# Experimental Research on the Properties of Rock-Filled Concrete
## 3 Experimental Tests for the Properties of Rock-Filled Concrete
### Porosity of Rock-Filled Concrete  
According to the appearance of core specimens, there exist some obvious defects within RFC, so it is necessary to measure the porosity of RFC. For reasonable results, test specimens should be representative, with neither too many nor too few voids or defects on the core surface. Meanwhile, in order to fully know the distribution of voids of RFC in different part, we collect the specimens every few meters along the depth. The measurement of porosity of RFC is made by a drying method. The main instruments include an electronic balance with accuracy of 0.01 g, water container, drying box, etc. The main steps are as follows: first, specimens are dehydrated by placing them into an oven under a temperature of 105-110 \({}^{\circ}\)C for 24 h, and the specimens are weighed after cooling to room temperature; then immersed in methanol for 12 h to saturation, and the saturation specimen weight and specimen buoyant weight when submerged in methanol are measured, finally the porosity of specimens is calculated [23; 24; 25]. The relationship between the porosity of RFC core specimens and depth is shown in Figure 6.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Types of Defects** & **Defect Characteristics** & **Defect Picture** & **Reason for Defects** \\ \hline \multirow{8}{*}{Large sized void in ITZ between SCC and rock block width, 4.0 cm depth. Honeycomb shaped void on the SCC surface is shown. This type of defect, with small scale, is located in the ITZ, making strip shaped distribution. In some place of defect zone, cohesion of SCC with RB is well, but in other place is bad, with a few fractures or mud. & There are some great concaves or wide fractures, existing on the surface of rock block, which make air contain into concaves or fractures, not to release totally, thus to form bubbles, while SCC casting process. Such bubbles contained within RFC can result in this defect. & This defect is caused by air film or mud on the surface of rock block, formed in SCC casting process. This defect can result in bad cohesion of SCC with rock block. \\ \hline \multirow{8}{*}{Bad cohesion in ITZ} & This type of defect is due to joints within rock block, influenced by attitude of joints, some of which, with erect or steep, can have great effect on quality of RFC. & The reason of this defect is joints containing in natural RB. If RB is very large, the number and scale of joints is also great, which can lead to great defects. \\ \hline \multirow{8}{*}{Void within SCC} & This type of defect exists in SCC, presenting sphere shape, with large number and small scale, some of which are relatively large, with 10 cm diameter, 5–10 mm depth. & This defect results  
As seen in Figure 6, the porosity of core specimens ranges from 0.34% to 22.37%, with great variation, which shows that the distribution of porosity is uneven, and some large voids exist in RFC. The average porosity of RFC in boreholes No. 1-6 was 12.74%, 12.53%, 11.78%, 12.53%, 14.97%, 21.71% respectively, with a total average porosity of 14.10%. A large porosity can indicate that the density of RFC is poor with a relatively loose structure and some defects in the area. The porosity of RFC obtained in our tests is larger than that stated by [PERSON] et al. [3], the core specimens in our tests were extracted along the dam height with some from the inner dam, hence the quality is difficult to control, compared with RFC samples gathered from the surface layer of poured RFC by trenching in [PERSON]'s test [3]. The porosity of RFC fluctuates with depth, which reveals the density of RFC changed, as the quality of RFC at the surface layer of the workspace is good, whereas at the bottom layer it is relatively bad. Likewise, the porosity data show a great dispersion, indicating obvious non-homogeneity of the RFC with some uneven defects.