Accelerating cement hydration with C-S-H seeds
![4 SEM images of crystalline C-S-H: A – killalaite (Ca6.4 [H0.6Si2O7]2 (OH)2), B – gyrolite (Ca1Si24O60 (OH)8(14+x) H2O) in a tobermorite matrix, C – hillebrandite (Ca2SiO3 (OH)2), D – xonotlite (Ca6 [Si6O17] (OH)2). Product formation is dependent on Ca/Si, treatment temperature and duration](/uploads/images/2019/w300_h200_x600_y117_Materials_John_Stephan_Figure4-98314817eb8a190a.jpeg)
![6 Compressive strength development during the first hours of cement hydration and over 28 days with 0.5 wt.-% C-S-H before and after optimization of the synthesis [19]](/uploads/images/2019/w300_h200_x325_y255_Materials_John_Stephan_Figure6a-ec439ee0ad2ec3bb.jpeg)
![7 Ultrasonic sound speed measurement of cement pastes with 0.5 wt.-% C-S-H before and after optimization of the synthesis [19]. The setting time could be accelerated by approximately 1.5 hours through non-optimized C-S-H and by further 2 hours through optimization](/uploads/images/2019/w300_h200_x348_y261_Materials_John_Stephan_Figure7-5f3f2cecac74bd5f.jpeg)
The acceleration of cement hydration through synthetic C-S-H shows great potential in increasing the early strength of cementitious systems. The selection of a suitable calcium-to-silicon ratio and optimized synthesis conditions results in a significant strength gain compared to non-optimized systems. Polymers may contribute during synthesis to stabilizing the C-S-H aggregates, thus enhancing the storage stability of the suspensions.
1 Introduction
According to the European climate and energy policy, the emission of greenhouse gases is to be reduced by 40 % by 2030 compared to 1990 [1]. The German cement industry contributes essentially to the issue with annual emissions of 17450 million t CO2 (2015). Nevertheless, their 1995 self-imposed climate goal of a 28 % reduction of energy conditioned CO2 emissions was achieved in 2012 [2]. The application of alternative fuels, together with more effective kilns and improved clinker mineralogy contributed to the achievement of climate goals just as well as the development of...
