Long-term durability testing on the MgO-activated slag cured in brine

Abstract

The corrosion of the concrete in the brine environment has been a challenging issue over years. CaO-activated slag was reported to have an improved anti-corrosion property over the ordinary Portland cement, but its shrinkage cracking remained a problem. MgO-activated slag had lower shrinkage and greater potential of improved corrosion resistance. However, its long-term behavior in the brine environment was still unknown. This paper presents an experimental testing on the durability of the MgO-activated slag paste when cured in the brine. Cube samples were prepared and cured in four single salt solutions and three mixed double-salt solutions. Each single salt solution contained one of the four chemicals of NaCl, Na 2 SO 4 , MgCl 2 , MgSO 4. The mixed double-salt solutions were "NaCl + Na 2 SO 4 ", "NaCl + MgCl 2 ", "Na 2 SO 4 + MgSO 4 ", with various molar ratios. The compressive strength of the MgO-activated slag samples cured in the different solutions was tested at different ages up to 365 days. The experimental results indicated that the MgO-activated slag could hardly sustain the strength after 150 days when cured in the brine solutions. It seemed that SO 4 2-> Cland Mg 2+ > Na + in terms of the corrosion damage to the MgO-slag paste. As indicated by the

Investigation of the Effects of Magnesium-Sulfate as Slag Activator

“…In particular, as the concentration of MS increases, the C-S-H gel peak tends to decrease slightly. This is consistent with Pan et al [14] report mentioned earlier. This slow hydration reactivity has already been reported in previous studies using sulfate such as Na 2 SO 4 or CaSO 4 .…”

“…However, as the concentration of MS increases, the C-S-H gel peak decreases slowly. Pan et al [14] reported that as the SO 4 increased, the C-S-H gel slowly disappeared and a significant amount of extensive ettringite was produced. Therefore, in this study using MS as an activator, the change of ettringite peak is clearly confirmed, but the change of C-S-H gel peak is not clear.…”

“…In studies on ordinary Portland cement, Na 2 SO 4 and magnesium sulfate (MgSO 4 , hereinafter denoted as MS) have been mainly used for sulfate immersion experiments [13]; these sulfates have been studied as important factors causing the deterioration of ordinary Portland cement. Meanwhile, degradation studies by sulfate immersion experiments have also been conducted on AASC [9,14], but some sulfates have also been used as activators in AASC. Sodium sulfate (Na 2 SO 4 ) [15][16][17][18] or gypsum (CaSO 4 •2H 2 O) [19,20] was used as an activator in the AASC study using sulfate.…”

Utilization of ladle slag for soil stabilization

“…These results confirm that Ca(OH)2 in LS acts as an alkali activator for GGBS, and this activator is consumed during the hydration process (Yi et al 2015a). Previous studies have proved that MgO can also activate GGBS (Gu et al 2014;Jin et al 2015;Pan et al 2017;Vedalakshmi et al 2003;Yi et al 2014aYi et al , 2016aYi et al , 2016b, and here the decrease of MgO peak from 14 days to 56 days in Fig. 3.7 indicates that the MgO in LS has played a similar role as the Ca(OH)2.…”

Mechanical Properties and Durability of Textile Reinforced Concrete (TRC)—A Review

“…Test results showed that, TRC could inhibit the intrusion of chloride ions due to the good self-compaction and anti-permeability characteristics of fine-grained concrete [ 153 ]. However, the strength of the concrete still would be decreased in the salt condition, because salt ions Cl − and SO 4 2− would react with Ca 2+ and Al 3+ in the cementitious material or the hydration products of the cementitious material and generate the hydrates breaking the microstructure of the specimens, and the concrete cracked [ 154 ]. If the cementitious material for TRC contains less content of Ca 2+ and Al 3+ , the durability of the specimens showed better resistance in the salt condition [ 154 ].…”