عملکرد اسلب های یکطرفه ی بتن سبک با استفاده از پومیس و اسکوریای آندزیت بازالتی با پتاسیم متوسط Performance of lightweight concrete one-way slabs using medium-K basaltic andesite pumice and scoria

Introduction Indonesia is an earthquake-prone zone where its geographic position occupies an active tectonic zone, three large tectonic plates, i.e., Indo-Australian Plate, Eurasian Plate and Pacific Plate meet each other in its territory (Team Works 2010). Therefore, the buildings especially high-rise buildings of reinforced concrete structures should be designed to be resistant from the possibility of earthquake (SNI 1726:2012 2012). One way to reduce the risk of earthquake hazard is by reducing the self-weight of the building so that the horizontal seismic force will also decrease. Using a lightweight concrete on its structural elements, it may be one effort to reduce the building’s selfweight. This structural lightweight concrete is generally produced from lightweight artificial or natural aggregates so that its density is relatively light while the compressive strength still fulfills structural requirements (ACI 213.R-03 2003). The artificial lightweight aggregates are factory products with controlled quality and most widely used in lightweight structural concretes. These aggregates are produced from a thermochemical sintering process of expanded natural materials or expanded industrial wastes such as clay or fly ash (Mehta and Monteiro 1993). The reduction of lightweight concrete density using these artificial aggregates to normal concrete is approximately 28% (Chandra and Berntsson 2003), thereby affecting the results of structural design and overall construction costs (ACI 213.R-03 2003). However, its production is relatively complicated, requires a high thermal energy and certainly produces air pollution so they are expensive, less energy saving and less environmentally friendly. As a substitute, natural lightweight aggregates such as pumice and scoria can be used; these aggregates are a volcanic eruption product that are abundant especially in volcanic areas and even easy to explore. Although their existences are only in certain areas and their qualities are very diverse, but the lightweight concretes obtained may be cheaper, conserve energy and be more environmental friendly (Suseno et al. 2017). Thus, both lightweight aggregates are natural resources that need to be considered as local construction materials for structural purposes, especially for developing countries that have not been able to produce artificial lightweight aggregates. Several studies on the use of pumice and scoria as aggregates on lightweight concrete were conducted previously, such as pumice and scoria from Turkey (Kilic et al. 2009), pumice and scoria from Papua New Guinea (Hossain 2004a, b), scoria from Saudi Arabia (Shannag 2011), pumice breccia from Central Java Indonesia (Widodo et al. 2014) and pumice and scoria from Yemen (Al Naaymi 2015). The investigated results showed that the lightweight concretes obtained can be categorized as lightweight structural concretes by adding admixtures or prewetting aggregates. The average density reduction with the same compressive strength is approximately 20% compared to normal concrete, so it may be significant to reduce its selfweight when used on structural elements. However, studies on the use of pumice and scoria lightweight concretes on structural elements have not been widely conducted until now.