作为一种新型的回填材料,自密实固化土(SCSS)以脱水减量后的灌注桩废弃泥浆为主要原料,这带来了在高流动性条件下协调工作性能与机械性能的问题。在本文中,引入羟丙基甲基纤维素(HPMC)和偏高岭土作为添加剂来解决这个问题。首先,通过渗水率试验对SCSS的可加工性和力学性能进行了调控和优化,流动性测试,和无侧限抗压强度试验。第二,本研究还使用X射线衍射(XRD)和扫描电子显微镜(SEM)研究了HPMC和偏高岭土对SCSS物理相和微观结构的影响。这样,结果表明,对SCSS的流动性有显著影响,也就是说,当用量达到0.3%时,SCSS的渗水率降低到1%以下,7天抗压强度达到峰值。同时,HPMC削弱了SCSS在7天至14天龄期的强度增长。然而,偏高岭土的加入提高了其抗压强度。XRD分析表明,添加剂对物理相没有明显影响。And,从SEM结果来看,可以看出,尽管HPMC的保水作用使水泥的水化更加彻底,在微观结构中可以观察到更多的钙矾石(AFt)。此外,可以观察到,由于偏高岭土具有很强的表面能,因此添加偏高岭土可以产生更多的水合硅酸钙(C-S-H)。由于上述因素,SCSS填充了颗粒之间的空隙,改善了颗粒之间的界面结构,从而提高了抗压强度。
As a new type of backfill material, Self-compacting solidified soil (SCSS) takes the abandoned slurry of cast-in-place piles after dewatering and reduction as the main raw material, which brings a problem of coordinating the working performance with the mechanical property under the condition of high mobility. In this paper, hydroxypropyl methyl cellulose (HPMC) and metakaolin were introduced as additives to solve this problem. First, the
workability and mechanical properties of SCSS were regulated and optimized by means of the water seepage rate test, the flowability test, and the unconfined compressive strength test. Second, this study also used X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate the effects of HPMC and metakaolin on the physical phase and microstructure of SCSS. In this way, the results showed that there was a significant impact on the flowability of SCSS, that is, when the dosage reached 0.3%, the water seepage rate of SCSS was reduced to less than 1%, and the compressive strength at 7 days reached its peak. At the same time, HPMC weakened the strength growth of SCSS in the age period of 7 days to 14 days. However, the addition of metakaolin promoted its compressive strength. XRD analysis showed that the additives had no significant effects on the physical phases. And, from the SEM results, it can be seen that although the water-retaining effect of HPMC makes hydration of cement more exhaustive, more ettringite (AFt) can be observed in the microstructure. In addition, it can be observed that the addition of metakaolin can generate more hydrated calcium silicate (C-S-H) due to the strong surface energy possessed by metakaolin. As a result of the above factors, SCSS filled the voids between particles and improved the interface structure between particles, thus enhanced the compressive strength.