基于临界钙矾石膨胀破坏的磷石膏基复合胶凝材料的配料计算研究

为制备大掺量磷石膏基复合胶凝材料,在确定主要水化产物类型的基础上,通过计算临界钙矾石膨胀破坏的边界条件,确定各组分最佳掺量范围,研究其对复合胶凝材料力学性能、干缩性能的影响,并通过X射线衍射（XRD）、扫描电镜（SEM）等测试方法研究水化产物的组成及发展规律。研究结果表明：通过理论配料计算,矿粉掺量为50%（质量分数）时,最大磷石膏掺量为26.3%（质量分数）,最小熟料掺量为23.6%（质量分数）。最佳配比组28 d胶砂抗压强度为45.2 MPa,线膨胀率小于0.04%;对比组28 d抗压强度仅有36.4 MPa,线膨胀率远大于0.04%。XRD、SEM表征结果表明,磷石膏基复合胶凝材料的水化产物主要是钙矾石（AFt）和水化硅酸钙（C-S-H）凝胶,氢氧化钙几乎反应完全;对比组钙矾石生成量远大于最佳配料组,微观结构存在大量裂缝。这说明理论配料计算可以有效用于磷石膏基复合胶凝材料的配比优化。

Study on formulation calculation of phosphogypsum-based composite cementitious materials based on expansion and failure of critical AFt

In order to prepare a composite cementitious material with large amount of phosphogypsum,on the basis of deter-mining the type of main hydration product,by calculating the boundary conditions of the critical ettringite expansion failure,the optimal dosage range of each component was determined and the effect of it on the mechanical properties and dry shrink-age properties of the composite cementitious materials was studied.The formation and development rule of hydration products by XRD and SEM were researched.The results showed that,by theoretical compounding,when the mineral powder dosage was 50%（mass fraction）,the maximum phosphorus gypsum dosage was 26.3%（mass fraction） and the minimum clinker dosage was 23.7%.The optimum ratio group was as follows：28 d,mortar compressive strength was 45.2 MPa,the limit expansion ratio was less than 0.04%.The control group was as follows：28 d,compressive strength was 36.4 MPa,the limit expansion ratio was much greater than 0.04%.The characteristic results of XRD and SEM showed that the hydration products of phosphogypsum-based composite cementitious materials were mainly AFt and C-S-H gels,and Ca（OH）₂ was almost completely reacted.The amount of ettringite produced in the control group was much larger than that of the optimal ratio group,and there were many cracks in the microstructure.The crack indicated that the theoretical ratio calculation can be effectively used to optimize the compatibility of the phosphogypsum-based composite cementitious material.