Inorganic Particles @ Polyurethane Urea/Cement Composites Preparation And Performance Study

The design of concrete structures tends to be more and more "super high-rise,large-span,complex".These building structures are more susceptible to adverse dynamic loads(earthquake loads,impact loads,etc.)in the environment during service.This will cause structural damage and reduce service life.This poses new challenges to the damping performance of concrete structures.Optimization of the damping performance of concrete materials is an important method to improve the damping performance of structures.This paper intends to prepare cement-based composites based on micro-constrained damping structure of inorganic particles @ polyurethane urea core-shell particles.First,three core-shell particles,silica fume @ polyurethane urea(SF@PUU),wollastonite @ polyurethane urea(WS@PUU),and fused silica powder@polyurethane urea(FSP@PUU),were prepared by non-homogeneous stepwise addition polymerization method.They were added to the cement paste as damping fillers to form micro-constrained damping structures inside the cement paste.The damping performance of cement-based composites is improved by the shear energy dissipation of PUU,the frictional energy dissipation of the composite interface,and the energy dissipation of the material itself,while retaining its mechanical strength.The microstructure and macroscopic properties of cement-based composites were characterized by scanning electron microscopy,infrared spectroscopy,thermogravimetry,X-ray diffraction,compressive strength and modal vibration tests,etc.It was found that the three kinds of core-shell particles had different degrees of improvement on damping performance of cement.Fused silica powder@polyurethane urea(FSP@PUU)has the best effect on the improvement of the damping performance of the composites.It is relatively dispersed in the cement.Therefore,the microscopic confined damping structure formed by FSP@PUU in cement can play a better the role of energy dissipation,thus effectively improving the damping performance of cement-based composites.The main research results of this paper are as follows:(1)Preparation and properties of SF@PUU,WS@PUU and FSP@PUU: The non-homogeneous stepwise addition polymerization method was used to realize the coating of PUU on the surfaces of SF,WS and FSP.Three types of core-shell particles,SF@PUU,WS@PUU and FSP@PUU,were successfully synthesized.It is proved that when the mass ratio of SF to A and B components is 3:1:0.9,WS to A and B components is 6:1:0.9,and FSP to A and B components is 10:1:0.9.The cladding process of the three core-shell particles is the best ratio.(2)Preparation and properties study of SF and SF@PUU/Cement composites:Through the modal vibration experiment,it is concluded that in the frequency range of175-300 Hz,when the content of SF@PUU is 2wt%,SF@PUU/Cement composites show the best damping performance.Its damping ratio is increased by 37% compared with cement paste.In this frequency range when content of SF is 4wt%,the damping effect of SF cement-based composite is the best.Its damping ratio is 18% higher than cement paste.The above experimental results show that SF@PUU can play a better energy dissipation role in cement.The damping properties of SF@PUU/Cement composites are mainly derived from the interfacial friction energy dissipation and the energy dissipation caused by the deformation of PUU.(3)Preparation and properties study of WS and WS@PUU/Cement composites:Through the modal vibration experiment,it is concluded that in the frequency range of1000-1500 Hz,when the content of WS@PUU is 4wt%,the damping performance of WS@PUU/Cement composites is the best.Its damping ratio is 35% higher than cement paste.In the frequency range of 175-300 Hz,WS/Cement composites showed the best damping performance.It has a 40% rise in damping ratio over cement cement paste.The above experimental results show that WS@PUU/Cement composites can play a damping performance in a higher frequency range.This may be due to WS@PUU fracture needs to absorb more vibration energy after WS is wrapped by PUU.So WS@PUU/Cement composites can play a damping performance in a higher frequency range.(4)Preparation and properties study of FSP and FSP@PUU/Cement composites:Through modal vibration experiments,when the content of FSP @ PUU is 6wt%,the damping performance of FSP @ PUU/Cement composites is significantly improved in the range of 175-300 Hz.Its damping ratio is increased by 58% compared with cement paste.In this frequency range,when the content of FSP is 6wt%,the damping performance of FSP/Cement composites is the best.Its damping ratio increases by 44%compared with cement paste.Thus,the damping performance of FSP @ PUU/Cement composites is improved.