## 2 Materials and Methods
### Methods
#### 2.2.2 Testing Methods  
X-ray diffraction (XRD) analyses of the powders and hydrated samples were conducted with a 3 rd generation Malvern Panalytical Empyrean XRD Diffractometer. Thermogravimetric analysis (TGA) of the blended cement was conducted with the Perkin Elmer DSC 7 analyser. The samples, after curing for 3, 7, 28 and 91 days, were blended and placed in the TGA equipment. The temperature was raised up to 1000 \({}^{\circ}\)C at a heating rate of 20 \({}^{\circ}\)C/min. Nitrogen gas of 50 mL/min was flashed into the chamber to avoid carbonation. As recommended by [PERSON] et al. [23], the blended cement samples were kept at 40 \({}^{\circ}\)C to allow for the removal of free water. The calcium hydroxide (CH) content of the samples was recorded after each curing period using equation 1 [23]. Calcium hydroxide content was calculated from the change in mass between temperatures 330 \({}^{\circ}\)C and 450 \({}^{\circ}\)C.  
\[CH,\,\%=\left[(Mass_{330^{\circ}\mathrm{C}}-Mass_{450^{\circ}\mathrm{C}}) \times\frac{4.113}{Mass_{40^{\circ}\mathrm{C}}}\right]\times 100 \tag{1}\]  
A thermometric TAM air conduction calorimeter was used to track the evolution of the hydration heat rate. Then, 5 g of the blended cement samples were mixed with distilled water and fixed inside the calorimeter at a working temperature of 20 \({}^{\circ}\)C. The attached computer automatically generated heat of hydration data continuously for up to 60 h.  
Using ASTM C305 [24], mortar samples were prepared for the determination of compressive strength using a water-to-binder ratio of 0.5 and a sand-to-binder ratio of 3. Mortar flow was determined according to methods prescribed by ASTM C1437 [25]. The Vicat method,  
Figure 3: XRD of calcined clay and silica fume.  
specified by ASTM C191 [26], was used to determine the normal consistency and setting times of all the cement samples. Soundness was determined using the Le Chatelier's apparatus as prescribed by EN 196-3 [27].  
A Frattini test was conducted with reference to BS EN 196-5:11 [28]. Then, 20 g of the samples were mixed with 100 mL deionised water in plastic vials, sealed tightly and kept at a temperature of 40 \({}^{\circ}\)C for 28 days. It was then filtered and titrated to determine the amount of Ca\({}^{2+}\) and OH\({}^{-}\). Determination of water sorptivity of the hardened blended cement paste was conducted utilising the sorptivity coefficient, as prescribed by ASTM C1585-13 [29]. Permeable porosity was determined using methods outlined by ASTM C642-13 [30].  
With reference to IS:13311 (part-1), ultrasound pulse velocity was used to determine how dense the hardened blended cement mortar was. This is an indication of how long it takes for a pulse to move from one side of the hardened mortar to the other using the ultrasound pulse velocity transducers. Drying shrinkage was determined according to the ASTM C490-07 standard [31]. The first reading was taken after 3 h of curing and recorded as \(L_{0}\). Final readings (\(L_{t}\)) were taken after 3, 7, 14, 28 and 91 days curing. The drying shrinkage of the samples were determined using Equation (2), where 250 (mm) is the effective length of the samples.  
\[\varepsilon_{t}=\frac{L_{t}-L_{0}}{250} \tag{2}\]  
For RCPT measurement, electrical current was allowed to pass through slices of mixed cement mortar samples for a total of six hours, using the ASTM C 1202 [32] RCPT technique. Sodium hydroxide and sodium chloride solutions were used to treat two slices of the same material, respectively. A potential difference of 60 V was preserved at the endpoints of the specimens. Samples were cured in water for 28 days before submerging in 5%-Na\({}_{2}\)SO\({}_{4}\) solutions to conduct the sulphate resistance test. Following a 90-day standing period, the impact of the 5%-Na\({}_{2}\)SO\({}_{4}\) solution on each subject's compressive strength and weight loss was assessed.