In addition, the degree of prewetting of the LWA is not consistently controlled, and so the properties of LWAC depends on the method and procedure of prewetting (Castro et al. Their water absorption measurements (after 24 h water-soaking) are not reliable giving a high variation even when experienced technicians follow a standard test method such as ASTM C 127 (ASTM International 2015). An SSD condition of LWA is hardly defined because taking out surface water of water-soaked LWA is very prone to experimental error. It is difficult to achieve a constant quality of the prewetting of LWA. The vacuum-soaking method, which involves evacuating air in a water container, accelerates the prewetting of LWA, which results in more complete prewetting and saves time for the process. Water-soaking LWAs, prepared by immersing them in water longer than 24 h, may be an ideal method to obtain fully water-filled pores of LWA. However, water-sprayed LWA is usually drier than its SSD condition and absorbs more water in a mix. Water-spraying on an LWA dump is the most preferred method in the field. Therefore, the prewetting needs to be carefully accomplished until the LWA reaches a saturated surface-dry (SSD) condition (the water absorption after 24 h water-soaking). The high water absorption causes poor workability, significant slump loss and blockage of concrete pumping when the LWA is not adequately prewetted. 2010 Kockal and Ozturan 2011 Shuguang et al. The water absorption of coarse LWA, however, ranges from 10 to 20% depending on the type of raw material and producing method (González-Corrochano et al. For example, the water absorption of granite aggregates are generally 0.5% by mass. The water absorption of normal aggregates is generally restricted by less than 3% while the specific limit varies according to the standard in a specific region.
Lightweight aggregates (LWA) are porous, which results in a higher water absorption compared to normal aggregates. Nevertheless, workability control of LWAC requires more attention to the details than ordinary concrete when it is applied in the field (Videla and López 2000). Its implementation is not different from the placement of ordinary concrete, and various guidelines dealing with LWAC are available in the literature: ACI 213R-14 (American Concrete Institute 2014) JASS 5 14 (Architectural Institute of Japan 2009) and KCS 14 20 20 (Korea Construction Specification 2016). Application of LWAC is therefore common these days (Walraven et al. More than a 20% decrease in self-weight of structural components, that is, a lower dead load, allows us to save construction materials for a designed structure. Lightweight aggregate concrete (LWAC) is beneficial to the design of structures and foundations.
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