改性镁渣的物化特性及水化活性试验研究

Experimental Study on Physicochemical Properties and Hydration Activity of Modified Magnesium Slag

镁渣的资源化利用是一个迫切需要解决的问题。以镁渣、改性镁渣为主要胶凝材料,通过复掺粉煤灰制备镁渣基胶结充填材料(UCGB)与改性镁渣基胶结充填材料(MCGB),并对两种充填材料的流动特性、力学性能、微观结构和水化特性进行对比分析。结果表明,改性镁渣与粉煤灰的掺和比例为4/1时,制备的MCGB试样具有优异的力学性能,养护28 d龄期的单轴抗压强度高达4.213 MPa。随养护龄期的增长,MCGB试样水化产生大量的C-S-H凝胶、 Ca(OH)_(2)晶体、丝状Ettringite等水化产物,并与其他硅酸盐氧化物([Fe, Mg, Al]_(2.5)[Si, Al]_(2)O_(5)[OH]_(4))交织团聚在一起,填充于试样内部的孔隙、孔洞之中,有助于提升MCGB试样的机械性能和耐久性。相比于MCGB试样,UCGB试样的机械性能并不理想,早期强度低,水化仅产生极少量Ettringite和Ca(OH)_(2)晶体,形成疏松多孔的微观形貌结构。此外,通过红外光谱曲线分析可知,改性镁渣原样位于997 cm^(-1)附近出现了β-C_(2)S的特征频率,而镁渣原样位于820 cm^(-1)附近出现了γ-C_(2)S的特征辨识谱带,结合X射线图谱分析得出,镁渣改性后其矿物相主要转变为β-C_(2)S,而镁渣原样的矿物相主要为γ-C_(2)S,本身几乎没有水化活性,不宜用作制备矿用胶凝材料。因此,该研究主旨在于制备以改性镁渣为主的新型矿用胶凝材料提供科学依据和指导。

The resource utilization of magnesium slag is an urgent problem.This paper uses magnesium slag and modified magnesium slag as the main cementing mate rials,and magnesium slag based cementing materials(UCGB)and modified magnesi um slag based cementing materials(MCGB)are prepared by adding fly ash.The flow characteristics,mechanical properties,microstructure and hydration charac teristics of the filling materials are compared and analyzed.The results show that when the mixing ratio of modified magnesium slag and fly ash is 4/1,the prepared MCGB sample has excellent mechanical properties,and the u niaxial compressive strength is up to 4.213 MPa after curing for 28 days.With the growth of curing age,MCGB sample hydration produces a large number of hyd ration products such as C-S-H gel,Ca(OH)_(2) crystal and filamentous Ettringi te,which are interwoven and agglomerated with other silicate oxides([Fe,Mg,Al]_(2.5)[Si,Al]_(2)O_(5)[OH]_(4)).Filling in the pores and holes insi de the sample is helpful in improving the mechanical properties and durability of the MCGB sample.Compared with the MCGB sample,the mechanical properties of the UCGB sample are not ideal.The early strength of the UCGB sample is low,and only a small amount of Ettringite and Ca(OH)_(2) crystals are produced by hydra tion,forming a porous microstructure.In addition,the infrared spectrum cur ve analysis shows that the characteristic frequency of β-C_(2)S appears near 997 cm^(-1) of the modified magnesium slag,while the characteristic identific ation spectrum band of γ-C_(2)S appears near 820 cm^(-1) of the magnesium slag.Combined with the X-ray spectrum analysis,the mineral phase of the modif ied magnesium slag mainly changes to β-C_(2)S.However,the mineral phase of the original magnesium slag is mainly γ-C_(2)S,which has almost no hydration activity,so it is unsuitable for mining as a cementitious material.Therefore,this study aims to provide scientific basis and guidance for the preparation of new mine cementitious materials based on modified magnesium slag.