Study On The Effect And Mechanism Of Biological Coating Activation On Rubber Mortar

The lower compressive strength of rubberized concrete caused by the weak adhesion between crumb rubber（CR）and cement paste since the hydrophobic surface of CR is a key bottleneck limiting its application.In this thesis,two bio-functional films,Dopamine hydrochloride（DA）and Tannic acid-Fe³⁺（TA@Fe）are proposed to modify CR to address the incompatibility between rubber and cement-based materials.Fourier-transform infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）,contact angle（CA）,scanning electron microscopy（SEM）,isothermal calorimetry and mercury injection analyzer（MIP）were carried out to characterize the changes of surface properties of CR and the interface transition zone（ITZ）between CR and cement paste,and reveal the function mechanism.A systematic experimental study of the mechanical and service properties of rubber cement-based materials before and after modification was conducted under the guidance of micro-and mcro-modulation.The specific research results are as follows:（1）As the biofunction coating,both of DA and TA@Fe can effectively enhance the wettability of the CR,and enrich the functional groups on the its surface.More importantly,the absorption capacity of CR for Ca²⁺can be strengthened by the mentioned above bio-functional coating thus achieving the activating effect.（2）PDA film can accelerate the hydration process of cement particles through chelating with Ca²⁺,increasing the Ca/Si to promote the formation of a denser interface transition zone between the CR and the cement paste,Moreover,the porosity of functional rubberized mortars was decreased.As a result,the compressive strengths of the produced mortars were improved by 1-24%at 3d,13-52%at 7d,and 37—68%at28d.The capillary water absorptions of CR mortars were also reduced by 28.6–41.8%,significantly enhancing the durability of the mortar.（3）The modification of CR by using TA@Fe coating,Ca²⁺in the cement paste was driven to migrate to the surrounding of CR in mortars through chelation reaction from bio-functional coating.This process promotes the formation of deposition of hydration products including some nano-size particles,filling the pores between CR and cement paste to reduce the size of cracks in ITZ.Therefore,the internal structure of the mortar is denser.（4）The functionalized coating made of TA and Fe³⁺molar ratio of 1:1 was the most optimal increasement in mechanical strength and durability of rubberized mortars.As a result,the compressive strengths of the produced mortars were improved by51.8%at 3d,24.6%at 7d,and 19.0%at 28d.Moreover,TA@Fe coating increased the C-S-H chain length by chelating with Ca²⁺,and reduced the chloride ion electric flux of the mortar and improved the durability.Figure[39]Table[7]References[163]...