Research Article A Study on the Influence of Sodium Silicate Concentration and SiO 2 :Na 2 ORatioonthePropertiesofLow-CalciumFlyAsh-Based Alkali-Activated Materials Cured at Ambient Condition Mohammad Idris Rasuli Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami Chuo-ku, Kumamoto 860-8555, Japan Correspondence should be addressed to Mohammad Idris Rasuli; 199d9224@st.kumamoto-u.ac.jp Received 8 December 2021; Accepted 31 January 2022; Published 31 March 2022 Academic Editor: Francesco Colangelo Copyright © 2022 Mohammad Idris Rasuli. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Low-calcium Fly ash-based alkali-activated materials (AAM) have some extraordinary properties such as high fire resistance and low shrinkage. However, they have lower strength and high setting time when curing at ambient temperature conditions. erefore, this research aimed to improve the strength and setting time of low-calcium fly ash-based AAM curing at ambient temperature conditions. e effect of the changes in concentration and modulus of sodium silicate and curing condition of the materials were studied on the properties of the AAM. Fly ash type II, 32% sodium metasilicate pentahydrate, 32 and 56% sodium disilicate solution, 8M sodium hydroxide, and standardized were used. Using 32% sodium disilicate solution significantly improved the flowability of mortar. Moreover, it increased the compressive strength and remarkably decreased the setting time of AAM at ambient temperature curing. e decrease in the concentration of sodium disilicate has a significant influence on the reactivity of fly ash. 1.Introduction Portland cement (PC) concrete has some remarkable properties such as the ability to cast in different shapes and sizes, high compressive strength, and reasonable cost. Moreover, its reinforcement by steel makes it an extraor- dinary construction material. According to these facts, Portland cement concrete is the most commonly used construction material in the world. Annual global produc- tion of ordinary Portland cement (OPC) reaches 4 billion tonnes [1]. But according to the statistics, OPC is responsible for the emission of 8% CO 2 of the globe [2]. erefore, they are not environmentally friendly materials and one of the major causes of global warming, which is a serious issue nowadays. When aluminum silicate materials such as fly ash and slag react with an alkali source, they produces a material that has binding properties [3, 4]. ese kinds of materials are called Geopolymer or alkali-activated materials (AAM). Compared to OPC, AAM is a more environmentally friendly material because they emit a much lower amount of CO 2 to the atmosphere [5, 6]. Moreover, they contain some by- products as their primary constituents, such as fly ash and slags [7]. Besides being environmentally friendly materials, AAM have some other advantages, such as obtaining high early strength and superior mechanical properties [8, 9]. ey have better resistance to fire, acid attack, and alkali-silica reaction [10–12]. Sodium hydroxide (NaOH) and sodium silicate solution (water glass) are the two prominent alkaline materials for the making of AAM [13]. According to the molar ratio (MR=SiO 2 :Na 2 O), sodium silicate has several types such as sodium metasilicate (MR = 1) and sodium disilicate (MR = 2) [14]. Conventionally, water glass is used at a concentration of around 50% [9, 15–18], which makes the solution to be viscose and sticky, and this causes AAM to have a workability problem. Sodium silicate solution not only provides an Hindawi Advances in Materials Science and Engineering Volume 2022, Article ID 7762507, 7 pages https://doi.org/10.1155/2022/7762507