Rapid Hardening of Cement by the Addition of a Mechanically Activated Al(OH)₃–Ca(OH)₂ Mixture

Abstract

Rapid hardening of cement was achieved in the present study by adding a mechanically activated Al(OH) 3 -Ca(OH) 2 mixture to the starting cement paste. Among the dominant parameters for hardening were the mechanical treatment time for the Al(OH) 3 powder and the Al(OH) 3 /Ca(OH) 2 ratio. The hardening mechanisms are discussed here in terms of the ionic concentration of the solution and the hydration products created when the Al(OH) 3 -Ca(OH) 2 mixture was added to water. Mechanical activation of the Al(OH) 3 powder accelerated dissolution into an aqueous alkaline solution and induced the formation of calcium aluminate hydration products. Those hydration products increased the compressive strength of the cement paste at a very early stage of hardening.

Investigation of Different NiO/NiAl2O4 Particles as Oxygen Carriers for Chemical-Looping Combustion

“…The influence of small additions of MgO and Ca(OH) 2 to the oxygen carriers were also investigated. The inclusion of MgO has earlier been found to have beneficial effects on the methane conversion, , and Ca(OH) 2 is a well-known additive to increase the mechanical strength of materials, such as cement . Further, Johansson et al have reported an increased strength when CaO was added to NiO particles supported by NiAl 2 O 4 .…”

Long-term effective remediation of black-odorous water via regulating calcium nitrate sustained-release

“…In the control group, its pH value was increased to 7.53 with transferring the water into reactors, which might be caused by the volatilization of acidic components, and then uctuated around 7.51 (± 0.54) with the depletion of acidic components. However, the pH value of the eco-concrete group was signi cantly increased and maintained to 8.89, which might be caused by the release of Ca(OH) 2 and Al(OH) 3 from calcium sulphoaluminate cement (Kitamura et al, 2000) and the increase of alkalinity resulting from denitri cation (Xing et al, 2018).…”

“…Moreover, with the participation of ecoN-concrete, lots of dissolved compounds (such as dissolved organic matters, S 2− , Fe 2+ ) were absorbed by the concrete rapidly (Xie et al, 2021). Simultaneously, the micro-occulation and coprecipitation effect of Ca 2+ , Ca(OH) 2 , and Al(OH) 3 released from the eco-concrete quickly removed the suspended colloids and particles (such as insoluble organic matters, suspended solids), which was the main reasons for turbidity in the black-odorous water (Kitamura et al, 2000). Therefore, a signi cantly decrease of COD and turbidity at the early stage of experiment were observed (Fig.…”

Mechanochemical Synthesis of Slow‐Release Fertilizers through Incorporation of Alumina Composition into Potassium/Ammonium Phosphates

“…I NTENSIVE investigations on mechanochemical phenomena have revealed a wide range of mechanochemical reactions, especially during high-energy dry milling, covering almost all the aspects of chemistry [1][2][3][4][5][6][7][8][9][10] and the interests in this field tend to rise continuously, considering the increasing number of the related papers published annually. Based on our efforts, 11,12 it has been found that the mechanochemical reactions depend on the crystal structures of starting materials and the starting materials which easily undergo polymorphous transformation from loose packing to close one of atoms seem to have high reactivity.…”