After 15 months of construction of a tunnel in Guangdong,white crystals gradually appeared in the inner wall of the tunnel and the drainage pipe,which affected the aesthetics and safety of the tunnel.Based on this case,it analyzes the source of the white crystals and proposes solutions:SEM,EDAX and XRD analysis of the white crystals sampled on site revealed that the main component is calcium carbonate;Combined with the analysis of the tunnel structure,the source of the white crystals may be underground water seepage crystallization,karst and concrete dissolution,analysis and judgment of the possibility of concrete dissolution is the greatest,so the problem is solved by improving the anti-dissolution performance of concrete.On the basis of the original mix ratio,mineral admixtures and hydrophobic dense materials are added,and the results show that adding mineral admixtures and hydrophobic compact materials RS can improve the performance of primary shotcrete,of which hydrophobic compact materials RS have a better effect.The hydrophobic compact material RS was applied in the field.Compared with the blank section,the amount of white crystals generated in the drainage ditch of the test section was reduced from 8 cm to less than 1 cm,the amount of core sample Ca(OH)2 dissolution was significantly reduced,and the problem of drain pipe clogging was solved.
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