تأثیر اسکوریا بر برخی ویژگی های مختلف بتن سبک Effect of Scoria on Various Specific Aspects of Lightweight Concrete

1. Introduction Structural lightweight aggregate concrete is made with lightweight aggregates, as defined in ASTM C330. This variety of concrete has a minimum 28-day compressive strength of 17 MPa, an equilibrium density between 1120 and 1920 kg/m3 , and a composition entirely of lightweight and normal-density aggregate materials (ACI 2003). Relatively low-density aggregates can be obtained by substituting classical aggregates of sand and pea gravel with artificially lighter aggregates, such as expanded polystyrene beads (Chen and Liu 2004; Khedari et al. 2003). Experimental works have shown that the characteristics of the aggregates are highly active in lightweight concretes, dictating the good mechanical, thermal, and acoustical performance of the final concrete (Lotfy et al. 2015; de Sensale and Goncalves 2014; Chi et al. 2003). Some modified types of concrete under thermomechanical loadings have been developed (De Sa et al. 2006; Burlion et al. 2005). The selection of materials is essential from the acoustical point of view. Materials can be classified into three main categories: transmission, reflection, and absorption. Good knowledge of these factors will help specialists to develop and implement sound-absorbing walls, which offer the best value for money with high acoustical performance levels. A micro perforated panel (MPP) was proposed (Maa 2007) as a next-generation alternative for porous sound-absorbing material, which has various issues related to health, hygienic, and environmental aspects. Many studies on MPPs have since been conducted (Kang and Brocklesby 2005; Asdrubali and Pispola 2007). Some studies on plate absorption were conducted. Others were more focused on radiation (Ruzzene 2004), and in particular, the vibration and radiation of sound from sandwich beams utilizing an MPP. Moreover, salt scaling is defined as the ‘‘superficial damage caused by freezing a saline solution on the surface of a concrete body’’ (Valenza II and Scherer 2007). Concrete scaling is caused by the formation of an ice lens, which induces constraints on the material periphery. The damage from the frost, and from scaling in particular (Valenza II and Scherer 2007), most frequently occurs in the wet regions of concrete in which the material surface is water-saturated under rigorous wintry conditions of severe frost. Several researchers have investigated the effects of scorias as replacements for cement, namely with respect to the mortar toughness, cement fraction (Al-Swaidani and Aliyan 2015; Bondar 2015; Lotfy et al. 2015; Ghrici et al. 2007; Rabehi et al. 2014), the fabrication of granulate forms for lightweight concretes (Mouli and Khelafi 2008), and thermal activation (Ezziane et al. 2007). Most studies have shown that scorias are economically sound and ecologically friendly building materials (Vlcˇek et al. 2014). Scoria, as lightweight aggregate, has been used in concrete to produce structural lightweight concrete, especially in Turkey (Yas¸ar et al. 2004). However, most of these works have not included the simultaneous research on the mechanical, thermal, and acoustic characteristics of the building materials incorporating scorias. In this study, the ability of scoria to replace all aggregates is emphasized. The objective of this research is to investigate the feasibility and effectiveness of using scorias in lightweight concretes.