# Influence of Milling Techniques on the Performance of Wheat Straw Ash in Cement Composites
## 2 Materials and Test Methods
### Mix Proportions and Experiments  
Mortar mixes were prepared using constant sand-binder and water-cement ratios of 2.75 and 0.4, respectively in accordance with ASTM C109 [27]. Table 2 reports the mix proportions. W1, W2, and W3 types ash were used to replace cement at a level of 20% (by weight) and denoted as W1/20, W2/20, and W3/20, respectively. Mortar cubes and prisms were made following ASTM C109 and ASTM C348 [27; 28], respectively. After 24 h, mortar specimens were detached from the molds and positioned in lime-rich water for further curing till designed testing age. Paste specimens were cast in poly vinyl chloride molds using a water-cement ratio of 0.4. The molds were sealed and kept in a curing chamber for 24 h at 20 \({}^{\circ}\)C; and 90% relative humidity. After a period of 24 h, the specimens were removed and kept in lime-saturated water for additional curing. The portions of the specimens crushed during compression testing were utilized to make specimens for SEM investigations. Thin specimens for SEM analysis were acquired and submerged in alcohol for 1 day then dried in a laboratory-scale oven at 60 \({}^{\circ}\)C; in accordance with the protocol discussed in reference [29]. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Composition**} & \multicolumn{8}{c}{**Weight (\%)**} \\ \cline{2-9}  & **OPC** & **WSA (Present Study)** & **RHA [11]** & **RSA [12]** & **POFA [14]** & **BA [13]** & **CCA [15]** \\ \hline SiO\({}_{2}\) & 20.81 & 65.71 & 91.9 & 76 & 57.7 & 87.4 & 66.38 \\ Al\({}_{2}\)O\({}_{3}\) & 6.30 & 3.74 & 0.25 & 0.69 & 4.5 & 3.6 & 7.48 \\ Fe\({}_{2}\)O\({}_{3}\) & 3.21 & 2.59 & 0.41 & 0.63 & 3.3 & 4.9 & 4.44 \\ CaO & 62.0 & 7.85 & 0.38 & 4.96 & 6.5 & 2.56 & 11.57 \\ MgO & 3.31 & 2.69 & 0.21 & 2.65 & 4.2 & 0.69 & 2.06 \\ Na\({}_{2}\)O & - & 2.46 & 0.05 & 1.36 & 0.5 & 0.15 & 0.41 \\ K\({}_{2}\)O & - & 3.28 & 2.78 & 9.89 & 8.2 & 0.47 & 4.92 \\ P\({}_{2}\)O\({}_{5}\) & - & 1.68 & 0.36 & - & - & - & - \\ SO\({}_{3}\) & 2.21 & 2.35 & - & 1.9 & 0.2 & 0.11 & 1.07 \\ LOI & 1.31 & 7.33 & 2.93 & - & 10.5 & 8.25 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of used WSA and other ARAs. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Mix ID**} & \multirow{2}{*}{**Cement (g)**} & \multicolumn{2}{c}{**WSA (g)**} & \multirow{2}{*}{**Sand (g)**} & \multirow{2}{*}{**Water (g)**} \\ \cline{3-4}  & & **W1** & & & & \\ \hline REF & 100 & 0 & 0 & 0 & 275 & 40 \\ W1/20 & 80 & 20 & 0 & 275 & 40 \\ W2/20 & 80 & 0 & 20 & 0 & 275 & 40 \\ W3/20 & 80 & 0 & 0 & 20 & 275 & 40 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mix proportions of mortar mixes. The particle size distribution and specific surface area of the ashes after each grinding process was studied using particle size analyzer (Malvern Mastersizer 2000), and surface area analyzer (3 Flex, micromerities instruments), respectively. X-ray fluorescence (XRF) (S8 Tiger) was used to obtain the chemical composition of the ash specimens. An X-ray diffractometer (RINT D/max 2500, 40 kV, 30 mA, scanning speed 2\({}^{\circ}\)/min, wavelength 1.54 A) was used to identify the amorphous and crystalline phases of SiO\({}_{2}\) in the ash specimens. Compressive strength of the mortar specimens was examined using a universal testing machine (UTM) (Shimadzu, CCM-200A; Shimadzu Corporation, Japan) at curing ages of 7, 28, and 90 days. Three replicates were used for each mix. Flexural strength of mortar prims was measured following ASTM 348 using a three-point bending machine (AG-I, Shimadzu, 250 kN, Shimadzu Corporation, Japan). Three samples were tested for each mix. The heat released from the paste specimens were measured using an Isothermal calorimeter (TAM AIR, TA Instruments, USA) at 23 \({}^{\circ}\)C for 40 h. Paste specimens were mixed and firmly sealed inside a high-density polyethylene (HDPE) container instantly after mixing and then placed inside the calorimeter. It is because of this reason initial peak could not be accurately measured.