Search

The low liquid limit silty soil in the North China plain area is generally unsuitable for direct use as roadbed and slope soil. In order to improve the performance of low liquid limit silty soil, xanthan gum was used as an improver. Through a series of tests, the improvement effect of xanthan gum on low liquid limit silty soil was studied. The test results showed that Xanthan gum as an improver could significantly improve the unconfined compressive strength of silty soil. With the increase in dosage and curing age, the unconfined compressive strength of improved silty soil continued to improve and eventually tended to stabilize. The optimal dosage and curing period were 2% and 7 days, respectively. In addition, Xanthan gum could greatly improve the permeability and disintegration of low liquid limit silty soil. The permeability coefficient of improved silty soil with a content of 0.75% Xanthan gum and a 7-day curing period was 4.73 × 10−4 m·s−1, which was only 1.10% of that of plain silty soil at the same curing period. After immersion in water for 12 h, the soil only experienced slight disintegration. The scanning electron microscope image showed that the gel generated by the hydration reaction of Xanthan gum could improve the compactness and integrity of the soil by filling the voids, thus significantly improving the mechanical and hydraulic properties of the low liquid limit silty soil. [ABSTRACT FROM AUTHOR]

In this study, we present the effects of 0.004~0.098 wt% Zr and thermo-mechanical processing (TMP) on the microstructure and mechanical properties of the China RAFM steel, CLAM, as a feasibility study for improving mechanical properties. The inclusions in ingots were characterized using optical microscope (OM) and scanning electron microscope (SEM), which could be classified as fine simple particles and large complex particles. The complexity of the alloy's inclusion composition increases with the increasing Zr concentration. The higher the Zr content, the more complex the composition of inclusions in the alloy. The average diameter of inclusions in 0.004Zr steel was the smallest, which was 0.79 μm and the volume fraction was 0.018%. The highest yield strength, tensile strength, elongation, and impact energy of 0.004Zr alloy at room temperature were 548.3 MPa, 679.4 MPa, 25.7%, and 253.9 J. The structure of the TMPed steels was all tempered martensite. With the increase in tempering temperature, the yield and tensile strength of the experimental steel gradually decreased, while the elongation and impact energy gradually increased. The 0.004ZrD and 0.004ZrH alloys had the best yield strength and impact energy, which were 597.9 and 611.8 MPa and 225.9 and 243.3 J, respectively. In addition, the alloys showed good thermal stability during the aging at 600 °C for 1500 h. It was discovered that TMP is a simple and practical industrial technique that could successfully enhance the mechanical properties of CLAM steel without sacrificing impact toughness. [ABSTRACT FROM AUTHOR]

• Under suitable parameters, reduced scale FW mock-up with complex cooling channels formed by SLM was realized. • Great forming quality and performance (exceed forgings and castings) were tested. • The effect of microstructure on mechanical properties was investigated by SEM and EBSD analysis, which proved anisotropy and provide reference for SLMed RAFM steel. The blanket, one of the most important parts in China Fusion Engineering Test Reactor (CFETR), is the carrier with core function for fusion reactor application. First wall (FW) is the key unit of the blanket, facing the plasma directly and playing a decisive role in the fusion reactor. In this study, the reduced scale FW U-shaped mock-up formed by selective laser melting (SLM) was investigated. The influence of microstructure anisotropy on mechanical properties from vertical direction (z-x) and horizontal direction (x-y) was researched and the feasibility of SLM technology applied to nuclear fusion was explored. Experimental results show that the grain structure is mainly polygonal cellular crystals in x-y direction and elongated columnar crystals in z-x direction under scanning electron microscope (SEM) observation. This grain growth mode is attributed to the complicated temperature field inside molten pool. The inverse pole figures (IPF) in electron backscatter diffraction (EBSD) analysis suggest that the SLMed 316 L in z-x direction has the preferred orientation in (110) and (111) in x-y direction. Compared with 316 L forgings, SLMed 316 L showed higher average tensile strength, elongation rate and Vickers hardness in 2 directions. The impact toughness was enhanced compared with previous references, which demonstrated that SLM technology is proved an effective way to fabricate FW in the nuclear fusion field. [ABSTRACT FROM AUTHOR]

Polymer-modified concrete and fiber concrete are two excellent paving materials that improve the performance of some concrete, but the performance of single application material is still limited. In this paper, polymer-modified concrete with strong deformation and fiber concrete with obvious crack resistance and reinforcement effect were compounded by using the idea of composite material design so as to obtain a high-performance pavement material. The basic mechanical properties of high-content hybrid fiber–polymer-modified concrete, such as workability, compression, flexural resistance, and environmental durability (such as sulfate resistance) were studied by using the test regulations of cement concrete in China. The main results were as follows. (1) The hybrid fiber–polymer concrete displayed reliable working performance, high stiffness, and a modulus of elasticity as high as 35.93 GPa. (2) The hybrid fiber–polymer concrete had a compressive strength of 52.82 MPa, which was 31.2% higher than that of the plain C40 concrete (40.25 MPa); the strength of bending of the hybrid concrete was 11.51 MPa, 191.4% higher than that of the plain concrete (3.95 MPa). (3) The corrosion resistance value of the hybrid fiber–polymer concrete was 81.31%, indicating its adjustability to sulfate attack environments. (4) According to cross-sectional scanning electron microscope (SEM) images, the hybrid fiber–polymer concrete was seemingly more integrated with a dense layer of cementing substance on its surface along with fewer microholes and microcracks as when compared to the ordinary concrete. The research showed that hybrid fiber–polymer concrete had superior strength and environmental erosion resistance and was a pavement material with superior mechanical properties. [ABSTRACT FROM AUTHOR]