Single-factor analysis and interaction terms on the mechanical and microscopic properties of cemented aeolian sand backfill

The use of aeolian sand(AS)as an aggregate to prepare coal mine cemented filling materials can resolve the problems of gangue shortage and excessive AS deposits.Owing to the lack of research on the mechanism of cemented AS backfill(CASB),the response surface method(RSM)was adopted in this study to analyze the influence of ordinary Portland cement(PO)content(x_(1)),fly ash(FA)-AS(FA-AS)ratio(x_(2)),and concentration(x_(3))on the mechanical and microscopic properties of the CASB.The hydration characteristics and internal pore structure of the backfill were assessed through thermogravimetric/derivative thermogravimetric analysis,mercury intrusion porosimetry,and scanning electron microscopy.The RSM results show that the influence of each factor and interaction term on the response values is extremely significant(except x_(1)x_(3),which had no obvious effect on the 28 d strength).The uniaxial compressive strength(UCS)increased with the PO content,FA-AS ratio,and concentration.The interaction effects of x_(1)x_(2),x_(1)x_(3),and x_(2)x_(3) on the UCS at 3,7,and 28 d were analyzed.In terms of the influence of interaction items,an improvement in one factor promoted the strengthening effect of another factor.The enhancement mechanism of the curing time,PO content,and FA-AS ratio on the backfill was reflected in the increase in hydration products and pore structure optimization.By contrast,the enhancement mechanism of the concentration was mainly the pore structure optimization.The UCS was positively correlated with weight loss and micropore content but negatively correlated with the total porosity.The R^(2) value of the fitting function of the strength and weight loss,micropore content,and total porosity exceeded 0.9,which improved the characterization of the enhancement mechanism of the UCS based on the thermogravimetric analysis and pore structure.This work obtained that the influence rules and mechanisms of the PO,FA-AS,concentration,and interaction terms on the mechanical properties of the CASB provided a certain theoretical and engineering guidance for CASB filling.

Temperature dependence of microscopic properties in diblock copolymer films:A dissipative particle dynamics simulation

Temperature dependence of microscopic properties in diblock copolymer films has been investigated by dissipative particle dynamics simulations. Results show the relation between mean-square bond length （MSBL） and system temperature can be described as a quadratic curve. The root-mean-square radius of gyration （RMSGR） and end-end distance （RMSED） increase gradually as the temperature rises and composition fraction changes from 0.1 to 0.5, in which the effect of the former is primary. Especially, the relation between RMSGR and temperature is nearly linear in the confinement-introduced direction. Density distribution of each component in the films can be controlled and adjusted effectively by its interaction with other components and boundaries. Moreover, the changes of system temperature and composition fraction can both affect the density distributions to a certain extent.

Research Analysis on the Microscopic Properties and Damping Performance of Carbon Nanomaterial-Modified Cement Mortar

The application of carbon nanomaterials, particularly graphene and carbon nanotubes, in cement-based composites is highly significant. These materials demonstrate the multifunctionality of carbon and offer extensive possibilities for technological advancements. This research analyzes how the integration of graphene into cement-based composites enhances damping and mechanical properties, thereby contributing to the safety and durability of structures. Research on carbon nanomaterials is ongoing and is expected to continue driving innovation across various industrial sectors, promoting the sustainable development of building materials.

Analysis of Calcined Red Mud Properties and Related Mortar Performances

Red mud(RM)is a low-activity industrial solid waste,and its utilization as a resource is currently a hot topic.In this study,the micro characteristics of red mud at different calcination temperatures were analyzed using X-ray diffraction and scanning electron microscopy.The performance of calcined red mud was determined through mortar strength tests.Results indicate that high-temperature calcination can change the mineral composition and microstructure of red mud,and increase the surface roughness and specific surface area.At the optimal temperature of 700°C,the addition of calcined red mud still leads to a decrease in mortar strength,but its activity index and flexural coefficient increase by 16.2%and 11.9%with respect to uncalcined red mud,reaching values of 0.826 and 0.974,respectively.Compared with the control group,the synergistic activation of calcined red mud with slag can increase the compressive and flexural strength of the mortar by 12.9%and 1.5%,reaching 8.7 and 62.4 MPa,respectively.Correspondingly,the activity index and flexural coefficient of the calcined RM and GGBS(Ground Granulated Blast furnace Slag)mixtures also increase to 1.015 and 1.130,respectively.

The physical, chemical, and microscopic properties of masonry mortars from Alhambra Palace （Spain） in reference to their earthquake resistance

Al-Andalus mortar is an ancient binding material （lime mortar） that was used for centuries in numerous historical buildings in Al-Andalus, Granada （Spain）. The physico-chemical and microscopic properties of Al-Andalus mortars in Granada were studied as part of an investigation into the mineral raw materials present in the territory of Spain. Scanning electron microscope and X-ray diffraction analyses of eight main types of mortars were performed to show the presence of calcite, gypsum, quartz, and muscovite minerals with organic fibers. Chemical analyses of the specimens showed that high SiO2＋Al2O3 ＋ Fe2O3 contents yielded high values of hydraulicity and cementation indices. A significant result of this study was that mortars with high hydraulicity and cementation indices have high mechanical strengths. This characteristic may be the main reason for the earthquake resistance of the historical Alhambra Palace.

Microscopic Theory of the Thermodynamic Properties of Sr_3Ru_2O_7

The thermodynamic properties of the bilayer ruthenate compound Sr3Ru2O7 at very low temperatures are inves- tigated by using a tight-binding model yielding the realistic band structure combined with the on-site interactions treated at the mean-field level. We find that both the total density of states at the Fermi energy and the entropy exhibit a sudden increase near the critical magnetic field for the nematic phase, echoing the experimental find- ings. A new mechanism to explain the anisotropic transport properties is proposed based on scatterings at the anisotropic domain boundaries. Our results suggest that extra cares are necessary to isolate the contributions due to the quantum criticality from the band structure singularity in Sr3Ru2O7.

Water-induced softening behavior of clay-rich sandstone in Lanzhou Water Supply Project,China

The strength of clay-rich sandstone decreases significantly when in contact with water due to softening effects.This scenario can pose a severe threat to the stability of water diversion tunnels during construction and operation periods.To address the issues related to water-induced softening in clay-rich sandstone zones in a water diversion tunnel of Lanzhou Water Supply Project,the microscopic and micromechanical variations of rocks due to increasing water content in two different zones i.e.zones A and B,were determined by various testing methods,such as X-ray diffraction(XRD),scanning electron microscopy(SEM),thin section microscopy,micro-indentation test,sonic velocity test,and slake durability test.The microscopic analysis confirms the presence of montmorillonite mineral which is the dominant problematic geomaterial in engineering application.The integrity and durability of clay-rich sandstone were determined with sonic velocity and slake durability tests to calibrate the results obtained by the micro-indentation test.It shows that the elastic modulus and hardness of clay-rich sandstone decrease with the increase of saturation time,up to 144 h,which is more significant and rapid during early stage of saturation.After 144 h of saturation,the elastic modulus decreases by 89% and 97%,and the hardness decreases by 89% and 99% for zones A and B sandstones,respectively.The results of slake durability and sonic velocity indicate that zone A sandsto ne remains 56.19% durability after 144 h of saturation,while zone B sandstone loses its durability merely after 72 h of saturation.The clay-rich sandstone starts to dissolve in water when the saturation time exceeds 144 h.The significant decreases in strength and durability of clay-rich sandstone due to water-induced softening are serious threats to tunnel stability.The improvements in the strength of surrounding rock mass by grouting and permeability by installation of drainage galleries can reduce the damage caused by water-induced softening.

Optimizing signal collection efficiency of the VIPA-based Brillouin spectrometer

Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows for non-invasive and direct assessment of the viscoelastic properties of materials.Recent advances of background-free confocal Brillouin spectrometer allows investigators to acquire the Brillouin spectra for turbid samples as well as transparent ones.However,due to strong signal loss induced by the imperfect optical setup,the Brillouin photons are usually immersed in background noise.In this report,we proposed and experimentally demonstrated multiple approaches to enhance the signal collction eficiency.A signal enhancement by>4 times can be observed,enabling ob-servation of ultra-weak signals.

Structures and magnetic behaviours of TiO_2-Mn-TiO_2 multilayers

The TiO2-Mn-TiO2multilayers are successfully grown on glass and silicon substrates by alternately using radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and the magnetic behaviours of these films are characterised with x-ray diffraction, transmission electron microscope （TEM）, vibrating sample magnetometer, and superconducting quantum interference device （SQUID）. It is shown that the multi-film consists of a mixture of anatase and rutile TiO2 with an embedded Mn nano-film. It is found that there are two turning points from ferromagnetic phase to antiferromagnetic phase. One is at 42 K attributed to interface coupling between ferromagnetic Mn3O4 and antiferromagnetic Mn2O3, and the other is at 97 K owing to the interface coupling between ferromagnetic Mn and antiferromagnetic MnO. The samples are shown to have ferromagnetic behaviours at room temperature from hysteresis in the M-H loops, and their ferromagnetism is found to vary with the thickness of Mn nano-film. Moreover, the Mn nano-film has a critical thickness of about 18.5 nm, which makes the coercivity of the multi-film reach a maximum of about 3.965 × 10^-2 T.