Wang Zhiming, Sun Yuning, Zhang Shuo, Wang Yonglong
School of Energy Science and Engineering, Henan Polytechnic University Jiaozuo 454002 China
State and Local Joint Engineering Laboratory for Gas Drainage and Ground Control of Deep Mines, Henan Polytechnic University Jiaozuo 454000 China.
RSC Adv. 2019 Mar 29;9(18):9993-10003. doi: 10.1039/c8ra09901d. eCollection 2019 Mar 28.
In this investigation, sodium silicate (SS) was mixed into rich-water (RW) materials consisting of Portland cement, calcium aluminate cement and gypsum for improved mechanical properties. The RW materials containing different amounts of SS were characterized by the compression test, mercury intrusion porosity, scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The results demonstrated that with the increase of SS additions, the early strength of the RW materials increases, and the long-term strength retrogression of the RW materials can be inhibited when the SS content is above 3%. Pore structures of the RW materials are improved significantly due to the filling effect of the calcium silicate hydration (C-S-H) gel from a reaction between silicate ions and Ca(OH), thus increasing the early strength of the RW materials. For the RW materials containing SS and cured for 0 to 14 days, there are more hexagonal hydrates including CaO·AlO·10HO (CAH) and 2CaO·AlO·8HO (CAH), more C-S-H gel and less ettringite crystals, which is of benefit to the strength of the material. The strength retrogression can be attributed to phase conversions from hexagonal hydrates (CAH and CAH) to cubic ones (3CaO·AlO·6HO) with lower intercrystal bonding forces. Furthermore, this phase conversion is inhibited effectively by the chemical reaction of silicate ions and CAH (or CAH), improving the long-term strength of the RW materials.
在本研究中，将硅酸钠（SS）混入由波特兰水泥、铝酸钙水泥和石膏组成的富水（RW）材料中，以改善其力学性能。对含有不同量SS的RW材料进行了抗压试验、压汞孔隙率测定、扫描电子显微镜、X射线衍射和傅里叶变换红外光谱表征。结果表明，随着SS掺量的增加，RW材料的早期强度增加，当SS含量高于3%时，可抑制RW材料的长期强度倒缩。由于硅酸根离子与Ca(OH)反应生成的硅酸钙水化物（C-S-H）凝胶的填充作用，RW材料的孔隙结构得到显著改善，从而提高了RW材料的早期强度。对于含有SS且养护0至14天的RW材料，存在更多的六方水化物，包括CaO·AlO·10HO（CAH）和2CaO·AlO·8HO（CAH），更多的C-S-H凝胶和更少的钙矾石晶体，这有利于材料的强度。强度倒缩可归因于六方水化物（CAH和CAH）向晶体间结合力较低的立方水化物（3CaO·AlO·6HO）的相转变。此外，硅酸根离子与CAH（或CAH）的化学反应有效地抑制了这种相转变，提高了RW材料的长期强度。
