Using compressive strength and mass change to verify the calcium oxychloride threshold in cementitious pastes with fly ash

Durability of Mortars Manufactured with Low-Carbon Binders Exposed to Calcium Chloride-Based De-Icing Salts

“…Similarly to the use of blast-furnace or pozzolanic cements, one of the most effective strategies to prevent the CAOXY formation in cementitious systems is the partial replacement of Portland cement with supplementary cementitious materials. However, Traore et al [16] recently supposed that the beneficial effect deriving from the use of fly ash on cement pastes is evident only when its use is higher than 15% by mass. Results reported in Figure 3 confirm the findings of Traore et al and indicated that mortars containing 5% of fly ash (FA5 and UFFA5), regardless of its fineness, are poorly resistant to the chemical attack by CaCl2, evidencing degradation similar to that of PC mortars.…”

“…CAOXY formation was observed and investigated in Portland cement-based mixtures since 1970's by Chatterji [9] and Collepardi et al [10][11][12]. Today, thanks to advanced testing techniques [13][14][15][16][17][18][19], this mode of damage is comprehensively studied in traditional concretes even if the exact damage mechanism is still unknown as reported in a recent review by Jones et al [20]. However, in the last few years, growing attention has been paid to sustainable alternative binders to Portland cement such as alkali activated materials [21][22][23], calcium sulphoaluminate (CSA) cements-based blends [24,25] or mixtures containing ultrafine supplementary cementitious materials [26,27].…”

Durability of concretes exposed to high concentrations of CaCl2 and MgCl2

“…Much research has been performed on damage mitigation in cement pastes [ 9 – 12 ] and mortars [ 10 , 13 , 14 ], but damage in concrete has been less studied, especially over long-term exposure periods [ 15 – 18 ]. Paste and mortar research has shown that damage is reduced due to the replacement of cement with supplementary cementitious materials (SCMs) [ 7 – 14 ], which consume calcium hydroxide in pozzolanic/latent hydraulic reactions [ 19 ].…”

“…The damage is observed to be proportional to the amount of calcium oxychloride that can form, and this amount is linearly correlated with the calcium hydroxide content in cement pastes [ 1 , 11 , 20 – 23 ]. Indeed, based on cement paste results, threshold levels of SCM replacement, calcium hydroxide content, and calcium oxychloride content (around 15 g/100 g cement paste) for damage have been proposed [ 11 , 12 , 23 ]. Apart from SCM replacement, paste damage reduces as the curing duration increases from 28 to 91-days, especially for Class F fly ash [ 10 ].…”