A new application of fluid loss agent in enhancing autogenous healing ability and improving mechanical properties of oil well cement

Enhanced autogenous healing is a desirable solution to improve the long-time durability and sustainability of cementitious materials . Herein, a self-healing agent, also is called cement-polymer composite additive (CPCA), was prepared by pretreatment of cement grains with polymer to accelerate the autogenous self-healing process. The polymer used in CPCA is the siloxane (vinyltrimethoxysilane) modified fluid loss agent (FLA-V), which can greatly reduce the fluid loss from the cement slurry to formation. Water contact angle test showed that the hydrophobic group in the FLA-V endowed CPCAs with different degrees of hydrophobicity , and CPCA-4 had better hydrophobicity. Results of hydration kinetics showed that the addition of CPCA-4 formed the graded hydration system , which densified the micro-structure and further improved the compressive strength of hardened cement. The compressive strength at 7 days was approximately 32.71% higher than that of plain cement. Furthermore, the strength recovery and crack width visualization test indicated that the addition of CPCA-4 enhanced the autogenous healing effectivity of the matrix. The compressive strength of the specimens with 5% CPCA-4 recovered 101.26% of its initial compressive strength after curing for 21 days. The micro-cracks measuring approximately 150 μm were completely sealed after healing for 28 days. The comprehensive measurements of the healed area indicated that the self-healing products mainly consisted of CaCO 3 , CH, and C–S–H.