降水对沥青结合料组分影响的化学机制分析

Analysis of the chemical mechanism of precipitation effects on asphalt binder

采用人工模拟周期浸泡法进行降水对沥青结合料化学影响的试验模拟,结合试验现象,通过沥青中不同组分与水的物理化学和化学作用分析沥青路面水损害中降水对沥青的软化作用.发现水对沥青组分的影响体现在几个方面:沥青中的强极性组分羧酸类和酚类等含氧化合物遇水会发生溶解和电离;亚砜类则可直接与水发生化学反应而提高介质酸性;沥青酸与集料中的碱金属氧化物和盐类反应生成的低价高级有机酸盐属低价皂类化合物,在有水存在的条件下会充当乳化剂,具有增溶作用;水中含有氢离子时,氢离子会与不溶于水的二价和其他高价有机酸盐类物质反应,置换其中的金属离子,生成新的沥青酸,这些酸类又会与低价碱金属化合物反应,生成加剧增溶作用的乳化剂.沥青与矿料之间的粘附是以沥青和矿料中的化学成分为物质基础的,沥青中存在有较多的极性物质时能良好地润湿矿料,水分使沥青变软、粘附性降低的作用与沥青组分在水作用下的变化有关.

The effect of precipitation on softening asphalt in asphalt pavement moisture damage is analyzed through the study of physical chemistry and chemical reaction among different components of asphalt and water.Soak method is used referring to artificial rainfall simulation cycles.Analysis is conducted on testing phenomena.The impact of water on the asphalt composition is reflected in several aspects：The strong polar asphalt components of carboxylic acid and phenolic compounds will dissolve with water and ionizing will occur.Sulfoxide class can react with water directly and its product can improve medium acidity.Asphalt acid and alkali metal oxides and salts can react and produce protosalt organic soap compounds.In the presence of water,these compounds will act as emulsifiers with the solubilization effect.When water contains hydrogen ions,they can react with divalent salts of organic acids,replace the metal ions,and generate new asphalt acids.These acids can respond with low alkali metal compounds and in turn aggravate solubilization.Adhesion between asphalt and aggregate is based on the chemical composition of the material.Asphalt with more polar substances can better wet aggregate.Softening of asphalt under water and reduction of adhesion are related to components changes under the effect of precipitation.