Different supplementary cementitious materials SCMs such as

Different supplementary cementitious materials (SCMs) such as fly ash, silica fume, and slag can be used to lessen ASR problem. Use of SCMs as partial replacement of cement reduces the alkali content of cement [1]. In addition, the porosity of the concrete can be enhanced by SCMs that will reduce the chances of moisture to initiate deleterious ASR expansion [1]. During pozzolanic activity of SCMs, negatively charged calcium silicate hydrate (C-S-H) is formed with a low calcium to silica ratio. This C-S-H reacts with alkali cations (Na+, K+) and reduces diffusivity of alkali cations into the concrete. In this way, ASR is mitigated by the use of SCMs [4]. About 30% rice hulls are produced during the paddy husking process [5]. It is used as MK-4827 not only for energy production in paddy milling process but also in various power plants. When rice hull undergoes the burning process, about 20% of it converts into RHA [5], [6]. About 738.2 million tons of paddies are produced in the world each year [7] of which about 70 million tons are RHA [8]. This significant amount of RHA is generally dumped in industrial premises that may cause environmental pollution. Moreover, RHA cannot be naturally degraded due to its siliceous compositions [9]. On the other hand, cement industries are responsible for about 7% of the total equivalent CO2 emissions [9], and one ton of cement production is responsible for about one ton of equivalent CO2 emission [8], [10]. Use of RHA in substitution of cement can reduce the CO2 footprint as well as ecological hazards [11], [12], [13]. Arkansas is the top of all six rice-producing states in the U.S. It contributes about 48% to the total rice production in the U.S. [14]. The largest rice miller in the world, Riceland Foods, Inc., a farmer-family based business that produces 125 million bushels of paddy annually, is situated in Arkansas [15]. Generally, Riceland Foods considers RHA as an agricultural waste product and disposes it to nearby industry premises, which may cause health hazards to the associated workers. Other SCMs such as fly ash and silica fume are expensive and may not be available locally. Hence, locally produced RHA can be used as an alternative SCM due to its high silica content [4]. Akhnoukh et al. [3] reported that Arkansas Department of Transportation (ARDOT) faced concrete pavement and barrier damages at various places across Arkansas in recent years. It may incur ARDOT extra maintenance cost, leading to inflation in the life cycle cost of the project. The factors that contribute to the concrete pavement distress due to ASR in Arkansas are the use of reactive aggregates, the trend of not using SCM in cement and availability of high moisture content in the air. It is suggested to incorporate SCM in highway projects to lessen ASR-related concrete pavement deterioration. Abbas et al. studied the mitigation of ASR in their corresponding study by incorporating RHA [1]. These researchers used Ordinary Portland Cement (OPC), four different percentages (i.e., 10%, 20%, 30% and 40% by weight of OPC) of RHA and reactive aggregate (sand from Dolomite-limestone rock) in their study. The cracking phenomena and the amount of CaO/SiO2 in the tested concrete samples were examined using scanning electron microscopy (SEM) technology and energy disperse X-ray spectroscopy (EDS) analysis, respectively. Reductions in ASR expansion were observed in the case of mortar bars containing RHA and a 40% replacement of OPC by RHA was found optimum. Additionally, SEM images showed no cracks in RHA modified mortar bars while cracks were found in the control specimen (0% RHA). The EDS analysis revealed that the presence of low CaO/SiO2 correlated to the reduction of ASR expansion.