Materials Performance

MAR 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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44 MARCH 2018 W W W.MATERIALSPERFORMANCE.COM COATINGS & LININGS per crack were 4.55 mm and 139 mm 2 , respectively. The addition of silane reduced the maximum crack width and crack area per crack. Compared to the reference sam ple, the maximum crack width and crack area of the sample with 1% silane were greatly reduced—to 2.13 mm and 27 mm 2 , respectively. Further increases in the silane dosage also decreased the maximum crack width and crack area per crack. The silane significantly improved the crack resistance of the mortar samples. This can be explained by the fact that silane hydrolyzed and the functional group 4 Si OH was obtained. 7 The reactive silanol groups became anchored to the cementitious materials or to the aggre gate and reinforced the interface between the silane and mortar. Because of the bridg ing action of the silane, the crack resistance of mortar was improved. The results presented in Figure 2 com p are th e w at er pro of in g prop er ti e s of unmodified (left) mortar and mortar with 5% silane (right) when the cracks appear. This comparison demonstrates that the mortar samples with silane showed excel lent waterproofing properties even after the cracks occurred. Carbonation Resistance Table 2 shows the relationship between silane dosage and carbonation depth at 3, 7, 14, and 28 days of carbonation. For mor tar samples with silane, the carbonation depths were lower when compared to the reference sample. Furth ermore, as th e silane dosage increased, the carbonation depth consistently decreased. This can be ascribed to Si OH groups that are produced by the hydroxylation of silane. 8 Because of the self polycondensation of Si OH groups, th e si loxan e p olym er n etw ork can b e obtained. Thus, the carbonation resistance of mortar was improved due to the inher ent advantages of siloxane, including excel lent thermal stability, good water rejection characteristics, and resistance to carbon ation and chemicals. Freeze-Thaw Cycles Figure 3 shows the loss ratio of samples at 50, 100, 150, and 200 cycles for the mor tar reference sample and samples with dif ferent silane additives. The mortar contain ing silane additives exhibited lower loss of TABLE 2. RESULTS OF CARBONATION DEPTH TESTING Samples Carbonation Depth (mm) 0% silane (reference) 2.90 1% silane 0.50 3% silane 0.45 5% silane 0.35 FIGURE 3 Results of freeze-thaw testing of mortar without silane (reference), and with 1, 3, and 5% silane. FIGURE 4 SEM images of mortar without silane (reference), and with 1 and 5% silane.

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