Concrete Incorporating Nanosilica Cured under Freezing Temperatures Using Conventional and Hybrid Protection Methods

Bond Strength of Nano-Modified Concrete under Freezing Temperature using Hybrid Protection

“…Moreover, the mixtures comprising nano-silica showed consumption of CH after 14 days of curing at -20℃, indicating the initiation of delayed pozzolanic reactivity by reacting with CH to produce secondary C-S-H gel. This pozzolanic reactivity was accompanied by the filler effect in the matrix [11][12][13][14][15], which substantiate the notable improvement in mechanical properties, including bond strength with steel re-bars, of these mixtures at 28 days. Likewise, as shown in Fig.…”

“…Based on previous investigations by the authors [13][14][15], preparations and mixing procedures were conducted at -5ºC inside an environmental chamber, where solid constituents of concrete were kept for 24 h prior to mixing. Cold mixing water (5±1ºC) was used to mimic winter tap water condition.…”

“…However, these studies were conducted for concrete cast and cured under normal temperatures (20 to 30℃), whilst research on nano-modified concrete in cold weather applications is still in early stages. For example, in recent studies by the authors [13][14][15], it was found that low w/b (0.32) concrete mixtures, cast and cured under cold temperatures down to -20 ℃, incorporating 2 to 6% nano-silica and calcium nitrate-nitrite solutions (CNAI), without and with fly ash, achieved acceptable performance in terms of hardening rates, hydration development, strength and durability properties. However, the bonding behaviour of these mixtures with unheated metallic reinforcement at freezing temperatures has not been investigated, which warrants further studies in this direction.…”

“…For all mixtures, the total binder content and water-to-binder ratio (w/b) were kept constant at 400 kg/m 3 and 0.32, respectively. These proportions produced concrete with balanced performance in terms of fresh, hardened and durability when cast and cured under mild and low freezing temperatures [13][14][15]. Well-graded river sand with fineness modulus of 2.9 and natural gravel with maximum size of 9.5 mm were used in this study.…”