Assessment of the long-term performance of SCC incorporating different mineral admixtures in a magnesium sulphate environment

Abstract

International audienceThe effects of mineral admixture type on the behaviour of self-consolidating concrete (SCC) in magnesium sulphate environments were investigated over the course of four years of exposure. Three mineral admixtures (limestone filler, fly ash and natural pozzolan) representing a wide range of compositions were used in the study. Twelve formulations covering three strength classes (30, 50 and 70 MPa) and four concrete mixtures were studied. Mass loss with physical deterioration, and dimensional and compressive strength changes due to magnesium sulphate attack were determined through microstructural analysis. The sulphate profiles of sulphur, magnesium, silicon, calcium and aluminium elements were also quantified through analyses of the samples. A complementary analysis by phase assemblages was performed on the degraded layers of concrete specimens. These test results indicate that the mineral admixture type greatly affects the durability performance of SCC under magnesium sulphate exposure. Among the tested mineral admixtures, natural pozzolan showed better long-term durability performance in the magnesium sulphate environment. The interaction between vibrated concrete and SCC is related to the nature of the mineral admixtures

Assessment of Mechanical Properties and Damage of High Performance Concrete Subjected to Magnesium Sulfate Environment

“…Between 0 and 196 days, the expansion ratio was negative except for HPC2 at 196 days, which was attributed to shrinkage of HPCs. This phenomenon of shrinkage for HPCs is consistent with the results of high strength self-consolidating concrete under magnesium sulfate attack [1]. The shrinkage of HPCs may be due to their autogenous shrinkage at early erosion time.…”

“…The main elemental compositions of EDS area for HPC2 at 392 days were C, O, Mg, Si, S, Ca, and Pt, and their weight percent was 21.70%, 22.54%, 0.48%, 3.20%, 0.31%, 11.10%, and 39.39%, respectively, the result of which indicated that the material in the blue square was also ettringite. The microstructure evolution of HPC2 under sulfate attack was in line with the results of Siad et al [1].…”

“…Between 0 and 224 days, the mass loss ratio was negative, which indicated that the mass of HPCs was increased during this time. The phenomenon of mass gain for HPCs is in line with the results of high strength self-consolidating concrete under magnesium sulfate attack [1]. The mass gain could be due to water filling cracks, and to the water used to precipitate the hydrated phase, such as ettringite [30].…”

“…Uysal and Sumer [13] have presented an experimental investigation on the influence of fly ash on durability of self-consolidating concrete under magnesium sulfate attack, and the results indicated that the addition of fly ash can substantially improve the resistance of selfconsolidating concrete against magnesium sulfate attack. Another study concerning the long-term performance of self-consolidating concrete under magnesium sulfate attack by Siad et al [1] has shown that the resistance of selfconsolidating concrete under magnesium sulfate attack can be improved due to the addition of natural pozzolan. Silica fume is also used as supplementary cementitious material for the production of HPC, because of its pozzolanic reactivity and microfiller effect.…”

“…Sulfate attack is generally leading to the volume change and cracking, which results in concrete deterioration. In addition, sulfates are widespread in environment, such as underground water, soil, sea water, or industrial waste water [1]. What is more, magnesium sulfate (MgSO 4 ) has the fastest, most severe effects on concrete [2].…”