Fluorescence Visualization Study Of Cement Hydration Process

Traditional SEM,X-ray diffraction,calorimetry and so on are usually used in the early research of cement hydration process.These methods often describe the overall reaction changes,and cannot analyze and monitor the interaction between different species,such as the combination process and chemical reaction between additives and different minerals.Therefore,a simple and intuitive method is needed to observe the change process of single ore in the hydration process,to clarify the interaction between cement minerals and additives and cement hydration mechanism,so as to provide more research approaches for the design and synthesis of new high-performance cement concrete.Due to the complex cement system,this paper selected the most important single ore-tricalcium aluminate（C₃A）and tricalcium silicate（C₃S）to focus on the research.Because polycarboxylate acid water-reducing agent（PCE）is an important additive in cement concrete,the surface functional group is rich,the small molecule N-（amino-ethyl piperazine）（AEP）grafted on the fluorescent dye PCE-AEP can emit blue fluorescence;Then,the hydration process of C₃A and C₃S was observed by laser confocal microscope using PCE-AEP as fluorescent dye.Finally,the mixing system of C₃A and C₃S is studied,and it is found that the proportion of raw materials can be determined by comparing the fluorescence area,which is of great significance for the identification of single mineral in the mixing system,and thus the visualization research of cement hydration process is prelim natively realized.The specific work of this paper is as follows:1.Suitable fluorescent dyes are screened by fluorescence intensity analysis.Fluorescein isothiocyanate,fluorescent peach B,Rhodamine B,PCE-AEP and other fluorescent dyes were added to the suspension of C₃A,C₃S,gypsum,C₃A+gypsum and ettringite.The selection conditions of fluorescent dyes were good water solubility,stable luminescence under strong alkaline conditions and a large number of calcium ions.Then the laser confocal microscope was used to observe the fluorescence intensity of each sample.After analysis,it was found that PCE-AEP could distinguish the difference of C₃A and C₃S,so as to realize the discrimination observation under the mixed system of C₃A and C₃S.2.Real-time laser confocal observation of single ore hydration.The fluorescence changes of C₃A and C₃S during hydration were observed by confocal laser microscopy.It was found that the hydration rate of C₃A was slowed down with the increase of gypsum content.The addition of PCE also slows down the hydration rate of C₃A.Due to the slow hydration rate of C₃S,the obvious fluorescence changes of C₃S could not be observed by laser confocal microscopy within 2 h.The results of XRD and hydration heat measurement can also prove the correctness of the observation results.3.Hydration observation of C₃A and C₃S mixed system.Five groups of samples with different mass ratios were set up for laser confocal microscope observation,and the same amount of PCE-AEP fluorescent dye was added,and the static hydration for 2 h.The total organic carbon adsorption detection and Zeta detection were performed simultaneously to verify the laser confocal observation results.The results showed that the fluorescence intensity of C₃A was much higher than that of C₃S after staining,indicating that the adsorption of C₃A to water reducing agent was much higher than that of C₃S.At the same time,the detection results of TOC and Zeta also show that the observation results are correct.By comparing the fluorescence area of minerals with the proportion of raw materials,the ratio of C₃A and C₃S can be determined quantitatively,which realizes the quantitative observation of hydrated minerals by fluorescence method.