# An Experimental Study on Alkali Silica Reaction of Concrete Specim Using Steel Slag as Aggregate
## 1 Introduction  
Concrete is one of the most widely used construction materials. It has excellent properties, such as durability, versatility, and low cost, and, it is made up of basic ingredients such as a binder, aggregate, and water. However, the massive demand for concrete over the past few decades has led to the depletion of natural sources of aggregate. To address this shortage, the development of concrete using recycled aggregate has become a vital urban sustainability project. To satisfy the demands for stronger and more durable concrete structures, extensive research on using industrial wastes as aggregate is underway. Example of typically in a recycled aggregate, steel slag is a waste product that is generated during the production of steel and makes up nearly 15-20% of the total amount of steel produced, by weight [1]. It is rapidly becoming an important construction material in sustainable development. Steel slag as aggregate in concrete provides several benefits such as improved strength, radiation shielding, and greater resistance to acid attack than conventional concrete [2; 3; 4]. However, steel slagcan cause expansion or cracks after backfilling [5], and cannot be reused as aggregate as it contains free calcium oxide (i.e., f-CaO) that causes expansion [6; 7]. F-CaO combines with H2O to produce a hydrate Ca(OH)2, it can increase steel slag volume by 98% [8]. This volume change disturbed the development of the steel slag as a concrete ingredient. Thus, to safely use steel slag in concrete, it must be secured the volume stability [7; 9]. On the other hand, the stabilized method for steel slag is reforming and aging. The reforming method is to react with f-CaO and additives such as sand, red mud, and aluminate based material as well as oxygen to the molten slag, resulting in the formation of stabilized steel slag. However, this process is used to supply additional heat to maintain the molten state of steel slag. So, this complex process is required to high cost [7]. Nevertheless, the reforming process does not affect the grade of steel, so it was needed to be secured to another stabilized method of steel slag. The aging method by leaving in a natural state was developed in the early 1990s in Japan. However, the initial aging method takes six-month or longer, and it requires a large space. So, various studies performed to develop the acceleration aging method [10]. As a result, the comparative studies for the aging method are performed, various aging methods with low cost and high efficiency have been proposed [7; 10; 11]. Meanwhile, durability of concrete is degraded by various chemical reactions such as carbonation, chemical erosion, alkali-silica reaction (i.e., ASR), etc. This process usually affected the materials used to make concrete. In particlar, it is well known that aggregates play an important role in the ASR [2; 12]. Pop-out and exudation of a viscous alkali-silicate fluid are other manifestations of this phenomenon. It was first described by [PERSON] in 1940, in his study of cracked concrete structures by ASR [13; 14; 15]. Considering the expansion due to ASR, the range of aggregate sizes that cause the highest expansion varies with the composition of the aggregate [16]. The alkali-silica-reactivity of the aggregate may damage the concrete if no preventative measures are taken. The most accurate method of determining the ASR of an aggregate is by verifying the applicable field data. However, due to the long-term nature of this degradation phenomenon (over several decades), it is difficult to simulate under experimental conditions. Several studies have been conducted to evaluate the deterioration caused by volume changes due to ASR, using accelerated expansion methods. However, this accelerated mortar bar test method (ASTM C 1260) has several drawbacks in the evaluation of ASR [17; 18]. Evidently, this test method misestimates ASR expansion because it uses high temperature and high hydroxide at a high temperature, and is performed over a short period of only 14 days.