粉煤灰基喷浆材料的流动性对实际工程应用有重要作用，为探究减水剂对粉煤灰基浆料流动性的调控机制，通过减水率、流动度、凝结时间、浆体黏度和剪切应力等表征，比较了不同减水剂掺量对浆体流动性能的影响，并筛选出最佳减水剂及用量。采用水化热测定仪、X射线衍射和扫描电子显微镜，探究了聚羧酸减水剂（PCE）对粉煤灰基浆料水化进程与时间的变化规律，提出了PCE对喷浆材料的水化机理。结果表明，PCE对粉煤灰基浆料流动性能改善最明显，饱和掺量为0.6%时，减水率可达29.3%;流动度由113 mm延伸至351 mm;初凝时间由32 min延长至149 min，终凝时间由42 min延长至182 min，出现明显缓凝现象。在早期水化进程中，PCE吸附作用会抑制C3A溶解，阻碍钙矾石（AFt）生长并改变其晶型。同时PCE络合作用会与Ca2+结合成络合物，影响Ca(OH)2生成，延缓Ca2+富集过程，延长诱导期。C3S的水化也受到抑制，使C-S-H成核数量减少，降低了第二水化放热峰。到水化进程中后期PCE的抑制作用失效，材料力学强度逐渐提升。PCE仅能延缓材料早期的水化进程，但对中后期的水化进程无影响。

The fluidity of fly ash-based shotcrete material plays a very important role in practical engineering applications. In order to explore the regulation mechanism of water reducing agent on the fluidity of fly ash-based slurry, the effects of different water reducing agent dosage on slurry flow performance were compared through the characteristics of reducing water rate, fluidity, setting time, slurry viscosity and shear stress，and the best water reducing agent and dosage were selected. The change law of hydration process and time of flyash-based slurry by polycarboxylate acid superplasticizer (PCE)was emphatically explored by using hydration heat analyzer, X-ray diffraction and scanning electron microscope and the hydration mechanism of shotcrete materials with PCE was proposed. The results show that PCE has the most obvious improvement on flow performance of fly ash base slurry. When the saturated content is 0.6%, the water reduction rate can reach 29.3%, the fluidity extends from 113 mm to 351 mm, the initial setting time is extended from 32 min to 149 min, and the final setting time is extended from 42 min to 182 min, with a significant delayed setting phenomenon. In the early hydration process, The adsorption of PCE can inhibit the dissolution of C3A, hinder the growth of ettringite (AFt) and change its crystal form. At the same time, the complexation of PCE can combine with Ca2+  to form complex, affecting the formation of Ca(OH)2, delaying the enrichment of Ca2+ and prolonging the induction period of cement hydration. The hydration of C3S is also inhibited, which reduce the number of C-S-H nucleation and the second hydration exothermic peak. In the middle and late stages of hydration, the inhibition effect of PCE fails and the mechanical strength of the material increases gradually. PCE can only delay the early hydration process, but has no effect on the middle and late hydration process.

0 引言

1 试验

   1.1 原料成分分析

   1.2 喷浆材料制备

   1.3 材料性能的表征

2 结果与讨论

   2.1 水泥-粉煤灰喷浆材料浆体流动性

   2.2 PCE对水化进程的影响

3 结论