Interface and crack propagation of cement-based composites with sulfonated asphalt and plasma-treated rock asphalt

Sulfonated asphalt and natural rock asphalt were used to toughen oil well cement paste (OWCP). The difference of micro-morphology, surface functional groups and heat resistance of two kinds of asphalt was studied. Rock asphalt was treated by low-temperature plasma, and the mechanism of improving hydrophilicity was further analyzed and explained. The toughness of cement-based composites with asphalt was analyzed from triaxial stress-strain curves. Interface characteristics between sulfonated asphalt or rock asphalt and cement paste were gained. The crack propagation in cement paste was discussed systematically by using SEM microscopic observation. The results show that the thermal stability of the rock asphalt is higher than that of the sulfonated asphalt. XPS analysis results show that oxygen-containing functional groups, such as C-OH, C=O, and C-O appear on the surface of rock asphalt treated by oxygen plasma. The surface free energy of plasma-treated rock asphalt was increased from 27.05 mJ.m(-2) to 53.29 mJ.m(-2), which indicates the improvement of hydrophilicity of the surface of rock asphalt. Triaxial stress-strain curve analysis results show that 3% content of sulfonated asphalt and treated rock asphalt can improve the toughness of oil well cement paste. A good interfacial transition zone with few micropores is found between the cement hydration products and sulfonated asphalt or treated rock asphalt by using SEM microscopic observation. SEM observation of crack propagation behavior in cement-based composites with asphalt indicated that sulfonated asphalt and plasma-treated rock asphalt improved the toughness of oil well cement by deflecting, bending and bridging the cracks. (C) 2020 Elsevier Ltd. All rights reserved.