# Influence of Aggregate Gradation on the Engineering Properties of Lightweight Aggregate Concrete
## 2 Experimental Details  
Artificial lightweight aggregates and natural normal weight aggregates were used to manufacture concrete in this research. The test materials included clean water, Type I Portland cement of Taiwan Cement Company (specific gravity = 3.15), normal weight coarse aggregates from a local river of Taichung City in Taiwan (specific gravity = 2.65, water absorption = 1.1%), normal weight fine aggregates (Taichung City, Taiwan) (specific gravity = 2.61, water absorption = 1.2%), and expanded shale lightweight aggregates (Figure 1), which were supplied from TianJin BaoMing Co., Ltd. of China. Three lightweight aggregates grades with uniform size were selected. The nominal grain sizes were 16 mm, 11 mm and 7 mm. A standard gradation fit with the ASTM C330 specification was used as the control batch. The maximum grain size was 19 mm (D\({}_{\text{max}}\) = 19 mm). The basic properties of lightweight aggregates are shown in Table 1. To obtain concretes with similar unit weight, selected lightweight aggregates from each grain size possess similar specific gravity and water absorption. In addition, the specific surface area (SSA = surface area of aggregates/volume of aggregates) defined by [PERSON] [13] was treated as an index of the aggregates grade. The SSA of three uniform-sized aggregates and the standard aggregate grades were calculated. The amount of aggregate for each grade and the SSA calculation are shown in Table 2. The relationship between the nominal grain size and aggregates SSA is drawn in Figure 2.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Grain Size (mm)** & **Nominal Grain Size (mm)** & **Particle Density (kg/m\({}^{3}\))** & **24 h Water Absorption (\%)** \\ \hline
12.5–19 & 16 & 1460 & 8.77 \\
9.5–12.5 & 11 & 1460 & 8.00 \\
4.75–9.5 & 7 & 1490 & 7.12 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Basic properties of lightweight aggregates.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Gradation**} & \multicolumn{3}{c}{**Amount (\%)**} \\ \cline{2-4}  & **19–12.5 mm** & **12.5–9.5 mm** & **9.5–4.75 mm** \\ \hline Standard gradation (S) & 40 & 30 & 30 & 573 \\ Nominal grain size 16 mm & 100 & 0 & 0 & 381 \\ Nominal grain size 11 mm & 0 & 100 & 0 & 545 \\ Nominal grain size 7 mm & 0 & 0 & 100 & 857 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Gradation and specific surface area (SSA) of coarse aggregates.  
Two water-cement ratios (w/c), 0.4 and 0.7, were selected to investigate the aggregate grade impact on the concrete properties. Under a fixed w/c, the amount of mortar, and aggregate volume, the aggregate grade was the only variable that was changed. The aggregates' grade effect on the concrete properties was explored. The differences between LWAC and NWC were analyzed and compared. The LWAC and NWC test mix-proportions are shown in Tables 3 and 4. In these tables, L indicates LWAC while N means NWC, and 0.4 indicates w/c. S represents the standard aggregate grade that met the ASTM C33 or ASTM C330 specification, and 16 means aggregates with a nominal grain size of 16 mm, respectively. The lightweight aggregates were oven-dried and pre-wet before mixing (the amount of 30 min water absorption was used).