Influence of colloidal nanosilica on hydration kinetics and properties of CaO/CaSO_(4)-activated slag binder

To solve the energy consumption and CO_(2) emission during cement production,the new binders must be developed as an alternative to cement.CaO/CaSO_(4)-activated slag binder is an eco-friendly and safe cementitious material;however,its low strength during initial stages limits its applications.In this study,colloidal nanosilica(CNS)was employed as an additive to improve the strength of CaO/CaSO_(4)-activated slag binder,and the effects of CNS on the workability,hydration kinetics,hydration products(type,quantity,and polymerization degree),and binder microstructure were thoroughly investigated.A moderate CNS content,through its nucleation effect,significantly increased the hydration rate of the nucleation and crystal growth(NG),phase boundary interaction(I)and diffusion(D)processes,which generated large quantities of calcium aluminosilicate hydrate(C-A-S-H)gel in the initial hydration stage.Meanwhile,the addition of CNS improved the polymerization degree of C-A-S-H gel.This amorphous reactant well-filled the pore space between slag particles and yielded a compact microstructure,consequently enhancing the binder strength.Considering the reduction in fluidity and the increase in production cost,the CNS mass fraction was controlled as3%,and the binder reached the satisfactory strengths of 3.87,24.47,31.43,and 41.78 MPa at 1,3,7,and 28 d,respectively.

Photocatalytic water splitting of ternary graphene-like photocatalyst for the photocatalytic hydrogen production

In recent times,there has been an increasing demand for energy which has resulted in an increased consumption of fossil fuels thereby posing a number of challenges to the environment.In the course finding possible solutions to this environmental canker,solar photocatalytic water splitting to produce hydrogen gas has been identified as one of the most promising methods for generating renewable energy.To retard the recombination of photogenerated carriers and improve the efficiency of photocatalysis,the present paper reports a facile method called the hydrothermal method,which wa s used to prepare ternary graphene-like photocatalyst.A“Design Expert”was used to investigate the influence of the loading weight of Mo and GO as well as the temperature of hydrothermal reaction and their interactions on the evolution of hydrogen(H 2)in 4 h.The experimental results showed that the ternary graphene-like photocatalyst has a strong photocatalytic hydrogen production activity compared to that of pure SiC.In particular,the catalyst added 2.5 wt%of GO weight yielded the highest quantum of 21.69%at 400-700 nm of wavelength.The optimal evolution H2 in 4 h conditions was obtained as follows:The loading weight of Mo was 8.19 wt%,the loading weight of GO was 2.02 wt%,the temperature of the hydrothermal reaction was 200.93℃.Under the optimum conditions,the evolution of H2 in 4h could reach 4.2030 mL.