Warm Mixtures Research Articles

Effect of Hydrated Lime on Indirect Tensile Stiffness Modulus of Asphalt Concrete Produced in Half-Warm Mix Technology.

Half-warm mix asphalt (HWMA) mixtures can be produced at temperatures ranging from 100 °C to 130 °C, depending on the production methods used. The lowest mixing temperature can be achieved by using water-foamed bitumen. The mixture should be characterized by a long service life, defined by the resistance to permanent deformation and high stiffness modulus at temperatures above zero. It is therefore important to ensure the adequately high quality of the bitumen binder. Bitumen 50/70 was provided with appropriate quality foaming characteristics (expansion ratio, ER, half-life, t1/2) by adding a surface-active agent (SAA) at 0.6 wt % before foaming. Then asphalt concrete (AC) 8 S was designed and produced with the recommended water-foamed binder. Hydrated lime, an additive substantially affecting asphalt concrete mechanical parameters, was used at 0, 15, 30, and 45 wt % as a partial replacement for the limestone filler. The influence of the amount of hydrated lime on the content of voids, indirect tensile stiffness modulus at −10 °C, 0 °C, +10 °C, +20 °C, and +30 °C, and the resistance to permanent deformation was investigated. Statistical analysis of the test results showed the quantity of 30% to be the optimum hydrated lime content. The AC 8 S resistance to permanent deformation was determined at the optimum hydrated lime content. The comprehensive evaluation revealed a synergistic effect between bitumen 50/70, modified before foaming with 0.6 wt % SAA and 30 wt % hydrated lime as the limestone filler replacement, and the half warm mixture AC 8 S, in terms of the standard requirements and durability of the HWMA concrete in pavement applications.

Influence of drying mode and feed per tooth rate on the fine dust creation in pine and beech sawing on a mini sash gang saw

The experimental results of the study focused on the effect of drying processes of modified air drying and warm air-steam mixture drying of pine and beech wood on the size of sawdust particles created in cutting using PRW-15M sash gang saw, are presented in the paper. Particle size analysis of dry sawdust was performed using two methods—sieving method and laser diffraction analysis. The results showed that the drying process did not affect the general particle size distribution of the sawdust, but the content of very fine dust particles in beech wood sawdust is many times higher when the beech wood was dried in the warm air-steam mixture drying process and sawn at a feed per tooth of 0.105 mm.

Laboratory evaluation of rheological behavior of binder and performance of stone matrix asphalt (SMA) mixtures containing zycotherm nanotechnology, sasobit, and rheofalt warm mixture additives

In recent years, using Stone matrix asphalt (SMA) has gained a lot of attention due to its high performance in rutting and low cost of pavement maintenance, however it consumes high energy like other hot mixtures during production. Also, as Warm mix asphalt (WMA) has several advantages like environmental concerns, many countriesshowed interest in using this new technology. One of the shortcomings of WMA is moisture sensitivity, which is investigated by several researchers. However, the interaction between various factors on moisture resistance of SMA mixture have not been investigated. Also, the addition of warm additives may affect other properties of mixtures. So in current work, the effect of WMA additives on rheological properties of binder and performance of mixtures were investigated. The present research aimed to evaluate the effect of three different gradations (9.5 mm, 12.5 mm, 19 mm), three warm additives (Sasobit, Rheofalt, Zycotherm) with various contents on water damage resistance and performance of warm SMA mixtures. The rheological behavior of original and warm modified bitumens was investigated by performing viscosity, dynamic shear rheometer (DSR), Linear Amplitude Sweep (LAS), Multiple Stress Creep Recovery (MSCR) tests. Performance properties of mixtures were investigated through four-point beam fatigue (FPB), resilient modulus, Indirect tensile strength (ITS), dynamic creep, and wheel track tests. The moisture sensitivity of modified mixtures was assessed through four different methods, such as: Resilient Modulus Ratio, Fracture Energy Ratio, Tensile Strength Ratio, and Texas boiling test. The LAS test results indicated that bitumen containing 1% Sasobit has the highest fatigue life in low strain levels, while in high strain levels, the Zycotherm modified binder has the highest fatigue life. The MSCR test outcomes revealed that binder containing 3% Sasobit has the highest rutting resistance. The outcomes revealed that the addition of warm additives enhanced moisture resistance of samples. Among warm modified mixtures, Zycotherm modified specimens had the highest resistance to water susceptibility. The results indicated that the addition of warm additives enhanced performance properties of mixtures. Among warm additives, 3% Sasobit has the highest effect on enhancing the rutting and fatigue behavior of mixtures.

Characteristics of warm mixed asphalt modified by waste polymer and nano-silica

The current research studied the characteristics of warm mixture asphalt (WMA) contain Polypropylene polymer (PP) and Nano- silica particles (NS). Two kinds of WMA were used: unmodified WMA and modified WMA contain 3% PP and NS (2–5) % by total weight of asphalt. The performance tests conducted to evaluate performance are: moisture resistance test, rutting resistance test, and fatigue resistance test. The obtained results refers that addition Nano- silica and Polypropylene improves performance of WMA. Also the results reveals that addition of Nano- silica and polypropylene as asphalt modifiers increase durability and improve performance of warm mixtures asphalt.

Evaluation of performance and productivity of bitumen modified by three different additives

Modifying the bitumen in bituminous mixtures has become an inevitable solution against the increasing traffic volume and its damaging effects on the environment. Today, the mostly used additive in bitumen modification is styrene–butadienestyrene (SBS). However, due to the high cost of polymers, the waste vehicle tires, (CR) which contain rubber have been used alternatively as an additive. In addition, in order to solve the workability problem caused by the use of additives and also to contribute to the performance, Sasobit, which is a warm mixture additive has been used recently. In this study, the effects of using together the SBS, CR and Sasobit each of which has an ability to improve the different properties of the binder, were evaluated by softening point, viscosity, dynamic shear rheometer, and bending beam rheometer tests and also economically. As a result, it was determined that there are triple binder types in many combinations that are more efficient than the single use of SBS according to high temperature performance, but when the low temperature behavior is evaluated, the number of combinations decreases. In general, 6%CR + 2%SBS + 2% Sasobit modified binders were found to be more efficient than 6% SBS modification.

Evaluation of the moisture damage of warm asphalt mixtures

Utilizing warm mix asphalt (WMA) for pavements attracts attention from around the world due to its benefits. The major benefit is decrease in fuel consumption and emissions. Warm asphalt mixtures are investigated by using organic additives; two additives (Asphaltan A and Asphaltan B) are utilized in this research. A program of laboratory testing is performed on WMA mixtures and hot mix asphalt (HMA) mixtures using two different additives and three contents. Two aggregate gradations were utilized with three values for each additive, and a total of 12 types of warm mixture and two types of HMA were produced. Warm asphalt mixtures were compacted utilizing a Marshall procedure, and optimum asphalt contents were found for each asphalt mixture. A moisture sensitivity test was carried out for all mixture types to find their moisture resistance. From the outcomes, most warm mixtures passed the minimum value of tensile strength ratio (TSR) (80%) as required by the AASHTO and some mixtures failed to meet this criterion, which indicates that the moisture resistance is a concern in warm mixtures. Also, the fracture energy values were higher for warm mixtures than HMA mixtures, which indicates a better resistance to cracking for WMA.

Evaluation of binder blending on warm mix asphalt recycling

A produção de misturas asfálticas com teores elevados de material fresado (RAP) sem prejuízo ao desempenho em campo ainda é um desafio. Nas reciclagens a quente e morna, o ligante presente no RAP é ativado, mas não se sabe quanto dele efetivamente interage com o ligante novo. Neste trabalho, é aplicado um procedimento laboratorial de extração por etapas que busca avaliar a homogeneidade do ligante asfáltico em duas misturas mornas produzidas em usina, uma delas com 25% RAP e a outra sem RAP (mistura de controle). As “camadas” de ligante obtidas foram testadas no Reômetro de Cisalhamento Dinâmico. Os resultados mostraram que, para a mistura com 25% RAP, os parâmetros analisados variaram de forma progressiva, diferente da mistura de controle. O procedimento se mostrou útil para avaliar a homogeneidade do ligante, o que está relacionado ao grau de interação entre ligantes e pode ser usado para assegurar um bom desempenho.

The Effects of Nano Bentonite and Fatty Arbocel on Improving the Behavior of Warm Mixture Asphalt against Moisture Damage and Rutting

The use of warm mix asphalt (WMA) technology has increased dramatically in recent years to protect the environment and reduce energy consumption. Despite numerous advantages, WMAs are less commonly used as a result of their lower performance in comparison to HMAs. One of the main reasons for the low performance of WMAs is their high moisture sensitivity. In recent decades, bitumen modifiers have been used to improve the performance of asphalt mixtures. One of the additives that has recently been used to modify the characteristics of bitumen, is bentonite. The grade of asphalt cement used in this study is PG 64 -22 and the Bitumen is modified with 1, 3, 5 and 7% nano bentonite. Also, 0.3% fatty Arbocel has been used for the preparation of WMA. Indirect tensile strength (ITS) test and Nicholson stripping test are used to determine moisture sensitivity and dynamic creep test and LCPC are also used to evaluate the rutting potential. The results indicate that, increasing the percentage of nano bentonite and applying 0.3% of fatty Arbocel improves the resistance of mixture against moisture damage. Also it was found that increasing the mixture hardness decreases the permanent displacement and rutting potential of WMAs. So, it is suggested that the consumption of these additives increases WMA’s lifetime and decreases its maintenance cost.

Avaliação de misturas asfálticas recicladas mornas com uso de ligantes convencional e modificado por polímero

Com o objetivo de avaliar tecnologias e práticas mais sustentáveis para a área de pavimentação, estudou-se o comportamento de misturas asfálticas recicladas mornas, utilizando ligantes convencional CAP 50/70 e modificado por polímero CAM 60/85-E. Foram ensaiadas quatro misturas asfálticas por ligante: convencional à quente, morna (sem RAP) e morna com 25% e 50% de RAP (em substituição à massa total de agregados virgens). As amostras foram dosadas pela metodologia Superpave e avaliadas quanto às propriedades de resistência, deformabilidade, adesão e coesão. As misturas mornas e convencionais apresentaram comportamento equivalente e o uso de ligante modificado elevou o desempenho das amostras. Houve uma melhora significativa nas propriedades das misturas com o uso de RAP, ressaltando-se o expressivo aumento de Flow Number e os resultados positivos de adesão e coesão, provavelmente, em decorrência do RAP apresentar ligante residual modificado com polímero.

Interspecies radiative transition in warm and superdense plasma mixtures

Superdense plasmas widely exist in planetary interiors and astrophysical objects such as brown-dwarf cores and white dwarfs. How atoms behave under such extreme-density conditions is not yet well understood, even in single-species plasmas. Here, we apply thermal density functional theory to investigate the radiation spectra of superdense iron–zinc plasma mixtures at mass densities of ρ = 250 to 2000 g cm−3 and temperatures of kT = 50 to 100 eV, accessible by double-shell–target implosions. Our ab initio calculations reveal two extreme atomic-physics phenomena—firstly, an interspecies radiative transition; and, secondly, the breaking down of the dipole-selection rule for radiative transitions in isolated atoms. Our first-principles calculations predict that for superdense plasma mixtures, both interatomic radiative transitions and dipole-forbidden transitions can become comparable to the normal intra-atomic Kα-emission signal. These physics phenomena were not previously considered in detail for extreme high-density plasma mixtures at super-high energy densities.

Laboratory evaluation of Iraqi asphalt mixtures containing aspha-min as warm mixture additive

Warm mixtures refer to the technology used to produce asphalt mixtures at temperatures lower than the temperatures required to produce hot mixtures asphalt. By using this technology, the fuel amount will be reduced, which shall have a positive effect on the environment. In this study, two types of asphalt mixtures were produced using locally available materials. The first type was hot mixtures asphalt (HMA), while the second type was warm mixtures asphalt (WMA), which also represent asphalt mixes containing 0.3% Aspha-min by the total weight. Several tests were performed to evaluate both types of mixtures including: Marshall Test, moisture sensitivity (Indirect Tensile Strength ratio TSR) tests, and rutting resistance (Wheels Tracking) test. The results have shown that the performance of HMA was better than the performance of WMA in accordance to moisture test. While for rutting re sistance test, both types had the same level of resistance. As for Marshall test results, both types were able to meet the specification limits. Furthermore, the use of hydrated lime as filler material improved moisture and rutting resistance of WMA, where the best results for WMA were obtained.

A two-constituent nonlinear viscoelastic model for asphalt mixtures

The goal of this study is to model the creep and recovery response of fine asphalt mixtures using a thermodynamically consistent nonlinear viscoelastic model. The model considers asphalt mixture to consist of two constituents: aggregate structure incorporating the asphalt–aggregate interface and asphalt binder. The efficacy of the model is evaluated using the response of warm fine aggregate mixtures (WFAM). These materials were produced using a polymer-modified binder of PG 76-22 and three warm mix additives (Sasobit, Advera and Rediset). Unaged and aged samples were subjected to creep stress levels of 75 and 400 kPa followed by rest periods. The model was quite successful in capturing the material behaviour as a single set of parameters were derived from the prediction of shear and normal stress responses for both 75 and 400 kPa stress levels. The presented model offers a unique feature in modelling the energy storage and dissipation of each of the two constituents. As such, one can examine the effect of changes in individual material properties on the material response and performance.

Environmental effects on the rheological properties of fine warm RAP-foamed bitumen mixtures using SATS conditioning protocol

ABSTRACT This paper uses the Saturation Ageing Tensile Stiffness (SATS) conditioning to evaluate the combined effects of moisture and oxidative ageing on the rheological characteristics of the Fine Aggregate Matrix (FAM) portion of various Foamed Bitumen Mixtures (FBMs) in combination with Reclaimed Asphalt Pavement (RAP) material produced at 90, 120 and 160°C (i.e. half-warm, warm and hot processes, respectively). A reference fine Hot Mix Asphalt (HMA) with RAP – no foamed bitumen – was also manufactured. Their rheological properties were determined through Dynamic Mechanical Analysis (DMA) tests on specimens tested in their unconditioned and after SATS conditioning states. Rheology of the recovered binders of all FAM mixes before and after SATS conditioning was also studied, and rheological parameters were used to link their long-term performance in terms of cracking susceptibility. The results showed an overall increase in the stiffness of the fine mixtures after the conditioning process, mainly due to oxidation of the bitumen. Although the half-warm and warm fine RAP-FBMs exhibited the highest increase in their complex shear modulus after SATS conditioning, rheological analysis of their corresponding binders indicated that their long-term performance in terms of cracking susceptibility might be superior to those of the hot RAP-FBM, and the HMA-RAP fine mixtures.

Comparative Assessment of Tensile and Shear Behavior of Cold, Warm and Hot Mix Asphalt Concrete

The environment awareness of toxic gases emissions during the production, transportation, and construction of hot mix asphalt concrete (HMAC) have led to the development of Warm, half warm, and cold mix asphalt concrete. Such development of alternative mixtures is considered as sustainable materials in asphalt concrete paving process. The temperature reduction in the mixing of binder during production, handling, and compaction of the mix results in saving energy, reduction of emissions and significant reduction in production costs. Warm and Cold mixtures technology is considered as more environmentally friendly option to prepare asphalt by adding the binder in the form of an emulsion. Very limited laboratory and practical experience are available in Iraq for these mixtures. However, no trial section was constructed yet which considers such sustainable techniques. Until recent time there were even no technical specifications giving rules for design and use of these warm and cold mixtures. In this investigation, asphalt concrete mixtures usually used for wearing course have been prepared in the laboratory using the traditional hot mix and the sustainable alternatives of warm and cold mix techniques. Emulsified asphalt was implemented as a binder in case of warm and cold mixtures. Specimens were subjected to indirect tensile strength and double punching shear strength determination at 25°C. It was concluded that lower bulk density for cold mix was obtained as compared to hot and warm mixtures. The tensile strength of warm mix and Cold mix are lower by (82.8 and 93.1) % than that of hot mix. The punching shear strength of cold mix is lower by 50 % than that of warm or hot mix.

泡沫沥青温拌技术在沥青路面SMA-13抗滑磨耗层中的应用研究

泡沫沥青温拌技术在沥青路面SMA-13抗滑磨耗层中的应用研究

Sustainable low-temperature asphalt mixtures with marginal porous volcanic aggregates and crumb rubber modified bitumen

This study presents the results of the principal engineering properties of asphalt-rubber warm mixtures (AR-WMA) with waste crumb rubber from used tyres and highly-vesiculated basalt of scoriaceous nature, also considered a residual or marginal aggregate according to standard specifications. The temperature reduction was carried out using a liquid surfactant chemical additive, of easier dosage than granular solid products and in a reduced proportion (0.5% by weight of bitumen). The results were compared both to asphalt-rubber hot mixtures and to hot mixtures with conventional bitumen, all of them with the same aggregates. With the surfactant additive it is possible to lower the production temperatures by up to a maximum of 5–10 °C complying with all the technical specifications for surface courses of pavements, and by up to 25–30 °C for inferior layers or in case of more lenient requirements. Even in the first case, it may compensate for the increase of energy and emissions due to the higher viscosity of the asphalt-rubber binder. With a temperature reduction of 40 °C, certain properties such as the moisture damage strength ratio, rutting resistance and stability were even superior compared to conventional mixtures without rubber (produced at 170 °C). The results obtained may be extrapolated to other volcanic regions both insular and continental areas where this type of aggregates are commonly found and with rigorous environmental requirements.

Effect of aging conditions on the fatigue behavior of hot and warm mix asphalt

The aging process has a significant effect on the mechanical properties of asphalt mixtures, especially on fatigue parameter. Many approaches have been suggested to better understanding of the fatigue behavior of asphalt mixes. However, in many of these cases, the effects of aging are not considered. In this study, investigations were conducted to more accurately predict the fatigue life of asphalt mixes, independent of their ages. In this regard, the responses of the existing fatigue models in a wider range of asphalt mixtures were validated. For this purpose, hot and warm asphalt mixtures were used in both aged and unaged conditions. For the production of warm mixtures, Sasobit and RheoFalt were used as modifier additives. Indirect tension (IDT) test, resilient modulus and four-point bending fatigue beam test were performed separately WMA and HMA specimens. The results indicated that in all specimens, the aging of the asphalt mixture was always accompanied by increasing fracture energy and failure resistance. In addition, it was also found that those fatigue models that were based on simple performance tests failed to well predict the fatigue life of mixtures independently of the type of compounds, aging and loading conditions. Eventually, validations indicated that the behavior of dissipated energy during repeated loading to failure, have a significant role to precisely characterize the fatigue behavior independent of their age.

Development and field testing of experimental seed mixtures for high elevation roadside locations in West Virginia

Non-native grass mixtures are often used to quickly establish ground cover on highway construction sites. Because soil is often mixed with parent material, reclamation is difficult in many of these locations. The inclusion of native seeds at two roadside locations in eastern West Virginia was evaluated in this study. The field sites had among the harshest climate conditions of the state, and the intent was to evaluate the establishment of varying seed mixtures at low/moderate and high elevations. Four experimental seed mixtures (mowable areas, cool season, warm season, and high elevation) were compared to two currently used seed mixtures for erosion control. Ground cover, biomass, compaction, and soil information were monitored over three growing seasons (2015–2017). Results show that the mowable area and cool season mixtures show promise at a wide range of elevations. While the warm season mixture did meet minimum ground cover (70%) at the low elevation location, the use will be limited due to slower time to establishment; however, the inclusion of the warm season mixture will meet the need of included native species in roadside reclamation. Experimental mixtures were resilient to periods of drought and high temperature throughout the study. The high elevation seed mixture did not perform better than the other experimental seed mixtures, so its use is not recommended for right-of-way locations in West Virginia. The cool season and mowable area mixtures likely meet this need.

Influence of warm-mix asphalt technology and rejuvenator on performance of asphalt mixtures containing 50% reclaimed asphalt pavement

Warm-mix asphalt (WMA) technology and rejuvenator are widely used nowadays because of numerous environmental and economic benefits. This study evaluated the effects of warm-mix asphalt (WMA) technology and rejuvenator on the rutting resistance, cracking resistance, and moisture susceptibility of three types of asphalt mixtures. The three types of asphalt mixtures were (a) an asphalt mixture with 50% reclaimed asphalt pavement (RAP), (b) an asphalt mixture with 50% RAP and rejuvenator, (c) a warm mixture containing 50% RAP. The WMA mixtures were plant-produced with a foaming technology commonly used in the United States. Laboratory performance tests included the Superpave indirect tension (IDT) test, tensile strength ratio (TSR) test, asphalt pavement analyzer (APA) rutting test, Hamburg Wheel-tracking test (HWT) and semi-circular bending (SCB) test. Research shows that the rejuvenator could improve the moisture and cracking resistance, but increase the rutting potentials and decrease the indirect tensile strength. In contrast with the mixture with 50% RAP, WMA technology showed promising results in the rutting resistance and moisture susceptibility. Besides, adoption of WMA technology was more cost-effective.

Rheological properties of Deurex – modified WMA binder containing SBS

ABSTRACTRecently, warm mixture asphalt (WMA) technologies drawn much attention for their benefits to environment and workability. Deurex is novel type of warm mixture asphalt additive, which is extracted from sugar cane. The objective of this study is to experimentally investigate the effect of Deurex on SBS modified asphalt. The Deurex was blended into SBS modified asphalt at the dosages of 2%, 3% and 4%. Physical properties tests including penetration, soft point and ductility, dynamic shear rheometer (DSR), and bending beam rheometer (BBR) tests were carried out. The test results showed that the increase in Deurex additive could significantly reduce the viscosity of SBS modified asphalt, which indicates that the Deurex can serve as an effective type of warm mixture asphalt additive. In addition, the results showed that the addition of Deurex can enhance the high temperature properties while lower the low temperature performance of SBS modified asphalt. However, as long as the Deurex dosage is not higher than 3%, the low temperature grade of WMA binder keep the same as the control binder.