CaO-SiO_(2)-H_(2)O水热反应的物相变化和物理性能研究

本文研究了钙硅比、压蒸温度、保温时间、成型压力和水固比,对CaO-SiO_(2)-H_(2)O体系物相变化和性能的影响,并采用XRD内标法确定物相含量。压制成型的试件在Ca/Si比约为0.666,180℃压蒸8h,可获得最优的干燥强度。Ca/Si比、温度过低,保温时间过短,石英的反应量偏低,强度降低;Ca/Si比过高会形成晶态的C_(2)SH,温度过高会形成较多的晶态托贝莫来石和硬硅钙石,对强度不利。压蒸温度从180℃提升至220℃,水化硅酸钙形貌从片状、层状、板状逐渐向棒状、纤维状转变。压制成型试件(水固比0.18)含水少,反应过程中传质受阻,其主要产物为非晶态的C-S-H凝胶,占比约70%,托贝莫来石占比不到3%,由此可知,对于模压法钙硅压蒸制品,非晶态水化硅酸钙为强度的主要影响者,而非托贝莫来石。提升水固比可有效促进托贝莫来石和硬硅钙石的结晶。无论何种配比和工艺条件下制备的压蒸试件,饱水后强度仅为干燥强度的36%~80%左右。

In this paper,the effects of calcium silicon ratio,autoclave temperature,curing time,molding pressure,and water-solid ratio on the phase changes and performance of CaO-SiO_(2)-H_(2)O system were studied,and the XRD internal standard method was used to determine the phase content of the reaction product.The best drying strength can be obtained by autoclaving the pressed specimen at a Ca/Si ratio of about 0.666,180℃,for 8 hours.With the Ca/Si ratio,temperature,and curing time increasing,the reaction amount of quartz is decreasing,and the strength decreases;Too high Ca/Si ratio CaO-SiO_(2)-H_(2)O system can form crystalline C_(2)SH,while too high temperature can form more crystalline tobermorite and xonotlite,which is detrimental to strength.When the autoclave temperature is increased from 180℃to 220℃,the morphology of hydrated calcium silicate gradually changes from sheet,layered,and plate shaped to rod and fiber shaped.The pressed specimen(water solid ratio 0.18)contains less water,and mass transfer is blocked during the reaction.Its main product is amorphous C-S-H gel,accounting for about 70%,and tobe mullite accounts for less than 3%.It can be seen that for calcium silicon autoclaved products,amorphous hydrated calcium silicate is the main contributor to strength,rather than tobermorite.Increasing the water solid ratio can effectively promote the crystallization of tobermorite and xonotlite.Regardless of the ratio and process conditions,the strength of the autoclaved specimen after being saturated with water is only about 36%~80%of the dry strength.