Influence of superplasticizer on composition and pore structure of C–S–H

Calcium Silicate Hydrates (C–S–H) is the main products of cement hydration, influence of different organic component (organic macromolecular or polymers) on composition and structure of calcium silicate hydrate has important implications. Pore structure parameters of pure C–S–H with specific surface area of 43.67 m2/g and average diameter of 9.75 nm (A), polycarboxylic organic macromolecular doped C–S–H with specific surface area of 139.86 m2/g and average diameter of 9.81 nm (B) and aliphatic organic macromolecular doped C–S–H with specific surface area of 114.96 m2/g and average diameter of 14.87 nm (C) were calculated based on nitrogen isotherm of adsorption and desorption, and the fractal dimension was calculated using two types of model (FHH and Neimark). The results show that compared with aliphatic organic macromolecule, polycarboxylic organic macromolecule is apt to form mesopore with smaller pore diameter, which contribute more to the total pore volume and have little effect on large pore. Aliphatic organic macromolecule contributes more to form mesopore with larger pore diameter and have little effect on smaller pore. Two kinds of organic macromolecule have effects on surface fractal characteristics, and the sequence of fractal dimension is A > C > B, which shows that the roughness or irregular degree of C–S–H becomes weak gradually, surface of samples becomes smooth. Difference between the surface fractal dimension of samples A and C derived from FHH and Neimark equation is not obvious compared to sample B.