Eco-Friendly Asphalt Containing Recycled High-Density Polyethylene (HDPE): Performance Assessment and Cost Analysis

Utilization of the recycled waste materials for new products is considered as a viable solution for saving the environment. This study paper targets the performance evaluation of hot-mix asphalt made with the modified bitumen 60/70 containing 3% and 5% of recycled high-density polyethylene (HDPE) (by the weight of optimum bitumen). First, the properties of modified bitumen mixtures including specific density, penetration depth, ductility, and softening point were measured. Then, the properties of asphalt mixtures made with the modified bitumen including rutting depth and resilient modulus were measured. Findings indicated the suitability of recycled HDPE available in Iranian market in the development of eco-friendly asphalt mixtures. Results showed a 49% decrease in penetration depth and a 15% increase in softening point for the suggested modified bitumen mixture containing 3% of recycled HDPE compared to those of control bitumen mixture, i.e.  the bitumen mixture containing 0% of recycled HDPE. Results also showed a 47% decrease in rutting depth and a 113% increase in resilient modulus of asphalt made with the bitumen mixture containing 3% of recycled HDPE compared to those of control asphalt mixture, i.e. the asphalt mixture containing 0% of recycled HDPE. The results showed that the suggested asphalt mixture can be an appropriate option to be adopted not only in moderate climates but also in tropical climates as its characteristics become comparable to those of the bitumen 40/50 and the bitumen 30/40. Replacing a portion of bitumen by the recycled HDPE not only improves the characteristics of asphalt, but also has a positive impact on reducing the natural resource depletion and environmental pollution resulting from burning and/or the retention of plastic waste left in nature. The suggested eco-friendly asphalt is also cost effective

A review of current techniques for the evaluation of powder mixing

Blending a mixture of powders to a homogeneous system is a crucial step in many manufacturing processes. To achieve a high quality of the end product, powder mixtures should be made with high content uniformity. For instance, producing uniform tablets depends on the homogeneous dispersion of active pharmaceutical ingredient (API), often in low level quantities, into excipients. To control the uniformity of a powder mixture, the first required step is to estimate the powder content information during blending. There are several powder homogeneity evaluation techniques which differ in accuracy, fundamental basis, cost and operating conditions. In this article, emerging techniques for the analysis of powder content and powder blend uniformity, are explained and compared. The advantages and drawbacks of all the techniques are reviewed to help the readers to select the appropriate equipment for the powder mixing evaluation. In addition, the paper highlights the recent innovative on-line measurement techniques used for the non-invasive evaluation of the mixing performance

Toward Development of Self-Compacting No-Slump Concrete Mixtures

No-slump concrete (NSLC) is one of the commercial types of concrete that is known as a type of concrete with almost zero flowability. No-slump concrete is normally used for typical applications, like pavements construction and massive dam structures. The specific feature of a no-slump concrete is its high shape holding ability. No fixed formwork is required for the construction. The main disadvantage of this type of concrete is that a great amount of energy is required for a proper compaction. Self-compacting concrete (SCC) is another commercial type of concrete that is known as a type of concrete that flows and fills the formwork under its own weight without applying any external energy. Although SCC is a relatively recent development, it has demonstrated substantial economic and environmental benefits in terms of faster construction, reduction of required manpower, better surface finishing, easier and vibration-free placing and reduced noise level. Therefore, SCC has recently found a wide use for different applications and structural configurations. However in comparison with NSLC, its demolding time for preserving its shape is much longer and fixed formworks are required for the construction. The first objective of this research project is to study the possibility of developing a self-compacting no-slump concrete (SCNSLC), which does not need compaction and also has a high shape holding ability shortly after placing in the formwork. The second objective is to develop a model, which can predict the rheological behaviour of a mixture based on the properties and proportion of the mix components. The study starts with a comprehensive study of mechanisms that govern the rheological behaviour of concrete in the dormant period, i.e. when the hydration effect is still ignorable. A fresh concrete mixture is considered as a two-phase system, paste and aggregates. The paste itself is divided into two components, the “void paste” and the “excess paste”. The void paste is the part of the paste which fills the void space between the aggregates in a compacted state. The excess paste is the rest of the paste used to form a nominal layer with an average constant thickness around every single aggregate particle. The void paste tries to keep the aggregate particles in their positions, while the excess paste tries to push the aggregate particles apart and promote their mobility. With respect to the dominant mechanism, mixtures are divided into three main classes: \u95 Class 1: High Excess Paste volume mixtures, where the excess paste effect is dominant. For these mixtures the capacity to deform is maximal. \u95 Class 2: Intermediate Excess Paste volume mixtures, where the effect of the void paste becomes significant and gradually increases with decreasing excess paste volume. The capacity of the intermediate excess paste volume mixtures to deform is lower than the high excess paste volume mixtures. \u95 Class 3: Low Excess Paste volume mixtures, where the void paste effect is dominant and the excess paste does not significantly affect the rheological behavior. For these mixtures the capacity to deform is minimal. Mix design The shape holding ability of mixtures is characterized by the shape preservation factor 0<SPF?1. The SPF shows the ability of a mixture to preserve its shape in the slump test after demolding. The SPF is the ratio of the cross sectional area of a 3D sample after and before demolding. A SPF is about 1 for a mixture which shows almost no deformation, i.e. a no-slump concrete mixture (NSLC). For a conventional self-compacting concrete mixture (SCC), with a spread diameter?~600 mm, the SPF is less than about 0.4. In this thesis it is found that the maximum SPF for mixtures that can compact under their own weight is about 0.7. A mixture with SPF?0.7 is denoted a Self-Compacting High Shape Preserving Concrete (SCHSPC). A mix design method is proposed for mixtures with a shape holding ability ranging from no-slump concrete mixtures (NSLC) with the shape preservation factor SPF?1 to conventional self-compacting concrete mixtures (SCC) with a shape preservation factor SPF?0.4. First the volume of the excess paste with a certain consistency is determined for a required shape preservation factor SPF. Then the volume of the total paste, i.e. the void paste plus the excess paste, and the volume of the aggregate are determined to obtain a required packing density of aggregate. In the next step, the quantities of the paste composition, i.e. amount of Portland cement CEM I 52.5, limestone powder, water and superplasticizer, are determined for the required paste consistency. Finally the deformability of the obtained mixture is checked by the slump test (experiment or numerical simulation). Numerical modeling For numerical flow analysis, the particle flow code 2D (PFC2D), ITASCA, is used. This program is based on the principles of a discrete element method (DEM). In this program a material is considered to be built of a finite number of individual elements. The behavior of such a system is described in terms of the movement of elements and the inter-element forces. In this study the correlation between the mix composition and the deformability of the mixtures was studied. The deformability of a mixture is characterized by the spread diameter (D) and the slump value (Hs). The focus is on simulation of rheological behavior of mixtures made with aggregates with a narrow particle size distribution. In the model a mixture is considered as an assembly of a finite number of individual two-phase elements. A two-phase element is defined as an aggregate particle surrounded with an excess paste layer. The force-displacement relation, which is adopted between the elements, is defined according to the interaction diagram, developed in this thesis. The interaction force is related to the inter-element distance, element size, consistency of the paste and the thickness of the excess paste layer. The approach showed to be promising for predicting the deformability of the mixtures made with aggregates with a narrow particle size distribution (Rmax/Rmin?2.0). The deformability of a mixture made with aggregate with a broad particle size distribution is considered to be the same as that of a mixture made with aggregate with a narrow particle size distribution with the same consistency of the paste and the same volume of the excess paste. This assumption is validated for the mixtures made with the aggregate particles with a shape deviation of about 3 % from the spherical shape, specific density between 2500-2600 kg/m3, maximum size of 8 mm, minimum size of 0.125 mm and the maximum fineness modulus of 5.0. The minimum fineness modulus of granular material is limited to 2.0 and 3.5 for aggregates with a narrow particle size distribution and with a broad particle size distribution, respectively. 0.125 mm is the boundary size between the aggregate particles and the powder particles.Structural EngineeringCivil Engineering and Geoscience

Effect of the mix composition on rheological behavior of a fresh granular-cement paste material

In this paper, the effect of the mix composition on rheological behavior of a mixture is studied by considering a two-phase model for a mixture. A mixture is decomposed into a granular and a paste phase. Paste itself is divided into the void paste and the excess paste. The slump test is used for evaluation of rheological behavior of a mixture. The results show that the granular-cement paste mixtures can be split into three main classes viz Granular-High Paste, Granular-Intermediate Paste and Granular-Low Paste. In Granular-High Paste class, the behavior is governed by the excess paste and the capacity of deformation of mixtures is maximal. In Granular-Low Paste class, the behavior is governed by the void paste and the capacity of deformation of mixtures is minimal. In Granular-Intermediate Paste class the behavior is determined by both the excess paste and the void paste, and the deformability is in between that of the two other extreme cases.Structural EngineeringCivil Engineering and Geoscience

Effect of the mix composition on rheological behavior of a fresh granular-cement paste material

In this paper, the effect of the mix composition on rheological behavior of a mixture is studied by considering a two-phase model for a mixture. A mixture is decomposed into a granular and a paste phase. Paste itself is divided into the void paste and the excess paste. The slump test is used for evaluation of rheological behavior of a mixture. The results show that the granular-cement paste mixtures can be split into three main classes viz Granular-High Paste, Granular-Intermediate Paste and Granular-Low Paste. In Granular-High Paste class, the behavior is governed by the excess paste and the capacity of deformation of mixtures is maximal. In Granular-Low Paste class, the behavior is governed by the void paste and the capacity of deformation of mixtures is minimal. In Granular-Intermediate Paste class the behavior is determined by both the excess paste and the void paste, and the deformability is in between that of the two other extreme cases

A performance -based method for granular based method for granular -paste mix design

In this paper a performance-based method for the design of granular-paste mixtures will be proposed. Focus will be on the selection and proportioning of constituents to produce a mixture with a pre-defined shape holding ability. Shape holding ability of mixtures will be characterized by the shape preservation factor SPF. This SPF shows the ability of a mixture to preserve its shape after being demolded from a slump test. SPF is the ratio of the cross sectional area of a sample after and before demolding. By increasing the flowability of a mixture, the SPF decreases. In this study a mixture is first decomposed into aggregate, void paste and excess paste. Then a combination of the consistency of the paste and excess paste volume is determined for a required SPF. Finally, depending on the aggregate grading, the volumes of paste and aggregates in the system are determined

A performance -based method for granular based method for granular -paste mix design

In this paper a performance-based method for the design of granular-paste mixtures will be proposed. Focus will be on the selection and proportioning of constituents to produce a mixture with a pre-defined shape holding ability. Shape holding ability of mixtures will be characterized by the shape preservation factor SPF. This SPF shows the ability of a mixture to preserve its shape after being demolded from a slump test. SPF is the ratio of the cross sectional area of a sample after and before demolding. By increasing the flowability of a mixture, the SPF decreases. In this study a mixture is first decomposed into aggregate, void paste and excess paste. Then a combination of the consistency of the paste and excess paste volume is determined for a required SPF. Finally, depending on the aggregate grading, the volumes of paste and aggregates in the system are determined.Structural EngineeringCivil Engineering and Geoscience

Simulation of macroscopic behavior of a self-compacting mixture based on DEM

Since the early 20th century, the necessity of modeling and monitoring fresh concrete behavior has been recognized by the industry with the objective to ensure adequate mechanical properties and a proper durability of concrete structures. Due to the rapid development of computer technology, the applications of computational simulation tools in the field of concrete technology has significantly increased and help us to understand the mechanisms of rheological systems. The development of proper rheological models and suitable numerical methods are considered as basic needs for a thorough understanding of the flow properties. The main challenge is finding a quantitative correlation between the model parameters and the properties and proportions of the mix ingredients. This paper presents a numerical approach for macroscopic behavior of a fresh self-compacting mixture using Discrete Element Method (DEM). The employed research is based on a conceptual idea where the grain-paste interaction is explicitly modelled as an interactive two-phase system. Each mixture is considered to be an assembly of “grain-paste” systems, which can be characterized according to the mix composition based on the “excess paste theory”. The macroscopic behavior is evaluated based on the slump flow test results. Simulations and experimental laboratory test results show good agreement

Simulation of macroscopic behavior of a self-compacting mixture based on DEM

Since the early 20th century, the necessity of modeling and monitoring fresh concrete behavior has been recognized by the industry with the objective to ensure adequate mechanical properties and a proper durability of concrete structures. Due to the rapid development of computer technology, the applications of computational simulation tools in the field of concrete technology has significantly increased and help us to understand the mechanisms of rheological systems. The development of proper rheological models and suitable numerical methods are considered as basic needs for a thorough understanding of the flow properties. The main challenge is finding a quantitative correlation between the model parameters and the properties and proportions of the mix ingredients. This paper presents a numerical approach for macroscopic behavior of a fresh self-compacting mixture using Discrete Element Method (DEM). The employed research is based on a conceptual idea where the grain-paste interaction is explicitly modelled as an interactive two-phase system. Each mixture is considered to be an assembly of “grain-paste” systems, which can be characterized according to the mix composition based on the “excess paste theory”. The macroscopic behavior is evaluated based on the slump flow test results. Simulations and experimental laboratory test results show good agreement.Structural EngineeringCivil Engineering and Geoscience