Yuan Huan, Deng Min, Chen Bi, Chen Weifeng, Mao Zhongyang
College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China.
Materials (Basel). 2020 Jan 9;13(2):308. doi: 10.3390/ma13020308.
In this paper, a tetramethylammonium hydroxide (TMAH) solution and homemade cement without alkali were used to eliminate the influence of the alkali-silica reaction (ASR) on the expansion of dolomitic rocks, and a NaOH solution was used as a comparison agent. The expansion of concrete microbars and dolomite powder compacts prepared from dolomitic rocks was tested. The expansion cracks and reaction products were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that TMAH reacts with dolomite crystals in dolomitic rocks to form brucite and calcite. Through X-ray diffraction and SEM-EDS analysis, it can be determined that the chemical reaction between TMAH and dolomite crystal was dedolomitization. The expansion stress test and concrete microbar expansion test suggest that the alkali carbonate reaction (ACR) can produce expansion. Although both the ASR and the ACR were observed in the NaOH reaction system, but ASRgel was not found in the cracks, indicating that the ASR may be involved in the expansion process of concrete microbars and that the ACR is the root cause of the expansion. However, under the curing conditions of the TMAH solution, many ACR products were found around the crack, indicating that the expansion of the concrete in this system was caused entirely by the ACR.
本文采用氢氧化四甲铵（TMAH）溶液和自制无碱水泥消除碱-硅酸反应（ASR）对白云质岩石膨胀的影响，并以氢氧化钠溶液作为对比剂。对由白云质岩石制备的混凝土微棒和白云石粉末压块的膨胀情况进行了测试。通过X射线衍射、光学显微镜、扫描电子显微镜（SEM）和能谱仪（EDS）对膨胀裂缝和反应产物进行了研究。结果表明，TMAH与白云质岩石中的白云石晶体反应生成水镁石和方解石。通过X射线衍射和SEM-EDS分析可知，TMAH与白云石晶体之间的化学反应为脱白云石化反应。膨胀应力试验和混凝土微棒膨胀试验表明，碱碳酸盐反应（ACR）会产生膨胀。虽然在氢氧化钠反应体系中同时观察到了ASR和ACR，但在裂缝中未发现ASR凝胶，这表明ASR可能参与了混凝土微棒的膨胀过程，而ACR是膨胀的根本原因。然而，在TMAH溶液养护条件下，在裂缝周围发现了许多ACR产物，这表明该体系中混凝土的膨胀完全是由ACR引起的。
