“…The mortar layer is difficult to be separated from the surface of aggregates, which makes its apparent density and water absorption significantly different from that of natural aggregate (Otsuki et al, 2003;Poon et al, 2004;Etxeberria et al, 2006;Pradhan et al, 2020). The crushing index, apparent density, and water absorption of natural aggregate (Gokce et al, 2004;de Juan and Gutiérrez, 2009;Butler et al, 2014;Duan and Poon, 2014;Fan et al, 2014;Sidorova et al, 2014;Arezoumandi et al, 2015;Pandurangan et al, 2016;Afroughsabet et al, 2017;McGinnis et al, 2017;Kim et al, 2016;Yang and Lee, 2017;Dimitriou et al, 2018;Gholampour and Ozbakkaloglu, 2018;Fan et al, 2020;Sasanipour and Aslani, 2020;Mi et al, 2021) are about 6%, 2,600-2,700 kg/m³, and 0.5%-1.8% respectively, while those of recycled aggregate (Gokce et al, 2004;de Juan and Gutiérrez, 2009;Butler et al, 2014;Duan and Poon, 2014;Fan et al, 2014;Sidorova et al, 2014;Arezoumandi et al, 2015;Pandurangan et al, 2016;Afroughsabet et al, 2017;McGinnis et al, 2017;Kim et al, 2016;Yang and Lee, 2017;Dimitriou et al, 2018;Gholampour and Ozbakkaloglu, 2018;Fan et al, 2020;Sasanipour and Aslani, 2020;…”