Triggered by the recent advance in materials synthesis and characterization techniques, there has been an increasing interest in manipulating properties of calcium silicate hydrates (C-S-H), which constitute the fundamental, strength-responsible building blocks of concretes. Concretes are the indispensable constituents of today’s modern infrastructures and simultaneously the most widely used synthetic material on the planet. Despite the widespread impact and high societal values, the production of their major binder component, Portland cement (PC), is the major culprit for global warming since it contributes to 5–10% carbon dioxide emission worldwide. Consequently, enhancing the ultimate strength and durability of concretes by tuning structural, compositional and mechanical properties of their basic building units and assembling them via bottom-up engineering is one of the key strategies to mitigate the aforesaid concerns. This is simply because the longer the concretes last, the less production of PC would incur. Furthermore, the current role of C-S-H in industry is not only confined to the context of construction materials but to diverse sectors of industry including drug delivery, CO2 sorbent and materials for bone replacement. This wide scope of potential applications can be ascribed to the high versatility regarding tunable structural properties such as porosity, size and morphology, all of which can be fine-tuned during the synthetic procedure. Among the listed properties, understanding and gaining control over morphological factors of C-S-H is particularly important since they are directly associated with their functional roles. C-S-H with various morphologies can be produced by altering key experimental conditions, which encompass types of synthetic procedure, precursor types such as different calcium and silicate sources and types of additives. This chapter discusses a variety of morphologies of C-S-H acquired in multiple environments. The latter include the hydration of PC or PC-blends containing supplementary materials such as slag, synthetic C-S-H produced using silica-lime reactions and crystalline CSH synthesized using hydrothermal treatment. At the end, the chapter will provide a complete review on the current range of morphologies for calcium silicate hydrate.
Part of the book: Cement Based Materials