Ingress of NaCl in concrete with alkali reactive aggregate: effect on silicon solubility
Ingress of NaCl in concrete with alkali reactive aggregate: effect on silicon solubility
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DOI：
10.1617/s11527-015-0788-y
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发表时间：
2016-10-01
影响因子：
3.8
通讯作者：
Heinz, Detlef
中科院分区：
文献类型：
--
作者：
Heisig, Anne;Urbonas, Liudvikas;Heinz, Detlef
混凝土在除冰盐（NaCl）作用下的碱-硅反应（ASR）破坏增强通常归因于氯离子在水泥水化产物中的结合。为了平衡电荷，OH-离子被释放到混凝土孔隙溶液中，从而增加碱度。然而，在NaCl侵入过程中，由于钾浸出导致的混凝土孔溶液的OH-浓度降低将降低SiO2溶解度，从而降低ASR损害。本工作结合膨胀测量与孔溶液分析的ICP-OES和XRD测量混凝土和水化水泥浆体。溶解度平衡计算与水文地球化学模拟程序PHREEQC。研究表明，孔隙溶液中OH-浓度的降低主要是由NaCl侵入过程中钾的淋溶作用引起的。OH-的浓度也降低，由于形成的弗里德尔盐从钙矾石，这是与硫酸盐的释放。虽然NaCl溶液中OH-浓度较低，但ASR损伤加剧，孔隙溶液中硅浓度较高。较高的硅溶解度是由较高的总碱浓度（其增加表面硅酸盐溶解度）、水络合物NaHSiO（3）（0）的形成和较高的离子强度来解释的。这些作用促进了硅酸盐矿物对ASR的敏感性，促进了碱硅凝胶的形成，最终促进了ASR的破坏。
Enhanced damage due to the alkali-silica reaction (ASR) in concrete exposed to deicing salt (NaCl) is usually attributed to binding of chloride ions in the hydration products of cement. To balance charge, OH- ions are released into the concrete pore solution which increases alkalinity. However, during NaCl ingress a decrease in the OH- concentration of the concrete pore solution due to potassium leaching would reduce SiO2 solubility and therefore ASR damage. The present work combines expansion measurements with pore solution analysis by ICP-OES and XRD measurements on concretes and hydrated cement pastes. Solubility equilibria calculations were performed with the hydrogeochemical simulation program PHREEQC. The investigations show that the OH- concentration of the pore solution is mainly lowered by potassium leaching during NaCl ingress. The OH- concentration also decreases owing to the formation of Friedel's salt from ettringite which is associated with the release of sulphate. Although the OH- concentration with NaCl is lower, ASR damage is intensified and the silicon concentration in the pore solution is higher. Higher silicon solubility is explained by the higher total alkali concentration which increases surface silicate solubility, the formation of an aqueous complex NaHSiO (3) (0) and a higher ionic strength. These effects promote the sensitivity of silicate minerals to ASR, the formation of alkali silica gel and finally ASR damage.