Effect Of Red Mud And Alkali Content On Properties Of M32.5 Cement-based Materials

Red mud is a solid waste discharged from alumina production process.Due to the lack of economic and effective ways to use it,it keeps accumulating many problems,such as resource shortage,environmental pollution and safety risks.In addition,the content of alkali in red mud is high.When red mud replaces part of ordinary Portland cement,cement clinker in high alkaline environment will cause adverse development of mechanical strength of mortar.Therefore,this paper proposes to use low-clinker M32.5 cement to cement red mud to improve the compatibility of red mud and cement-based materials,and use alkali in red mud to assist to stimulate the auxiliary materials in M32.5 cement-based materials to form a composite cementation system.The main contents are as follows:(1)The chemical composition,mineral composition and microscopic morphology of red mud were analyzed to explore the influence of red mud on the basic properties of M32.5 cement-based materials,and the optimal dosage of red mud was determined.As the amount of red mud is mixed more,the setting time of cement mortar is longer and the flow ability is worse.The optimal amount of red mud is 10%,at which the compressive strength of the mortar is slightly lower than that of the control group.Moreover,red mudcement mortar showed better resistance to chloride ion penetration,and water absorption rate was also better than that of the control group.(2)The content of free alkali in red mud was tested to further explore the influence of the content of free alkali in red mud on the fresh mixing performance,compressive strength,durability and micro structure of mortar.The increase of alkali content in red mud will slightly prolong cement setting time.In the early stage,by increasing the red mud alkali content caused the compressive strength of cement mortar to first increased and then decreased;the compressive strength of cement mortar gradually decreased in the later stage,mainly due to the dilution effect of red mud.The increase of red mud alkali content enhanced the chloride ion penetration resistance of cement mortar,reduced the capillary water absorption of mortar,and improved the durability of cement mortar.(3)Red mud in M32.5 cement-based materials will affect the performance of cement mortar through filling effect,dilution effect and auxiliary activation effect.In the early hydration stage of M32.5 cement,the auxiliary activation effect of red mud on cement and the filling effect play a dominant role;while with the age growth and alkali content consumption,the dilution effect of red mud plays a major role in the mortarIn this paper,the influence of red mud on the hydration process of M3 2.5 cementbased materials was explored through experiments.The experimental results showed that red mud and its alkali content have significant influence on the mechanical properties and durability of M32.5 cement-based materials,which provides a technical basis for further accelerating the large-scale resource utilization of red mud.Figure 24 Table 15 Reference 98...