# Cow Dung Ash in Mortar: An Experimental Study
## 3 Results and Discussion
### Effects of CDA on Hardened Mortar Properties
#### 3.2.3 Compressive Strength  
Figure 4 illustrates the cube compressive strength of mortar specimens at different curing periods with varying percentages of cow dung ash. It can be observed from Figure 4 that there was a linear decrease in the compressive strength of the mortar with an increase in the percentage of CDA used, and the greatest reduction was observed for the specimens containing 30% CDA across all curing periods. The observed reduction in compressive strength is expected, given that the water absorption increased and bulk density decreased with increasing CDA content. The slow rate of strength development can be attributed to the low CaO content present in CDA. As a result, the formation of the C-S-H gel is hindered due to the reduction in cement content. Additionally, the presence of pozzolanas, known for reducing early strength and slowing down hydration, contributes to this delayed strength development. Regardless, in all cases, the strength of the mortar improved as the curing period progressed. The highest compressive strength, measuring 40.79 MPa, was achieved after 56 days, while the lowest value of 15.07 MPa was recorded after 3 days of curing. Based on the findings, there was no significant difference in the compressive strength of specimens containing 5% CDA and those in the control mix, and this result is consistent with the findings reported in [30]. Moreover, even at 15% replacement of cement with CDA,  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**CDA Content**} & \multicolumn{4}{c}{**Bulk Density [Kg/m\({}^{3}\)]**} \\ \cline{2-5}  & **3 rd Day** & **7 th Day** & **28 th Day** & **56 th Day** \\ \hline
0\% & 2568.80 & 2585.60 & 2589.86 & 2594.40 \\
5\% & 2560.00 & 2582.00 & 2588.00 & 2590.40 \\
10\% & 2493.34 & 2558.67 & 2561.34 & 2576.00 \\
15\% & 2489.34 & 2498.00 & 2555.08 & 2560.00 \\
20\% & 2466.66 & 2480.00 & 2513.20 & 2544.00 \\
25\% & 2452.00 & 2464.00 & 2492.50 & 2504.00 \\
30\% & 2428.00 & 2460.00 & 2480.96 & 2488.00 \\ \hline \hline \end{tabular}
\end{table}
Table 6: The bulk density of the reference and CDA-containing mortar specimens.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**CDA Content**} & \multicolumn{4}{c}{**Water Absorption [\%]**} \\ \cline{2-5}  & **3 rd Day** & **7 th Day** & **28 th Day** & **56 th Day** \\ \hline
0\% & 10.03 & 9.90 & 9.74 & 8.35 \\
5\% & 10.64 & 10.54 & 10.14 & 9.71 \\
10\% & 11.05 & 10.96 & 10.20 & 9.75 \\
15\% & 11.38 & 11.25 & 11.12 & 9.78 \\
20\% & 11.90 & 11.49 & 11.46 & 11.04 \\
25\% & 12.15 & 11.34 & 11.30 & 11.22 \\
30\% & 12.30 & 12.10 & 11.80 & 11.34 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Water absorption of the reference and CDA-containing mortar specimens.  
the reduction in compressive strength at the age of 56 days was not found to be significant. In comparison to the control mix sample, it was observed that at a curing time of 28 days, the compressive strength of the mortar specimens containing 20%, 25%, and 30% CDA decreased by 5.66 MPa, 6.51 MPa, and 8.87 MPa, respectively. As per the Indian Standard, IS 2250 [34], the cement and sand mortar should have a minimum compressive strength of 11.5 MPa and 17.5 MPa at the end of 3 and 7 days, respectively. It can be observed that all the mortars containing CDA samples met the specified standards.