Asphalt Absorption Research Articles

Long-term performance of chemically modified cotton straw fibers in micro-surfacing asphalt mixtures

Using agricultural wastes in asphalt pavements presents a promising solution to enhance pavement performance and utilize agricultural wastes simultaneously. In the paper, the fibers are made from recycled cotton stalks. Chemical modifiers are chosen to enhance the adherence of fiber asphalt binders. Different modified fibers are added to the SBR-modified emulsified asphalt. The modified asphalt binders are then utilized to prepare asphalt mixtures. Comparative studies on construction performance, road performance, and durability were carried out. Results showed that water consumption and bitumen aggregate ratio at the micro-surfacing were increased after adding fiber. Fibers with low hygroscopicity, rough surface, and high asphalt absorption rate had better adhesion properties. The long-term performance of a micro-surfacing mixture was most remarkably improved by the CH3COOH-modified cotton straw fibers, demonstrating a 10.07 % drop in rutting depth, a 9.13 % decrease in abrasion value, and a 41.13 % gain in shear resistance compared to the micro-surfacing mixtures with unmodified fibers. The study concluded that modified fiber micro-surfacing asphalt mixes are more suitable for seasonal frozen regions than the conventional mixes. The findings offer a theory foundation for the future development of cotton straw fibers in road engineering.

Research on Basalt Fiber Oil/Asphalt Absorption Performance and Test Methods Suitable for Asphalt Mixture with Different Structures

A basalt fiber asphalt mixture could improve the road performance of pavements and prolong the service life. The oil/asphalt absorption capacity of basalt fiber affects the road performance of asphalt mixtures to a certain extent. However, using kerosene as the medium to measure the oil absorption rate of bundle fibers by the vibration method, as the Chinese specifications recommends, is unreasonable. Therefore, the aim of this paper is to study the effect of the basalt fiber morphology on the oil absorption rate and the oil/asphalt absorption test methods suitable for asphalt mixtures with different structures (dense-graded and gap-graded), and to also explore the appropriate method to determine the oil/asphalt absorption rate of fiber to kerosene and asphalt. The results showed that the filamentous basalt fiber (FBF) was easier to disperse uniformly in asphalt than the bundled basalt fiber (BBF), and the oil absorption capacity of the FBF could more accurately characterize the actual working state of the fiber in the asphalt mixture. For the gap-graded asphalt mixture, the appropriate method to measure the fiber oil absorption rate is the combination of the vibration and centrifugation methods, while the fiber asphalt absorption rate is measured by the vibration method. For the dense-graded asphalt mixture, the combination of the extrusion and centrifugation methods are more reasonable to determine the fiber oil absorption rate, while the extrusion method is suitable for determining the fiber asphalt absorption rate. The concept of an effective fiber oil absorption rate is proposed to characterize the ability of fiber to adsorb kerosene in asphalt mixtures with different structures. A temperature of 160 °C is recommended as the test temperature to determine the fiber asphalt absorption rate. Kerosene as the asphalt absorption test medium could not directly reflect the ability of fiber to adsorb asphalt.

Performance Evaluation of Asphalt Concrete Incorporating Steel Slag Powder as Filler under the Combined Damage of Temperature and Moisture

Recycling steel slag into asphalt concrete is an important way to save natural resources and protect the environment. The high asphalt absorption and adsorption and the sensitivity of steel slag aggregate (SSA) to the combined damage of temperature and moisture (volume expansion and poor durability under freeze-thaw cycle damage) still pose risks for the use of SSA in asphalt concrete. It is urgent to develop new utilization methods of steel slag. With this in mind, the material properties of steel slag powder (SSP) and performance characteristics of asphalt concrete incorporating SSP filler were evaluated in this research. The SSP was prepared in the laboratory by grinding steel slag with a particle size of 2.36–4.75 mm. Firstly, the material properties of SSP including the specific surface area, particle gradation, apparent density, chemical compositions, and thermal stability were analyzed. Steel slag (2.36–4.75 mm) and common limestone powder (LP) filler were used as control groups. The grindability of steel slag and the advantages of using SSP as a filler in asphalt concrete were preliminarily analyzed based on the test results of material properties. Then, the Superpave method was used to design asphalt concrete incorporating SSP and LP. Considering that steel slag is sensitive to the combined damage of temperature and moisture, the main engineering performance of asphalt concrete after the combined damage of temperature and moisture was evaluated to further reveal the feasibility of using SSP as a filler. Two combined damage modes, namely hot water damage and freeze-thaw cycle damage, were applied. Results suggest that although the steel slag is more difficult to grind compared to limestone particles, grinding steel slag into SSP has improved the uniformity of its material properties. Good uniformity of material properties, high alkalinity, and excellent thermal stability of SSP give it some advantages in its application in asphalt concrete. Although the freeze-thaw cycle damage has a slightly more significant effect on the engineering performance of asphalt concrete than hot water damage, compared to the asphalt concrete with LP filler, even after freeze-thaw cycle damage for three cycles asphalt concrete incorporating SSP still possesses comparable or better volume stability, mechanical performance, high-temperature deformation resistance, low-temperature crack resistance, fatigue crack resistance, and fatigue durability.

Effects of Fiber Type on the Mechanical Properties of the Open-Graded Friction Course Mixture.

The open-graded friction courses (OGFCs) have a large number of interconnected voids, which may cause serious water damage to the pavement. Hence, the road performance needs to be investigated. In this study, the mechanical properties of OGFCs containing two different fibers (lignin and mineral fiber) were investigated. Based on the procedure proposed by the Chinese specification JTG F40-2004, OGFCs were designed with the asphalt content between 4.1 and 4.7 wt % to find the optimal asphalt content (OAC). The mesh-basket draindown test was used to check the fiber's stabilization and absorption of bitumen. OGFCs containing the lignin/mineral fiber with OAC would be preferred in terms of the bulk specific gravity. These results indicate that the fiber can bring higher air voids to the OGFCs, and the different specific gravities of fibers may primarily account for the result. Both the lignin and mineral fibers can bring much more asphalts padded in the pores of mineral aggregates and subsequently larger OAC in OGFCs due to their higher asphalt absorption. Performance experiments were carried out to check the dynamic stability and moisture susceptibility of OGFCs containing the lignin/mineral fiber. The study suggests that the lignin and mineral fiber can be used to adjust the internal environment of OGFCs, enhancing the moisture damage resistance and improving the rutting resistance of OGFCs at high temperatures.

Analysis of the influence of additional plastic waste (HDPE) as Mixed Asphalt AC-WC on Marshall Parameters

<p>Flexible pavement structures that use asphalt as a binder are currently the mainstay of the Indonesian people because of their large load-bearing capacity and economical construction costs. One type of flexible pavement used is asphalt concrete with the top surface layer or Asphalt Concrete Wearing Course (AC-WC). The use of asphalt from the petroleum refining process is one of the problems because its availability is decreasing. However, the condition of the road pavement which has a limited life requires periodic repairs to maintain the condition of the road. In addition, there are also problems regarding the processing of plastic waste which is still not optimal. Based on data published by the National Waste Management Information System in 2020 as much as 18.3% of the total waste generated. This figure increased by 2.3% from the previous year. Sukoharjo Regency also experienced an increase in sales of plastic waste by 1.16% from 14.04% (in 2019) and now to 15.20% (in 2020). Plastic is one type of polymer in the thermoplastic polymer group which is processed by organic chemical compounds. One type of plastic that is often used is High Density Polyethylene (HDPE) which has strong, light and flexible properties that can soften at a temperature of 130-137"℃" and harden again if. In this study, HDPE plastic bag waste was used as a pure asphalt substitute with variations in the proportion of substitution of 2%, 4%, 6%, 8%, 10%. Where this study aims to analyze the effect of adding HDPE plastic waste as a mixture of AC-WC asphalt on asphalt parameters. From the research conducted, the use of asphalt content of choice is 5.7%. With the results of the mixture with HDPE asphalt mixture HDPE has increased with the addition of variations of HDPE. The flexibility of HDPE asphalt mixture decreased according to the flow meter reading. At a content of 2% HDPE has the largest percentage of VIM, flow, and proportion of VMA, but has the lowest value and percentage of VFB. The best range of HDPE content is in the percentage of 4%-6% because it can increase the value of a more flexible mixture and optimal asphalt absorption. The use of HDPE plastic waste is an alternative in waste treatment and can reduce the use of asphalt. It can be concluded that HDPE plastic bags can be used as an alternative to bitumen substitutes that meet the requirements of Bina Marga 2018 Revised 2nd Edition.</p>

Short- and Mid-Term Loose Mix Conditioning Protocols for Asphalt Overlay Balanced Mix Design and Quality Control and Quality Acceptance

Many aspects of balanced mix design (BMD) and performance-related quality control and quality acceptance (QC/QA) testing depend heavily on how the asphalt mixes are conditioned. There is, therefore, a critical need for practical loose mix conditioning protocols. The main objective of this study was to establish practical loose mix condition protocols for both the BMD and QC/QA phases. To develop these protocols, this paper reviewed the field performance and pavement lives of more than 200 test sections around the United States and found most of these test sections were 50-mm thick asphalt overlays where cracking is evident in 1 to 4 years. Based on this finding, the paper developed two conditioning protocols for asphalt overlays: short-term and mid-term. The short-term conditioning is intended for volumetric design, BMD rutting performance test, and QC/QA testing at asphalt plants, while the mid-term conditioning is mainly for BMD cracking performance test. A series of IDEAL cracking tests were then conducted with 13 mixes and the test results confirmed the validity of the mid-term conditioning protocol. It was also found that conditioning time affected mix cracking resistance significantly. The longer the conditioning time, the poorer the cracking resistance. When conditioned too long, the normalized cracking resistance difference among various mixes diminished. For asphalt mix composition, binder source (or quality) and asphalt absorption are two significant factors affecting the normalized cracking resistance of asphalt mixes; in contrast, mix type, asphalt binder content, and the use of rejuvenator had insignificant influence.

Use of tricalcium silicate to evaluate asphalt absorption on steel slag: Atomic simulation and micro-scale characterization

The study investigated asphalt absorption on steel slag at molecular- and micro-scale. The diffusion of saturate, aromatic, resin, and asphaltene (SARA) was evaluated using tricalcium silicate as a representative of steel slag. Specifically, atomic structures of asphalt were observed using molecular dynamics (MD). Ultraviolet and nanoindentation tests eventually verified the simulative findings. Results denote that SARA diffuses in accordance with Arrhenius's law. Due to the electron density and polarity, resins and asphaltenes perform higher diffusion rates near steel slag. The colloid structure of asphalt is more sensitive to moisture contents. The interior pores in steel slag exhibit fluorescence effect and tend to absorb non-polar components of asphalt with lower moduli and hardness, which agrees well with the distribution found via MD. The interfacial bonding of steel slag-asphalt under the coupling of temperature and humidity is weakened due to the variation of colloid structure of asphalt and the self-association of asphaltenes.

Investigation of the Performance of Ceramic Fiber Modified Asphalt Mixture

Ceramic fiber (CF) is a novel thermally resistant material with the potential to improve the high-temperature performance of asphalt mixture. In this study, asphalt mixtures with 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% CFs were prepared. The Marshall test, wheel tracking test, Marshall immersion test, freeze-thaw splitting test, and low-temperature bending test were conducted to evaluate the performance of the CF-modified asphalt mixture. The morphologies of these asphalt mixtures were observed using scanning electron microscopy to analyze the modification mechanism. The results showed that the CFs could improve the mechanical properties, high-temperature stability, moisture susceptibility, and low-temperature cracking resistance of asphalt mixture, with the optimum CF content being 0.4%. Further microscopic analysis showed that the CFs improved the performances of asphalt mixture through forming three-dimensional network structure, asphalt absorption, bridging cracks, and pulling-out effect.

Effect of different fibers on the properties of asphalt mastics

Asphalt mastic is a key component affecting the performance of asphalt mixtures. Fibers can efficiently improve the performance of asphalt mastic. Four types of fibers, including two types of flocculent fibers (lignin fibers and sepiolite fibers) and two types of bundle fibers (basalt fibers and aramid fibers), were selected to study the effect of fiber morphology on the performance of asphalt mastic in this study. Firstly, the thermal stability, the asphalt absorption, and the microscopic morphology of various fibers were tested. Secondly, relevant performance tests, including penetration, softening point, bending beam rheometer test (BBR), and dynamic shear rheology test (DSR) test, were conducted on asphalt mastic samples prepared with various fibers. The results show that the flocculent and the bundle fibers played different roles in asphalt mastic. The flocculent fibers could stabilize asphalt, while the bundle fibers could enhance the toughness. The addition of fibers into asphalt mastic improved rutting resistance.

Evaluating four typical fibers used for OGFC mixture modification regarding drainage, raveling, rutting and fatigue resistance

Fiber is an essential additive used in asphalt mixture due to its asphalt absorption and reinforcement characteristics, especially for Open-Graded Friction Course (OGFC) mixture. However researches about the influence of varying fibers types on OGFC mixture are not adequate. In this study, 4 typical fibers, namely lignin fiber, basalt fiber, polyester fiber, and polyacrylonitrile fiber were evaluated. Their raw material sources, appearance and physical properties were compared. Also, resultant mixture drainage property, raveling resistance, rutting resistance, stiffness and fatigue life were evaluated using Schellenberg binder drainage test, Cantabro test, Hamburger Wheel Tracking test, and Four-Point-Bending test, respectively. Different fiber contents (0.15%, 0.3% and 0.45%) were considered. Results show that fiber modification improves the mixture overall performance, but the improvement notably differs between fiber types. Lignin fiber has a small density, which renders it the best improvement on mixture drainage property. But lignin fiber has little tensile strength and shows the least improvement on OGFC mixture mechanical properties. The other three fibers are strong filaments that can physically crosslink with each other and demonstrate better performance than lignin fiber. Polyester fiber exhibits the best improvement and thus is recommended. Increasing the fiber content does not necessarily facilitate the improvement due to the agglomeration issue during mixing. An optimal fiber content exists for each fiber type, which is 0.3%, 0.15%, 0.3%, and 0.15% for lignin fiber, basalt fiber, polyester fiber, and polyacrylonitrile fiber, respectively.

The simulation of short-term aging based on the moisture susceptibility of asphalt concrete mixtures

Abstract Asphalt concrete exhibit significant changes in its physical properties owing to the loss of volatile components and oxidation through the short-time aging of the binder that results from exposure to high temperatures during production in mixing plants. Because the moisture susceptibility of asphalt concrete mixes is highly dependent on binder chemistry and its physical property, consequently, the aging affects the moisture resistance of asphalt concrete pavements. However, the degree of this effect varies according to the morphology of the asphalt concrete mixture in addition to the mixture production temperature. The objective of the current AASHTO R30 guidelines for the short-term aging of asphalt concrete is to mimic the oxidation and asphalt absorption into the aggregates that would occur for a typical dense hot-mix asphalt mixture. Within these guidelines, two variables are addressed, namely temperature and time. It is well documented in the literature that the production of asphalt mixtures with different aggregate gradation types as well as temperatures as in the case of warm mix asphalt affects the short-term aging conditions. Based on the aforementioned preface, research on this topic has become necessary. To this end, job mix formulas were prepared in the laboratory for four types of wearing course mixes: dense-graded hot-mix asphalt, open-graded friction course hot-mix asphalt, gap-graded hot-mix asphalt (stone matrix asphalt) and dense-graded warm-mix asphalt. The prepared job mix formulas were forwarded to a mixing plant, and four tons of asphalt concrete mixtures were produced (1 ton each) across four different batches. Samples were taken to the laboratory, and specimens were prepared and tested to determine their moisture susceptibility based on an indirect tensile strength ratio procedure. I contrast, laboratory-produced mixes with the same mix gradations as those of the plant-produced mixes were prepared and subjected to different aging conditions (temperature and time). Their moisture resistance was then evaluated. Finally, short-term aging conditions that accurately simulate the aging process at the mixing plant were determined.

Effect of hydration and silicone resin on Basic Oxygen Furnace slag and its asphalt mixture

The primary purpose of this research was to evaluate the effect of hydration and silicone resin on material characteristics of Basic Oxygen Furnace (BOF) slag and performances of BOF slag asphalt mixture. BOF slags modified by different methods were prepared. Surface textures, elements distributions, pore characteristics and volume stability of various BOF slags were first studied. Then the performances of asphalt mixtures containing various BOF slags including volume stability, thermal property and moisture resistance were well evaluated. Results showed that the combined modification of hydration and silicone resin can lower the asphalt absorption of BOF slag, and improve the asphalt mixture's volume stability and thermal efficiency, which meant the applicability and economy of BOF slag asphalt mixture got enhanced when proper combined modification was applied on BOF slag.

Utilization of gneiss coarse aggregate and steel slag fine aggregate in asphalt mixture

Natural resource shortage and environmental pollution issue have promoted the recycling of inferior natural resources and solid wastes in asphalt pavement. While steel slag fine aggregate and inferior gneiss aggregate are rarely used in asphalt mixture in China due to some poor performances. The primary objective of this research was to explore the feasibility of simultaneously using gneiss coarse aggregate and steel slag fine aggregate in asphalt mixture. A new method to improve the quality of steel slag fine aggregate was proposed first. Raw material characteristics directly related to asphalt adhesion and absorption were fully detected then. Performances of asphalt mixture including Marshall stability and quotient, crack resistance, moisture susceptibility, volume stability and deformation resistance were evaluated finally. Results showed that modified WSFA (Weathered Steel Slag Fine Aggregate) presented lower asphalt absorption than original WSFA. Asphalt mixture consist of gneiss coarse aggregate and modified WSFA obtained better crack resistance, moisture resistance, volume stability and deformation resistance.

The Characteristics of Asphalt Concrete Binder Course (AC-BC) Mixture with Bottom Ash as Aggregate Substitute

Highways serve nearly 80-90% of the population mobility and flow of goods. Utilization of bottom ash, a waste from coal combustion, in highway construction is one of the alternatives to reduce environmental pollution and support Clean Development Mechanism Program of Kyoto Protocol. The aim of this study is to analyze the characteristics of AC-BC mixture that uses bottom ash as partial substitute of fine aggregate and comparing with a standard mixture. Laboratory tests are performed on two different types of mixtures. The tests show that optimum asphalt content for AC-BCStandard mixture is 5.20% while AC-BCBottom Ash mixture is 5.25%. Bottom ash has higher porosity along with a little break field and has round shape so that the asphalt absorption is bigger than the crushed stone. Bottom ash can be used as an alternative aggregate to increase the value of flow of the AC-BC mixture, thus converting waste to valuable material.

Laboratory investigation on the brucite fiber reinforced asphalt binder and asphalt concrete

To investigate the modification of brucite fiber, fiber reinforced asphalt binder and asphalt mixtures were prepared and tested. Lignin fiber, basalt fiber and polyester fiber were used for comparative studies. Water absorption, oven heating, mesh-basket draindown were designed to evaluate the fiber wettability, thermostability, asphalt absorption and stabilization. Cone penetration test and dynamic shear rheometer test were applied to research the shear resistance rheological property and rutting resistance of fiber reinforced asphalt. In addition, the microstructure of fibers and reinforced asphalt binders were analyzed via scanning electron microscopy. Moreover, the engineering properties, containing high temperature stability, low temperature cracking resistance and moisture susceptibility, were conducted. Results show that brucite fiber has a better state of preservation in humid environment and thermostability than lignin fiber. It obtains a better effect on asphalt absorption and stabilization than basalt fiber and polyester fiber. Besides, the brucite fiber can effectively improve the rutting resistance and shear prevention of asphalt binders. The brucite fiber obtains a spatial networking to enhance the adhesion and stabilization of asphalt binders. The results also indicate that the asphalt mixture mixed with brucite fiber shows great high temperature stability, low temperature cracking resistance and moisture susceptibility.

Stabilizing and reinforcing effects of different fibers on asphalt mortar performance

Physical properties of different fibers (mineral, cellulose, or carbon fiber) and their stabilizing and reinforcing effects on asphalt mortar performance were studied. Scanning electron microscopy was used to study the effect of fiber’s microstructure on asphalt mortar’s performance. Laboratory tests of mesh-basket draindown and oven heating were designed and performed to evaluate the fibers’ asphalt absorption and thermostability. A cone penetration test was used to study the flow resistance of fiber-modified asphalt mortar. Results showed that fiber can form a three-dimensional network structure in asphalt, and this network can be retained at high temperature. This network of fibers favors the formation of a thick coating of mastic without asphalt draining down. Cellulose fiber possessed a greater effect on asphalt absorption and stabilization than did the other fibers (mineral and carbon fiber). A dynamic shear rheometer was used to evaluate their rheological properties and rut resistance. Results indicated that fiber can effectively improve the rut and flow resistance of asphalt mortar. However, the bending beam rheometer results demonstrated that the addition of fiber had negative effects on the creep stiffness and creep rate of asphalt mortar.

Rheological behavior of basalt fiber reinforced asphalt mastic

The characters of basalt fiber are analyzed and compared with commonly used fibers. The rheological behaviors of the basalt fiber reinforced asphalt mastic are investigated by the dynamic shear rheological tests and the repeated creep tests. The results show that basalt fiber has excellent reinforced performances, such as high asphalt absorption ratio, low water absorption ratio, high tensile strength, high elastic modulus and high temperature stability. The rutting factor of the fiber reinforced asphalt mastic is higher than the plain asphalt mastic and the reinforced effects are more remarkable under high temperature. The rheological performances of the asphalt mastic demonstrate a good linear relationship between different temperature and loading frequency. The creep stiffness modulus of the asphalt mastic at different loading time can be expressed by power function. Improved Burgers model is used to represent the rheological behaviors of the asphalt mastic with basalt fiber and the model parameters are estimated.

Application of density gradient column to flexible pavement materials: Aggregate characteristics and asphalt absorption

Accurate measurements of aggregate volumetric properties are essential to a satisfactory mix design and successful production of pavement. Moreover, determination of aggregate asphalt absorption is required to correctly estimate air voids and optimal binder content. The objective of this research was to apply the density gradient column technique to flexible pavement materials and to investigate aggregate volumetric properties, asphalt absorption and their possible correlation. Results indicated that the density gradient column can accurately measure piece-by-piece volumetric properties and asphalt absorption, and revealed a very good correlation between asphalt absorption and aggregate void volume (as reflected by the aggregate bulk density).

Laboratory Investigation of Brucite Fiber in Stabilizing and Reinforcing Asphalt Binder

The purpose of this study is to evaluate brucite fiber's properties, stabilizing and reinforcing effects, and corresponding mechanism when used for asphalt binder. Commonly used fibers such as lignin fiber, basalt fiber, and polyester fiber were chosen for comparative studies. Laboratory tests of water absorption, oven heating, and mesh-basket draindown were designed and performed to evaluate their wettability, thermostability, asphalt absorption, and stabilization, respectively. The cone penetration test was applied to study the resistance to shear of fiber modified asphalt; the standard dynamic shear rheometer test was conducted to evaluate the rheological properties and rutting resistance of fiber modified asphalt; and Scanning Electron Microscopy (SEM) analyses was introduced to observe fiber's microstructure characteristic and its spatial network in asphalt binder. The results indicate that brucite fiber has improved the moisture susceptibility property and thermostability more than lignin fiber. It has better asphalt absorption and stabilization effects than basalt fiber and polyester fiber. Meanwhile, brucite fibers can effectively improve asphalt binder's resistance to rutting and shear, and dynamic shear modulus. Brucite fiber can effectively reinforce the asphalt matrix through its functions of spatial networking, adhesion and stabilization of asphalt binder.

Laboratory investigations of activated recycled concrete aggregate for asphalt treated base

Asphalt treated base ATB-25 was designed containing recycled concrete aggregate (RCA), which was pretreated with three types of activators in various amount. Crushed value, water absorption, density and adhesion with asphalt of RCA were tested. Four mixtures of ATB-25 were designed containing different contents of RCA: 0%, 30%, 60% and 100%. Marshall test, rutting test, water stability test and low-temperature bending test were conducted to evaluated road performances of above mixtures. It was found that the voids and microfractures existing in RCA led to large water absorption and crushed value and low density and strength. Application of activator effectively decreased crushed value and water absorption and enhanced adhesiveness with asphalt due to closing of voids in RCA. The activation effect of organic silicon resin was superior to that of metatitanic resin acceptor and silane resin acceptor. Because of asphalt absorption by microfractures, asphalt content and oil absorption of ATB increased as RCA content increasing. While effective asphalt content of different mixture were basically the same, indicating that RCA and natural aggregate had the same effective thickness of asphalt film. Residual Marshall Stability, tensile strength ratio and low-temperature bending strain of ATB decreased with RCA content increasing. Low-temperature bending strain decreased to 1728.5με when RCA content increased to 100%, which was less than the required value of specification of China. No obvious relationship was found between dynamic stability and RCA content, but dynamic stability of all ATB mixtures containing RCA satisfied the requirement in specification of China. ATB-25 mixtures containing less than 60% of RCA satisfied all the requirements of specification of China.