# Properties of a Lightweight Fly Ash-Slag Alkali-Activated Concrete with Three Strength Grades
## 2 Experimental Program
### Test Methods  
The slump test of the fresh concretes was conducted according to the Chinese standard GB/T 50080-2016 [29]. After 28 days of standard curing, according to the test method prescribed by [28], the apparent wet density and dry density of all the concretes were measured with small cubes (100 mm \(\times\) 100 mm \(\times\) 100 mm). For the apparent wet density, the samples \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Mix ID** & **FA** & **BFSP** & **SS** & **SH** & **Sand** & **NWA** & **LWA** & **Added Water** & **W/S** & **SP** \\ \hline NAAC-1 & 183 & 122 & 110 & 44 & 773 & 1094 & - & 13.1 & 0.29 & - \\ NAAC-2 & 234 & 156 & 122 & 49 & 764 & 1023 & - & 11.5 & 0.25 & 1.4 \\ NAAC-3 & 298 & 199 & 131 & 52 & 735 & 958 & - & 5.9 & 0.21 & 2.8 \\ LAAC-1 & 216 & 144 & 110 & 44 & 858 & - & 605 & 13.1 & 0.26 & 2.1 \\ LAAC-2 & 266 & 177 & 122 & 49 & 844 & - & 531 & 8.3 & 0.22 & 3.3 \\ LAAC-3 & 339 & 226 & 124 & 50 & 790 & - & 462 & 5.5 & 0.18 & 4.8 \\ \hline \hline \end{tabular} SSS–sodium silicate; SH—sodium hydroxide; NWA—normal-weight aggregate; LWA—lightweight aggregate; SP—superplasticizer.  
\end{table} 
Table 4: Mixture proportions of the alkali-activated concretes (AACs) (kg/m\({}^{3}\)). were directly measured on a dry surface in air. Before the dry density measurement, the sample was placed into an oven at 105 centigrade degrees until there was no more weight loss. Then, the dry density of the sample was calculated by measuring the weight and volume when the sample was cooled to room temperature under dry conditions. Ultrasonic pulse velocity (UPV) on the cube sample with the size of 100 mm \(\times\) 100 mm \(\times\) 100 mm was measured at 28 days using a PUNDIT (Portable Non-Destructive Indicating Tester) in accordance with ASTM C597-1640 (2009) [30]. A pair of transducers of 50 mm in diameter was performed across the cube at a frequency of 54 kHz, one as a transmitter and the other as a receiver. Since the moisture content of the concrete had an obvious effect on the UPV measurements, all samples were tested under the same saturated surface dry conditions to evaluate the measuring results of the different mixtures. In line with the Chinese standard GB/T50081-2002 [31], the compressive stress-strain relationship tests were carried out with prismatic specimens. The form and size of these specimens were described above. Uniaxial compression tests in this study were performed on a HUALONG (Jinan, China) WAW-800 servo hydraulic testing machine. The maximum loading scope of the testing machine is 800 kN, the precision is 0.0015 kN and the loading rate ranges from 0.01 mm/min to 10 mm/min. Details of the test setup and measuring instruments are shown in Figure 1. Two linear variable differential transformers were placed vertically on two opposite sides of the specimen to measure the axial (vertical) displacement, which were labelled as \"1#LVDT\". The 2# and 3# LVDTs were placed horizontally to monitor lateral displacement during loading. In the meantime, the axial and lateral strains of the control, NAAC and LAAC were also measured by the strain gauges, and Figure 1 also gives the arrangement of the strain gauges. The load was measured with a load sensor mounted on the top of the specimen. The load, strains, axial and lateral deformation of the specimens were collected and recorded by a Donghua-602 (Liyang, China) fully automatic data acquisition instrument, which has the capacity of record 100 data points per second. All the uniaxial compressive tests were performed at a displacement-controlling rate of 0.1 mm/min and ended when the load descended to 15% of the peak load. The axial deformation referred to in this study is the average value of the vertical LVDT and the axial strain gauges.