纳米材料与无碱速凝剂的相容性及协同机理研究

Study on compatibility and synergistic mechanism ofnano materials and alkali free accelerator

纳米材料能够显著增强水泥基材料的力学性能和耐久性能,为拓展纳米材料在喷射混凝土中的应用。研究了液体无碱速凝剂在固定掺量条件下,不同种类和维度的纳米材料对水泥净浆的凝结时间及胶砂抗压强度的影响,并分析了纳米材料与无碱速凝剂之间的协同促进机理。研究结果表明,不同种类纳米材料对水泥净浆凝结时间的影响程度不同,所有纳米材料均能够缩短水泥净浆的凝结时间,零维纳米SiO_(2)的影响程度最大,凝结时间由空白组的110 s降低到65 s。同时,掺加零维纳米SiO_(2)的水泥胶砂6 h和1 d抗压强度分别提升了22.8%和41.2%。XRD和SEM结果表明,纳米材料与速凝剂之间的良好相容性归因于纳米材料的化学反应活性和高需水量,并通过填充效应、晶核效应、化学反应活性和界面过渡区结构优化等作用,在降低了水泥净浆实际水灰比的同时促进钙矾石和氢氧化钙水化产物的增加,从而缩短了凝结时间及提升了水泥胶砂的抗压强度。

Nano materials can significantly enhance the mechanical properties and durability of cement-based materials.In order to expand the application of nano materials in shotcrete,the effects of different kinds and dimensions of nano materials on the setting time of cement paste and the compressive strength of mortar were studied in this paper under the condition of fixed content of liquid alkali-free accelerator.The synergistic promotion mechanism between nano materials and alkali-free accelerator was also analyzed.The results show that different kinds of nano materials have different effects on the setting time of cement paste,and the setting time of cement paste can be shorten by all nano materials.The influence degree of zero dimensional nano SiO_(2) is the greatest,which the setting time is reduced from 110 s of the blank group to 65 s.Meanwhile,the 6 h and 1 d compressive strength of mortar with zero dimensional nano SiO_(2) increased by 22.8%and 41.2%respectively.XRD and SEM results show that the good compatibility between nano materials and accelerator attributes to the chemical reaction activity and high water demand of nano materials.The actual ratio of the water to cement and the content of ettringite and calcium hydroxide hydration products were reduced and promoted respectively through the effects of filling effect,crystal nucleus effect,chemical reaction activity and interface transition zone structure optimization,thus,the setting time of the cement paste is shortened and the compressive strength of cement mortar is improved.