This function is helpful to improve the energy absorption capacity and flexural capacity of the structure without cracking, and can also increase the fatigue life, sound absorption capacity and seismic resistance of the structure.
In addition, the strength of rubber concrete can be enhanced through special pretreatment process and the addition of additives, such as silica fume and mineral filler.
At a certain volume dosage, the damping ratio and dynamic static elastic modulus ratio of rubber concrete materials are improved compared with ordinary concrete, which shows that rubber concrete can not only actively dissipate the input vibration energy through material damping, but also can block the transmission of vibration, with a damping effect.
Ordinary concrete rubber concrete Figure 3 Failure pattern of rubber concrete cube under compression [2] The type of rubber aggregate has a certain influence on the strength and elastic modulus of rubber concrete.
Rubber concrete is prepared by cutting waste rubber tires into rubber powder or rubber particles (production process is shown in Figure 1), and adding them into ordinary concrete as aggregate to replace sand and gravel.
5), and pretreatment of rubber aggregate with silane coupling agent can improve the damping ratio of materials (as shown in Fig.
Rubber concrete shows unique advantages that ordinary concrete does not have, such as light weight, elastic shock absorption, noise reduction and sound insulation, good air and water permeability, ductility and toughness.
At present, there are different conclusions about the damping performance of rubber concrete.
Figure 4 Impact of rubber aggregate type on the strength and elastic modulus of rubber concrete [2] Figure 5 Impact of modification measures on the strength and elastic modulus of rubber concrete [2] Figure 6 Relationship between compressive strength and damping ratio of rubber concrete and particle size [2] Figure 7 Impact of modification measures on damping ratio of rubber concrete [2] Mechanical analysis shows that rubber aggregate increases the porosity of concrete, and the elastic modulus difference between rubber aggregate and cement paste, rigid aggregate, The weak interface connection, holes and cracks around the rubber aggregate are the reasons why the mechanical properties of rubber concrete are lower than that of ordinary concrete, but also the factors that make rubber concrete have the advantage of high damping and energy consumption.
It is suitable for vibration environment.
Silane coupling agent can realize coupling between rubber aggregate and cement paste, and NaOH solution can remove hydrophobic substances on the surface of rubber aggregate, so that both can improve the interface bonding condition..
Replacing sand and stone with rubber particles can reduce the consumption of natural aggregate, which is beneficial to environmental protection.
It is generally believed that it is reasonable to control the rubber content within 20%.
Compared with the reference concrete, when the weight content of rubber powder is 0.5%~2.5%, the damping coefficient of concrete can be increased by 50%~60%, but the increase range does not change much with the rubber content; When the rubber powder content exceeds 2.5%, the damping coefficient of concrete increases rapidly with the increase of rubber powder content, which is 1.3~2.3 times higher.
However, some studies have found that rubber powder has an obvious effect on improving the damping ratio of concrete.
The preparation process and economy of rubber concrete are not different from ordinary concrete, but in the long run, rubber concrete is the reuse of waste rubber resources with huge reserves, which not only improves the utilization rate of resources but also has good economic value.
Some scholars have defined it as “elastic concrete”.
Figure 1 Industrial production process of tire waste as rubber aggregate [1] is different from traditional concrete.
Considering the strength, elastic modulus and damping ratio, the optimum particle size group of rubber is 1.18-2.36mm.
Three types of rubber aggregates are selected: rubber particles, which are recorded as “particle size group-P”; Rubber fiber, marked as F; Rubber sheet, marked as C.
With the increase of rubber particle size, it increases first and then decreases, and is smaller than the strength and static elastic modulus of ordinary concrete (as shown in Figure 4); However, the type of rubber aggregate has little influence on the damping ratio of the material (as shown in Figure 6).
The standard concrete strength and the corresponding rubber content can be selected according to the demand, and the rubber concrete with the required strength can be configured.
Figure 2 Different types of rubber aggregate forms [2] The viscoelastic rubber aggregate inside the rubber concrete can play a certain role in buffering the external load, relieving the stress concentration in the internal void of the concrete, slowing down the crack development, and changing the concrete damage form into ductile damage (as shown in Figure 3).
Many studies have reported the increase of impact resistance of rubber concrete, which is mainly due to the improvement of energy absorption capacity of materials.
Some studies believe that with the increase of rubber content, the damping ratio, dynamic elastic modulus and stiffness of concrete decrease.
Pretreatment of rubber aggregate with NaOH solution can restore the strength and elastic modulus of rubber concrete to a certain extent (as shown in Fig.
Recycling them in concrete structures is an effective and sustainable treatment scheme.
The research shows that 10% rubber content (taking the volume replacement rate of sand as an example) will reduce the compressive strength of benchmark concrete (ordinary concrete before replacing aggregate with rubber particles) by 19%, 20% rubber content will reduce the strength by 37%, and the impact resistance of 20% rubber content will be doubled.
However, the addition of rubber aggregate decreases the compressive strength, anti splitting strength and dynamic and static elastic modulus of concrete, but the damping ratio increases and the impact resistance becomes stronger, and this trend increases with the increase of rubber content and size.
7).
The shapes of different types of rubber aggregates are shown in Figure 2.
The experimental study on the dynamic performance of rubber concrete mainly focuses on the impact resistance and damping performance.
With the increase of rubber content, a flatter stress-strain relationship, higher cyclic loading capacity and damping were observed.
Random stacking and burning will cause environmental and safety problems.
The damping coefficient of ordinary concrete ranges from 0.9% to 2.0%, and decreases with the increase of compressive strength and elastic modulus.
Thanks to the flexibility and low specific gravity of rubber aggregate, the ductility of concrete after adding rubber is better.
Damping property is one of the most essential properties of various mechanical properties of materials.
Waste tires are the main waste in the world.
