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The Huaihe River Basin (HRB) is located in the climate transition zone between north and south of china, where cold and warm air flows are easily encountered, resulting in frequent extreme precipitation events occurred in this area. In this study, in order to extract the spatiotemporal distribution characteristics of extreme precipitation in the HRB, the optimal edge distribution functions were used to fit the precipitation series to obtain the extreme precipitation threshold, and then six indicators were used to describe the spatiotemporal distribution characteristics of extreme precipitation. The results show that the number of occurrences and the amount of precipitation in the HRB are generally greater in the southern part than in the northern part, but the intensity of precipitation in the eastern coastal areas is greater than in the inland areas. The Weibull function has the best fitting effect on both the precipitation and precipitation intensity series in the five zones of the HRB. As the cumulative probability increases, the area with the largest precipitation amount is Zone 1, and the area with the largest precipitation intensity is Zone 3. The spatial variation trends of extreme precipitation and intensity-based extreme precipitation in the HRB are roughly the same. The area with more extreme precipitation is in the southwest of the basin, while the area with higher precipitation intensity is on the eastern coast of the basin. The number of extreme precipitation occurrences has a decreasing trend in most of the basin, and the precipitation amount also has a decreasing trend, but the precipitation intensity has an increasing trend in the southern and northern parts of the basin. Both the start date and end date of extreme precipitation have an increasing trend, indicating that the occurrence time of extreme precipitation has a tendency to delay. This study can provide an important reference for the prevention of extreme precipitation disasters in the HRB. [ABSTRACT FROM AUTHOR]

By combining the nearest surface distribution function and hydration kinetic equation, analytical equations are proposed to determine the pore phase and solid phase evolution in the interfacial transition zone (ITZ). In addition, the numerical models for concrete with a single flat aggregate are constructed based on the CEMHYD3D hydration model. The results show that the degree of hydration is the main factor affecting the ratio of the average porosity to the matrix porosity in the ITZ. With an increase in the aggregate volume fraction and interface thickness, the volume fraction of the ITZ first increases and then decreases. The degree of overlap increases linearly with the interface thickness and the aggregate volume fraction. As the distance from the aggregate surface increases, high-density C-S-H increases, while low-density C-S-H and calcium hydroxide phases decrease. Finally, the predicted results using the analytical equations and numerical simulation are verified by testing via back-scattered electron microscopy, which indicates that the experimental results are more consistent with the predicted results of the analytical model than with those of the numerical model. [ABSTRACT FROM AUTHOR]

• The carbon reduction rate can reach 23.01% and 28.52% when the fly ash replacement rate is 24.5% and the stone powder is 8.33%. • The calculation method of carbon emission factor of manufactured aggregate is proposed. • The carbon emission factor of manufactured sand is 7.651 kgCO 2 /t, and the carbon emission factor of manufactured crushed stone is 8.483 kgCO 2 /t. • The change rate of compressive strength and carbon reduction rate were fitted by Gaussian distribution function. The fitting accuracy can reach more than 93 %. In recent years, it has become an inevitable trend to replace natural sand with manufactured sand. Manufactured sand is accompanied by carbon emissions from production to use. This study regarded this process as the process of manufactured sand from "cradle" to "adult". Based on the case, the energy consumption and carbon emissions of the process were tracked, the carbon emission factors of the manufactured sand and the manufactured gravel were determined, and the carbon emissions of the manufactured sand concrete (MSC) were calculated. On the other hand, the Gaussian distribution function is used to fit the compressive strength change rate and carbon reduction rate of manufactured sand concrete under different stone powder replacement rate and fly ash replacement rate. The fitting accuracy can reach more than 93%. The fitting results show that the fly ash replacement rate is 24.45%, and the stone powder replacement rate is 8.33%. The mix ratio is the optimal mix ratio, and the carbon reduction rate can reach 23.01% and 28.52%, respectively. [ABSTRACT FROM AUTHOR]

• An extrusion-based 3D printer for concrete with the largest aggregate size of 20 mm was introduced. • The range of ratios of cement and aggregate of printable concrete with coarse aggregate was recommended. • The direction-dependent mechanical properties of 3D printed concrete were investigated. • The voids distribution and the microstructure of interlayer area in 3D printed concrete were studied through X-CT and SEM. Concrete with coarse aggregate in the 3D concrete printing (3DCP) has broad prospects for high strength, low cost and shrinkage. In this study, an extrusion-based 3D printer was designed and utilized to print concrete with the largest aggregate size of 20 mm. Printable concrete with coarse aggregate was designed by different volume ratios of cement to aggregate (C/A). Then the effect of C/A on the printability and direction-dependent mechanical performance was investigated. X-ray micro-computed tomography (X-CT) was used to detect and analyze the voids distribution characteristics of printed specimens. Scanning electron microscope (SEM) investigations of microstructure at the interlayer area were conducted. Results indicated that the initial flowability of printable concrete should be within 178–200 mm, and the recommended printable C/A was within 0.35–0.60. The decrease of C/A improved the maximum printing height and mechanical performance but weakened the shape-stability of the multi-layer structure. X-CT results indicated that reducing excess slurry content caused by the decline of C/A decreased the compactness of the printed structure. The compressive strength and flexural strength of 3D printed specimens showed a direction-dependent characteristic, mainly related to the non-uniform distribution of voids revealed by X-CT. SEM images revealed the "micro-bridging" morphology in the interlayer area and proved that there were carbonation and structural weakening problems at the surface and surrounding of this area. [ABSTRACT FROM AUTHOR]