# Experimental Research on the Properties of Rock-Filled Concrete
## 1 Introduction  
Rock-filled concrete (RFC) is a new form of massive concrete with enough integrity, density, lower heat of hydration. It is formed by self-compacted concrete (SCC), with properties of good fluidity and anti-separation, filling into voids of filled rock through its self-weightty, without any need for vibrating compaction [1; 2; 3]. By comparison with common massive concrete, cement consumption of RFC is quite low, but its content of rock block (RB) is very high, which can dramatically reduce construction cost, remarkably shorten construction period, and improve construction efficiency as well [4]. Thus, RFC not only takes full advantage of low heat of hydration of SCC, but also makes the best of high strength of rock block [2; 4; 5]. In spite of a lower cement consumption, RFC has relatively high compressive strength, and was widely applied in hydraulic engineering in China for more than 60 newly constructed RFC dams [3], such as the Baoquan pumped storage power station (height of dam 36.90 m, completion date 2006/4), the Qingyu reservoir dam (height of dam 42.30 m, completion date 2012/11), the Hutiaxoxia reservoir (height of dam 55.00 m, completion date 2013/5), the Sangwan reservoir (height of dam 16.96 m, completion date 2011/9), the Koushang reservoir (height of dam 58.40 m, completion date 2013/9), as well as dam reinforcement projects, for example, the Hengshan reservoir dam risk removal and reinforcing project in Shanxi Province in 2010 [6]. The quality of RFC is mainly influenced by SCC, rock block, interfacial transition zone (ITZ) between SCC and rock block, so it is quite difficult to control the quality of RFC. How to control qualityof RFC has become a key subject in RFC projects, and has attracted the attention of many researchers. At present, research on the properties of RFC mainly focus on the mix proportions of SCC [6; 7; 8; 9; 10; 11], and properties of ITZ [12; 13; 14; 15; 16; 17]. Reasonable mix proportions of SCC, a key factor to guarantee SCC with high fluidity and good segregation resistance, and the performance of ITZ in RFC, have been widely researched by many scholars and engineers for decades. For example, the distribution law of porosity in ITZ [18; 19], the thickness of ITZ [12], the effects of ITZ on permeability and compressive strength [20], as well as elastic modulus of concrete [13], have been intensively studied, which has greatly boosted the development of RFC technology; but there remain some questions to be solved in this field. Because these studies are based on lab experiments, where the size, shape of rock block and the thickness of casting layer are quite different to actual projects, the decrease of rock block size will certainly influence the properties of RFC. The diameter of the rock block chosen was 150-200 mm by [PERSON] [5], and 53-75 mm by [PERSON] [15], while it may be up to 1 m in actual projects. It is well known that some concaves indentations on the surface of rock blocks and fractures within rock blocks decrease gradually as the size of rock blocks decreases; as a result RFC specimens in the lab cannot entirely represent the performance of RFC in actual projects. Especially, large sized rock blocks used in projects whose shape and joints are very difficult to control in construction will result in the formation of sealed spaces in the process of rock block piling, which can cause non-uniform RFC properties, with obvious and centralized defects, compared to lab RFC. Aside from the difference of rock block grade between the lab and actual projects, there exist many discrepancies, such as construction conditions, situation conditions, and worker experience, which can inevitably result in distinct deviations of RFC performance in actual projects. Unfortunately, research on this subject is scarce, and we do not know the performance differences of RFC produced in the lab and actual projects.