| dc.description.abstract | Calcium sulfoaluminate cement is a kind of calcium sulfoaluminate (C4A3S̅), dicalcium silicate (also known as Belite soil, abbreviated as C2S) and tetracalcium aluminum ferrite (C4AF). The special cement composed of ingredients has the properties of rapid early strength development, short setting time, good fluidity and small dry shrinkage. In consideration of its chemical reaction and economical considerations, calcium sulfoaluminate cement clinker (CSA) is required , Portland Type I cement (OPC) and anhydrous gypsum (CS̅) are blended together to form calcium sulfoaluminate cement composite cement.
This study will be divided into three phases: ＂the influence of material parameters on the hydration characteristics and strength development of cement paste＂, ＂research on engineering properties of CSA cement mortar＂, and ＂establishment of multiple relationship of CSA cement mortar＂. The first stage is mainly to prepare cement slurry with a fixed water-binder ratio of 0.30, according to the difference between the binary binder system (CSA - CS̅ system, OPC - CSA system) and the ternary binder system (OPC - CSA - CS̅ system) Proportion combination, evaluate the interaction between materials, and explore the relationship between the ratio of different materials and hydration characteristics and its development potential as super early strength cement; the second stage mainly uses cement mortar to verify its hydration characteristics and hardening characteristics , and evaluate whether the CSA cement composite binder meets the requirements of the ASTM C1600 standard based on safety and durability; the third stage mainly uses non-destructive testing methods to establish the strength development of the CSA cement composite binder based on the results within one day of age At the same time, evaluate the relationship between the proportion of materials and their hydration properties, hard solid properties and durability properties, and establish a ternary phase diagram.
In terms of cement paste, increasing the proportion of CS̅ in the CSA-CS̅ system can be beneficial to its early and late strength development. The cement slurry specimen with a water-binder ratio of 0.30 can reach a maximum of 68 MPa in 3 hours, and it is still strong at 28 days. It can have a compressive strength greater than 110 MPa. At the same time, when the amount of CS̅ is sufficient (CS̅/CSA = 1/2, 1/3), it can meet the setting time requirements of ASTM C1600. In the OPC-CSA composite binder system, when the CSA content is higher than 20%, its final setting time will be less than 10 minutes, and its early (within 24 hours) strength development tends to increase with the increase of CSA content. When it is 25%, it can have better development potential of super early strength cement, but the strength development after 1 day of age will decrease with the increase of CSA content.
For cement mortar, the CSA - CS̅ system (CS̅/CSA = 1/2, 1/3, 1/4, 1/5) can meet the strength requirements of the MRH grade in ASTM C1600, while OPC - CSA and OPC - CSA - The CS̅ system performs best with high CSA content and high CS̅ ratio. Among them, when the ratio of OPC = 70 % and CS̅/CSA = 1/2, it can meet the strength requirements of the MRH grade. The ratio of OPC = 70 % and CS̅/ CSA = 1/3 means that it has a strength performance close to GRH level; in terms of durability, the order of durability is CSA - CS̅ system > OPC > OPC - CSA - CS̅ system > OPC - CSA system > CSA.
In terms of non-destructive testing, when the maturity method is used to evaluate the relationship between the compressive strength of cement paste, the relationship between the two has a good correlation at 3 hours and 6 hours (R2 > 0.8); but as the strength after 24 hours The detection method is relatively inaccurate (R2 = 0.1 ~ 0.8); and the ultrasonic wave velocity method has a strong correlation (R2 > 0.95) in evaluating the compressive strength of cement paste, which shows that it is feasible as a strength detection method; When discussing the relationship between various proportions and different properties in the meta-phase diagram, it is possible to conduct experiments with fewer proportions, and predict the results of other proportions that have not been tested under the same age and different proportions under the same water-cement ratio conditions. And the trend can be judged by the color of the color block. | en_US |