## 1 Introduction  
Global urbanization is the inevitable outcome of rapid social and economic development. The speed of urbanization has reached an unprecedented level over the past few decades. During the progress of urbanization, impervious pavement materials, such as cement concrete and asphalt concrete, have expanded rapidly, and almost all city areas have been covered with these impermeable materials, thereby causing major and fatal urban flooding [1; 2; 3]. Multiple flood disasters have proven that conventional rainwater management approaches and existing flooding defense structures are ineffective. It is extremely urgent to seek new solutions for the mitigation of flooding impacts and urban water management [4; 5; 6; 7]. Pervious concrete, as an important part of a sponge city, was developed as an alternative to traditional impervious pavement materials [8; 9]. Its porous structure enables storm water to permeate into the ground and mitigate storm water runoff. Due to its unique structure, pervious concrete has had many other advantages with regard to alleviating the urban heat island effect, reducing noise pollution, improving water quality, and maintaining the urban ecological balance [10; 11; 12]. These advantages have made pervious concrete an environmentally friendly and sustainable material in paving applications. The development of the automotive industry has led to worldwide pollution from waste tires. Incineration is the most simple and direct way to dispose of waste tires. However, this method will cause serious environmental pollution and is forbidden in many countries [13; 14]. Lots of effort has been made to recycle and reuse waste tires in a more environmentally friendly and economical way [15]. Generally, it is an effective method to smash tires into crumb rubber or tire chips and use them as additives in pavement materials. The main component of waste tires is cross-linker copolymer, which has a certain recovery deformation ability [16; 17; 18]. Waste tire rubbers are usually classified into different particle sizes, and are used as partial or full aggregate replacements in pavement materials. They have been used as additives in ordinary cement concrete and asphalt concrete for many years and are verified as a positive material in improving ductility and freeze-thaw durability [19; 20; 21]. Many studies have been conducted on waste tire rubbers as an additive in traditional cement concrete and asphalt concrete. The effect of rubber addition on the properties of mixtures is related to rubber type, particle size, and incorporation level [15]. In general, rubber incorporation into cement concrete and asphalt concrete has a negative effect on the concrete's mechanical properties. However, it can greatly improve concrete's anti-deformation ability and durability, which makes rubber modification widely used as an additive. Granulated rubber has generally been used as the replacement for fine aggregate in concrete. The addition of rubber has always resulted in a decrease of compressive strength and flexural strength, and strength loss increases with the increasing rubber content [22; 23; 24]. However, it is not absolute; crumb rubber treated with an NaOH solution significantly improves the compressive strength of rubber-modified concrete [25]. With regards to the durability of rubber-modified concrete, the addition of rubber has been positive in enhancing freeze-thaw, impact, abrasion, and acid attack resistance [22; 23; 24; 25]. There are many mature studies about rubber-modified concrete, but fewer on rubber-modified pervious concrete [26]. [PERSON] et al. [27] studied the effect of rubber particle sizes and dosages on the density and indirect tensile strength of rubber-modified pervious concrete. Crumb rubbers of 0.08-1 mm and 0.6-2.5 mm were used to replace the coarse aggregate with the equivalent volume method. The dosages were 5% and 10%. The results of the experiment indicate that coarse rubber has a greater positive effect on the density and indirect tensile strength than fine rubber.