Waste Crumb Rubber Research Articles

The continuous swelling-degradation behaviors and chemo-rheological properties of waste crumb rubber modified bitumen considering the effect of rubber size

The chemo-rheological properties of crumb rubber modified bitumen are always unstable due to the mutable and uncontrollable swelling-degradation degree of crumb rubber in bitumen matrix. The study aimed at exploring the continuous swelling and degradation behaviors of crumb rubber modified bitumen (CRMB) considering the influence of rubber size through monitoring the dynamic viscosity changes of CRMB binders. Moreover, the synergistic effects of swelling-degradation degree and rubber size on the chemical and rheological properties of CRMB were investigated. The results revealed that the rubber size significantly influenced the swelling and degradation behaviors of CRMB. The reduction of rubber size shortened the equilibrium swelling and degradation time, while increased the related viscosity dramatically. Moreover, during the degradation process, the decrease of rubber size could accelerate the continuous swelling rate, increase the maximum viscosity and reduce the continuous swelling time of CRMB. Meanwhile, the high swelling degree and large rubber size were beneficial to enhance the high temperature properties, while the CRMB binder with high degradation degree showed the better low-temperature property, workability and wider Newtonian flow region. Furthermore, the degradation degree promoted the formation of free hydroxide groups, aldehydes, carboxylic acids and esters, while the swelling process increased the average molecular weight of whole liquid phase in CRMB binder. The outputs from this fundamental study are beneficial to provide the guidance to preparation conditions optimization of CRMB binders with different viscous property standards.

Fracture behavior of a sustainable material: Recycled concrete with waste crumb rubber subjected to elevated temperatures

Recycled aggregate concrete (RAC) made from construction and demolition wastes has several environmental benefits. Fire is one of the most common disasters in buildings, and RAC is a brittle construction material; therefore, the bearing capacity of RAC structures under high temperatures should be considered. According to previous studies, crumb rubber made of waste tires can further reduce damages to RAC under high temperatures. Meanwhile, fracture behaviors are one of the key characteristics of concrete materials that need to be considered, but few studies have focused on their behavior when subjected to elevated temperatures. Rubber-modified RAC (RRAC) notched beam specimens with three recycled aggregate substitutions (0%, 50%, and 100%), and four rubber contents (0%, 2%, 4%, and 6%), exposed to high temperatures (200 °C, 400 °C, and 600 °C), were tested using the three-point bending test. The fracture behaviors of the RRAC, including the crack mouth opening displacement, fracture energy, and fracture toughness were analyzed. The results show that the effect of rubber particles on the unstable fracture toughness is greater than that on the initial cracking toughness of RAC after exposure to high temperatures. However, the enhanced effect of rubber on the fracture resistance decreases after subjecting it to a high-temperature treatment owing to the softening and eventual decomposition of rubber at high temperatures. Consequently, in order to avoid the drawbacks introduced by rubber, a rubber content of more than 4% is not recommended considering the mechanical and fracture performance of RRAC.

RETRACTED ARTICLE: Recycling of waste crumb rubber into a commercial materials

Nowadays, there is an increase in heavy vehicles. These vehicles come with more wheels which has consequently increased tyre usage. Tyre rubber material is non-biodegradable. It takes more than a century to degrade. Its lifetime ensures that the tyres in heavy vehicles be changed only once in 4 or 5 years. However, it is noticed that there is an increase in scrap tyres every year. The non-degrading nature of tyre affects the environment and the whole ecosystem. Sometimes, dumping or storing of these old tyres in one place increases the breeding of mosquitos, insects, and bacteria. This causes infectious diseases in people. Wood waste in the form of powder is pressed into crumb rubber using hot pressing technology. The wood rubber composite was taken from crumb rubber and waste wood has excellent mechanical properties. After performing the tensile, tear, and thermal tests, it was found that the tensile strength of commercial material is 7.848 Mpa which is closer to virgin rubber (10 Mpa). The yield/break force was found to be > 120 N. The percentage elongation and yield elongation is found to be nearly 180% which is closer to the properties of virgin rubber. In addition to the mechanical properties, it also has a water absorption rate which is closer to 1 part in a thousand and chemical resistance rate shows very little erosion similar to virgin rubber. This makes fabricated recycled crumb rubber useful for commercial applications like flooring, sound insulation, heavy-duty performance, and vibration absorption too. In this work, crumb rubber has been selected to reduce the usage of natural raw materials.

Enhanced Storage Stability and Rheological Properties of Asphalt Modified by Activated Waste Rubber Powder.

Segregation of waste crumb rubber powder (WR) modified asphalt binders the large-scale application of WR in asphalt. The method of microwave activation combined with chemical activation (KMWR) was proposed to improve storage stability and rheological properties of WR modified asphalt in this work. Storage stability and rheological properties of virgin asphalt, MWR modified asphalt, and KMWR modified asphalt were comparatively studied by the standard segregation test, bending beam rheometer (BBR) test, and dynamic shear rheometer (DSR) test. The effect of composite activation on waste rubber powder particles was studied by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and Brunauer–Emmett–Teller (BET) tests. The main results showed that after the physical and chemical composite activation, the storage stability of waste rubber powder modified asphalt was significantly improved, WR modified asphalt had better crack resistance, better rutting resistance, and better fatigue performance. After physical and chemical activation, WR was desulfurized, and a large number of active groups was grafted on the WR particles.

Studi Eksprerimental Pengaruh Penambahan Limbah Karet Tterhadap Kuat Tekan Beton

Building strength that is not up to standard can even be a very bad thing for building users where if the strength is not sufficient then the building will collapse and even collapse if something happens, such as an earthquake and other things. Therefore, this journal aims to mix the strength of concrete with the planning standard which is the INDONESIAN NASYONAL STANDARD (SNI), and also this report is a concrete mixing that aims to help the surrounding environment regarding crumb rubber waste, can this waste be used for concrete mixes which aims to reduce the use of coarse aggregate and can increase the compressive strength of concrete, the increasing need for the use of concrete materials, is directly proportional to the increase in the basic needs of concrete constituents which are generally sourced from nature. This research was conducted at the construction materials laboratory of the Putra Indonesia University campus "YPTK" Padang, this research is a concrete mix design used is 1%, 2.5%, 5%, 10%, and in this mix planning aims to reduce the use of coarse aggregate , and the design of this concrete has a concrete treatment time with a span of 3, 7, 21, 28 days, from the results of concrete design which is more focused on the maximum concrete strength time is 28 days, the compressive strength of concrete without mixture is 19.52 Mpa and concrete with 1% concrete mixture is 21.03 Mpa, 2.5% is 13.29 Mpa, 5% is 14.52 Mpa, and 10% is 12.86 Mpa. With a sample cylinder size of 150x300 mm, from the results of this study, we can see that mixing concrete with crumb rubber waste can increase the compressive strength of concrete, but if mixing concrete with too much crumb rubber can cause the concrete to become weak and even unfit.

Mechanical and damping properties of composite rubber with waste crumb rubber tire and silica sand

The use of waste crumb rubber tire to reduce earthquakes impact on buildings is one of promising environmentally friendly solutions. Waste rubber tire will increase with the increasing number of vehicles. The purpose of this research is to study the mechanical and damping properties of waste rubber tire containing silica sand. Eleven different composites were produced with variation of the amount of waste rubber tire from 0, 25 and 50-per hundred rubber towards rubber compound based on their weight. The local silica sand consists of 10-phr, 20-phr, 30-phr, and 40-phr will be added on rubber compound containing 25 and 50-phr waste rubber tire respectively. Tensile strength, modulus of elasticity, shear modulus, and damping properties will be tested and researched. Composites of waste rubber tire with silica sand have lower tensile strength and modulus of elasticity with the addition of silica content. The shear modulus increased by loading silica sand and reached a maximum at filling of 40-phr. The damping properties also increased with the addition of silica sand and waste rubber tire, with the highest damping properties reached 10.40% on 40-phr silica sand and 25-phr waste rubber tire from the natural rubber damping properties of 3.10%. This study provides an overview of the effect of waste rubber tire and the interaction of silica sand on rubber properties experimentally.

Effect of age and waste crumb rubber aggregate proportions on flexural characteristics of self‐compacting rubberized concrete

AbstractGeneration of waste has been a significant problem in recent decades in many engineering fields. Self‐compacting rubberized concrete (SCRC) is a new type of SCC, which replaces part of natural aggregates by rubber aggregates in SCC to increase the application range of waste tyre rubber. This study investigates the effect of age and crumb rubber aggregate ratio on fresh and mechanical performance. Eight different SCRC mixtures using 2–5 mm rubber aggregates to replace 10%, 20%, 30%, and 40% natural aggregates by volume respectively, and 5–10 mm rubber aggregates to replace 10%, 20%, 30%, and 40% natural aggregates by volume respectively, are tested after 7, 28, 56, and 91 days for their mechanical properties. Results show that both the compressive and the tensile strength increase with the aging time, both of these properties drop with the amount and size of the crumb rubber content. Similar to compressive and tensile properties, flexural toughness and the modulus of rupture showed increased with the aging time. Small addition of crumb rubber has shown improvements in both rupture and fracture toughness properties, which diminishes when the crumb rubber content becomes significantly large.

Research on highly dissolved rubber asphalt prepared using a composite waste engine oil addition and microwave desulfurization method

• The highly dissolved rubber asphalt was prepareed using a compound method of waste engine oil and microwave desulfurization. • The extraction of non-diddolved rubber was utilized to evaluate the solubility of rubber asphalt. • The solubility, rheological properties and storage stability of the prepared rubber asphalt were studied. • The highly dissolved rubber asphalt is potentially to improve the performance of rubber asphalt pavement. Using recycled rubber waste in the construction of asphalt pavements not only improves pavement performance, but also promotes sustainable development. Consequently, rubber asphalt pavements have received significant attention in recent years. However, conventional rubber asphalt has numerous disadvantages such as low solubility, high viscosity, uneven dispersion, and poor storage stability. In this study, a composite method involving waste engine oil addition and microwave desulfurization to prepare highly dissolved rubber asphalt was proposed. Four types of rubber asphalt—conventional rubber asphalt, microwave-treated rubber asphalt, rubber asphalt with added waste engine oil, and highly dissolved rubber asphalt using the proposed composite method—were prepared and tested. The solubility, rheological properties, and storage stability of the prepared rubber asphalt specimens were studied. Specifically, the extraction of undissolved rubber was used to characterize the solubility of rubber asphalt. The results demonstrate that the solubility of the highly dissolved rubber asphalt prepared using the composite method was around 40%, which is 10%–20% higher than that of conventional rubber asphalt. The low-temperature performance and storage stability of the highly dissolved rubber asphalt improved significantly, and it also exhibited good high-temperature performance. The findings obtained herein indicate that the proposed composite treatment method for waste crumb rubber can significantly improve the performance of rubber asphalt, thereby promoting the application of rubber asphalt in the construction of asphalt pavements.

Performance Evaluation of Waste Crumb Rubber/Silica Fume Composite Modified Pervious Concrete in Seasonal Frozen Regions

The waste crumb rubber (WCR) and silica fume (SF), as industrial waste and byproduct, are widely used as additives in road construction materials, which can not only realize waste utilization and protect the environment but also reduce the consumption of building material resources. At present, most of the research has focused on the properties of concrete modified only by WCR or SF; there are few studies concentrated on composite modified concrete by the two, especially the study on pervious concrete (PC). This article aims to study the mechanical strength, deformability, and freeze‐thaw (F‐T) resistance of waste crumb rubber/silica fume composite modified pervious concrete (RSFPC). The RSFPC and control specimens were manufactured in the lab. The experiments of compressive strength, flexural strength, flexural failure strain, flexural elastic modulus, and F‐T cycles were conducted. In addition, the properties of RSFPC were compared with WCR and SF single modification PC. The results indicate that the composite modification of WCR and SF can give full play to the advantages of the two materials so that the strength property and elastic modulus of PC will not be decreased and the F‐T resistance and deformability can be greatly improved. Compared to a single modification group by WCR or SF, RSFPC has a more balanced and comprehensive performance, which will greatly expand the application of PC.

Physical, rheological and morphological characterization of modified asphalt binder with differing crumb rubber contents

Waste crumb rubber (CR) which is obtained from scrap tires can be successfully used as an asphalt binder modifier for the purpose of attaining the economic benefits with a desirable performance. The wet process was used in this study to investigate the rheological, morphological, and physical changes that would occurred to asphalt binder as a result of the interaction with different rubber contents, that is, 5%, 7%, 10%, 12% and 25%. The penetration, viscosity, softening point, ductility, Superpave performance grades, multiple stress creep recovery (MSCR) of the prepared modified binders were measured under different ageing conditions and temperature ranges. Furthermore, atomic force microscopy (AFM) scanning technique was also conducted in tapping mode to characterize the microstructure of these binders. The obtained results showed that as the rubber content increased, the viscosity and softening point values increased with a reduction in the penetration and ductility values. Rubber content of 10% was ranked as the higher percentage of rubber in terms of bumping the performance grade by at least two grades at high testing temperatures. The grading performance tests based on rutting index (G*/sin δ°) and non-recoverable creep compliance index (Jnr) showed a comparable result for ranking the stiffer binder with a greater resistance to rutting. However, most of crumb rubber modified binders failed to meet the stress sensitivity criteria of MSCR test. AFM images can be considered as a new effective and suitable tool that should be adopted for further microstructural analysis.

Engineering Performance and Activation Mechanism of Asphalt Modified by Microwave and Diesel Pre-Processed Waste Crumb Rubber

Engineering Performance and Activation Mechanism of Asphalt Modified by Microwave and Diesel Pre-Processed Waste Crumb Rubber

STUDY OF BENTONITE USAGE IN ENVIRONMENTALLY FRIENDLY CONCRETE

Production of cement generates a huge amount of carbon dioxide emissions into the environment, utilization of pozzolanic materials in concrete is a better solution for this environmental problem. Several studies are conducted for using of pozzolanic materials such as fly ash, ground granular blast furnace slag, and silica fume as a pozzolanic material in concrete. A few studies were available on using bentonite in concrete. Bentonite is mainly clay contains rich amount of silicain which obeys the pozzolanic properties. The objective of present study is to find out the effectiveness of using bentonite and waste rubber crumb in the design mix of concrete. An experimental investigation is performed on concrete mixtures to study the effect of using bentonite as a partial replacement of cement and conducting an environmentally friendly concrete using crumb rubber in the concrete mixtures as a partial replacement of fine aggregates. Cement is partially replaced by volume (2%, 5%, 10%, 15%, 20%) with Bentonite and fine aggregate is partially replaced (5%, 20%, 25%, 30%, 40%) with crumb rubber. Slump tests were conducted to evaluate the workability of fresh concrete. Compressive strength of cubes at 7days and 28 days, splitting strength and abrasion strength at 28 days are studied and compared with conventional concrete. A part of research work addresses the effect of using bentonite and waste rubber crumb on durability of concrete. For this purpose, specimens were submerged in solution containing 50 g/l of NaOH and H2SO4. Based on the test results, the ideal percentage of mix which shows maximum compressive strength is identified. The results showed that the compressive strength of the concrete was generally increases when bentonite replaced a part of the cement and decreases with the replacement of fine aggregates by the waste crumb rubber. Although the using of bentonite and crumb rubber decreases the compressive strength. The optimal mixture from the laboratory experimental investigation is 5% reduction of cement content and 20% of fine aggregates replacement that exhibited a compressive strength of 30 MPa at 28 days. The test results substantiate the feasibility to develop environmentally friendly concrete using bentonite and crumb rubber in the concrete mixtures. فى هذا البحث ،تم دراسة استخدام البنتونیت کبدیل جزئی للأسمنت ومخلفات المطاط کبدیل جزئى للرکام الناعم فى الخرسانة الصدیقة للبیئة، تم مقارنة نتائج إختبارات قابلیة التشغیل ومقاومة الضغط و مقاومة الشد الغیر مباشر (الانفلاق) ومقاومة البرى والإستدامة بالخرسانة التقلیدیة.أوصت الدراسة بإمکانیة إستخدام البنتونیت حتى 5% کبدیل للأسمنت وإستخدام مخلفات المطاط حتى 20% کبدیل للرکام الناعم فى الخلطات الخرسانیة.

EVALUATION THE EFFECT OF WASTE LO-DENSITY POLYTHLENE AND CRUMBRUBBER ON PHYSICAL PROPERTIES OF ASPHALT

Nowadays, Polymer Modified Binder (PMB) is necessary due to its valuable characteristics on asphalt pavement layers with increase in traffic volume and loads. However, current trend in asphalt modification is prefer the waste and by product materials for ensuring the sustainability and cost effectiveness. Therefore, to analyze the effect of waste Crumb Rubber Modifier (CRM) and waste Low-Density Polyethylene (LDPE) on the asphalt binders’ physical properties, CRM/LDPE modified asphalts with different contents were prepared and investigated in this study. Measured physical characteristics were softening point, penetration, ductility and viscosity tests. Conversions of CRM and waste LDPE to functional materials have been introduced in this research study as a practical approach to improve the asphalt binder’s physical properties. CRM and LDPE in the form of fine having a particle size under 250 µm were used as additives to liquid asphalt, individually and collectively by weight of virgin asphalt, i.e., (5.0%, 15.0% and 25.0% of CRM) and (2.5. %, 5.0%, 7.5% and 10.0% of LDPE), after mixed with CRM and LDPE, the asphalts showed decrease in penetration, increase in softening point and rotational viscosity. This referring that both intermediate and high temperature rheological characteristics of the asphalts have been improved by the modification of waste CRM and LDPE, because that mean the stiffness of asphalt binder increases when changing these characteristics and Thus, the asphalt mixture will become more stiff and resistant to possible failures, the Physical properties of the CRM or LDPE modified asphalts are largely dependent on the waste CRM or LDPE content, and many other enhanced characteristics of the mechanical aspect can be targeted using the composite of both CRM and LDPE. However, such result confirms the validity of waste polymer in modifying the asphalt binder.

Performance of Asphalt Mixture using Waste Materials

A large number of solid wastes are being produced each day. This wastes, especially plastic and rubber effects the environment. So, nowadays these kinds of wastes are used in flexible pavements. In this project, the performance of the asphalt mixture using waste plastic and crumb rubber was determined. The aggregate were partially replaced by waste plastic (0.5%,1%,1.5%,2%,2.5%) and crumb rubber (0.5%,1%,1.5%,2%,2.5%). Also, 10% of fly ash is used in addition to filler material. Various tests like specific gravity, Water absorption, Impact test and Crushing strength for aggregate and softening point, Penetration test, Viscosity test, Specific gravity test and Binder content test for bitumen were conducted in obtained asphalt mixture. A Marshal stability test is also conducted to find the performance of the asphalt mixture. All the test results are compared with the results of the conventional mixture. The result obtained shows the plastic waste incorporated asphalt mixture does not affect the performance of the pavement also reduces the rutting and fatigue of the flexible pavement.

Employment of crumb rubber tyre in concrete masonry bricks

Recently in India, there is an exponential growth in automobile sector leading to increasing demands of tires which further results in huge tire waste after their service life. In light of utilization of this waste tires in construction industry, the investigation mainly focused on the use of waste crumb rubber as a partial replacement of fine aggregates in the production of lightweight masonry bricks. Also, in order to support the sustainable environment, an attempt has been made to utilize tire waste in the form of crumb rubber for the production of bricks. In this study, waste crumb rubber tires were used in partial replacement of fine aggregates for developing bricks. The bricks were developed with varying percentages of crumb rubber i.e. 5%, 10%, 15%, 20% by volume of fine aggregates maintaining water/cement ratio as 0.43 for all chosen mixes. The influence of crumb rubber was studied on both fresh mixes as well as hardened bricks. The fresh properties such as slump and density were studied and quantified the flow ability. The mechanical properties as compressive strength, tensile strength and impact resistance of hardened concrete bricks were studied and regression analysis was carried out to estimate the tensile strength. It is observed that the slump and water absorption increased linearly with increase in percentage of crumb rubber. Upto 10% of crumb rubber, initial rate of water absorption was found increased thereafter it is found to be decreased with increase of crumb rubber. It was also observed that compressive and tensile strength showed linear decrement with increase in percentage of crumb rubber. It was observed that the energy absorption increased by 3.66 times for CR20 mix as compared to CM. It was also observed that the empirical relation helps in predicting the tensile strength and found matching well.

Laboratory studies on strength behavior of concrete added with tire derived products

Concrete is considered the most commonly used building material. The significant exploitation of crumb rubber waste in concrete. Reductions in strength comparatively high unevenness in durability performance are major factors preventing in concrete. This research focused on using crumb tire rubber as partial replacement of fine aggregate mixed with concrete. This Study reveals that the study of rubberized concrete with replaced control concrete. Ravage tire rubber in the form of scrap rubber was replaced for sand as fine aggregates from 0% to 15% in multiples of 3%. Investigative studies were performed with and without KOH treatment solution and the results were compared with Compressive strength, split tensile strength and flexural strength obtained in the laboratory. The test results showed that even though the compressive strength is condensed when using the crumb tires, it can meet the strength requirements partial replacement of rubber. It was observed that 6% replaced non treated and 9% of treated crumb rubber for compressive strength. For a split tensile strength optimum replace of crumb rubber as 9% for non-treated rubber and 12% for treated crumb rubber. In the flexural strength of specimens, steady raises were observed as the percentage of crumb rubber was increased. However treated and non-treated crumb rubber replacement of fine aggregate flexural strength good for up to replacement of 15% both. In these study tire crumb rubber as promising materials used in concrete to save natural mineral resources in some extent.

UTILIZATION OF CRUMB RUBBER AS AGGREGATE IN HIGH CALCIUM FLY ASH GEOPOLYMER MORTARS

This research was carried out to find out the possibility of utilizing tire crumb rubber waste as fine aggregate in fly ash-based geopolymer mortars (GPMs). The effect of replacement of river sand with crumb rubber at the levels of 0, 25, 50, 75, and 100% by volume on the geopolymer mortar properties including workability, dry density, compressive strength, flexural strength, thermal conductivity, ultrasonic pulse velocity (UPV), water absorption, and porosity were studied. The results were compared to those of the Portland cement-based mortars (PCMs). The test results demonstrated that the higher crumb rubber content resulted in the less dense matrix of mortar. However, GPMs with crumb rubber resulted in a significant improvement in flexural strength. The average ratio of flexural to compressive strengths of GPMs was 25% compared to 15% of PCMs. Also, the lower dry density and thermal conductivity of GPMs indicated better insulating properties than those of PCMs.

Experimental and analytical study of dynamic properties of UGM materials containing waste rubber

The permanent deformation characteristic is an important material property in determining the traffic-induced load-carrying ability of unbound granular materials (UGM). Since the repeated load triaxial test (RLT) is time-consuming, complicated, and expensive, it is highly desirable that a relatively simple and quick test can be used for estimating the permanent deformation of pavement materials in the base and subbase layers. In practice, the design engineers usually rely on California bearing ratio and unconfined compression strength tests which are static tests and very much less reliable and accurate compared to dynamic tests such as the Clegg impact hammer and dynamic lightweight cone penetrometer tests. No attempt had been previously made to correlate Clegg impact value and dynamic lightweight penetration index with the permanent deformation of construction and demolition (C&D) aggregates containing crumb rubber. On the other hand, information about the dynamic behaviour of construction and demolition (C&D) materials together with waste crumb rubber, as a green and environmentally friendly pavement material, is very limited. In the current research, a serial of RLT, the Clegg impact hammer tests, and the new dynamic lightweight cone penetrometer tests were performed to evaluate the strength and stiffness of UGM incorporating different sizes/percentages of crumb rubber. The main aim of this study was to develop a simple and reliable indirect approach for estimating the permanent deformation of UGM containing crumb rubber. Based on the experimental results, it was concluded that rubber could be blended with C&D aggregates for base/subbase applications. Also, according to the analytical results, CIV and DLPI could be considered as reliable and acceptable testing methods for estimating the permanent deformation of the unbound granular materials incorporating crumb rubber for the design of flexible pavement since there was a good correlation between the testing results and the phenomenological models.

Effect of microwave-activated crumb rubber on reaction mechanism, rheological properties, thermal stability, and released volatiles of asphalt binder

Waste crumb rubber (CR) can be used in asphalt pavement construction to develop eco-friendly and sustainable pavements. The objective of this study was to investigate the reaction mechanism, high-temperature properties, thermal stability, and volatiles released by CR-modified asphalt (CRMA) activated using microwaves (i.e., ACRMA). The chemical characteristics determined via Fourier-transform infrared spectroscopy revealed that mainly physical reactions occurred in the CRMA before and after activation; however, the swelling reaction in the ACRMA was more efficient than that in the CRMA. These results were confirmed by gel permeation chromatography and atomic force microscopy. The high-temperature performance of the ACRMA was slightly better than that of the CRMA. Additionally, according to stress creep and recovery test results, the microwave activation reduced the stress sensitivity of the rubber-modified asphalt. Thermogravimetric curves indicated that the microwave activation reduced the decomposition temperature of the rubber-modified asphalt. Moreover, the total amount of released volatiles for the base asphalt was significantly larger than that for rubber-modified asphalts, indicating that the CR suppressed the total amount of released volatile gases from the asphalt during the pyrolysis of asphalt. But the addition of CR can increase the release of some toxic gases in CRMA and increase the toxicological potential of asphalt fumes. However, in the initial pyrolysis of rubber asphalts, microwave treatment can reduce the generation of toxic gases. In the later stages of this process, the introduction of rubber particles before and after activation has little effect on the released volatiles.

Study on the Performances of Waste Crumb Rubber Modified Asphalt Mixture with Eco-Friendly Diatomite and Basalt Fiber

A sustainable and environmentally friendly society is developing rapidly, in which pavement engineering is an essential part. Therefore, more attention has been paid toward waste utilization and urban noise pollution in road construction. The object of this study was not only to investigate the mix proportion of waste crumb modified asphalt mixtures with diatomite and basalt fiber but also to evaluate the comprehensive performances including sound and vibration absorption of modified asphalt mixtures. Firstly, the mix proportion scheme was designed based on Marshall indices and sound and vibration absorption properties according to the orthogonal experimental method. Considering the specification requirements, as well as better performances, the optimal mix proportion was determined as follows: diatomite content at 7.5%, basalt fiber content at 0.3%, and asphalt-aggregate ratio at 5.5%. The range and variance analysis results indicated that asphalt-aggregate ratio has the most significant influence on volumetric parameters, diatomite has the most significant influence on sound absorption, and basalt fiber has the most significant influence on vibration reduction. Furthermore, the conventional pavement performances and sustainable sound and vibration absorption performances of modified asphalt mixtures were also analyzed. The results showed that the performances of modified asphalt mixtures were improved to different extents compared to the base asphalt mixture. This may be attributed to the microporous structure property of diatomite and the spatial network structure formed by basalt fibers. The pavement as well as sound and vibration absorption performances of the waste crumb modified asphalt mixture with diatomite and basalt fiber would be a good guidance for asphalt pavement design.