Relationship between the particle size and dosage of LDHs and concrete resistance against chloride ingress

Abstract

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Use of ZnAl-Layered Double Hydroxide (LDH) to Extend the Service Life of Reinforced Concrete

“…In the above-mentioned studies, the intercalated anions were nitrite (corrosion inhibitor), nitrate, carbonate, and chloride. The most commonly studied LDH is by far MgAl-LDH [20][21][22]24,27,32,35,[37][38][39][41][42][43][44][45][46][47]49,50], followed by CaAl [16][17][18]26,[32][33][34]40], hydrotalcite [23,29,36], and modified hydrotalcite [25,28,31]. ZnAl-LDH is a new composition that has been studied in only two papers [51,52].…”

“…The use of LDH to control the cement hydration kinetics has been studied by several groups [18][19][20][21]. However, most of the work with LDH in concrete is dedicated to the mitigation of steel rebars corrosion, either in chloride media [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] or carbonated concrete [32,[41][42][43][44][45][46][47][48]. Many studies have been done in simulated concrete pore solution [35,38,43,46], just a few in mortar [31,43] and only one in concrete [16].…”

Recent Advances on the Application of Layered Double Hydroxides in Concrete—A Review

“…Depending on the type of LDH in use, it can have a positive effect on the mechanical properties of concrete especially its compressive strength, see Table 1. LDHs have hexagonal platelet like structures and if they are able to retain their structure in mature concrete, the resulting concrete can also show enhanced flexural strength as these thin LDH platelets can act as micro-beam elements [97] between cementitious materials and therefore help in an efficient transfer of bending stresses. Table 1 presents a compilation of compressive and flexural strength enhancement of concrete together with type of LDH and dosages used by different authors.…”

“…From Table 1, it can be observed that Ca based LDH has a profound positive effect on mechanical properties whereas multiple entries report a Mg based LDH to have a negative or inconclusive effect on mechanical properties. Qu et al [97] used Ca based LDH and observed a strong increase in the compressive strength and flexural strength in samples with LDHs as compared with reference samples. A 17.2% increase in compressive strength was observed in samples with 1% dosage of LDH (mean particle size 3.2 µm) but only 1.7% strength increase for 2% LDH, see Figure 4.…”

“…The authors concluded that overall dosages up to 2% can have a positive influence on mechanical properties of concrete. Higher dosages than 2% can be the threshold for particle agglomeration [97].…”