Binder Thickness Research Articles

Performance Analysis Relevant to Primary Design Parameters of Pervious Concrete: A Critical Review

Pervious concrete (PC) is a structural element with environmental benefits. The industrial application is highly limited by restrictions in predicting performance owing to high uncertainties and issues in mass-producing with uniform characteristics. Primary performance indicators of PC are compressive strength, porosity, and permeability, where the porosity distribution and pore characteristics are crucial in its mechanical properties. Although compaction can improve uniformity in the properties of concrete, it is properly employed in PCs to ensure connectivity between pores and thereby enhance permeability. The compactability of fresh concrete predominantly depends on binder thickness dictated by aggregate-to-binder (A/B) ratio, water-to-binder (W/B) ratio, aggregate size, shape distribution of aggregates, and interfacial transition zone. In addition, the method of compaction, the compaction energy, and the distribution of compaction energy in the concrete matrix affect the above. The concrete compaction methods and their effectiveness vary between laboratory studies and field-scale installations. This state-of-the-art critical review of literature reviews the performance parameters of PC, compaction types and methods, compactability of PC, and models currently employed to optimize the mix design. It also highlights the potential trends for future studies to assist optimization of compaction in PC. The authors believe that this comprehensive review would assist professionals in developing a standard code of practice for using PC concrete.

Research on Temperature Field of Controllable Bonded Prestressed Structure Based on Electrothermal Method.

Controllable bonded prestress represents an innovative advancement stemming from retard-bonded prestress systems, distinguished by its intrinsic controllability in bonding. The controllable bonded binder can be artificially heated and cured rapidly through DC heating after the completion of prestressed tension, allowing for enhanced control over the process. FLUENT simulates controllable bonded prestressed structure's temperature field, yielding a 1.73% max error validated against measured data. Based on the theory of heat transfer, the maximum error of the calculated temperature field of the controllable bonded test beam under DC heating using the Stehfest numerical algorithm is 1.28%, which exhibits a strong alignment with both simulated and measured results. The parameter analysis identifies current, binder thickness, and steel-strand diameter as key temperature distribution influencers. The relationship between the current and heating time follows a quadratic inverse pattern. Increasing the heating current can significantly reduce the duration of heating. Under identical heating conditions, the temperature of the controllable binder is directly proportional to its thickness. A higher thickness results in a higher temperature. Additionally, larger diameters of steel-stranded wire lead to a lower heating efficiency.

Meso-scale adhesive/cohesive failure behaviors of porous asphalt mixtures considering random inhomogeneous distribution of binder

Durability failure is the main concern of porous asphalt mixtures (PAC) and is caused by adhesive failure on aggregate-binder interface or cohesive failure within the binder. Adhesive/cohesive failure behaviors of PAC are dependent on the adhesive/cohesive properties of binder, which are influenced by the thickness and composition of binder. The aim of this study is to develop a meso-scale finite element modeling (M−FEM) considering the random inhomogeneous distribution of binder to investigate the meso-scale adhesive/cohesive failure behaviors of PAC. In the M−FEM, two types binder (mastic and mortar) with different thickness were reconstructed. The adhesive/cohesive properties of mastic and mortar with different thickness were evaluated by a modified pull-off test and used to determine the model parameters. A zero-thickness cohesive element was embedded into the interface between aggregate-binder and within binder, and the cohesive element parameters were determined and assigned based on the binder thickness. M−FEM with and without considering the random inhomogeneous distribution of binder (Model B and Model A) were constructed. The adhesive/cohesive strength of mastic increased with the thickness and reached a peak value at the thickness of 0.8 mm. The adhesive/cohesive strength of mortar increased with the thickness. The initial cracking point of Model A and Model B are different. In the cracking extension stage, adhesive failure was found in Model A, while both adhesive and cohesive failure behaviors were found in Model B. The random inhomogeneous distribution of binder has a significant impact on the damage initiation, stress distribution, stress transfer, and evolution of adhesive/cohesive failure behaviors of PAC. M−FEM considering the random inhomogeneous distribution of binder is more reasonable in the simulation of adhesive/cohesive failure behaviors. Increasing the binder thickness may have a contribution to the improvement of durability of PAC.

Utilization of copper slag waste in alkali-activated metakaolin pervious concrete

This study aims to evaluate the feasibility for preparing alkali-activated metakaolin (AAM) pervious concrete incorporating copper slag (CS) waste. The effects of replacement of metakaolin with CS on the total void ratio, water permeability, mechanical properties, and abrasive resistance of the pervious concretes were investigated. Hydration heat evaluation, SEM, and XRD were conducted to reveal the components interaction. The results showed that the total void ratio and water permeability of the pervious concretes increased with adding CS, since the binder thickness for coating aggregate correspondingly reduced due to the higher density for CS than metakaolin. Although the reactivity of CS was lower than that of metakaolin, the pervious concrete with 30% CS still obtained the comparable compressive and flexural strengths to the concrete without CS. It is mainly attibuted to the strength compensation caused by the CS micro-aggregate effect and a denser microstructure. Adding CS in the concretes obtained a satisfactory abrasive resistance owing to the high paste strength and low wear loss. This study extends the knowledge of using CS in AAM pervious concrete and broadens the CS application scenarios, which is beneficial for consuming CS waste and reducing carbon emissions and costs of pervious concrete preparation.

Investigating mechanical performance and interface characteristics of cold recycled mixture: Promoting sustainable utilization of reclaimed asphalt pavement

The recycling and sustainable utilization of reclaimed asphalt pavement (RAP) are the key method to improve resource conservation and reduce energy consumption in roadway construction. The cold-recycled technology has been regarded as a promising recycling one because it can achieve mixing at room temperature and high utilization of RAP. Investigating the mechanical mechanism of cold-recycled asphalt mixture (CRAM) is the basis for large-scale application. Thus the splitting tests were carried out to study the influencing law of the material components on the strength performance of CRAM by varying RAP, cement and asphalt content. Then the effects of material component on the strength mechanism were further revealed by the interface characteristics analysis, including void and filler parameters, binder and interface transition zone (ITZ) thickness. The results show that the CRAM with more RAP has a higher splitting strength and the aged asphalt contributes to the reduction of void number around the aggregate interface, indicating a stronger bonding effect with binder. The asphalt mixture has lower void size, void number and porosity than cement mixture, and shows more uniform distribution of binder thickness and lower void distribution difference between the ITZ and the mortar phase, which is conducive to force uniformly and prevent stress concentration within mixture. The above outcomes confirm the effects of strength improvement from RAP and the void increment from cement, and the contents could be reasonably increased for RAP and strictly controlled for cement to ensure strength performance of CRAM while promoting saving energy and environmental protection.

Investigation on the comprehensive durability and interface properties of coloured ultra-thin pavement overlay

Coloured pavement provides benefits for improving functionality and safety in pavement infrastructure. In this investigation, a coloured ultra-thin pavement overlay was prepared with a resin-based binder and artificial coloured ceramic aggregates. The overlays were prepared in various binder thicknesses (0.8 mm, 1.2 mm, and 1.6 mm) and aggregate spreading ratios (50 %, 75 %, and 100 %). The specimens were experimentally tested with a wheel abrasion tester followed by the analysis of apparent colour loss, rutting depth, mass loss, and skid resistance in accordance with a proposed comprehensive durability evaluation method. The colour-cooling performance was evaluated with the sunlight simulation test. In addition, the interface properties were tested based on the flexural toughness test, pull-off test, and shear test. The comprehensive durability evaluation results indicated that coloured overlay with 1.2 mm binder depth and 75 % aggregate spreading ratio had the highest durability score among all samples. The sunlight simulation test results verified the positive cooling effect of the coloured overlay on the pavement structure. The bottom-up cracking resistance based on the flexural toughness test was also improved with overlays by comparing that with specimens without covering. The pull-off test and shear test results illustrated that the interface adhesion was correlated to environmental temperature and binder thickness. This study provided a comprehensive durability scoring method for coloured ultra-thin functional overlays, and the optimized material compositions enhanced the durability and interface adhesion, which could be utilized for future field applications of coloured ultra-thin functional overlays and contribute to infrastructure sustainability.

Suitable Ultra-Thin Asphalt Binder Achieved the Energy Equilibrium

The tensile behaviour of asphalt binder films confined between aggregate particles as an adhesive was investigated to evaluate the direct adhesion bond between asphalt binder and surface of aggregate utilizing several laboratory experiments. The results were interrogated in terms of the mechanical, chemical and surface free energy theories. The preformed tests include dynamic shear rheometer (DSR), sessile drop and direct tension tests. The experimental results demonstrated a strong relationship between the internal work represented by bond energy and the external work represented by the practical work required to fracture from the direct tension test that can be used to estimate asphalt binder-aggregate combinations performance. A simulation for the adhesion behaviour using a static model in terms of external work and internal work to predict the suitable asphalt binder thickness required to prevent fatigue and rutting failures was proposed as a new design criterion for asphalt pavement. Keywords: Internal and external bonding work, asphalt binder, SFE, fracture work, direct tension test, DSR.

Chemo-mechanical model predicted critical SOCs for the mechanical stability of electrode materials in lithium-ion batteries

The electrochemical performance and capacity retention of lithium-ion batteries significantly depend on the structural integrity of electrode materials. Understanding of the mechanical failure mechanisms in the active and inactive material phases of the electrode is critical to predict safe operation conditions, and to design next generation electrodes. The mechanical failure of the electrode can be effectively avoided by tailoring the lithiation kinetics and the size of the active and inactive materials. To predict the critical state of charges (SOCs) for mechanical failures, we develop a fully coupled chemo-mechanical model, and examine the effect of stress–concentration coupling on the maximum stored capacity. We focus on three types of mechanical failures: particle fracture, binder yielding, and debonding at the particle–binder interface. The simulations show that the medium-sized particles achieve larger capacity with no mechanical failure. Moreover, the simulation results reveal that as the binder modulus and charge rates increase, the safe zone shrinks considerably, while the binder thickness imposes no significant effect. These findings provide a fundamental insight into providing optimized charging protocols for minimum capacity retention due to mechanical failures at the electrode.

Investigation of Factors Causing Nonuniformity in Luminescence Lifetime of Fast-Responding Pressure-Sensitive Paints.

Factors that cause nonuniformity in the luminescence lifetime of pressure-sensitive paints (PSPs) were investigated. The lifetime imaging method of PSP does not theoretically require wind-off reference images. Therefore, it can improve measurement accuracy because it can eliminate errors caused by the deformation or movement of the model during the measurement. However, it is reported that the luminescence lifetime of PSP is not uniform on the model, even under uniform conditions of pressure and temperature. Therefore, reference images are used to compensate for the nonuniformity of the luminescence lifetime, which significantly diminishes the advantages of the lifetime imaging method. In particular, fast-responding PSPs show considerable variation in luminescence lifetime compared to conventional polymer-based PSPs. Therefore, this study investigated and discussed the factors causing the nonuniformity of the luminescence lifetime, such as the luminophore solvent, luminophore concentrations, binder thickness, and spraying conditions. The results obtained suggest that the nonuniformity of the luminophore distribution in the binder caused by the various factors mentioned above during the coating process is closely related to the nonuniformity of the luminescence lifetime. For example, when the thickness of the binder became thinner than 8 μm, the fast-responding PSPs showed a tendency to vary significantly in the luminescence lifetime. In addition, it was found that the luminescence lifetime of fast-responding PSP could be changed in the depth direction of the binder depending on the coating conditions. Therefore, it is important to distribute the luminophore uniformly in the binder layer to create PSPs with a more uniform luminescence lifetime distribution.

A Parametric Analysis on the Influence of the Binder Characteristics on the Behaviour of Passive Rock Bolts with the Block Reinforcement Procedure

An extensive parametric analysis of 729 typical cases was developed with a calculation procedure allowing to simulate in detail the behavior of the passive bolts and their interaction with the surrounding rock. The parametric analysis allowed to evaluate the effectiveness of the bolts, on the basis of the extent of the stabilization forces produced, in relation to the geometric and mechanical characteristics of the binder used in the realization of the bolts. Different bolt diameters and lengths, binder thickness and elastic moduli and block displacement values with respect to the horizontal plane have been considered. It has been possible to detect how such parameters have a great influence on the mechanical behavior of the bolt and on the extent of the stabilizing forces which are applied to the potentially unstable rock block. For this reason, therefore, the definition of the characteristics of the binder (and in particular the thickness of the binder around the steel bar and the elastic modulus of the binder itself) cannot be assessed only in relation to application aspects, but it must be able to consider the effects on the efficiency of the bolt and in particular on the stabilization forces on the potentially unstable rock block.

Enhancement of porous asphalt mixture for resisting environmental conditions using modified asphalt

Open-graded-friction-course (OGFC) is a hot asphalt mixture usually utilized as a private purpose wearing course, because of open graded asphalt mixture and aggregates skeleton (stone-on-stone) contact, it contains a relatively high air voids percent, after compaction which are permeable to water. In this research one sort of gradation was used (9.5 mm) NMAS for preparing the OGFC asphalt mixtures, penetration grade 40/50, crushed aggregate, asphalt content prepared with 4 % and up to 6 % by weight of mixture with 0.5 % increments. Optimum asphalt content (OAC) was selected based on these criteria: air voids content, asphalt draindown, permeability, and abrasion resistance (aged and un-aged) condition. The mix performance had been investigated by indirect tensile strength and moisture sensitivity measured according to the (AASHTO T283-14). Results illustrate that the increasing of asphalt binder content leads to decrease in the air voids content, abrasion loss and permeability values, while with draindown increase, conversely, the indirect tensile strength test (ITS) had been meaningfully increased for both conditions and this is a perfect signal of resistance against humidity susceptibility. It can be resolved that the increasing of asphalt binder % in OGFC asphalt mixture, leads to increase the thickness of asphalt binder covering around the aggregates. On the other hand the outcome indicated that the addition of 4 % styrene-butadiene-styrene (SBS) to asphalt mixture gradation equaled to “9.5 mm NMAS” tends to improve the mix properties and exhibit higher TSR by (18.5, 16.4 and 13.7) % increases, as compared with original asphalt; at asphalt content (5.1, 5.6 and 6.1) %, respectively. Based on the above evaluation, the use of SBS gives the asphalt mixture better volumetric and performance properties which improved the adhesion between aggregate and asphalt that leads to reduced stripping of HMA, horizontal deformation, and increased the tensile stiffness modulus value.

Quantification of Airfoil Aerodynamic Uncertainty due to Pressure-Sensitive Paint Thickness

In this paper, uncertainty quantification is used to investigate the propagation of the uncertainty of the pressure-sensitive paint (PSP) thickness distribution to the uncertainty of aerodynamic force measured. Specifically, airfoil surface pressure coefficient () and aerodynamic lift coefficient () of a natural laminar flow wing are analyzed with uncertain PSP thickness distribution. The airfoil with PSP applied is parameterized by using a novel parameterization method based on radial basis function interpolation. As a characteristic of wing aerodynamic performance, is determined by surface pressure distribution, which can be affected by uncertainties of PSP binder thickness. A kriging response surface method has been used to develop a surrogate model to represent the Reynolds-averaged Navier–Stokes solution of the flow around the airfoil with PSP. This enables the use of Monte Carlo simulations to obtain stochastic output, including the probability of the occurrence of significantly inaccurate output values affected by the inputs subjecting to Gaussian distributions. An error margin and associated probability for its occurrence are recommended to account for uncertainties for the aerodynamic force occurring in the PSP measurement.

Effects of binder concentration on the nanometric surface characteristics of WC-Co materials in ultra-precision grinding

The influence of the binder concentration on the nanometric surface characteristics of WC/Co in ultra-precision grinding is investigated in the present work. The results firstly show that the surface finish of the ground WC/Co changed with increasing Co content, and the machined surfaces were covered by many micro-pits and surface burs induced by the plastic deformation and the prior removal of Co binder, which also led to the micro-chipping of the WC grains near the boundaries for the lack of support by Co. Many finer scratching grooves in the feed marks appeared, but the periodic grinding grooves caused by the feed of the diamond wheel became unclear with increasing Co content and the vibration induced marks on the machined surface turned to be primary, the spatial frequency of which is identified to be around 130 1/mm by the Fast Fourier transform. In addition, for the isotropic of the statistical size of the WC grains and the thickness of Co binder along each direction, a circular symmetry shape of the spatial frequency forms and the radius increases with increasing Co content.

Evaluation of Moisture Susceptibility for Modified Open Graded Friction Course Mixes Used Styrene Butadiene Styrene

Open-graded-fraction-course (OGFC), is a hot asphalt mixture usually utilized as a private purpose wearing course, because of open graded asphalt mixture and aggregates skeleton (stone-on-stone) contact, it contain a relatively high air voids’ percentage, after compaction which are permeable to water. In this research one type of gradation was used (12.5 mm) NMAS, to preparing the OGFC asphalt mixtures, penetration grade 40/50, crushed aggregate, asphalt content prepared with 4 % and up to 6 % by weight of mixture with 0.5 % increments. Optimum asphalt content (OAC) was selected based on these criteria, air voids content, asphalt draindown, permeability, and abrasion resistance (aged and un-aged) condition. The mix performance had been investigated by indirect tensile strength and moisture susceptibility (sensitivity) measured according to the (AASHTO T283-14). Results illustrate that the increasing of asphalt binder content leads to a decrease of the air voids content, abrasion loss and permeability values, while draindown increase, conversely, the indirect tensile strength (ITS) had been significantly increased for both conditions and this is a gaod suggestion to resistance alongside moisture susceptibility. It can be decided that the increasing of asphalt binder percent in OGFC asphalt mixture, leads to an increase in the thickness of binder coating around the aggregates. On the other hand, the influence of modifier that prepared with 4% styrene-butadiene-styrene (SBS) on OGFC asphalt mixture tends to improve the mix properties and exhibit higher (TSR) as compared with original asphalt by (31, 27.7 and 24.4) % at asphalt percent (4.8, 5.3 and 5.8) %, respectively. The SBS improved the adhesion between aggregate and asphalt which leads to reduce stripping of HMA, horizontal deformation, and increased the tensile stiffness modulus value.

Fracture toughness of cemented carbides obtained by electrical resistance sintering

The unique combination of hardness, toughness and wear resistance exhibited by WC-Co cemented carbides (hardmetals) has made them a preeminent material choice for extremely demanding applications, such as metal cutting/forming tools or mining bits, in which improved and consistent performance together with high reliability are required. The high fracture toughness values exhibited by hardmetals are mainly due to ductile ligament bridging and crack deflection (intrinsic to carbides). In this work two WC-Co grades obtained by using the electric resistance sintering technique are studied. The relationships between the process parameters (cobalt volume fraction, sintering current and time, die materials, etc.), the microstructural characteristics (porosity, cobalt volume fraction, carbide grain size, binder thickness and carbide contiguity) and mechanical properties (Vickers hardness and fracture toughness) are established and discussed. Also the presence of microstructural anisotropy and residual stresses is studied. The sintering process at 7 kA, 600 ms and 100 MPa, in an alumina die, followed by a treatment of residual stress relief (800 °C, 2 h in high vacuum), allows to obtain WC-Co pellets with the best balance between an homogeneous microstructure and mechanical behaviour.

Measured bond strength of asphaltic material using developed blister method

The blister test was aimed to develop and establish a simple, partial and reliable laboratory adhesion test method for direct measurement of the adhesive bond strength of bitumen and aggregate. Blister test was conducted by a device manufactured locally to measured bond strength of asphaltic material. Materials that used in this work were asphalt and aggregate. The local asphalt cement was obtained from Durah refinery, south–west of Baghdad .The aggregate used for comparison was limestone. This paper presents the development of pressure–loaded blister test and apparatus to measure the adhesion of asphaltic materials. The blister test provides the interfacial fracture energy, which is related to the adhesion strength. In this test air is injected at the interface between the substrate (aggregate disc) and adhesive layer (asphalt) to create blister. The air pressure and blister height were measured as function of time. By using two parameters, the interfacial fracture energy is calculated. In this paper was found that the energy required to displacement the asphalt binder increased with time until failure (adhesion failure) due to loss of adhesion between aggregate substrate and asphalt binder and also the required energy to failure decreased with increased binder thickness.

A direct characterization of interfacial interaction between asphalt binder and mineral fillers by atomic force microscopy

The property of asphalt mastic directly affects the service performance of asphalt mixtures and pavements. Previous studies have demonstrated that the interaction between asphalt binder and mineral fillers has a significant effect on the performance of asphalt mastics. However, the interaction hasn’t been characterized by direct tests. In this study, an adsorption–separation test of asphalt binder on surface of mineral fillers was conducted to separate the structure asphalt binder and free asphalt binder. Atomic force microscope (AFM) PeakForce QNM mode was used to characterize the morphology and mechanical property of asphalt binder at different distances to filler surface. Results show that the effected thickness of binder–filler interaction was around 1 μm. Within this specific thickness, the “bee” structure of asphalt surface disappears gradually, and the modulus increases significantly when the tested samples are closer to the aggregate surface.

Optical characterization and modelling of paint top-coatings for low-emittance applications

The study reports on characterization of low-infrared-emittance paint top-coatings for interior building applications in which the thermal radiation becomes important in comparison with thermal conductance. The top-coating that consist of a binder with aluminium flakes has been optically characterized in the infrared wavelength range in order to determine single flake and binder emittance from reflectance measurements. The single flake emittance was found to be 0.12 for non-leafing cornflake. The absorption coefficient that determines the binder emittance as a function of binder thickness was 0.060 [μm]−2 and 0.085 [μm]−2 for Lumiflon and polyester respectively. These results were used as parameters in a simple model of the flake-binder top-coating to investigate how the emittance of the top-coating was influence by the two components and compared with a state-of-art low-emittance commercial paint. It was found from the modelling that replacing the polyester binder with Lumiflon reduces the infrared emittance (at room temperature) from 0.36 to 0.30. Increasing flake reflectance from 0.88 to 0.96 and at the same time reduce flake thickness from 2 to 1μm gives an emittance of 0.20. However, the real samples prepared with Lumiflon showed a severe degradation caused by the flakes floating up closer to the surface which indicates a viscosity problem that needs to be solved for practical use. Thinner flakes with higher reflectance can be found if vacuum metallised pigments are used instead of ball-milled.

Effect of treatment temperature on the microstructure of asphalt binders: insights on the development of dispersed domains.

This paper offers important insights on the development of the microstructure in asphalt binders as a function of the treatment temperature. Different treatment temperatures are useful to understand how dispersed domains form when different driving energies for the mobility of molecular species are provided. Small and flat dispersed domains, with average diameter between 0.02 and 0.70 μm, were detected on the surface of two binders at room temperature, and these domains were observed to grow with an increase in treatment temperature (up to over 2 μm). Bee-like structures started to appear after treatment at or above 100°C. Moreover, the effect of the binder thickness on its microstructure at room temperature and at higher treatment temperatures was investigated and is discussed in this paper. At room temperature, the average size of the dispersed domains increased as the binder thickness decreased. A hypothesis that conciliates current theories on the origin and development of dispersed domains is proposed. Small dispersed domains (average diameter around 0.02 μm) are present in the bulk of the binder, whereas larger domains and bee-like structures develop on the surface, following heat treatment or mechanical disturbance that reduces the film thickness. Molecular mobility and association are the key factors in the development of binder microstructure.

A Comparative Study on Properties of Malaysian Porous Asphalt Mixes with Different Bitumen Contents

Inadequate bitumen content in porous pavement construction may result in incomplete coating of aggregates which a thin bitumen film can oxidize rapidly resulting in premature failure of the pavement. This and presents the effects of porous asphalt prepared with 4.0% and up to 6.0% binder content with 0.5% increments binder. Bitumen penetration grade 60/70 and crushed granite were used in preparing the porous asphalt specimen. The porous asphalt mixes were compacted by applying 50 blows on each face using a Marshall Impact compactor. The specimens were tested for air voids, indirect tensile strength and water permeability and abrasion loss. The moisture sensitivity was assessed according to the AASHTO T283 procedures. The result shows that the increasing of bitumen content has decreased the, bulk density air voids, coefficient of permeability and abrasion loss values However, the Indirect Tensile Strength (ITS) has significantly increased and this is a good indication to resistance against moisture sensitivity. It can be concluded that the increasing of bitumen content in porous asphalt has increased the thickness of binder coating around the aggregates. This results reduction in air voids and water permeability, on the other hands it increases resistance to disintegration and ITS value which give better resistance to moisture sensitivity of porous specimens.