Evolution of Biofilm and Its Effect on Microstructure of Mortar Surfaces in Simulated Seawater

To explore the role of biofilm formation on the corrosion of marine concrete structures, we investigated the attachment of biofilm on mortar surfaces in simulated seawater and the influence of biofilm on the microstructure of mortar surfaces. The results show that the evolution of biofilm on mortar surfaces in simulated seawater is closely related to the corrosion suffered by the mortar, and the process of biofilm attachment and shedding is continuous and cyclical. It is found that the specimens in the absence of biofilm attachment are more severely eroded internally by the corrosive medium in simulated seawater than those in the presence of biofilm attachment. For the specimens without biofilm attachment, after 60 days, gypsum forms,and after 120 days, the number of pores in the mortar is reduced. In contrast, for the specimens in the presence of biofilm attachment, gypsum could only be detected after 90 days, and fewer pores are filled. Therefore, the formation of biofilm could delay the invasion of the corrosive medium into the interior of mortar during the evolution of biofilm on mortar surfaces, mitigating the corrosion of mortars in seawater.

An Investigation into the Performances of Cement Mortar Incorporating Superabsorbent Polymer Synthesized with Kaolin

Cement-based materials are fundamental in the construction industry,and enhancing their properties is an ongoing challenge.The use of superabsorbent polymers(SAP)has gained significant attention as a possible way to improve the performance of cement-based materials due to their unique water-absorption and retention properties.This study investigates the multifaceted impact of kaolin intercalation-modified superabsorbent polymers(K-SAP)on the properties of cement mortar.The results show that K-SAP significantly affects the cement mortar’s rheological behavior,with distinct phases of water absorption and release,leading to changes in workability over time.Furthermore,K-SAP alters the hydration kinetics,delaying the exothermic peak of hydration and subsequently modifying the heat release kinetics.Notably,K-SAP effectively maintains a higher internal relative humidity within the mortar,reducing the autogenous shrinkage behavior.Moreover,K-SAP can have a beneficial effect on pore structure and this can be ascribed to the internal curing effect of released water from K-SAP.

Infuences of Different Admixtures on the Drying Shrinkage Characteristics of Metakaolin-based Geopolymer Mortar

To investigate the influences of different admixtures on the drying shrinkage of polymer mortar in a metakaolin base,the experiments of VAE(vinyl acetate ethylene copolymer),APAM(anionic polyacrylamide)and CPAM(cationic polyacrylamide)on the drying shrinkage properties of geopolymer mortar were designed under normal temperature curing conditions.An SP-175 mortar shrinkage dilatometer was introduced to measure the dry shrinkage of geopolymer mortar.Meanwhile,the drying shrinkage properties of geopolymer mortar are exhibited by the parameters of water loss rate,drying shrinkage rate,drying shrinkage strain and drying shrinkage coefficient.The experimental data are further fitted to obtain the prediction model of dry shrinkage of geopolymer mortar,which can better reflect the relationship between dry shrinkage rate and time.Finally,the experimental results demonstrate that the dry shrinkage of geopolymer mortar can be significantly increased by adding 4%VAE admixture,meanwhile under the condition that the polymer film formed by VAE reaction can strengthen and toughen the mortar.2.5%APAM admixture and 1.5%CPAM admixture can enhance the dry shrinkage performance of geopolymer mortar in a certain range.

Failure Characteristics of Rock-like Mortar Specimens with Arc-shaped Flaws under Freezing-thaw Cycles and Uniaxial Compression

To investigate the freeze-thaw(F-T)damages and failure characteristics of rock mass with arc-shaped joints in cold regions,three types of cement mortar specimens with different central angles and prefabricated arc-shaped flaws are subjected to uniaxial compressive tests under different F-T cycles.Experimental observations show that the uniaxial compressive strength of specimens are significantly influenced by F-T cycles and their failure modes are mainly affected by the central angleαof the prefabricated flaws.Unlike the specimens with a central angle of 60°,the specimens with a central angle of 120°and 180°have greater curvature of flaws,so tensile cracks occur in the arc-top area of their prefabricated flaws.According to experimental images observed by environmental scanning electron microscope(ESEM),as the number of F-T cycles increases,the deterioration effect of the specimen becomes more obvious,which is specifically reflected in the increase of the mass loss,peak stress loss,and damage variables as a power function,and the peak strain decreases as a quadratic polynomial.According to numerical results using two-dimensional particle flow code(PFC2D),it is found that F-T cycles cause more damage to the specimen in the early stages than in the later ones.The area of the concentrated compressive stress zone in the middle is decreased due to the increased number of F-T cycles,while the area of the surrounding tensile-shear stress zone is increased.The models appear different failure modes due to the release of concentrated stress in different tensile-shear zones.

Influence of Recycled Concrete Fine Powder on Durability of Cement Mortar

In this paper,the durability of cement mortar prepared with a recycled-concrete fine powder(RFP)was examined;including the analysis of a variety of aspects,such as the carbonization,sulfate attack and chloride ion erosion resistance.The results indicate that the influence of RFP on these three aspects is different.The carbonization depth after 30 days and the chloride diffusion coefficient of mortar containing 10%RFP decreased by 13.3%and 28.19%.With a further increase in the RFP content,interconnected pores formed between the RFP particles,leading to an acceleration of the penetration rate of CO_(2)and Cl^(−).When the RFP content was less than 50%,the corrosion resistance coefficient of the compressive strength of the mortar was 0.84-1.05 after 90 days of sulfate attack.But the expansion and cracking of the mortar was effectively alleviated due to decrease of the gypsum production.Scanning electron microscope(SEM)analysis has confirmed that 10%RFP contributes to the formation of a dense microstructure in the cement mortar.

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.

Effect of Partial Replacement of Fly Ash by Decoration Waste Powder on the Fresh and Mechanical Properties of Geopolymer Masonry Mortar

This study aims to investigate the feasibility of using decoration waste powder(DWP)as a partial replacement for fly ash(FA)in the preparation of geopolymer masonry mortar,and to examine the effect of different DWP replacement rates(0%-40%)on the fresh and mechanical properties of the mortar.The results showed that each group of geopolymer masonry mortar exhibited excellent water retention performance,with a water retention rate of 100%,which was due to the unique geopolymer mortar system and high viscosity of the alkaline activator solution.Compared to the control group,the flowability of the mortar containing lower contents of DWP(10%and 20%)was higher.However,as the DWP replacement rate further increased,the flowability gradually decreased.The DWP could absorb the free water in the reaction system of geopolymer mortar,thereby limiting the occurrence of geopolymerization reaction.The incorporation of DWP in the mortar resulted in a decrease in compressive strength compared to the mortar without DWP.However,even at a replacement rate of 40%,the compressive strength of the mortar still exceeded 15 MPa,which met the requirements of the masonry mortar.It was feasible to use DWP in the geopolymer masonry mortar.Although the addition of DWP caused some performance loss,it did not affect its usability.

On calculating glacial isostatic adjustment

Modeling the earth's fluid and elastic response to the melting of the glaciers of the last ice age is the most direct way to infer the earth's radial viscosity profile.Here,we compare two methods for calculating the viscoelastic response to surface loading.In one,the elastic equation of motion is converted to a viscoelastic equation using the Correspondence Principle.In the other,elastic deformation is added to the viscous flow as isostatic adjustment proceeds.The two modeling methods predict adjustment histories that are different enough to potentially impact the interpretation of the observed glacial isostatic adjustment(GIA).The differences arise from buoyancy and whether fluid displacements are subjected to hydrostatic pre-stress.The methods agree if they use the same equations and boundary conditions.The origin of the differences is determined by varying the boundary conditions and pre-stress application.

Paleoenvironmental changes recorded by grain size of loess/paleosol sequence from the Chifeng City,Northeastern China since the Last Glacial

The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local environment.In this study,grain size end-member analysis of the Dajiugang(DJG)section deposited since the Last Glacial in Chifeng City,NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China.Results showed that the Chifeng loess comprises three grain size end-members(EM),EM1(7.38μm),EM2(49.4μm)and EM3(90.00μm),indicating the three transport dynamics of dust delivered to the region.The EM1 represents atmospheric dust as the background.The EM2,mainly derived from relatively distant-sources deposition,and EM3,material transported over a short distance,correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon(EAWM),respectively.Results of climate reconstruction,combined with other records,showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon(EASM)during the stadial-period[Marine Isotope Stage(MIS)4 and MIS 2 stage].The climate was predominantly warm and humid,with weak EAWM and surface winds and strong EASM in interstadial-period(MIS 3 and MIS 1 stage).Comparisons between indicators,e.g.,EM3,the LR04 benthicδ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.

Study on physical and mechanical properties of cement asphalt emulsified mortar under track slab

Purpose–During the construction process of the China Railway Track System(CRTS)I type filling layer,the nonwoven fabric bags have been used as grouting templates for cement asphalt(CA)emulsified mortar.The porous structure of nonwoven fabrics endowed the templates with breathability and water permeability.The standard requires that the volume expansion rate of CA mortar must be controlled within 1%–3%,which can generate expansion pressure to ensure that the cavities under track slabs are filled fully.However,the expansion pressure caused some of the water to seep out from the periphery of the filling bag,and it would affect the actual mix proportion of CA mortar.The differences in physical and mechanical properties between the CA mortar under track slabs and the CA mortar formed in the laboratory were studied in this paper.The relevant results could provide important methods for the research of filling layer materials for CRTS I type and other types of ballastless tracks in China.Design/methodology/approach–During the inspection of filling layer,the samples of CA mortar from different working conditions and raw materials were taken by uncovering the track slabs and drilling cores.The physical and mechanical properties of CA mortar under the filling layer of the slab were systematically analyzed by testing the electrical flux,compressive strength and density of mortar in different parts of the filling layer.Findings–In this paper,the electric flux,the physical properties and mechanical properties of different parts of CA mortar under the track slab were investigated.The results showed that the density,electric flux and compressive strength of CA mortar were affected by the composition of raw materials for dry powders and different parts of the filling layer.In addition,the electrical flux of CA mortar gradually decreased within 90 days’age.The electrical flux of samples with the thickness of 54 mm was lower than 500 C.Therefore,the impermeability and durability of CA mortar could be improved by increasing the thickness of filling layer.Besides,the results showed that the compressive strength of CA mortar increased,while the density and electric flux decreased gradually,with the prolongation of hardening time.Originality/value–During 90 days’age,the electrical flux of the CA mortar gradually decreased with the increase of specimen thickness and the electrical flux of the specimens with the thickness of 54 mm was lower than 500 C.The impermeability and durability of the CA mortar could be improved by increasing the thickness of filling layer.The proposed method can provide reference for the further development and improvement of CRTS I and CRTS II type ballastless track in China.

Influence of Ultra Fine Glass Powder on the Properties and Microstructure of Mortars

This study focuses on the effect of ultrafine waste glass powder on cement strength,gas permeability and pore structure.Varying contents were considered,with particle sizes ranging from 2 to 20μm.Moreover,alkali activation was considered to ameliorate the reactivity and cementitious properties,which were assessed by using scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),and specific surface area pore size distribution analysis.According to the results,without the addition of alkali activators,the performance of glass powder mortar decreases as the amount of glass powder increases,affecting various aspects such as strength and resistance to gas permeability.Only 5%glass powder mortar demonstrated a compressive strength at 60 days higher than that of the control group.However,adding alkali activator(CaO)during hydration ameliorated the hydration environment,increased the alkalinity of the composite system,activated the reactivity of glass powder,and enhanced the interaction of glass powder and pozzolanic reaction.In general,compared to ordinary cement mortar,alkali-activated glass powder mortar produces more hydration products,showcases elevated density,and exhibits improved gas resistance.Furthermore,alkali-activated glass powder mortar demonstrates an improvement in performance across various aspects as the content increases.At a substitution rate of 15%,the glass powder mortar reaches its optimal levels of strength and resistance to gas permeability,with a compressive strength increase ranging from 28.4%to 34%,and a gas permeation rate reduction between 51.8%and 66.7%.

Flooding(or breaching)of inter-connected proglacial lakes by cascading overflow in the arid region of Western Mongolia(Mt.Tsambagarav,Mongolian Altai)

This study investigates the glacial lake outburst flood(GLOF)hazards in the Tsambagarav mountain range in Western Mongolia,focusing on the Khukhnuruu Valley and its interconnected proglacial lakes.Over the last 30 years,significant glacier retreats,driven by rising temperatures and changing precipitation patterns,have led to the formation and expansion of several proglacial lakes.Fieldwork combined with satellite data and meteorological analysis was used to assess the dynamics of glacier and lake area changes,with particular focus on the flood events of July 2021.The research reveals a substantial reduction in glacier area,particularly in the Khukhnuruu E complex,where glacier area decreased by 19.3%.The study highlights the influence of increasing temperatures and summer precipitation,which have accelerated ice melt,contributing to the expansion and eventual breaching of lakes.Additionally,lake area changes were influenced by the steepness of the terrain,with steeper slopes exacerbating peak discharge during floods.Of the studied seven lakes(Lake 1 to Lake 7),Lake 1 experienced the most dramatic reduction,with a decrease in area by 73.51%and volume by 84.84%,followed by Lake 7.This study underscores the region's vulnerability to climate-induced hazards and stresses the need for a comprehensive early warning system and disaster preparedness measures to mitigate future risks.

Glacial debris flow susceptibility mapping based on combined models in the Parlung Tsangpo Basin,China

Machine learning(ML)-based prediction models for mapping hazard(e.g.,landslide and debris flow)susceptibility have been widely developed in recent research.However,in some specific areas,ML models have limited application because of the uncertainties in identifying negative samples.The Parlung Tsangpo Basin exemplifies a region prone to recurrent glacial debris flows(GDFs)and is characterized by a prominent landform featuring deep gullies.Considering the limitations of the ML model,we developed and compared two combined statistical models(FA-WE and FA-IC)based on factor analysis(FA),weight of evidence(WE),and the information content(IC)method.The final GDF susceptibility maps were generated by selecting 8 most important static factors and considering the influence of precipitation.The results show that the FA-IC model has the best performance.The areas with a very high susceptibility to GDFs are primarily located in the narrow valley section upstream,on both sides of the valley in the middle and downstream of the Parlung Tsangpo River,and in the narrow valley section of each tributary.These areas encompass 86 gullies and are characterized as"narrow and steep".

Glacial lakes under climate change: the imperative for comparative studies of microbial carbon metabolism in the Qinghai-Xizang Plateau and the Arctic

Glacial lakes,intimately linked to glacier termini,are crucial landscape features of the Qinghai-Xizang Plateau(QXP,Qinghai-Tibet Plateau)and the Arctic.Climate warming has accelerated glacier retreat and the rapid expansion of glacial lakes in both regions.Despite being typically considered harsh environments,these lakes serve as vital reservoirs for microbial biodiversity and carbon metabolism.In the face of climate change,glacial lake ecosystems over the QXP and the Arctic are undergoing unprecedentedtransformations.Thisopinioneditorial highlights the significance of conducting research and establishing long-term monitoring programs focused on microbial carbon metabolism in these glacial lakes.

Substitution of Aggregates in Concrete and Mortar with Coltan Mining Waste: Mechanical, Environmental, and Economic Impact Case Study

The mining process involves drilling and excavation, resulting in the production of waste rock and tailings. The waste materials are then removed and stored in designated areas. This study aims to evaluate the mechanical strength and the environmental and economic impact of using Coltan Mining Waste (CMW) as a substitute for aggregates in concrete and mortar production. To achieve this, the CMW needs to be characterised. The Dreux Gorisse method was primarily used to produce concrete with a strength of 20 MPa at 28 days. The mortars, on the other hand, were formulated according to the NF P 18-452 standard. The environmental impact of using CMW as substitutes for natural aggregates in the production of concrete and mortar was analysed using SimaPro software. The results showed that mortars and concrete made with CMW have comparable compressive strengths to the reference mortar and concrete;reduce the negative impact on ecosystem quality, human health, resources, and climate change. It has also been shown that the substitution of aggregates by CMW reduces the cost of concrete and mortar as a function of the distance from the aggregate footprint.

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.

The Effect of Graphene Oxide on Mechanical Properties of Cement Mortar

Cement is widely used in engineering applications,but it has both the characteristics of high brittleness and poor bending resistance.In this paper,the effects of different amounts ofgraphene oxide on the flexural strength and compressive strength of cement mortar were studied by doping a certain amount of graphene oxide with cement mortar,and the strengthening mechanism of graphene oxide on cement mortar was obtained through microstructure detection.It is found that graphene oxide has a significant enhancement effect on the macroscopic mechanical properties of cement mortar,and graphene oxide provides nano-nucleation sites and growth templates for cement mortar,accelerates the hydration process,reduces the voids between hydration products,greatly increases the compactness,and improves the macroscopic properties of cement-based materials.

Revisiting East Asian monsoon change during the Last Glacial Maximum using PMIP4 simulations

利用PMIP4多模式试验数据,本文重新检查了末次冰盛期(距今约21000年)东亚季风变化.结果表明:相对于工业革命前期,所有5个模式一致模拟显示末次冰盛期东亚季风减弱,冬季和夏季减幅分别为1%-18%和2-32%;不同模式中东亚季风环流变化的空间分布存在差异,这主要源于该时期大尺度变冷和海平面气压梯度变化的空间分布不同;由于模式之间的差异和重建记录之间的不确定性,未来有待开展更多模拟和重建工作以更好地理解冰期东亚季风变化.

Effects of Cationic Surfactant on Fresh and Hardened Properties of Cement-Based Mortar

The objective of this study is to analyze the effects of using surfactant(CTAB)and cellulose nanofibers(NFC)as an admixture in cement mortars.We examined composite properties as porosity,compression energy,thermal conductivity and hydration.The results showed that with the addition of 0.7%by weight of NFC per emulsion in the presence of a cationic surfactant(CTAB).The new material produced presented a dry porosity between 4.7%and 4.4%,compressive strength between 9.8 and 22.9 MPa,and thermal conductivity between 0.95 and 2.25 W·m^(−1)·K^(−1).Thus we show better mechanical and thermal performance than that traditional Portland cement mortar with a density similar.In addition,the mortar made by emulsion of ordinary portland cement,cellulose nanofiber and organophilic clay(OC)treated with cetyltrimethylammonium bromide(CTAB)obtained has good resistance under high temperature and water,as well as excellent thermal insulation performance under high temperature and humidity conditions.This study verified that the presence of NFC promotes hydration,leading to the production of more calcium silicate and portlandite gel.

Evolution and bathymetry of glacial lake at the lowest elevation in Nepal Himalaya

One of the prominent impacts of climate change induced glacier retreat in the Himalayas is the formation and expansion of glacial lakes. The newly formed glacial lakes are mostly located in higher altitudinal regions(4200-5800 m) of Himalaya,however, a new glacial lake(Kapuche, 28.446° N and 84.116° E) have been reported to be emerged in the relatively low elevation area of ~2450 m above sea level(masl) in the Nepal Himalaya. This short communication presents the remote sensing-based evolution and field-based bathymetry of Kapuche lake, and further discusses its formation process and lake type for being a glacial lake at the lowest elevation in Nepal Himalaya.