土木工程专业英语带译文.ppt

The carbon dioxide in the air reacts with the alkali in the cement and makes the pore water more acidic, thus lowering the pH. Carbon dioxide will start to carbonate the cement in the concrete from the moment the object is made. This carbonation process will start at the surface, then slowly move deeper and deeper into the concrete. The rate of carbonation is dependent on the relative humidity of the concrete - a 50% relative humidity being optimal. If the object is cracked, the carbon dioxide in the air will be better able to penetrate into the concrete. 空气中的二氧化碳与水泥中的碱反应，使孔隙水变酸，从而降低pH值。 二氧化碳将开始使混凝土中的水泥发生碳酸盐化。 这种碳酸化过程将从表面开始，然后慢慢地向混凝土深入。 碳化速度取决于混凝土的相对湿度 - 50％的相对湿度是最佳的。 如果物体破裂，空气中的二氧化碳会更好地渗透到混凝土中。 * When designing a concrete structure, it is normal to state the concrete cover for the rebar (the depth within the object that the rebar will be). The minimum concrete cover is normally regulated by design or building codes. If the reinforcement is too close to the surface, early failure due to corrosion may occur. The concrete cover depth can be measured with a cover meter. However, carbonated concrete only becomes a durability problem when there is also sufficient moisture and oxygen to cause electro-potential corrosion of the reinforcing steel. 在设计混凝土结构时，说明钢筋的混凝土保护层（钢筋的物体内部的深度）是正常的。 最小混凝土保护层通常由设计或建筑规范进行确定。 如果钢筋太靠近表面，可能会发生由腐蚀引起的早期失效。 具体的保护层深度可以用测量仪来测量。 然而，碳化混凝土只有在有足够的湿气和氧气引起钢筋的电位腐蚀时才会变成耐久性问题。 * * One method of testing a structure for carbonation is to drill a fresh hole in the surface and then treat the cut surface with phenolphthalein indicator solution. This solution will turn [pink] when in contact with alkaline concrete, making it possible to see the depth of carbonation. An existing hole is no good because the exposed surface will already be carbonated. 测试碳化结构的一种方法是在表面钻一个新的孔，然后用酚酞指示剂溶液处理切割表面。 与碱性混凝土接触时，该解决方案会变成粉红色，从而可以看到碳酸化深度。 现有的孔不好，因为暴露的表面已经被碳酸化了。 Chapter 6 Chlorides 氯化物 Chlorides, including sodium chloride, can promote the corrosion of embedded steel rebar if p