I'm measuring the setting time of a calcium phosphate cement using an apparatus that records how much resistance a needle (connected to a load cell) encounters over time. This process provides data on time and weight (in grams), which I then convert into tension in MPa. My question is, how can I determine the initial and final setting times? The samples being tested have visible identification marks throughout the 3-hour measurement period. Attached is a result of a measurement in the time interval of 10 min, as an example.
The initial and final setting times of calcium phosphate cement (CPC) can vary based on its composition and specific formulation. Generally, the setting times are as follows:
1. **Initial Setting Time**: This is the time period during which the cement paste starts to lose its plasticity and begins to harden. For calcium phosphate cement, the initial setting time typically ranges from about 5 to 15 minutes.
2. **Final Setting Time**: This is the time period required for the cement paste to completely lose its plasticity and attain sufficient hardness. For calcium phosphate cement, the final setting time is usually in the range of 30 to 60 minutes.
These times can be adjusted by modifying the cement composition, the liquid-to-powder ratio, the temperature, and the presence of setting accelerators or retarders. It's essential to follow the specific manufacturer's guidelines for precise setting times of a particular CPC formulation.
according to this book - DOI: 10.5772/intechopen.74607
The initial setting time of calcium phosphate cement (CPC) refers to the time it takes for the cement to lose its workability after being mixed with a liquid. The final setting time indicates when the cement has completely hardened.
These times can vary depending on the specific formulation of the CPC, but typical ranges are:
i. Initial setting time: 5-15 minutes
ii. Final setting time: 15-45 minutes
Several factors can influence the setting times of CPC, including:
1. Liquid-to-powder ratio: A lower liquid-to-powder ratio will generally result in faster setting times.
2. Particle size and morphology: Smaller particles and more elongated morphologies can lead to faster setting.
3. Setting modifiers: Additives can be incorporated into CPC to accelerate or retard setting.
ASTM C403 provides a good example of how to create a plot that shows initial and final setting times, defined as 3.5MPa and 27.6MPa by C403. C403 is a penetration test using a spring-loaded device. It sounds like you might be using a Vicat method. ASTM C191 covers setting times for hydraulic cement using a Vicat needle. I expect that ASTM also tells you how to calculate initial and final setting times.
At first you need to plot those data...
Imagine the tension data plotted as a graph with time on the x-axis and tension (MPa) on the y-axis. In the initial stages, the tension will gradually increase as the cement starts to stiffen. This initial rise will be reflected in a positive slope on the curve.
As the cement reaches its initial setting time, the rate of tension increase will slow down. This slowdown corresponds to the minimum point on the derivative curve, which will appear as a flattening or a slight dip in the slope of the tension data curve.
Following the initial setting, the tension will continue to increase at a slower pace until it reaches the final setting time. This phase will be reflected by a renewed increase in the slope of the tension data curve. The final setting time corresponds to the maximum point on the derivative curve, where the slope reaches its peak before starting to decline again.
By examining the tension data curve and its derivative, you can pinpoint these inflection points to determine the initial and final setting times of your calcium phosphate cement.
- Badges
- Science topic
- Similar topics
- Chemistry