Speaker
Description
This paper presents a mathematical model developed to investigate the thermal modeling of calcium aluminate cement (CAC). A control volume is employed to simulate the heat balance behavior in CAC blocks with dimensions of 16 cm × 4 cm × 4 cm. These blocks were exposed to a constant temperature of 1450 °C to analyze the thermal effects during times.
Figure 1- The one-dimension control volume
Applying a heat balance approach to the control volume leads to the temperature distribution formula shown in Equation (1)
(1)
This partial differential equation is solved using an explicit finite difference method, assuming uniform boundary and initial temperatures
(2)
The CAC used in this study contains 50% Al₂O₃. The mixtures consist of 150 g of calcium aluminate cement with 450 g of silica sand and 75 cc of water are cured in a chamber maintained at 20 ± 1 °C and 90% relative humidity for 24 hours. The blocks were then exposed to uniform heat at 1450 °C for different time intervals.
Figure 2 illustrates the temperature distribution across the x-direction of the blocks over time. After 8 hours, the temperature becomes uniform.
Figure 2- Variation of temperature inside CAC blocks
Mechanical strength of different blocks (σc) is measured and the following empirical exponential decay formula is developed. Where, σ0 is initial mechanical strength (MPa), φ is porosity and m is constant (here is 0.55 to yield the best fit for experimental data, see Figure 3)
(3)
Porosity is calculated using a straightforward approach.
(4)
Figure 3- Mechanical strength prediction
The mechanical strength degradation is attributed to phase decomposition, porosity increase, cracks, and loss of ceramic bindings.
Effects of changing the physical parameters of the CAC like conductivity, density, and heat capacity can be investigated simply by changing them in the model.
Affiliations
Quality Control Department, Modalal Cement Company, Kermanshah, Iran
| Keywords | Calcium-Aluminate, Cement, CAC, Modeling, Mechanical strength |
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