利用拜耳法赤泥制备高铁阿利特-硫铝酸钡钙水泥

Preparation of high brownmillerite alite-barium calcium sulphoaluminate cement with Bayer red mud

利用赤泥、磷石膏、钡泥替代部分天然原料制备高铁阿利特-硫铝酸钡钙水泥,研究水泥熟料中不同C_(4)AF(4CaO·Al_2O_(3)·Fe_2O_(3))设计含量(赤泥掺量)对水泥矿物形成、工作性能、力学性能和水化产物的影响。借助XRD、 SEM-EDS、金相显微镜分析熟料的矿物形成情况及水泥水化产物形貌。结果表明:水泥熟料中C4AF设计含量为20%~35%时,熟料中C_(4)AF、 C_(3)A、C_(3.75)B_(0.25)A_(3)S、 C_(3)S和C_(2)S矿物均形成,且随着C_(4)AF设计含量的增加, C_(3)S的形成量减少、 C_(2)S的形成量增加, C_(3)S的结晶边沿逐渐被铁铝中间相溶蚀,水泥的凝结时间逐渐延长;当C_(4)AF设计含量小于30%时,水泥的28 d抗折、抗压强度趋于平稳;过多的C_(4)AF会抑制C_(2)S向C_(3)S的转变,高铁阿利特-硫铝酸钡钙水泥中C_(4)AF设计含量不宜超过30%,即配料时赤泥的掺量不超过16.4%;水化产物中钙矾石(AFt)和C-S-H的形成量是抗折、抗压强度变化的主要原因。

High brownmillerite alite-barium calcium sulphoaluminate cement was prepared with bayer red mud,phosphogypsum and barium mud to substitute part of natural raw materials.The effects of different design content of C_(4)AF in clinker(red mud content)on clinker mineral formation,cement working properties,mechanical properties and hydration products were studied.The mineral composition and distribution of clinker and the morphologies of cement hydration products were analyzed by XRD,SEM-EDS and metallographic microscope.The results show that the minerals of C_(4)AF,C_(3)A,C_(3.75)B_(0.25)A_(3)S,C_(3) S and C_(2) S are formed as the C_(4)AF design is 20%-35%.With the increase of C_(4)AF design,the formation of C_(3) S decreases and that of C_(2) S increases,the crystalline edge of C_(3) S is gradually dissolved by iron-aluminum mesophase,the setting time of cement is gradually prolonged.The 28 d flexural strength and compressive strength of cement tend to be stable as the design content of C_(4)AF is less than 30%.The above analysis shows that the formation of excessive C_(4)AF inhibits the transition from C_(2) S to C_(3) S.The designed content of C_(4)AF in high brownmillerite alite-barium calcium sulfoaluminate cement should not exceed 30%and the ration of red mud doesn’t exceed 16.4%in raw material.The formation amount of ettringite(AFt)and C-S-H in hydration products is the decisive factors for the change of flexural strength and compressive strength.