Sulfate attack on mortars: physical aspects, products and microstructures

• 作 者: KaiweiLiu[1]MinDeng[2]AiguoWang[3]DaoshengSun[3]
• 机 构: College of Materials Chemistry and Engineering, Anhui Jianzhu University, Hefei 230022, China
• 出 处: The 14th International Congress on the Chemistry of Cement (
• 发表日期: 2015年期

　　This paper investigated the damage process of mortars that were immersed in solutions containing 3000 mg SO42-/1 or 33800 mg SO42-/1, which were used to simulate sulfate concentrations in the field and accelerated laboratory test solutions.The consequences of external sulfate attack were investigated by visual aspects,expansion, compressive strength and ultrasonic velocity.The mineral phases and microstructures were investigated using X-ray diffraction (XRD) and Scanning electron microscopy (SEM) after 90, 150, 300 and 600 days of immersion to analyze the process during sulfate attack.The kinetics and degradation mechanisms were both affected by the sulfate concentrations in the solutions.Gypsum was detected in the mortars that were immersed in the accelerated test sulfate solution while only ettringite was formed in the low sulfate concentration.The sulfate concentration is the key factor for gypsum formation at a given pH value.Fine ettringite result in expansion, which caused the formation of gaps between the sand and paste and the cracks.Gypsum and large ettringite crystal are just deposited in the cracks or gaps, which contributed to little or no expansion.In additional, gypsum formation was accompanied by the consumption of calcium hydroxyl, which resulted in the decrease the compressive strength.