Synthesis and properties of a silane and copolymer-modified graphene oxide for use as a water-reducing agent in cement pastes

The addition of graphene oxide (GO) to cement paste significantly increases its toughness, however its fluidity is adversely affected. GO was first reacted with vinyltrimethoxysilane to produce a silane-modified graphene oxide (S-GO), which was then copolymerized with acrylic acid and a water reducing agent, isobutaenol polyoxyethylene ether (molecular mass 2400), to obtain a silane and copolymer-modified GO (P-S-GO) which acted as a water-reducing agent of the cement paste. A copolymer without GO was prepared under the same conditions for comparison. The structure, elemental composition and dispersibility of GO, S-GO and P-S-GO in a simulated cement environment (saturated lime water) were investigated by FTIR, XRD and a sedimentation test. The fluidity and rheology of the cement pastes with added GO, copolymer or P-S-GO were investigated. Results showed that vinyltrimethoxysilane reacted with the -OH group on the GO sheets to form an ether bond and the copolymer was grafted onto a vinyl group of S-GO by an addition reaction to produce the P-S-GO. The P-S-GO has a better dispersibility in saturated lime water with a negligible amount of aggregation compared to GO and a significant agglomeration occurs for GO. The addition of the P-S-GO to the cement pastes improves the fluidity and rheological properties compared with GO, offsetting the negative impact of GO and increasing the toughness of the resulting cements.