Research On Preparation And Mechanical Properties Of Geopolymer Based CFB Desulfurization Slag And Silicon Manganese Slag

Geopolymer is a new environmental-friendly inorganic cementitious material,it is a three-dimensional network structure which is composed of the Si-O and Al-O tetrahedron.Its raw materials are very rich,in theory,any solid powder rich in silicon and aluminum can be used to prepare geopolymers,and the preparation process is simple.Circulating Fluidized Bed?CFB?desulfurization slag and silicomanganese slag are discharged as industrial waste slag,hich not only wastes resources but also causes environmental pollution,but they are rich in SiO₂ and Al₂O₃ which have the conditions to prepare geopolymers.In this paper,geopolymer was prepared by CFB desulphurization slag and silicon manganese slag and the mixture of sodium silicate and NaOH solution was used as the alkali activator.Silicon manganese slag/CFB desulphurization slag ratio,grinding time,sodium silicate/NaOH ratio,NaOH solution concentration and the curing temperature were analyzed by orthogonal experiment of five factors and four levels?L16?4⁵??,the best preparation conditions and factors affecting the sequence were analyzed by the range and variance analysis of the mechanical properties of the geopolymer.At the same time,SEM,XRD and FT-IR were used to analyze the microstructure and reaction mechanism of geopolymer,the reasons for the geopolymer with efflorescence were explained and some new ideas for the preparation of geopolymer were provided.?1?Through orthogonal experiment,the best preparation conditions of 28d compressive strength of geopolymer was determined as A1B3C3D3E1,namely silicon manganese slag/CFB desulphurization slag ratio is 0,grinding time is 55min,sodium silicate/NaOH ratio is 1.5,NaOH solution concentration is 12M and curing temperature is45?,its compressive strength can reach about 43MPa.The best preparation conditions of28d flexural strength of geopolymer was determined as A1B2C2D4E3,namely silicon manganese slag/CFB desulphurization slag ratio is 0,grinding time is 55min,sodium silicate/NaOH ratio is 1,NaOH solution concentration is 14M and curing temperature is 65?,its flexural strength can reach about 7MPa.At the same time,according to the range and variance analysis,the order of influence of various factors on compressive and flexural strength is D>E>A>B>C,among them,factor D and factor E are the main influencing factors.?2?Through SEM analysis,it was found that there were many obvious cracks on the surface and inside of the geopolymer products in groups e and g,which was caused by the evaporation of water from the pore in the geopolymer during high-temperature curing.In the other groups,the geopolymer structure was more compact because of the geopolymer reaction,there was a large number of C-S-H gels,quartz and calcite were observed in the interior,in which the smaller gel particles filled between the pores and the larger particles,making the structure more compact.?3?It was found that the components of geopolymer mainly contain quartz,calcite,nepheline and merwinite by XRD analysis of the geopolymer products,which is basically consistent with the SEM observation.?4?It was found that the strong absorption band appeared between 600cm^-11 and1200cm^-11 by FT-IR analysis,which was related to the asymmetric tensile vibration of Si-O-Al and Al-O-Si,and was an important symbol of geopolymer.1021 cm^-11 is the asymmetric telescopic vibration absorption peak of Si-O-Al in the geopolymer,and 706 cm^-11 is the bending vibration peak outside the O-H plane in the geopolymer.?5?Some of the geopolymer specimens produced efflorescence,which was mainly caused by the excessive Na⁺in the alkali activator with the evaporation of water which reacted with CO₂ in the air to produce white floc on the surface of the material.By XRD analysis,the main components were sodium carbonate and sodium bicarbonate.