Study On Autogenous Shrinkage Characterization Of Cement Pastes Using Electrical Resistivity Measurement

The hydration characterization of cement-based material can be reflected by its electrical development when cement hydrating and the cement hydrating is the inherent reason of autogenous shrinkage which comes out after initial setting. There is an inner relationship between them and it is practicable to use electrical resistivity measurement doing research on autogenous shrinkage. The autogenous shrinkage of cement-based materials can be influenced by mineral admixtures and chemical admixtures like fly ash and expansive agent which is usually used in modern concrete technology. The main content and conclusions of the thesis is shown as follows. 1. The electrical resistivity and autogenous shrinkage development of cement pastes was investigated which were prepared with different water cement ratio at 0.3,0.35 and 0.4. The results show that the electrical resistivity and autogenous shrinkage of the cement paste decreased with the increase of water cement ratio. There is a positive relationship between the electrical resistivity and autogenous shrinkage of the cement pastes. 2. The electrical resistivity and autogenous shrinkage development of cement pastes was investigated which were prepared with different fly ash content at 10%,20% and 30%. The results show that: as the fly ash content increase, before setting, the electrical resistivity of the cement paste increased and decreased after hardening. And after 24 h, there is a linear relationship between the electrical resistivity and autogenous shrinkage of the cement pastes, which means the electrical resistivity can be used to predict the autogenous shrinkage of cement paste. 3. The evolution of electrical resistivity and autogenous deformation of Portland cement pastes with different dosages of expansive agent was investigated. The cement was replaced by 20% fly ash first which is used to ensure the cement content is the same, then 6%, 10% 14% expansive agent was used to replace the fly ash. The results show that the electrical resistivity and autogenous deformation of the cement paste increased with the increase of dosage of expansive agent. An empirical equation was summarized which can used to predict the autogenous deformation with the electrical resistivity and dosage of expansive agent. Compressive strength of these samples was also obtained, and the results show that the replacement of expansive agent at 6% have a best development in microstructure, it can compensate the autogenous shrinkage of paste and not decrease the long-term strength.