Preventive Measures and Mechanisms of Concrete Deterioration due to ASR under Marine Environments

本财政年度的研究结果分为两类，即含蛋白石砂浆在氯化钠溶液和人工海水中的反应产物及其在海洋环境中的膨胀行为。以往实验的主要结果如下：(1)所有含蛋白石的砂浆在1N的氯化钠溶液中浸泡过程中，大量的Ca(OH)2被耗散。(2)在含蛋白石的砂浆中，在1N的氯化钠溶液中浸泡超过1个月后，在部分和空隙中都发现了大量的含氯钙矾石。砂浆的膨胀量可能越大，砂浆中钙矾土的含量就越多。(3)浸泡砂浆试件的氯化钠溶液浓度对碱/蛋白石比相对较低的砂浆的膨胀率影响很大。然而，在高碱/蛋白石比范围内，氯化钠溶液的浓度对砂浆的膨胀几乎没有影响。在连续几年的后续试验中，得到了以下新的发现：(1)单位水泥含量为450 kg/cm~3的活性骨料混凝土试件的裸露表面发生了快速膨胀。这一事实表明，由于碱-硅酸反应，海水的喷射正在影响混凝土的膨胀。(2)发现混凝土中的碱含量越少，暴露在海洋环境中的混凝土的膨胀越大。

The results obtained in this fiscal year are divided into the two categories, i. e. the one on the reaction products and expansion behavior in opal-bearing mortars immersed in NaCl solutions and an artificial sea water, exposed to a marine environment.The major results obtained in the former experiments are summarized as follows ;(1) Great amounts of Ca (OH)2 in all mortars with the opal were dissipated during the immersion in 1 N NaCl solution.(2) Great amounts of the chloride-bearing ettringite was found in the portions as well as in voids in opal-bearing mortars immersed in 1 N NaCl solution for longer than one vear. It is likely that the greater the expansion of mortars, the greater the amount of ettringite found in the mortars.(3) The concentration of NaCl solution in which mortar specimens were immersed, greatly influenced the expansion of mortars with relatively low alkali/opal ratio. However, in the range of high alkali/opal ratio, the concentration of the NaCl solution little influenced the expansion of the mortars.The following new findings were obtained in the latter experiments which have been successively carried out for these several years.(1) Rapid expansions occurred on the exposed surfaces in reactive aggregate-bearing concrete specimens with the unit cement content of 450kg/cm3. This fact suggests that spray of sea water is influencing the expansion of the concrete due to the alkali-silica reaction.(2) There is found a trend that the less the alkali content in the concretes, the greater the expansion of the concretes exposed to the marine environment.