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In order to study the effect of composite clays on the mechanical properties, water absorption and salt tolerance of a hydrogel, a poly(acrylic acid-co-acrylamide)/bentonite/kaolin composite hydrogel was prepared. Acrylic acid and acrylamide have been used as water absorbent monomers. N,N′-methylene bisacrylamide was used as a crosslinking agent while potassium persulfate was used as an initiator. The water preserving capability, repeated water absorption, salt resistance and the mechanical properties of the composite hydrogel are analyzed and discussed. The results show that a small quantity of bentonite can increase the storage modulus of the composite hydrogel, whereas the excess clay had an unfavorable effect on the mechanical strength of the composite hydrogel. Both bentonite and kaolin significantly improved the water preserving capability, repeated water absorption and salt resistance of the composite hydrogel. Optimum values for the amounts of bentonite and kaolin were found to be 10% and 5%, respectively.

Melamine (M), phenol (P) and formaldehyde (F) were used as raw materials to synthesize a melamine–phenol–formaldehyde resin (MPF) which was used as shell material to prepare a self-healing microcapsule with E-51 epoxy resin as the core, via in situ polymerization. Fourier transform infrared spectroscopy, environmental scanning electron microscopy and laser particle size analysis were used to characterize the surface morphology, structure and properties of the microcapsule. The influence of the reaction conditions on the properties of the microcapsule was investigated by orthogonal testing. The mass ratio between the MPF shell and the epoxy resin core was found to be 1.2:1.0, optimum pH for shell formation was found to be 3, the emulsification speed was 800 r/min, the acidification speed was 400 r/min and the acidification temperature was 60°C. Under these conditions, the prepared microcapsules are regular and spherical with a smooth, dense surface and uniform particle size with a normal distribution. The microcapsules remained well dispersed and did not aggregate. The orthogonal test revealed that the average particle size and yield of the microcapsules are mainly determined by the core/shell mass ratio, whereas the reaction temperature had a greater impact on the core content of the microcapsules. Although the best microcapsule samples showed poor anti-permeability in ethanol, they exhibited good thermal, isothermal and storage stabilities. This indicates that they may be stored at a constant temperature.

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Environmentally friendly and cheap composite green cementitious materials have been prepared from carbide slag, fly ash, fluegas desulphurisation (FGD) gypsum, and granulated blast-furnace slag (GBFS) without using cement clinker. Orthogonal testing was used to investigate the effects of the raw materials on the amount of water required for reaching standard consistency and consistency, setting time, slump value, and strength of the produced materials after curing for 7 d and 28 d. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used for the analysis of the sample microstructure and hydration products as well as for the exploration of possible hydration mechanisms. We found that, among the utilised raw materials, the addition of FGD gypsum had the most significant effect on the setting time and amount of water required for reaching standard consistency and consistency, while the addition of GBFS deeply affected the slump value. e optimal activation results were obtained when the mass ratio of carbide slag : fly ash : GBFS : FGD gypsum was equal to 12