# Temperature Impact on Engineered Cementitious Composite Containing Basalt Fibers
## 2 Materials and Methods
### Mix Designs and Preparation of Specimens  
The geometrical characteristics and volume fraction of the chopped fibers and matrix rheology are among the most important parameters in the mix design that may strongly affect the fiber distribution in the ECC matrix [76]. The parameter for fiber volume fraction has been widely examined in the studies presented in the literature review. The amount of BF content in ECC mixes in the previous studies generally ranged from 1% to 5% of the total ECC volume. However, the findings in these studies suggest using a fiber volume fraction of 2.5%. Based on the literature, fibers with shorter lengths have shown better distribution, while the longer length of chopped BFs provides a more efficient crack-bridging ability. Hence, an average length of 10 mm was selected for the utilized BFs, which is consistent with the literature. To determine the proportions of cementitious composite, in the experimental study, a base mix was designed to achieve a target 28 day cylinder compressive strength of 40 MPa. For the control mix, the proportioning of the ingredients is as per Table 3. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Length of Fiber** **(mm)** & **Equivalent** **Diameter (\(\upmu\)m)** & **Water Absorption(\%)** & **Tensile Strength** **(N/mm\({}^{2}\))** & **Melting Point** **(C.)** & **Elastic Modulus (GPa)** & **Ultimate Elongation (\%)** \\ \hline
10 & 13–20 & \textless{}0.5 & 4100–4800 & 1050 & 93–110 & 1.3–3.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mechanical characteristics of basalt fiber (BF). Figure 1: The basalt fibers (BFs) used in the production of the ECC mixture. The mix proportion of the BF-ECC in this experiment was the same as the mix design as the reference mix, while the BF and superplasticizer contained 2.5% of the volume fraction and 7.84 (kg/m\({}^{3}\)) of the ECC content, respectively. Water-reducing admixture was added to the ECC to obtain the same flow compared to the reference mixture. The utilized water-reducing admixture was a polycarboxylate-based superplasticizer with a specific gravity of 1.05 (g/m\({}^{3}\)) and pH of 7. The ratios of the sand, fly ash, and water to cement in the reference and fiber-included mixes were 0.8, 0.25, and 0.37, respectively. Uniform fiber distribution is a crucial factor for enhanced mechanical properties, especially tensile strength and ductility in ECC [76]. Applying a correct mixing sequence of the material can enhance the mechanical properties and improve fiber distribution [77]. In the first step, the ingredients were weighed and prepared separately. The equipment used for mixing ingredients was a rotary 60-L pan-type concrete mixture supplied with 220 V AC power and a frequency of 50 Hz. The mixing rotational speed of the mixture was around 35 rpm in compliance with EN 12390-2. In the first stage, the solid ingredients, including silica sand, cement, and fly ash were premixed in a mixing vessel with a nominal speed for a couple of minutes before liquid loading. At the same time, the superplasticizer was added to water and stirred for 2-3 min. Then, the liquid mixture was poured into the dry mixture and mixed for another 3 min in accordance with the procedure explained by [PERSON] et al. [78]. The fibers were split into strands for a more even dispersion in the cementitious matrix and to prevent agglomeration. Then the well-separated fibers were uniformly sprinkled into the cementitious composite while the stirring mill was working at normal speed for 3 min. Typically, an even fiber distribution and proper consistency of the cementitious mortar can be achieved after 3 min of mixing time advised by [PERSON] et al. [79] and [PERSON] et al. [80]. The mix of composition continued for 7 min at normal speed to ensure an even distribution of the chopped fibers in the mixture. The fresh ECC was poured into molds and compacted according to the ASTM standards.