# Study on the Properties of Cement-Based Cementitious Materials Modified by Nano-CaCO\({}_{3}\)  
[PERSON]  
1 Department of Civil Engineering, School of Civil Engineering & Architecture, NingboTech University, No. 1 Qianhu South Road, Yinzhou, Ningbo 315100, China 1  
[PERSON]  
2 Department of Structural Engineering, College of Civil Engineering and Architecture, Zhejiang University, No. 866 Yuhangtang Road, Xihu, Hangzhou 311400, China 2  
[PERSON]  
1 Department of Civil Engineering, School of Civil Engineering & Architecture, NingboTech University, No. 1 Qianhu South Road, Yinzhou, Ningbo 315100, China 1  
[PERSON]  
1 Department of Civil Engineering, School of Civil Engineering & Architecture, NingboTech University, No. 1 Qianhu South Road, Yinzhou, Ningbo 315100, China 1  
Footnote 1: email: {cran.cran. loosens until it collapses. Therefore, improving the properties of hydration products of cementitious materials is a more controllable and manageable method to increase the durability of concrete structures. In the early 1990s, [PERSON], a British scholar, found that 70% of cement hydration products were calcium-silicate-hydrate (C-S-H) gel, and the cement slurry was composed of primarily nanomaterials condensed by C-S-H gel particles on a microscopic level [8]. [PERSON] [9] and [PERSON] [10] et al. found that the specific surface area of C-H-S gel was about 180 m\({}^{2}\).g\({}^{-1}\), and the average particle size of C-S-H gel was about 10 nm, which sets up a theoretical basis for the study of cement-based materials on the nanometer scale. Through the nano-modification of cement-based materials, we could further optimize the microstructure of cement-based materials, so as to strengthen the mechanical properties and durability of concrete structures. The main mechanism of nanomaterials on the acceleration of hydration is to react with Ca(OH)\({}_{2}\) and speed up the formation of C-S-H gel. The majority of studies [11; 12; 13; 14] have focused on nanosilica. The addition of Nano-SiO\({}_{2}\) could effectively decrease the content of free Ca(OH)\({}_{2}\) in cement paste [15] and cement mortar [16], through reacting with Ca(OH)\({}_{2}\) and reducing the ion exchange between the matrix and the external environment. As a result, the leakage of Ca\({}^{2+}\) can be controlled and the stability of the microstructure can be improved. Except for nanosilica, other nanomaterials have been investigated, including Nano-CaCO\({}_{3}\)[17], nanoclays [18], titanium dioxide [19], carbon nanotubes [20], graphene nanoplates [21; 22] etc. [PERSON] et al. [23] found that Nano-CaCO\({}_{3}\) could significantly accelerate the early hydration reaction, in which the accelerating effect is positively proportional to the dosage. The promotion was mainly found to be attributed to the acceleration of the hydration of C\({}_{3}\)S and the formation of the dominant hydration product, C-S-H gel, through the reaction of Nano-CaCO\({}_{3}\) and Ca(OH)\({}_{2}\), by the same group people and their colleagues [24]. Except for speeding up the hydration, other modifications have been studied by adding various nanomaterials, such as to the compressive strength [24; 25; 26; 27], deformation capacity and durability [24; 25; 26], corrosion resistance [28] and electrical conductivity and wave-absorbing properties [29]. With the addition of 1% and 3% Nano-SiO\({}_{2}\), the compressive strength of cement-based materials at 28 days could be increased by about 50%, and the deformation capacity and durability of cement-based materials were also significantly improved [24; 25; 26]. [PERSON] et al. [30] studied the performance changes of Nano-SiO\({}_{2}\)-modified concrete under the condition of a salt crystallization cycle by SEM (scanning electron microscope) and XRD (X-ray diffraction).