稀土尾矿蒸压砖的制备及强度性能研究

以堆浸稀土尾矿为主要原料,掺入适量河砂、石灰及石膏,制备稀土尾矿蒸压砖。以水固比、石灰掺量和石膏掺量为考察因素,制品抗压强度为考察指标,通过正交试验确定最佳原料配比;再在骨料河砂总掺量不变的情况下,通过调整细、中、粗骨料的配合比,对骨料的级配进行优化;并借助XRD和SEM对优选制品进行微观表征,研究制品强度的形成机理。结果表明,在水固比为0.16、石灰掺量为20%、石膏掺量为2%、细骨料掺量为15%、中骨料掺量为12%、粗骨料掺量为3%、成型压力为20 MPa、蒸汽压力为0.8 MPa、恒压时间为2 h的条件下,蒸压砖制品可获得最高抗压强度21.5 MPa,强度性能达到GB 11945-1999 (《蒸压灰砂砖》)规定的MU20等级;微观结构分析表明,蒸压砖内部形成了水化硅酸钙和托贝莫来石等水化产物,并在骨料颗粒间的物理咬合与紧密接触的协同作用下,产生了优良的强度性能。

Preparation and Strength Performance of Rare Earth Tailing Based Autoclaved Bricks

IUsing the heap-leaching rare earth tailing as main raw material, autoclaved bricks were prepared with addition of appropriate content of river sand, lime and gypsum. In order to obtain the optimum raw material ratio, orthogonal tests were conducted on condition that water-solid mass ratio, lime content and gypsum content were acted as the affecting factors, and the 1 d compressive strength of autoclaved brick product was employed as index of evaluation. After that, gradation of aggregate was optimized by adjusting mass percentage of fine, intermediate and coarse aggregate in the total aggregate, on condition that the content of total aggregate in the solid raw material remained constant. Moreover, in order to investigate the strength formation mechanism, the selected product was characterized by XRD and SEM analyses. Results showed that, with water-solid mass ratio of 0.16, lime content of 20%, gypsum content of 2%, fine aggregate content of 15%, intermediate aggregate content of 12%, coarse aggregate content of 3%, forming pressure of 20 MPa, autoclaved curing pressure of 0.8 MPa and autoclaved curing time of 2 h, the autoclaved brick product can reach the highest compressive strength of 21.5 MPa, satisfying the required strength performance of MU20 in standard of GB 11945-1999. Microstructure analyses indicated that, the autoclaved brick can possess excellent strength performance, with the aid of the formed hydration products (such as calcium silicate hydrate and tobermorite) and the good particle contact arising from proper gradation of aggregate.