Reactive powder concretes (RPCs) were developed through careful design and control of the composite microstructure. Enhanced properties were achieved through optimization of the gradation and arrangement of the inert particles, as well as through designing the reactive components (e.g., coarse-ground oil-well cement and silica fume) to govern the hydration product morphology. Recently, a process has been developed for synthesis of cement with nanometer-scale particle sizes with tailorable chemical compositions. The addition of nanocements to RPCs is unique because it influences the early hydration reaction of the cement in RPC for nano-sized hydration products. The replacement of a small fraction of the conventional cement with these nano-sized reactive particles reduces the induction period in cement hydration and initiates a faster conversion to the hydration products. Integration of nanocements may also lead to a denser product microstructure with higher ultimate compressive and tensile strengths. Potential also exists to reduce the permeability of the RPC and to strengthen the interfacial transition zones within the material. With such improvements, nanocement can serve as a means to optimize RPC systems for enhanced properties and may further enhance the durability of RPC.

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Development of a reactive nanocement is a new approach to improve the physical and chemical properties of construction materials. However, due to the decreased size of cement particles, beam damage during transmission electron microscope (TEM) observation becomes more severe than in conventional cement. In this work, irradiation damage to nano-C 2 S (dicalcium silicate) is observed and studied by in-situ evolution of diffraction patterns (DP), high resolution TEM (HRTEM), and electron energy-loss spectroscopy (EELS). The results show that the damage to nano-C 2 S occurs through a decomposition reaction. Nano-C 2 S is first amorphized, and then re-crystallized into CaO nano-crystals with average size of 7 nm surrounded by an amorphous matrix of Si and SiO 2 . During this process, C 2 S particles exhibit volume shrinkage. The damage energy causing the reaction was analyzed and electron-electron inelastic scattering produced radiolysis and heat, leading to the observed phenomena.

Phosphatic clay is a by-product of phosphate strip mining, particularly in Florida, USA. This waste material occupies about 100 000 acres of land which could be utilized for other causes. Thus, its use as an alternating cementing material for the addition into the mixing matrix of cement paste and concrete to yield higher strength would be profitable for both materials involved. But the biggest drawback faced is that the phosphatic clay possesses high water holding capacity. The water is thus not available for mixing purposes when added to cement paste and concrete and is thus known as bound water. It is therefore essential to determine the amount of bound water to phosphatic clay which shall not be available for the hydration reaction of cement in cement paste and concrete.