Mass Change Prediction Model of Concrete Subjected to Sulfate Attack

Kwang-Myong Lee,Jae-Im Park,Soon-Oh Kwon,Su-Ho Bae

doi:10.1155/2015/298918

Abstract

The present study suggested a mass change prediction model for sulfate attack of concrete containing mineral admixtures through an immersion test in sulfate solutions. For this, 100% OPC as well as binary and ternary blended cement concrete specimens were manufactured by changing the types and amount of mineral admixture. The concrete specimens were immersed in fresh water, 10% sodium sulfate solution, and 10% magnesium sulfate solution, respectively, and mass change of the specimens was measured at 28, 56, 91, 182, and 365 days. The experimental results indicated that resistance of concrete containing mineral admixture against sodium sulfate attack was far greater than that of 100% OPC concrete. However, in terms of resistance against magnesium sulfate attack, concrete containing mineral admixture was lower than 100% OPC concrete due to the formation of magnesium silicate hydrate (M-S-H), the noncementitious material. Ultimately, based on the experimental results, a mass change prediction model was suggested and it was found that the prediction values using the model corresponded relatively well with the experimental results.

Highlights

Concrete structures exposed to soil, groundwater, and seawater environments are subject to performance degradation due to sulfate attack
In case of water-binder ratio (W/B) = 32%, compressive strength of binary blended cement (BBC) concrete and ternary blended cement (TBC) concrete containing mineral admixture was higher than 100% ordinary portland cement (OPC) concrete
In case of W/B = 43%, compressive strength of BBC concrete and TBC concrete was found to be generally lower than 100% OPC concrete

Summary

Introduction

Concrete structures exposed to soil, groundwater, and seawater environments are subject to performance degradation due to sulfate attack. In case of sodium sulfate (Na2SO4) attack, the reaction of sulfate ion (SO42−) and calcium hydroxide generated by cement hydration forms gypsum, which results in softening and loss of strength of cement paste. In this case, the gypsum reacts with calcium aluminate hydrate (C4AH13), monosulfate (C4A S H12), and tricalcium aluminate (C3A) to produce secondary ettringite, which accompanies volume increase, and results in expansion and cracking [5,6,7]. As the increased brucite reacts with S2H, C-S-H gradually loses lime and becomes converted to noncementitious M-S-H [6, 8, 9]

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Conclusion