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Improving the polishing resistance of cement mortar by using recycled ceramic

https://doi.org/10.1016/j.resconrec.2020.104796Get rights and content

Abstract

Recycling of construction and demolition (C&D) waste is one of the most effective ways to develop sustainable pavements. In this study, the feasibility of using ceramic waste as an alternative source for fine aggregate to improve the polishing resistance of cement mortar is investigated. The recycled fine aggregates used in this study originate from sanitary ceramic waste; the physical and chemical properties of the Recycled Ceramic Aggregates (RCA) were determined. The optimal RCA content in the mortar was determined based on the mechanical strength of the resulting composite. The polishing resistance of coarse and fine RCA was characterized with the Polished Stone Value (PSV) test and the Wehner/Schulze (W/S) test, respectively. The test results indicate that the polishing resistance of RCA is significantly better than that of commonly used mineral aggregate. Lastly, the self-developed Aachen Polishing Machine (APM) was applied to validate the improvement of RCA on the polishing resistance of cement mortar under realistic loading conditions. The cement mortar containing RCA exhibits a better long-term polishing resistance than the traditional mortar. The results from this study provide insights into the application of RCA in concrete pavements and the improvement of material properties.

Introduction

Construction and demolition (C&D) waste is the largest waste source by volume in the EU and accounts for about one third of the total waste production. The C&D waste consists of numerous materials, including concrete, bricks, ceramic, wood, glass, metals, plastic and others. This has a large influence on the environment and leads to severe pollution and greenhouse gas emissions that drive global climate change (European Commission 2016). In particular, the mass production of ceramics, which has a high mechanical strength as well as high resistances to abrasion and chemicals has also resulted in an increased amount of ceramic waste (Lu et al., 2019; Torgal and Jalali, 2011; Almeida et al., 2016; Ferrara et al., 2019). It is reported that an estimated 1.4 million tons of ceramic waste are produced yearly from ceramic manufacturing in EU alone. As the majority of this waste is unable to be recycled by the ceramic industry, a large amount is disposed of in landfills. This corresponds to an economic loss of €5.25 billion annual and huge amount of landfills have been stopped in European countries (European Union 2010).

Proper management and recycling or reusing of ceramic waste have been recognized to deliver major benefits in terms of sustainability, since some of its components are valuable resources. Therefore, a great amount of research has been devoted to promoting the application of C&D waste in various industries including architectural engineering (Senthamarai and Manoharan, 2005; P. Torkittikul and Chaipanich, 2010; Pacheco-Torgal and Jalali, 2010; De Brito and Saikia, 2012; Medina et al., 2012; Elci, 2016; García-Ten et al., 2016) as well as pavement engineering (Huang et al., 2009; Silvestre et al., 2013; Muniandy et al., 2018; van de Ven et al., 2011; Feng et al., 2013). Silvestre et al. (Silvestre et al., 2013) used the Recycled Ceramic Aggregates (RCA) to partially substitute natural grains in hot mix asphalt and reported that the replacement of 30% of the natural aggregate with RCA leads to an increase in plastic deformation resistance and an increased tensile strength but results in a decreased resistance to moisture damage. In another study conducted by van de Ven et al. (van de Ven et al., 2011), it was also observed that some smooth pieces of coarse ceramic aggregates detached from the asphalt mixture samples after mechanical tests, which indicates a poor interfacial adhesion between bitumen and ceramic aggregates.

The poor interfacial adhesion between bitumen and ceramic aggregates can be attributed to the fact that the recycling process of ceramic waste fails to eliminate the ceramic glaze on the surface (Feng et al., 2013). Considering that the adhesive deficiencies between bitumen and ceramic aggregates pose potential risks to the application of RCA in bitumen-bound asphalt concrete, the addition of RCA in cement based concrete pavements represents a more attractive approach based on previous research (Huang et al., 2009; Feng et al., 2013; De Brito et al., 2005).

The skid resistance of pavements is crucial in ensuring transportation safety since it decreases the probability of skidding of vehicles; a pronounced surface texture also prevents hydroplaning (Mataei et al., 2016). To date, numerous studies have been carried out regarding the skid resistance of both asphalt and concrete pavements. The skid resistance can be regarded as the friction between tires and pavement surface, and it is intrinsically determined by the surface texture and the materials (D. Wang et al., 2017; D. Wang et al., 2018). The surface texture characteristics include the micro-texture and the macro-texture (Mataei et al., 2016; Wang et al., 2014). The former, with an unevenness wavelength below 0.5 mm, is known as the intrinsic fine irregularities on the surface of the aggregate particles. The latter describes the unevenness with a wavelength of 0.5–50 mm, which is generally denoted as the distance between individual aggregates (Hu et al., 2018; D. Wang et al., 2018; D. Wang et al., 2017).

Due to the superior flexibility and low construction costs, asphalt pavements are widely applied for various types of pavements across the world (Horvath and Hendrickson, 1998; Zhang et al., 2019). However, low temperature cracking, fatigue cracking, rutting, and aging are prominent issues, significantly restricting the durability of asphalt pavements. In comparison to asphalt pavements, concrete pavements are mainly applied on airfields and pavements subject to high traffic volumes due to the high stiffness and durability. In these specific cases, the speed of the vehicles is very high, in which case the skid resistance of the pavement is crucial to ensure safe mobility.

The development of the skid resistance is different in concrete and asphalt pavements due to the different contributions of binder materials. In asphalt pavements, the bitumen binder negatively contributes to the skid resistance of the pavement; the skid resistance of asphalt pavements will increase when the bitumen film is worn down (Wang et al., 2013). The cement paste in concrete has an opposite effect. After construction concrete pavement surfaces can generally be subdivided into three zones, as shown in Fig. 1. The uppermost zone mainly consists of cement paste. The zone immediately below consists of cement paste with fine aggregates. These two upper zones form the surface mortar. Underneath is the third zone, consisting of concrete (mixture of cement paste, fine and coarse aggregates). In the course of the service life, the cement paste in the surface mortar is removed by the combined effects of traffic and environmental conditions, resulting in an increasing exposure of fine aggregates, which increases the roughness. To ensure the skid resistance of concrete pavements, numerous techniques of texturing the concrete have been successfully developed. Surfacing technologies are used to generate favorable macrotextures; however, the micro-texture is also essential for the skid resistance of pavements. The micro-texture as well as its evolution throughout the pavement's service life depends entirely on the surface mortar (Kolias, 1994; Yetgin and Cavdar, 2011; Samani et al., 2016). Therefore, the ability of fine aggregates to resist polishing is the key component in retaining a good micro-texture and skid resistance in concrete pavements.

The important role of fine aggregates for the skid resistance of concrete pavements relies on the application of high-quality mineral aggregates, which is economically and environmentally expensive. Taking into consideration the high resistance of ceramic to abrasion, and the economic and environmental benefits of recycling C&D waste, the incorporation of RCA as fine aggregates in concrete pavements is a promising approach for adding value to pavement engineering while recycling ceramic waste. It can reduce the amount of ceramic waste that is disposed of in landfills, decrease the requirement of the mineral material extracted from natural quarries while improving the polishing resistance of cement mortar.

In this research, the application of RCA reclaimed from sanitary ceramic waste in concrete pavements is investigated based on the following four aspects: (1) The physical and chemical material properties of RCA; (2) Polishing resistance of RCA: including the evaluation of both fine (Wehner/Schulze, W/S test) and coarse (Polishing Stone Value, PSV test) RCA; (3) Mechanical properties and design optimization of cement mortar containing RCA and (4) Experimental validation of the polishing resistance of cement mortar containing RCA. The results provide insights into achieving higher recycling ratios of ceramic and minimizing the dependency on aggregate from natural resources.

Section snippets

Raw materials

CEM I Portland cement was selected based on the European standard EN 196-1 to fabricate cement mortar specimens. The CEN standard sand was used according to the European standard EN 206-1 as fine aggregates. Fig. 2 depicts the grain size distribution of the selected standard sand.

The RCA used in this study are obtained by crushing sanitary ceramic waste, toilet and bathroom demolition waste. The sanitary ceramic waste was first washed to remove contaminants. Then the naturally dried ceramic

Physical and chemical properties of the raw materials

The measured Blaine specific surface area of the selected cement was 4290 cm²/g and the density of RCA was determined to be 2390 kg/m3. Table 2 presents the measured chemical compositions of the cement and ceramic aggregates. The ceramic waste used this study was found to be mainly composed of SiO2 and Al2O3 oxides, while CaO and SiO2 oxides are the major components of the cement. The XRD results of cement and RCA are shown in Fig. 9, Fig. 10, respectively. The mineral composition of cement is

Conclusion

The mechanical performance and surface durability of RCA as well as cement mortar based on RCA were investigated and compared to conventional pavement materials in this study. The main results can be summarized as follows:

  • The designed concrete mortar with RCA exhibits very favourable mechanical properties. When replacing 40% and 70% of the traditional aggregates, the flexible and compressive strength is almost the same as for samples of traditional concrete pavement. However, after 100% of the

CRediT authorship contribution statement

Guoyang Lu: Conceptualization, Methodology, Writing - original draft, Methodology. Zepeng Fan: Data curation, Formal analysis, Writing - original draft. Zengqing Sun: Investigation, Writing - original draft. Pengfei Liu: Formal analysis, Writing - review & editing. Zhen Leng: Supervision, Methodology, Writing - review & editing. Dawei Wang: Supervision, Methodology, Writing - review & editing. Markus Oeser: Writing - review & editing.

Acknowledgments

This work was supported by the National Key Research and Development Program of China under Project Num. 2018YFB1600100 and the German Research Foundation (project Num. OE 514/4-2). The authors gratefully acknowledge their financial support.

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