Evaluation of sulfate resistance of calcined dolomite activated ground granulated blast furnace slag

Aggressive environments significantly influence the durability and serviceability of hardened cement and concrete. This paper presents an evaluation of the resistance of ground granulated blastfurnace slag (GGBS) activated with calcined dolomite, as a novel alkali activator, to 5% sodium sulfate attack and 5% magnesium sulfate attack. Two calcined dolomites, D800 and D1000, were prepared in the laboratory at 800 °C and 1000 °C respectively. The results demonstrated the good potential of using calcined dolomite activated slag in resisting sulfate attack. Immersion in Na2SO4(aq) led to an increase in strength in both the D800 (D800S) and the Portland cement CEM I 52.5N (PCS) activated slag, with a more pronounced effect in the former, while a decrease in the D1000 (D1000S) activated slag. On the other hand, calcined dolomite activated slag 25 had less strength loss than PCS after MgSO4 attack. The products of sulfate attack and the deterioration processes are also analyzed by a range of tests including pH, weight change, corroded depth, XRD, TGA and SEM/EDS. After Na2SO4 attack, the main product on D800S and D1000S was gypsum with a larger amount in the later. Gypsum, thaumasite and M-S-H were the main products of D800S and D1000S after MgSO4 attack. The better resistance of D800S to sulfate attack was attributed to the absence of portlandite in the hydrated paste. On the other hand, the presence of portlandite in D1000S led to the inhomogeneous sulfate ions inward progression hence the severe deterioration of sample was observed.This study was supported by the China Scholarship Council, the Key Project of the Natural Science Foundation of China (41230636) and the National Basic Research Program of China (2011CB710605). The second author also wants to thank the Cambridge Trust and the China Scholarship Council for the financial support.This is the author accepted manuscript. The final version is available from ASCE via http://dx.doi.org/10.1061/(ASCE)MT.1943-5533.000139