Toward a Socio-Political Approach to Promote the Development of Circular Agriculture: A Critical Review.

Under the dual pressure of ensuring global food security and coping with the effects of climate change, many countries have proposed projects of circular agriculture to mitigate the vulnerability of agricultural systems. However, due to the different utilizations of agricultural resources in different countries, there are still some important limitations and obstacles to the promotion of agricultural recycling technologies. This review discusses global circular agriculture projects from a social science perspective. We found that (1) current research on circular agriculture is concentrated in the field of natural sciences with a focus on technological upgrading, neglecting social, political and economic research; (2) top-down circular agriculture projects rely on infrastructure and technical inputs for management, which undermines the focus on public participation and is limited by the timing and intensity of state intervention; (3) the development model led by enterprises or associations relies on cooperation and benefit games with farmers, and its sustainability depends largely on changes in the regulation of the agricultural waste utilization system. Based on this, this review argues that circular agriculture projects are not only technical issues in the field of natural sciences, but also strongly influenced by social development. For future research, we strongly recommend cross-disciplinary cooperation, not limited to technology development.

The Effect of Fineness on the Hydration Activity Index of Ground Granulated Blast Furnace Slag.

To improve the properties of ground granulated blast furnace slag (GGBS) and utilize ground granulated blast furnace slag efficiently, this study investigates the effect of fineness on the hydration activity index (HAI) of ground granulated blast furnace slag. The hydration activity index of GGBS with six specific surface areas (SSAs) was characterized by the ratio of compressive strength of the prismatic mortar test block. The particle size distribution of GGBS with different grinding times was tested by laser particle size analyzer. The paste of different specific surface area GGBSs in different curing ages was investigated at the micro level by X-ray diffraction, scanning electron microscope, energy dispersive spectrometer, thermogravimetric scanning calorimeter, and differential scanning calorimeter. The effect of particle distribution of GGBS on the hydration activity index of different curing ages was studied by gray correlation analysis. The results indicated that the compressive strength and hydration activity index increases with the increase of a specific surface area of GGBS at different curing ages. The hydration activity index at different curing ages is almost a linear role for specific surface areas. With the increase in the specific surface area of GGBS, the content of Ca(OH)2 in paste decreases gradually. When GGBS was added into a mortar test block, the hydrate calcium silicate gel in paste changed from a high Ca/Si ratio to a low Ca/Si ratio. The 0-10 micron particles of GGBS particle distribution were highly correlated with the hydration activity index at different curing ages.