Effect of moisture damage on gap-graded asphalt mixture incorporating electric arc furnace steel slag and copper mine tailings

Water damage is a vital factor affecting the durability of gap-graded asphalt. There is an urgent need for a pragmatic and reasonable test to evaluate this parameter. Previous research has proposed that tensile strength ratio is a promising test for this application. Therefore, the aim of this paper is to evaluate the effect of moisture damage on gap-graded asphalt mixture incorporating electric arc furnace (EAF) steel slag and copper mine tailings (CMT). Four material mixtures of eight mix designs were investigated. Each mix was conditioned in water for 24-hour and 48-hour before testing. The study adopted retained strength index (RSI), durability index (DI) and tensile strength ratio (TSR) to describe the durability of gap-graded asphalt incorporating EAF steel slag and copper mine tailings. The results reveal that all the mixes fulfill the prescribed criteria. Also, there is a strong correlation between the retained strength index and the durability index with a strong coefficient of determination, R 2 of 0.9543. The results of the study further showed that gap-graded asphalt mixture incorporating EAF steel slag and copper mine tailings did not seem to pose any problem

Volumetric properties and leaching effect of asphalt mixes with electric arc furnace steel slag and copper mine tailings

This study focuses on the potential of electric arc furnace (EAF) steel slag and copper mine tailings as asphalt paving materials with respect to issues of volumetric properties and leaching. In this study, four different asphalt mixes were investigated; each contained EAF steel slag and copper mine tailings of various proportions. Apart from the microstructure analysis of the materials, a toxicity characteristics leaching procedure (TCLP) test was conducted on both the mixes and the aggregates. All the mixes were evaluated by the following parameters: Voids in the mineral aggregates (VMA), voids in total mix (VTM), voids filled with asphalt (VFA), Marshall stability and flow and specific gravity. F-test ANNOVA was used to evaluate the degree of significance of the mixes with each of the evaluated standards. It was observed that the mixes containing either EAF steel slag or copper mine tailings or both gave better results than the control mix. In terms of the TCLP test, none of the detected hazardous elements exceeded the standard limits, which indicates the possibility of using them as construction materials

Characteristics and utilization of steel slag in road construction

Presently, the rate of utilization of steel slag in Malaysia is rather too low compared to some advanced countries. Many studies focused on the better way to increase the usage of industrial by-products in order to ease disposal problems. Enormous quantities of steel slag were deposited in yards, causing environmental pollution. Like other metallurgical slags, steel slags exhibit a great potential to be used as aggregate in highway construction. The assessment and evaluation of this material should be based on environmental, economic and technical factors before it can be used in road construction. In terms of technical perspective, steel slags must met the required test requirements that are needed for natural aggregates used for similar purposes. The degree of slag utilization needs to be improved as an important measure to these problems. The physical and chemical properties of slag were reviewed and the various areas of its applications are highlighted. The principal setback of its use; volumetric instability which results from hydratable oxides can be checkmated through appropriate methods like aging and steam test. In order to sustain its uses, microstructure analysis that can identify any harmful materials present in it is suggested. There is also an urgent need of standard methods to assess its suitability as highway construction materia

Evaluation of factors influencing strength of foamed bitumen stabilised mix

Over recycling of asphalt pavements involves mixing of existing pavement material with stabilizing agent such as foamed bitumen, bitumen emulsion, cement or lime and placed on the milled pavement and compacted. The strength of foamed bitumen stabilized mix is influenced by factors such as cement content, moisture level and curing time. It was found that the strength in terms of resilient modulus, Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS) values, increased with curing time and percentage of active filler. It was also found that the maximum strength in terms of resilient modulus, Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS) was not at Optimum Moisture Content (OMC) and the strength decreased as the RAP proportion increased

Evaluation of rutting potential and skid resistance of hot mix asphalt incorporating electric arc furnace steel slag and copper mine tailing

In order to promote the use of waste materials in road construction, this paper presents the laboratory results of a study investigating the rutting potential and skid resistance of hot mix asphalt incorporating electric arc furnace (EAF) steel slag and copper mine tailings. To achieve this objective, four different mixes incorporating copper mine tailings and EAF steel slag in different proportions are investigated. The aggregates are blended with the optimum bitumen content of PG(76-22) and 80/100 bitumen binders. The rutting potential of all the mixes is evaluated by the asphalt pavement analyzer (APA), while the skid resistance is measured by the British Pendulum Skid Resistance Tester. The results show that the mix with 20% copper mine tailing and 80% EAF steel slag has the highest skid number, mean texture depth and the least rut depth. It is also observed that the rate of rutting decreased with loading cycles and 70 to 80% of the rut depth is attained at 4000 cycles using the APA

Evaluation of rutting potential and skid resistance of hot mix asphalt incorporating electric arc furnace steel slag and copper mine tailing

550-558In order to promote the use of waste materials in road construction, this paper presents the laboratory results of a study investigating the rutting potential and skid resistance of hot mix asphalt incorporating electric arc furnace (EAF) steel slag and copper mine tailings. To achieve this objective, four different mixes incorporating copper mine tailings and EAF steel slag in different proportions are investigated. The aggregates are blended with the optimum bitumen content of PG76-22 and 80/100 bitumen binders. The rutting potential of all the mixes is evaluated by the asphalt pavement analyzer (APA), while the skid resistance is measured by the British Pendulum Skid Resistance Tester. The results show that the mix with 20% copper mine tailing and 80% EAF steel slag has the highest skid number, mean texture depth and the least rut depth. It is also observed that the rate of rutting decreased with loading cycles and 70 to 80% of the rut depth is attained at 4000 cycles using the APA

Evaluation of asphalt mixtures incorporating electric arc furnace steel slag and copper mine tailings for road construction

This study evaluates the suitability of using electric arc furnace (EAF) steel slag and copper mine tailings (CMT) as substitution for conventional aggregates used in pavements for roads and highways. Four mix designs containing EAF steel slag and CMT at different proportions were investigated. Mix 1 was 100% granite, Mix 2 consisted of 80% granite and 20% CMT, Mix 3 consisted of 80% EAF steel slag and 20% CMT while Mix 4 consisted of 40% granite, 40% EAF steel slag and 20% CMT. Marshall stability, moisture susceptibility, indirect tensile resilient modulus and dynamic creep tests were used to evaluate the laboratory performance of the mixtures. The findings reveal that substituting natural granite aggregates with CMT and EAF steel slag improved the performance properties of asphalt mixtures. The mixture containing 80% EAF steel slag and 20% CMT produced the best results. The resilient modulus results show that the resilient modulus of the mixes decreased as the temperature increased. Also, the aging process significantly increased the resilient modulus and dynamic creep modulus values. Thus, the study has revealed that the mining by-products (CMT) and metallurgical by-products (EAF steel slag) can be utilized as aggregates in road construction

Volumetric properties and leaching effect of asphalt mixes with electric arc furnace steel slag and copper mine tailings

This study focuses on the potential of electric arc furnace (EAF) steel slag and copper mine tailings as asphalt paving materials with respect to issues of volumetric properties and leaching. In this study, four different asphalt mixes were investigated; each contained EAF steel slag and copper mine tailings of various proportions. Apart from the microstructure analysis of the materials, a toxicity characteristics leaching procedure (TCLP) test was conducted on both the mixes and the aggregates. All the mixes were evaluated by the following parameters: Voids in the mineral aggregates (VMA), voids in total mix (VTM), voids filled with asphalt (V FA), Marshall stability and flow and specific gravity. F-test ANNOVA was used to evaluate the degree of significance of the mixes with each of the evaluated standards. It was observed that the mixes containing either EAF steel slag or copper mine tailings or both gave better results than the control mix. In terms of the TCLP test, none of the detected hazardous elements exceeded the standard limits, which indicates the possibility of using them as construction materials

Influence of active filler, curing time and moisture content on the strength properties of emulsion and foamed bitumen stabilized mix

Foamed bitumen and emulsion are common stabilizing agents that are currently used for recycled asphalt pavement construction throughout the world. The strength of stabilized Reclaimed Asphalt Pavement (RAP) is influenced by factors such as filler content, moisture level and curing time. This paper describes the strength impact of ordinary Portland cement as active filler, the length of the curing time and moisture content on the foamed bitumen and emulsion stabilized mix. The basic objective of the paper is to evaluate the effect of active filler (Ordinary Portland Cement), curing time and moisture content on the strength of foamed bitumen and emulsion treated mix. The foamed and emulsion treated samples with various contents of RAP and crushed stone aggregates were tested for their strength properties. The resultant strength increases in terms of resilient modulus, Unconfined Compressive Strength (UCS) and the Indirect Tensile Strength (ITS) values, were correlated with the length of curing time, using various percentages of active filler and proportions of RAP in the pavement mix. It was found that the strength decreased with increased RAP content, however if 100% RAP is to be used then the required pavement strength can be achieved by utilizing a higher active filler ratio. The effect of moisture content variation on foamed bitumen and emulsion treated samples with high percentage of RAP is not significant

Engineering properties of asphalt binders containing nanoclay and chemical warm-mix asphalt additives

In the effort to promote the construction of green pavement the asphalt concrete industry has been mak-ing consistent effort to use warm-mix asphalt (WMA) in their construction. The objective of this study was to improve the properties of the asphalt binders through the addition of nanoclays and chemical WMA additive. An asphalt binder of 80/100 penetration grade was modified with different percentages of Nanoclay A (montmorillonite clay surface modified with 35–45 wt.% dimethyl dialkyl (C14–C18) amine), Nanoclay B (montmorillonite clay surface modified with 35–45 wt.% octadecylamine, and 0.5–5.0 wt.% aminopropyl-triethoxysilane), and chemical WMA additive (fatty polyamines polymer non-ionic component). After modification, the asphalt binders were named Nanoclay A modified asphalt binder (NCMB A), Nanoclay B modified asphalt binder (NCMB B), and chemical WMA modified asphalt binder (CWAA). The rheological characteristics of the unmodified and modified asphalt binders were evaluated using the rotational viscosity, dynamic shear rheometer, and bending beam rheometer tests. Results of the tests showed that NCMB B and CWAA significantly reduced mixing and compaction tem-peratures. However, only NCMB B showed a significant increase in rutting and fatigue resistance when compared with base asphalt binder. A change in chemical bond was also observed in the tested binders after long-term aging, which suggests that the addition of modifier could delay the aging process. © 2016 Elsevier Ltd. All rights reserved