基于氮吸附的水泥-沥青复合硬化体孔结构分析

Study on Pore Structure of Hardened Cement-asphalt Paste by Nitrogen Adsorption

水泥沥青砂浆是一种多相多孔的复合材料,其组分为水泥-沥青共同形成的复合胶凝体。为了解水泥沥青砂浆中的孔隙结构,应用低温氮吸附法分析了不同水泥-沥青质量比的水泥-沥青复合硬化体中BET比表面积、2～200nm孔分布随龄期的变化。测试结果显示:水泥-沥青复合硬化体的BET比表面积显著低于硅酸盐水泥石,随龄期增长而增大;在氮吸附法有效的孔径分析范围内(2～200nm),随龄期的增长,孔径50nm以下的孔数量增长显著,28d龄期CAB浆体的微分孔径分布曲线在5～7nm及20～50nm出现的分布峰,可分别归结于水化产物数量的增长及水化产物的填充作用;沥青含量对孔分布及孔结构形成有显著影响,随沥青含量的增大,复合硬化体的BET比表面积降低,小于50nm的孔数量减少。

Cement-asphalt binder acts as a binding component in cement-asphalt mortar, which is a porous composite. Nitrogen adsorption method is adopted to investigate the pore structure of cement-asphalt binders with various asphalt content at different ages. Test results show that the BET specific surface area of harden cement-asphalt paste increases with the growth of curing age,and is much lower than that of harden Portland cement paste. In the valid testing range of Nitrogen adsorption （2~200 nm）, the amount of pores smaller than 50 nm increases with the curing age. At the age of 28 d,due to the increase in the amount of hydration products and their filling effect, there are the peaks in the pore distri- bution curve around 5~7 nm or between 20 nm and 50 nm respectively. The content of asphalt affects the distribution and development of pore size. With the increase in asphalt content, there is a decrease in both BET specific surface area and the amount of pore smaller than 50 nm.