# Cow Dung Ash in Mortar: An Experimental Study
## 3 Results and Discussion
### Effects of CDA on Microstructure of Mortar  
#### 3.3.1 Thermal Decomposition  
Figures 7-9 illustrate and compare the thermogravimetric (TGA) analyses of mortar samples containing 10%, 20%, and 30% CDA, respectively, after being cured for 28 days. In all figures, the weight loss was determined by subtracting the level of the lower line y-axis from that of the upper line y-axis. According to Figure 7, after 28 days of curing, the mortar sample containing 10% CDA underwent a weight loss of 23% at a heating temperature of 450 \({}^{\circ}\)C due to the decomposition of CaO and water from C-H. The weight loss decreased by 8% after an increase in temperature to 500 \({}^{\circ}\)C, and then increased again up to a heating temperature of 600 \({}^{\circ}\)C. From 600 to 750 \({}^{\circ}\)C, the weight loss of the mortar sample significantly decreased by 15% due to the decomposition of water and the C-S-H gel, as well as the carbonation of CO\({}_{2}\) from CO\({}_{3}\). In the case of the 28-day cured mortar sample containing 20% CDA (Figure 8), the trend of thermal stability was almost similar to that of the 10% CDA sample. The mortar samples containing 10% CDA revealed that the Ca(OH)\({}_{2}\) dehydrated and lost approximately 25% its weight at a temperature of 450 \({}^{\circ}\)C, with only a 7% weight reduction up to 500 \({}^{\circ}\)C. Additionally, the figure elucidates that there was no further weight loss when the heating temperature was increased from 500 \({}^{\circ}\)C to 550 \({}^{\circ}\)C. However, both CaCO\({}_{3}\) and the C-S-H gel released CO\({}_{2}\) and water, respectively, and lost 13% of their weight as the temperature increased from 500 \({}^{\circ}\)C to 700 \({}^{\circ}\)C. Further increases in temperature did not appear to affect the thermal stability of the mortar. The percentage weight loss for the mortar sample containing 30% CDA, which was cured for 28 days, is presented in Figure 9. It can be noticed that the weight loss of the mortar continuously decreased with an increase in temperature up to 450 \({}^{\circ}\)C due to the evaporation of water from the C-H gel. It can also be observed that it exhibited a weight loss of 11% due to the evaporation of water from the C-H gel, which was relatively smaller than that of the 10% and 20% CDA mortar samples. Furthermore, the weight loss due to carbonation and dehydroxylation was insignificant compared to the other samples, with a combined weight loss of about 8% at a heating temperature between 450 \({}^{\circ}\)C and 700 \({}^{\circ}\)C. This indicates that either there were no CaO, CO\({}_{2}\), and H\({}_{2}\)O molecules in the C-S-H gel and CaCO\({}_{3}\), as all these oxides were released at a temperature of 450 \({}^{\circ}\)C, or the heating temperature might not have been sufficient in order to remove the oxides. Generally, for all the mortar samples containing 10%, 20%, and 30% CDA, the thermal stability of 28-day cementitious pastes would not be significantly affected in a temperature range of approximately 500-600 \({}^{\circ}\)C.  
Figure 7: TGA curve of CDA10 after 28 days of curing.