Hydration Mechanism of the Hydrogen-Rich Water Based Cement Paste Sumit Chakraborty, Byung Wan Jo,* and Muhammad Ali Sikandar Department Civil and Environmental Engineering, Hanyang University, Seoul, South Korea 133791 *S Supporting Information ABSTRACT: With the aim to speed up the construction process, utilization of the hydrogen-rich water as a cement set accelerator would be a unique approach. The investigation deals with the effectiveness of the hydrogen-rich water in controlling the setting and the hydration behavior of cement. Analyzing the setting time using Vicat apparatus, the initial and final setting time of the control cement is measured to be 197 ± 6 and 257 ± 3 min, respectively, while the same is measured to be 8 ± 3 and 14 ± 3 min, respectively, for the 0.5 ppm hydrogen-rich water- based cement sample. The change in surface potential of the hydrogen-rich water based cement paste may lead to agglomerate the cement particle immediately. Additionally, the hydration test reveals that the hydrogen-rich water accelerates the cement hydration reaction. This phenomenon is primarily governed by the rapid dissolution of the cement component, followed by the early nucleation and flocculation of the hydrated products, which is confirmed monitoring the amount of hydrated cement product using analytical tools. Finally, based on the zeta potential measurement, a plausible model has been proposed to explain the overall performances of the hydrogen-rich water. 1. INTRODUCTION Nowadays, the development of the green and sustainable construction material is sought around the world. 1−3 Addition- ally, the world’s increasing need is to speed up the construction process for saving money and energy as well. Usually, the admixtures are used to control the performances of the concrete magnificently. 4,5 In fact, the admixtures are the type of ingredients that are added to the concrete mix to improve the quality and manageability of the concrete. 5,6 In general, two types of the admixture such as mineral admixture and chemical admixture are used to improve the quality of concrete. The mineral admixtures such as fly ash, ground granulated slag, and silica fume, etc., are the waste products of the several industries, which are relatively cheap and added during the production of cement. 7,8 Additionally, the chemical admixtures are the water- soluble chemicals that are added in a relatively small quantity to the concrete for achieving the desired properties. 4−6 The chemical admixtures may interact with the concrete constituents and affect the properties of the fresh and hardened concrete. The common chemical admixtures are classified as set retarding, air entrainment, water reducing, set accelerating, shrinkage reducing, superplasticizers, and corrosion inhibiting admix- ture. 4−6,9,10 Typically, the chemical admixtures control the performances of the concrete altering the cement hydration reaction equilibrium. 4−6 The cement hydration reaction is a combination of the complex reactions occurring among the chemical phases such as tricalcium silicate (3CaO.SiO 2 ), dicalcium silicate (2CaO.SiO), tricalcium aluminate (3CaO.Al 2 O 3 ), tetra-calcium aluminoferrite (4CaO.Al 2 O 3 Fe 2 O 3 ), and water. 11 It is reported elsewhere that the addition of a foreign substance alters the cement hydration reaction equilibrium, which in turn disturbs the nucleation and growth of the hydrated products. 12−15 An understanding of the cement hydration reaction mechanism in the presence of the chemical admixture is now a crucial aspect of the cement research. 4 Usually, the set retarding admixtures are used to delay the cement hydration kinetics. While, the set accelerator is used to speed up the pace of construction by reducing the induction time. 5,6 In fact, the set accelerators are used to increase the production rate of the concrete, reduce the damaging risk of the concrete structures at an early age, and repair the structure very quickly. Calcium chloride is known to be the most commonly used cement set accelerator. 4 Additionally, calcium formate, calcium nitrate, calcium nitrite, calcium thiosulfate, sodium thiocyanate, sodium and potassium carbo- nate, lithium carbonate, and triethanolamine can also be used as the set accelerator. 5,6,16 Reviewing the literature, it is apparent that the chemical admixture controls the performances of the concrete in a particular application. 5 However, it possesses a negative effect on the other desired properties such as volume stability, long-term strength, freeze−thaw durability, alkali-aggregate reaction, Received: February 11, 2016 Revised: April 4, 2016 Article pubs.acs.org/JPCC © XXXX American Chemical Society A DOI: 10.1021/acs.jpcc.6b01444 J. Phys. Chem. C XXXX, XXX, XXX−XXX