## 1 Introduction  
Pervious concrete is one of the most typical components in the construction of sponge cities. The purpose of sponge cities is mainly to alleviate the heat island effect and to improve the hydrological environment of the city [1, 2]. Previous concrete is a kind of special porous concrete that is not prepared by physical or chemical foaming but by using gap-graded aggregates, usually without fine aggregates. Previous concrete has a large number of tortuous and interconnected pores. Rainwater can be drained off into the groundwater through these pores [3, 4]. Although the spatial structure of a pore, such as pore size, tortuosity, connectivity, and pore distribution, has an influence on the permeability coefficient, strength and durability of the pervious concrete to a certain extent, the porosity is still the controlling factor of these characteristics [5, 6]. Therefore, the current mix design methods of pervious concrete are based on the porosity [7, 8]. However, the design method of [PERSON]'s permeable concrete is too complex to adapt to the actual engineering environment [7]. The design method of CJ/T-135 is too simple [8], and the theoretical results are quite different from the actual results. Meanwhile, it is expected that a sufficient supply of aggregates has a significant impact on the development of pervious concrete. Therefore, China's restrictions on the exploitation of natural pores have created favorable conditions for the utilization of iron tailings [9]. Iron tailings are a kind of mining waste produced from the concentration of iron ore in the beneficiation process [10]. At present, there are approximately 5 billion tons of iron tailings in China, and the annual growth rate is approximately 600 million tons [11]. However, the utilization rate of iron tailings is only 7% [12]. Iron tailings are mainly used for recovery [13], fire blocks [14], ceramsite [15], concrete aggregate [16], mineral admixture in the process and concrete industry [17], and additions in the ceramic industry [18] and other fields. Work by [PERSON] [19] studied the heavy metal leaching of iron tailings, which shows that the concentration of heavy metal leaching of iron tailings is within the range of Chinese standards of GB/T 5085.3 [20]. Table 1 summarizes the variables and properties of pervious concrete using different aggregates [21; 22; 23; 24; 25; 26; 27; 28]. We can draw two conclusions from Table 1: (1) The substitution of solid waste for the natural aggregate of pervious concrete has attracted much attention. (2) The variables of the studies mainly focus on the replacement amount and aggregate size as well as the binder type and curing conditions. Although investigations on pervious concrete have been reported extensively, there are few reports on the feasibility of iron tailings as coarse aggregates in pervious concrete. In this paper, iron tailings-based pervious concrete with different target porosities was prepared by a mix design procedure to study the feasibility of iron tailings as coarse aggregates. The effective porosity, measured porosity, dry density, compressive strength and permeability coefficient of the pervious concrete were measured and analyzed to obtain the key technologies for preparing iron tailings-based pervious concrete.