An amphoteric hydrogel: Synthesis and application as an internal curing agent of concrete

Abstract

A new crosslinked amphoteric hydrogel (PAC) was synthesized and evaluated as an internal curing agent of concrete. PAC was prepared from acrylamide (AM) and 4-(2-((carboxylatomethyl)dimethylammonio)ethoxy)24-oxobut-2-enoate (CMD) through free-radical polymerization by using ammonium persulfate (APS) as an initiator and methylene-bisacrylamide (MBA) as a crosslinker. The structure of the prepared polymer was verified by the IR spectra. The effects of the polymerization variables on the swelling capacity of PAC were investigated. The water absorbency of PAC was found to increase with increasing CMD/AM ratio, reach a maximum value, and decrease afterword. Increase of either APS or MBA content decreased the water absorbency. The highest water absorbency of PAC hydrogel (P7) achieved in deionized water, 0.1M NaCl solutions and 0.1M CaCl 2 solutions, was 306 g/g, 32 g/g, and 22 g/g, respectively. Compared with a commercial acrylate-based hydrogel 283HA, P7 was less sensitive to the existence of Ca 21 ions in cement pore solutions, and more effective in reducing the cracking tendency of cement pastes. Finally, mortars incorporated with proper amounts of P7 showed smaller drying shrinkage and higher compressive strength than that without hydrogel present. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42175.

Synthesis, Application and Effect of Hybrid Nanocomposites Based on Hydrogel and Nanoclay in Cement-Mortars

“…Therefore, research on chemical admixtures has been carried out, mainly regarding water control [ 6 ], because most of the cement hardening chemical reactions occur in this component [ 7 ]. Water control is a method that is found to ensure the more effective hydration of cement particles, which contributes to the development of a more uniform microstructure and pore structure [ 8 , 9 ], improving the mechanical properties and durability [ 10 ] of cement-based materials. This procedure is denominated as an “internal cure”, and its function is not only to assist cement hydration but also to maintain high humidity in the cement matrix [ 11 ] to avoid small deformations, cracks, and low mechanical properties [ 12 ].…”

“…Thus, several studies on cement-based composites have been developed with the application of synthetic commercial superabsorbent polymers, based on acrylamide, acrylic acid, sodium acrylate, methyl acrylate, and so on, in cementitious materials as internal curing agents [ 17 , 18 , 19 , 20 ]. The main characteristics of these polymers are the absorption and release of water over time [ 21 ], which effectively contribute to the maintenance of the internal moisture of the cementitious matrix since traditional curing methods, such as wet and membrane curing, are considered external curing methods [ 9 ].…”

“…Recent research [ 9 , 22 ] has demonstrated the promising application of hydrogels in cement matrices, and understanding the behavior of polymers in cementitious materials is necessary for the optimum design of internal curing [ 23 ]. Hydrogels are also known as hydrophilic absorbent polymers.…”