## 2 Experimental Investigation
### Materials  
Two types of reinforcing bars--namely, basalt FRP, and steel bars--are used in this study. The basalt fibre-reinforced polymer (BFRP) bars were provided by Jiangsu Ocean-power New Material Technology Co., Zhenjiang, China. The BFRP bars were produced via a pultrusion process, in which the continuous basalt fibres were embedded in an epoxy resin with minimal fibre volume. The bars used in the study were 400 mm long, with two bar diameters of 6 mm and 10 mm, and a spiral-wound surface. The steel rebars used in this study were 10 mm deformed steel bars from a local manufacturer.  
The mechanical properties of the BFRP and steel bars were previously compared by the second author [24] in a study on the bond behaviour of basalt FRP bars in normal concrete. The material properties of the BFRP bars were then cross-checked against those given by the manufacturer at Deakin's testing facility [24]. The test results confirmed the values provided by the manufacturer, and the results are detailed in Table 1 below.  
The steel bars and the basalt FRP bars used in this study are also shown in Figure 1 below:  
The concrete used in this study is a 40 MPa novel ambient-cured self-compacting geopolymer concrete (SCGC) developed by the authors [8]. The SCGC, which was produced in the Structures Laboratory at Deakin University's Geelong Waurn Ponds Campus, exhibits self-compacting properties and eliminates the need for compaction and vibration of the specimens [9; 25; 26]. The newly developed SCGC consists of fly ash, slag, and micro fly ash as binder materials and anhydrous sodium metasilicate as an alkali activator, along with fine and coarse aggregates without use of any superplasticisers. The fly ash and micro fly ash for the SCGC are sourced from Cement Australia and Fly Ash Australia, respectively. Also, the slag and sodium metasilicate are sourced from Independent Cements and Redox, Melbourne, Australia respectively.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Bar Type**} & **Nominal Diameter** & **Tensile Strength** & **Elastic Modulus** \\  & **(mm)** & **(MPa)** & **(GPa)** \\ \hline BFRP & 6 & 1000 & \(\geq\)55 \\ \hline BFRP & 10 & 1260 & \(\geq\)55 \\ \hline Steel & 10 & 620 & 200 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mechanical properties of BFRP and steel bars [1].  
Figure 1: Basalt FRP and steel pull-out bars used in this study.  
The mixing and casting of the SCGC was carried out using the same procedure as mentioned in the previous study by the authors [8]. The mixing, casting, and curing of the pull-out specimens was carried out in laboratory environmental conditions of 23 \(\pm\) 2 \({}^{\circ}\)C at a relative humidity of 50% in Deakin University's Geelong Waum Ponds Campus. Prior to casting, the fresh properties of the SCGC were determined using the slump flow and T500 tests. In this study, 12 additional cylinders (200 mm \(\times\) 100 mm) were prepared from the same batch of SCGC in order to determine the mechanical properties after 28 days of curing under ambient conditions. The additional cylinders will help in confirming the mechanical properties of the pull-out specimens. The mix proportion and average strength characteristics of the SCGC used in this study are given in Table 2 below [8]:  
A laboratory pan mixer with a maximum capacity of 200 kg was used for the mixing of the SCGC, and the slump flow and T500 of the SCGC mix were tested using an Abrams Cone. The slump flow of the current SCGC mix is shown in Figure 2 below: