赤泥低钙烧结脱碱硅钙渣制备轻质免烧砖

Preparation and characterization of unfired lightweight bricks using dealkalized calcium silicate residue from low-calcium sintering red mud

为实现赤泥的充分利用,以脱碱硅酸钙渣、水泥和砂为原料,采用压实成型技术制备了轻质免烧砖,并利用XRD、FTIR和SEM等方法研究了原料配方和成型压力对免烧砖物理性能的影响。脱碱硅酸钙渣以不规则的蜂窝状颗粒形式存在,主要由硅酸钙水合物和部分CaTiO_(3)、CaCO_(3)和SiO_(2)组成。结果表明,增加硅酸钙渣的含量可以提高免烧砖的抗压强度,降低体积密度,但过量的硅酸钙渣会降低抗压强度和软化系数,增加吸水率。当硅酸钙渣用量在50%~70%时,免烧砖的抗压强度为15.10~24.16 MPa,体积密度为1.3~1.5 g/cm3,软化系数为0.77~0.91,吸水率为28.41%~43.52%。在养护过程中,水化反应产生的水化硅酸钙和水化铝酸钙使原料颗粒絮凝在一起,增强了免烧砖的强度。免烧砖中重金属和钠离子的浸出表明硅酸钙渣轻质免烧砖对环境无害。

In order to achieve the full utilization of red mud,the unfired lightweight bricks were prepared by compaction molding technology using dealkalized calcium silicate residue,cement and sand,and the effects of raw material formula and molding pressure on the physical properties and phase transition of unfired bricks were investigated by X-ray diffraction(XRD)analysis,Fourier transform infrared spectroscopy(FTIR)and scanning electron microscopy(SEM)methods.The dealkalized calcium silicate residue presented as irregular honeycomb particles is mainly composed of calcium silicate hydrate(C-S-H)and some CaTiO_(3),CaCO_(3) and SiO_(2).Increasing the content of calcium silicate residue increases the compressive strength of unfired bricks and reduces bulk density,but excessive calcium silicate residue reduces the compressive strength and softening coefficient,and increases water absorption.When the consumption of calcium silicate residue reaches 50%−70%,the compressive strength,bulk density,softening coefficient and water absorption of the unfired bricks are in the range of 15.10−24.16 MPa,1.3−1.5 g/cm3,0.77−0.91 and 28.41%−43.52%,respectively.During the curing process,the calcium silicate hydrate(C-S-H)and calcium aluminate hydrate(C-A-H)gels produced by hydration reactions flocculate the raw material particles together to strengthen the strength of the unfired bricks.The leaching results of heavy metals and Na ions show that the unfired lightweight bricks are harmless to the environment.