution in N,N-dimethyl-2,4,6-tribromoaniline have been proposed. The high efficiency of acetyl-and α-hydroxyethyl ferrocene as a smoke suppressor of epoxy composites is shown.

Effects of Filler⁻Bitumen Ratio and Mineral Filler Characteristics on the Low-Temperature Performance of Bitumen Mastics.

This study analyzed the effects of the filler–bitumen interaction of the content and the meso powder characteristics of the mineral filler on the low-temperature performance of bitumen mastics. Control strategies for the mineral filler content (filler–bitumen ratio (RFB)) were also determined. Panjin #90 bitumen and styrene–butadiene–styrene polymer-modified bitumen were used in the experiment. Four kinds of limestone powder were used, all of which satisfy the Chinese standard for powder particle size but exhibit different meso characteristics. Each kind of limestone powder was used to prepare bitumen mastic samples under five different RFBs. The meso voids in the unit mass (Vg) of the four kinds of mineral filler were tested on the basis of the principle of the Rigden void ratio. The fixed bitumen–free bitumen ratio in the bitumen mastic samples was determined using Vg, bitumen density, and RFB. The low-temperature cohesive strength of the bitumen mastics was used as the control index for critical failure, whereas variation rates of bending creep stiffness at low temperature were used as the control index for fatigue failure. Results showed that the effects of the filler–bitumen interaction of the content and the meso characteristics of the mineral filler are significant and such effects are determined by the fixed bitumen–free bitumen ratio. The optimal fixed bitumen–free bitumen ratio in the bitumen mastics under two low-temperature conditions (−30 °C and −10 °C) can be determined on the basis of the influence of the fixed bitumen–free bitumen ratio on the critical and the failure control indices. Moreover, RFB can be obtained through reverse calculation. The mineral filler content can therefore be precisely controlled, which is crucial for the rational use of mineral filler and for the improvement of the pavement performance of bitumen mastics at low temperatures.

An experimentally-based viscoelastic behavior of asphalt mastic at high temperatures

Mastic properties play important role in the performance of asphalt concrete, especially for high temperature performance. The objective of this paper was to describe the viscoelastic behavior of asphalt mastic at high temperatures and determine the regression constants of the models. Two different asphalt binders namely AS-70 base asphalt binder and SBS modified asphalt binder were selected to mix with the mineral filler. For each asphalt binder, asphalt mastic samples were prepared at five different mass percentages, as 0.6, 0.9, 1.2, 1.5 and 1.8. The viscosity and rheological properties were tested under different temperatures using Brookfield RVDV-III rotating viscosimeter and Dynamic Shear Rheometer (DSR). The test results indicated that, for the modified asphalt mastic, increasing mineral filler content in the mastic caused a significant increase in the viscosity, while the effects were not significant on the base asphalt mastic. The filler showed no obvious effect on the temperature sensitivity of the mastic. The creep characteristic of base asphalt mastic can be modeled by the Maxwell model. The Burgers model was the most appropriate to model the creep characteristic for the modified asphalt mastic. The relaxation function of Burgers model can successfully fit relaxation behavior of the mastic.

Correlação da energia de fratura com parâmetros reológicos de ligantes e mástiques asfálticos

A energia de fratura é uma propriedade relacionada com a contribuição de ligantes asfálticos à resistência à fadiga de misturas asfálticas e, portanto, tem grande influência no comportamento mecânico de pavimentos flexíveis, particularmente no desenvolvimento e propagação de trincas. Esta pesquisa tem o objetivo de contribuir para um melhor entendimento dos efeitos do fíler mineral e do ligante asfáltico na relação da energia de fratura com os parâmetros reológicos de ligantes e mástiques asfálticos, em temperaturas intermediárias. Para a determinação da energia de fratura foi realizado o ensaio Binder Fracture Energy (BFE), desenvolvido na Universidade da Flórida, em função do tipo e teor do fíler mineral e do ligante asfáltico. Os resultados mostram que a energia de fratura pode ser relacionada com o módulo de cisalhamento dinâmico (G*) e com o ângulo de fase (δ), obtidos em ensaios no reômetro de cisalhamento dinâmico (DSR), com a rigidez [S(t)] e com a taxa de relaxação [m(t)], obtidos em ensaios de fluência de viga à flexão (BBR). No entanto, todas as correlações são tênues, reforçando a hipótese de que uma inferência mais adequada sobre o desempenho à fadiga de uma mistura asfáltica pode ser obtida quando a energia de fratura é utilizada juntamente com propriedades fundamentais tradicionais.