Abstract: In this study, common and modified rubber aggregates were used to prepare common/modified rubber aggregate cement mortar (CRM/MRM) with different content and particle sizes, and the effects of rubber on the fluidity, rheology and mechanical properties of mortar were investigated. The results show that: in terms of fluidity, CRM has a low fluidity of only 90~95 mm, while MRM has a fluidity of 220~225 mm and good uniformity. In terms of rheology, CRM is characterized by dilatant fluid (shear thickening) and MRM is pseudoplastic fluid (shear thinning). And the thixotropy and rheology of both increase with the increase of rubber content. In terms of mechanical properties, the incorporation of rubber significantly reduced the compressive and flexural strength of mortar, and the decrease of flexural strength is less than that of compressive strength. The 28 d compressive and flexural strength of the modified rubber system increases by 70.5 % and 32.6 %, respectively, compared with the unmodified system. Large particle size rubber is more conducive to maintaining flexural strength. Microscopic analysis shows that the modification treatment reduces the thickness of the rubber-cement interface transition zone from 160 μm to 80 μm, eliminates the interface holes and forms a gradient hardness structure, which promotes the transformation of the material failure mode from brittleness to ductility.

Key words: cement mortar, rubber aggregate, modification, fluidity, rheology, mechanical property, micro mechanism