PSI - Issue 45

Huailiang Chen et al. / Procedia Structural Integrity 45 (2023) 104–108

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Huailiang Chen et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1. Introduction With the popularity of automobiles and the continuous growth of the transportation industry, a large number of waste tires are generated every year. Modern recycling technology has made it possible to reduce the cost and difficulty of disposing of waste tires. Recycled products of waste tires such as rubber powder, rubber granules, and steel wire can bring considerable benefits. The application of recycled rubber in the construction industry provides another viable option for the massive consumption of this material. Initially, recycled rubber particles were introduced to partially replace fine or coarse aggregates to form rubber concrete, aiming to reduce the use of natural aggregates. Recycled rubber can also be used for non-structural applications including wall coatings(Zhu, Thong-On & Zhang 2002), masonry mortars(Di Mundo et al. 2020), render mortars(de Souza Kazmierczak et al. 2020), pavements(Li, Saberian & Nguyen 2018), self-consolidating mortars (Uygunoğlu & Topçu 2010) and lightweight foamed mortar (Eltayeb et al. 2020a). Initially, rubber mortar has a lower weight, improved toughness, impact energy absorption, sound insulation, and heat insulation capabilities than ordinary mortar. Crumb rubber mortar (CRM) has been considered a promising building material (Corinaldesi, Mazzoli & Moriconi 2011; Eltayeb et al. 2020b, 2020c, 2022). Compared with other constituent materials of mortar, rubber particles have completely different physical and mechanical properties. The internal structure of rubber mortar becomes more complicated, although the addition of rubber particles does not produce new hydration products. Existing research mainly focuses on conducting laboratory tests to compare the mechanical properties of rubber mortar and ordinary mortar. Different researchers have inconsistent results when testing the compression strength reduction rate of rubber mortar. Therefore, it is of great significance to use theoretical methods to study the compressive strength of mortar with added rubber particles. Duarte et al. (2015) and Duarte et al. (2017) developed a 2D mesoscale model of rubber concrete to study its compressive strength and indirect tensile strength. Li et al. (2019) and Diao et al. (2020) proposed a 3D mesoscale to analyse the direct tensile strength of self-compacting rubber concrete. The shape of rubber particles was simplified as a sphere and the interface transition zone of rubber particles and mortar matrix was considered. Chen et al. (2023) proposed a mesoscale model to investigate the indirect tensile and flexural properties of CRM. The above research concluded that numerical simulation was a feasible tool to study the influence of rubber particles on the mechanical properties of concrete. However, the above models did not consider the random distributions of rubber particles. Detailed investigation on rubber content, and rubber sizes effect on concrete strength was not available either. There are limited numerical simulations of rubber mortars in the existing literature. To fill the above research gap, a mesoscale CRM model is developed in this paper where rubber mortar is regarded as a three-phase material composed of rubber, mortar matrix, and interface transition zone. Four influencing factors including interface strength, rubber aggregate position, mortar matrix strength, and treating rubber particles as pores are analyzed. Then, a fitted formula is proposed to predict the compressive strength of rubber mortar. The accuracy of the strength prediction formula is verified through comparing with experimental results. 2. Experiment program 2.1Mix proportions The natural sand volume in the ordinary mortar is replaced by untreated crumb rubber particles with a nominal size of 2-4mm at 6%,12%, and 18%. The mix codes for the three types of CRM samples are marked as CRM6, CRM12, and CRM18, respectively. The mixture components are same as in previous study(Chen et al. 2021, 2023). 2.2 Specimen preparation and test program The compressive test is conducted according to ASTM C109 at UniSA structural lab, with a load rate of 0.33MPa/s. There are three test samples for each type of rubber mortar mixture with a size of 50*50*50mm.