Properties and economics evaluation of utilization of oil shale waste as an alternative environmentally-friendly building materials in pavement engineering

Highlights

• The optimal range of oil shale waste residue.

• Material characteristics analysis of oil shale waste residue.

• Road performance analysis of oil shale waste residue asphalt mixture.

• Economic analysis based on Analytic Hierarchy Process.

• The test road verifies the practicality of the oil shale waste asphalt mixture.

Abstract

In recent years, oil shale has been exploited as an alternative resource for oil, and at the same time, a large amount of oil shale waste has been produced. However, many environmental problems have arisen with the accumulation of oil shale waste, so huge economic and environmental benefits will be generated along with the reuse of oil shale waste. This paper evaluates the application of oil shale waste residue in pavement engineering through Marshall test, rutting test and splitting test. By exploring the alternative particle size range of oil shale waste in three asphalt pavement (AC-16, SMA-13, OGFC-16), a comprehensive utilization method is obtained that satisfies both the strength requirement and the cost. The experimental results show that in the three asphalt pavements, the asphalt mixture with excellent road performance can be obtained as the oil shale waste residue instead of the stone material with the particle size ranging from 0.075 mm to 2.36 mm. Compared with ordinary asphalt pavement, the comprehensive performance of AC-16 asphalt pavement is increased by about 30%, the cost is reduced by 3.2%; the comprehensive performance of SMA-13 asphalt pavement is increased by about 25%, and the cost is reduced by 0.6%; the comprehensive performance of OGFC-16 asphalt pavement is increased by about 20%, and the cost is reduced by 3.5%. Overall, the test results show that the oil shale waste residue instead of the fine aggregate in the asphalt mixture can not only effectively utilize the oil shale waste, but also improve the engineering performance of the asphalt pavement.

Introduction

Asphalt has been widely used in airfield and high-grade road pavement due to its numerous advantages such as smoothness, low-vibration, high-automated construction, and easy maintenance [1], [2], [3], [4]. However, it has been observed that the production of asphalt mixtures requires a large amount of natural resource expenditure, the most expensive of which is natural stone resources. Therefore, the production of asphalt mixture has been moving towards sustainable development [5], [6], [7].

The main goal of sustainable development is to rationalize the use of natural resources, and social and environmental issues are minimized [8], [9], [10]. In the past few years, the main direction of research has been to use environmentally friendly materials in asphalt pavement engineering to improve pavement performance [11], [12], [13], [14]. The use of industrial waste is a promising solution to reduce environmental pollution from waste dumping and to reduce material costs [15], [16]. Tarbay et al. presents the use of waste materials (marble and granite) and byproduct material (steel slag) as alternative to the mineral conventional filler. The test results show that all materials enhanced rutting resistance compared to the traditional limestone filler [17]. Abo El-Naga et al. investigated the effect of using polyethylene terephthalate waste plastic materials (PTP) on improving the performance and properties of asphalt pavement. The conclusion indicated that addition of 12% of PTP increased the pavement service life 2.81 times and saved ~20% of the asphalt layer thickness [18]. Saberian et al. assessed the effect of crushed glass on the behavior of the crushed recycled materials together with crumb rubber for road pavement applications. The results indicated that the blends of waste materials, as a low-carbon concept, could be a viable and satisfactory alternative solution for future base/subbase applications [19].

Oil shale, a kind of saprolite-type solid combustible argillaceous rock, whose color ranges from light gray to dark brown, and its ash content is higher than 50%.Oil shale is an “unconventional oil and gas resource” that produces shale oil, dry distillation gas, and semi-coke under heating conditions. Carbon shale carbonization can produce shale oil, which is an important alternative resource for petroleum. If the proven oil shale in the world is converted into shale oil, the reserves are almost twice that of oil reserves [20], [21]. It is called “artificial petroleum” and “synthetic liquid fuel.” Many petrol, diesel and chemicals are extracted from shale oil and processed again, making it an important replacement for the 21st century [22]. According to statistics released by the US Energy Information Administration, there are nine countries with concentrated oil shale in the world, namely the United States, China, Canada, Australia, Morocco, Congo, Brazil, Italy and Jordan, world shale oil reserves total approximately 11 trillion to 13 trillion tons, far exceeding oil reserves [23].

Whether domestic or foreign, in the process of oil shale development and utilization, a large amount of waste is inevitably generated, and the massive accumulation of these oil shale wastes will seriously pollute the environment [24], [25]. Due to the accumulation of oil shale waste, the forests and lakes in northern Estonia are seriously polluted, and the Maoming area of Guangdong Province in China is also suffering from oil shale waste [26], [27], [28]. In the process of direct combustion or retorting of oil shale waste, organic matter is quickly removed to form a porous structure, and the porous structure of oil shale waste slag makes oil shale waste residue widely used [29], [30]. Mohammad et al. added oil shale ash powder to cement mortar or concrete for strength testing. The test results show that the compressive strength is best when the oil shale dust is 10%. In addition, when the oil shale dust is less than 30% of the cement replacement, the compressive strength is not significantly affected [31]. AL-Hasan added different amounts of oil shale ash powder to cement concrete to test its performance. From the data point of view, the compressive strength and thermal conductivity of concrete decrease with the increase of oil shale ash powder production, and the concrete strength still increases with the extension of the specimen age [32]. Mymrin et al. attempted to demonstrate the possibility of oil shale waste ash as a binder. They incorporated oil shale waste ash into the natural clay base and found that the hardening strength of the clay base can be significantly improved, and other properties are not affected, it proves that oil slag waste can be used as a bonding material [33]. Fen et al. studied the cementation properties of oil shale ash powder by XRD, IR, NMR, ICP and other technical means. The study found that the oil shale ash produced at 700 °C~900 °C is very similar to the cement, and its strength basically meets the cement standard 42.5# [34]. Wei et al. Prepare a long-life asphalt mixture by drying and sifting the burned oil shale waste [35]. J. Adamson et al. conducted an experimental study on the effects of oil shale ash on arable soil. The researchers pointed out that it is necessary to pay attention to and ensure the safety of oil shale waste for soil improvement [36]. Lembi-Merike Raado et al. classify oil shale waste into two categories, the first is CFB and the second is PF. They add two different oil shale waste powders to cement concrete in different proportions with limestone. In the middle, and testing the strength of cement concrete, the test proved that the appropriate amount of PF ash and CFB ash can improve the compressive strength, expansion rate and durability of concrete [37].Arina Koroljova et al. mixed oil shale ash powder with cement for the stabilization of soft soil materials. The results showed that oil shale waste slag powder can not only improve concrete strength, but also effectively control costs [38].

According to the author's knowledge, most of the current re-use of oil shale waste is concentrated in agriculture and building materials, and there is very little research on replacing stone with shale waste. Martinazzo, R et al. used the product of oil shale distillation in Brazilian soil to evaluate the tendency of soil pollution. Experimental results show that it is feasible to use oil shale waste residue in soil [39]. Haibin Wei et al. mixed oil shale ash and fly ash into silty clay to obtain a new type of road and material, and studied its freeze–thaw cycle. The experimental results show that the microstructure changes in the cycle are the main factors that cause the elastic modulus to decrease [40]. Since oil shale waste is an acidic inorganic material, its compatibility with asphalt is a major problem that hinders its application in asphalt pavement. A silane coupling agent is a novel coupling agent containing two functional groups, one is a hydrophilic functional group, which is easy to react with an inorganic material, and the other is an organophilic functional group, which is easy to chemically react with an organic polymer material, and thus the silane coupling agent can effectively improve the compatibility of organic materials with inorganic materials, especially acidic inorganic materials. In this paper, the Marshall stability test is used to determine the best alternative range of oil shale waste replacement stone, and it is tested by rutting test, low temperature splitting test, bending failure test, water immersion Marshall stability test and self-designed freeze–thaw cycle Marshall test. Performance has been verified. In addition, the economics of oil shale waste instead of fine aggregates were analyzed and the experimental road was paved.