Abstract:The influence of different slag dosages on the compressive strength and chloride ion diffusion coefficient of slag con-crete was studied.The pore structure of concrete was tested using mercury intrusion porosimetry,and the microscopic mechanism of slag concrete's resistance to chloride ion diffusion was analyzed by combining the chloride ion content of slag concrete at different penetration depths.The results showed that the resistance to chloride ion erosion of slag concrete samples with a 40%dosage(W/C=0.3)was significantly improved.Compared with the untreated group,the 30-day compressive strength of the sample increased by ap-proximately 15.9%,while the chloride ion diffusion coefficient and porosity decreased by approximately 32.6%and 16.8%,respectively.The denser microstructure effectively reduces the chloride ion concentration inside the erosion surface,demonstrating a better in-hibitory effect on chloride ion erosion and diffusion.

Abstract:This study synergistically incorporated polyethylene(PE)fibers and sulphoaluminate cement(SAC)into the FGD gypsum matrix.Response surface methodology(RSM)was employed to systematically analyze the effects of the water-to-binder ra-tio,PE fiber content,SAC content,and their interactions on the dry flexural strength and softening coefficient of the composite ma-terial.The optimal mix proportion was determined based on the established regression model.The results demonstrated that:the in-teraction between the water-to-binder ratio and SAC had the most significant impact on the softening coefficient;while the interac-tion between the dosage of PE fiber and the dosage of SAC most significantly influenced the dry flexural strength.The composite exhibited optimal comprehensive performance at a water-to-binder ratio of 0.35,PE fiber content of 1.1%,and SAC content of 11.6%.The relative errors between model-predicted values and experimentally measured values were all below 5%,confirming the model's reliability.The water-to-binder ratio modulated the matrix compactness;PE fibers effectively bridged cracks and enhanced matrix toughness;SAC incorporation promoted the formation of ettringite and optimized the pore structure.The synergistic effects of these factors significantly improved the macroscopic properties of materials.

Abstract:The hydrophobic aeolian sand mortar was prepared using aeolian sand as fine aggregate and fly ash modified by Aluminate Ester Coupling Agent(AGA)via a wet process,where the modified fly ash replaced 40%of cement by mass.Its water absorption characteristics were evaluated,and the modification mechanism was analyzed by means of SEM,XRD,and FT-IR.The results show that the water contact angle of the modified fly ash first increases and then decreases with increasing AGA content.Under the conditions of 5%AGA content and 1 h of stirring,the fly ash achieves super-hydrophobicity.The mortar prepared with this fly ash shows a surface water contact angle of 140.35°,and its cumulative water absorption is reduced by 73%compared with the control group.The physical modification mechanism of AGA on fly ash is attributed to the adsorption of long-chain alkyl groups,which reduces the surface energy and alters the surface microstructure.The chemical mechanism involves the esterification reaction between alkoxy groups in AGA and hydroxyl groups(such as Si—OH and Al—OH)on the fly ash surface,forming Si—O—Al/Al—O—Al covalent bonds and thus achieving molecular anchoring.

Abstract:This study investigates the effects of flux components Na2O and CaO on the foaming behavior,pore structure,physical and mechanical properties of foamed ceramics prepared from lithium tailings by characterization techniques such as high-temperature microscopy and XRD.The results show that an increase in Na2O content can lower the firing temperature of the foamed ceramics and enhance the foaming ability of the samples.However,when the Na2O content exceeds 5.5%(mass fraction),it leads to pore coalescence,increased pore size,and reduced mechanical properties of the samples.An increase in CaO content raises the sintering temperature,but due to its promotion of Si—O chain depolymerization,it decreases the melt viscosity,thereby reducing the stability of the foam system and narrowing the firing temperature range of the green body.When the CaO content exceeds 3.5%(mass fraction),the pore size distribution of the samples widens,the bulk density increases,and the compressive strength decreases.A comprehensive analysis indicates that foamed ceramics with low bulk density,small and closed pores,as well as excellent compressive strength can be prepared when the Na2O content is 4.5%and the CaO content does not exceed 3.5%.

Abstract:To study the influence of typeⅡcalcium sulfoaluminate-calcium oxide composite expansion agent on expansion effi-ciency,compressive strength,durability,and volume stability of the SCC under different temperature conditions was compared.The results show that the expansion efficiency of the expansion agent could be stimulated when cured in the high temperature environ-ment for appropriate time,but the expansion efficiency will be lost if the environment temperature is too high.The expansion effi-ciency of the expansive agent cured at 20℃and 30℃environment is better,the compressive strength of SCC at the early age showed an upward trend,but the strength developed very slowly in the later period,electric flux and volume stability decreased significantly.The expansion efficiency of the expansion agent is significantly reduced under the curing conditions of 40℃and 50℃for more than 2 hours which cannot meet the requirements of type Ⅱ expansive agent in standard GB/T 23439-2017"Expan-sive agents for concrete".The drying shrinkage of self-compacting concrete cannot meet the requirements of Q/CR 596-2017"Specification of self-compacting concrete for high-speed railway CRTSⅢ slab ballastless track".It is recommended to carry out construction operations at night in summer.

Abstract:In this paper,the silicon graphene insulating particles were obtained through the pre-mixing of the graphite polystyrene particles with mineral silica liquid to prepare modified composite silicon graphene insulation panel with middle embeded vacuum insulation panel.Taking the equivalent thermal conductivity as the thermal performance parameter,the physical properties of thermal impedance of silicon graphene sandwiched composite insulation panel with embeded vacuum insulation panel was studied and discussed.The effects of same layer replacement and vertical replacement thickness of sandwiched vacuum panel wrapped in silicon graphene on the equivalent thermal conductivity of the insulation panel were analyzed and studied.Meanwhile,the tensile mechanical properties of the sandwiched vacuum insulation modified silicon graphene composite insulation panels were compared and verified.The research results show that the prepared silicon graphene sandwiched composite insulation panel embedded with vacuum insulation panel exhibits excellent thermal performance,and the thermal performance is reduced by nearly 50%after sandwich embedding compared with the original silicon graphene panel,as low as 0.03 W/(m·K).Additionally,compared with the original panel,the tensile strength exhibits a high preservation degree and no much attenuation,which meeting the requirement as specified in standard JG/T 536-2017"Thermosetting composite polystyrene foam insulation board".

Abstract:This article analyzes and compares the application conditions,standard background,testing items and methods of GB/T 24267-2009"Sealants for fire resistance"and GB 23864-2023"Firestop sealants",as well as the changes in the new and old standards of GB 23864.The research results indicate that the testing items and methods are completely different,the burning char-acteristics of the sealants using the vertical method of GB/T 2408-2008"Plastics-Determination of buring characteristics-Horizontal and vertical test",while the firestop sealants tested using the surface ignition method of GB/T 8626"Test method of flammability for building materials".In standard GB 23864-2023,firestop sealants had added heating conditions for power generation station fire on the basis of building fiber fires,and revised the requirements for furnace pressure.The new version of the standard for firestop sealants stipulate that substances harmful or irritating to the human body shall not be added,but there is no specific testing method specified.

Abstract:Based on field investigations of leakage defects in a shield tunnel section of Jinan Metro Line 6,this study conducted statistical and in-depth analysis of leakage types,distribution characteristics,and their root causes.Addressing the issue of secondary leakage following cement-based grouting,the permeability,injectability,and expansive property were identified as key indicators to select a novel acrylic resin grout.The results revealed that water seepage dominates leakage incidents(74%),with segment joints(83%),particularly circumferential joints,being the predominant leakage locations,highlighting them as the critical focus for waterproofing;The acrylic resin grout exhibits excellent injectability(capable of penetrating micro-cracks as fine as 0.05 mm with a permeability of 2.205×10-10 cm2)and high water-absorption expansion ratio(187%),enabling effective sealing of leaks,and making it well-suited for treating fine crack seepage in humid environments.

Abstract:In this study,the amorphous Fe(OH)3 was synthesized,and its role in the dehydration and transformation process of dihydrate gypsum was investigated in depth.Additionally,the influence of amorphous Fe(OH)3 on the hydration and hardening properties of building gypsum was further discussed.The results indicated that amorphous Fe(OH)3 accelerated the dehydration process of dihydrate gypsum and enhanced the dehydration efficiency at low temperatures.Moreover,due to the strong hygroscopic nature of amorphous Fe(OH)3,it significantly increased the water demand for standard consistency of building gypsum and markedly reduced the strength of the hardened body.Additionally,Fe(OH)3 was not fully decomposed during the low-temperature calcination process for producing building gypsum.Instead,it coated the surface of gypsum crystals,leading to a reduced hydration rate,delayed hydration process,impaired crystal interlocking,increased porosity of the hardened body,and diminished strength.

Abstract:The experiment utilizes 28 kHz power ultrasonic waves to perform surface strengthening treatment on concrete speci-mens with a water-cement ratio of 0.40～0.60.Microhardness testers and ball indentation impact testers are used to measure the hardness and impact resistance of the concrete surface.This study aims to investigate the effects of ultrasonic surface strengthening on the surface hardness and impact resistance of cement concrete.The experimental results show that the surface hardness of the strengthened concrete is 28.48%～39.74%higher than that of the non-strengthened group;under impact heights of 5,10,15 cm,the dynamic hardness of the strengthened concrete is increased by 6.90%～8.81%,6.95%～9.32%,and 2.23%～6.61%,respectively,compared to the non-strengthened group.SEM analysis indicates that ultrasonic surface strengthening treatment improves the compactness of the C-S-H gel.Nanoindentation analysis reveals the presence of UHD phase in the C-S-H of the strengthened layer,improving the gel structure of the strengthened layer,thereby enhancing the surface hardness and impact resistance of the concrete.

Abstract:Traditional backfill materials have general economy and insufficient fluidity.Controlled Low-Strength Materials (CLSM)were prepared by compound mixing of Construction and Demolition waste(C&D)and Recycled Powder(RP).The variation laws of flowability and unconfined compressive strength of CLSM under different water-to-solid ratios and different RP/C&D ratios were studied,and the phase composition and micro-morphology were explored by XRD and SEM.The results show that with the increase of water-to-solid ratio,the flowability of CLSM increases significantly,while the compressive strength decreases;with the increase of RP/C&D ratio,the flowability of CLSM increases,and the compressive strength first increases and then decreases.When the water-to-solid ratio is 0.7 and the RP/C&D ratio is 0.36,the flowability and compressive strength meet the requirements of municipal pipeline backfilling.

Abstract:This study introduces a novel method for preparing ultra-high-performance concrete(UHPC)using a weak alkaline activation system,in which Na2CO3 replaces the traditional NaOH and water glass.Ultrafine mineral powder was used as a substitute for mineral powder,and the effect of ultrafine mineral powder replacement rate on the compressive strength of weak alkali activated UHPC was studied.XRD,FTIR,SEM and other microscopic analyses were used to analyze its hydration products.The findings demonstrate that as the replacement rate of ultrafine mineral powder increased,the compressive strength of weak alkali activated UH-PC significantly improved.Concrete prepared with 100%ultra-fine mineral powder exhibits a compressive strength of up to 109.22 MPa.At 28 days,the content of intermediate polymers in UHPC activated by sodium carbonate exceeded 60%,and the hydration products were not completely generated,resulting in a low degree of polymerization.As the hydration reaction continued,the degree of polymerization of the hydration products gradually increased,and the compressive strength gradually increased.

Abstract:A microscopic characterization and mechanical property test of a new reinforcing material for SMW method piles was carried out based on a foundation water retaining wall project of a certain public housing in Hengqin,Zhuhai.The mechanism of the new curing agent was analyzed,and the practical application effect of the material was further verified through field tests.The results show that the strength of the consolidated soil with 19%dosage of the new curing agent is 3.4 MPa,which is 1.8 MPa higher than that of the consolidated soil with 20%dosage of cement after 28 days.The new curing agent achieves the consolida-tion of soft soil by adhering and wrapping the soil with the hydration gel products(C-S-H,C-A-S-H)generated.Meanwhile,the system consolidates the cementitious products by the needle-like and rod-like ettringite(AFt)generated in a way of reinforcing and bridging.The field application verification shows that the use of solid waste-based soft soil curing materials in the SMW method can adapt to the construction operations such as the insertion and withdrawal of steel sections.The core sampling effect is signifi-cantly better than that of cement,and the strength meets the design requirements(≥0.8 MPa).

Abstract:The influence of sodium silicate and sodium hydroxide(NaOH)as alkali activators on the physical properties of foamed concrete was studied by testing the apparent density,compressive strength,porosity and XRD patterns of foamed concrete with coal gangue used to replace cement.Experimental results demonstrate that the coal gangue powder can promote hydrogen per-oxide solution to foam better in alkaline environment after replacing part of cement,forming excellent pore structure,and effectively reducing the weight of foam concrete.

Abstract:A tensile test of thermoplastic polyolefin(TPO)homogeneous waterproofing membrane at different temperatures was carried out to analyze its tensile deformation behavior.With temperature as the variable and breaking strength,yield stress,and e-lastic modulus as the investigation parameters,combined with the tensile deformation characteristics of the TPO homogeneous wa-terproofing membrane,the fracture stress-temperature relationship was analyzed.Then,the regression relationship models of breaking stress-temperature and fracture strain-temperature of the TPO homogeneous waterproofing membrane was obtained.The results in-dicate that the proposed regression relationship models of fracture stress-temperature and fracture strain-temperature are in good agreement with the experimental results and have excellent reliability.Through calculations based on these regression rela-tionship models,quantitative comparison of TPO homogeneous waterproofing membrane at different temperatures and regression cal-culation of strength at room temperature can be achieved,providing technical support for solving the problem of temperature insta-bility during the tensile performance test of TPO homogeneous waterproofing membrane at the engineering site.

Abstract:Linear polycarboxylate superplasticizers were modified with acrylic monomers(DMAEMA、HEMA)and cyclic func-tional groups(TMPTMA、TMPTA),and five hyperbranched polycarboxylate superplasticizers(PCEs)with different branching structures were synthesized under room temperature redox initiation system.The influence of hyperbranched topological structure on the dispersibility,viscosity reduction effect,and slump retention of PCEs in cement-based materials was studied.The results indicate that when the water reducing agent dosage is 0.12%,and the water cement ratio is 0.29,the acrylic acid ester monomer(DMAEMA,HEMA)significantly improves the dispersibility of the polycarboxylate superplasticizers,while the introduction of cyclic functional group monomer(TMPTMA,TMPTA)has limited improvement in dispersibility but can enhance the slump retention performance.Under the same dosage of polycarboxylate superplasticizer and same flowability,the compressive strength of mortar with PCEs added at each age showed varying degree of improvement compared to the control group.

Abstract:By conducting finite element analysis on ALC partition panels in actual project,the seismic performance of the components was explored by changing the height-width ratios,axial compression ratios and plate thicknesses.The seismic properties of the components under low-cycle repeated loads were studied by finite element software.The results showed that as the width of the components increased from 600 mm to 900 mm,the properties of the components were greatly improved.With the axial compres-sion ratio increased from 0.10 to 0.40,the bearing capacity of the component also increases.As the axial compression ratio increas-es from 0.10 to 0.40,the stiffness of the component first increases and then decreases,and the bearing capacity and stiffness of the component are gradually increased when the plate thickness is creased from 60 mm to 150 mm.

Abstract:In this paper,four types of recycled carbon fibers were used to prepare reinforced concrete.The effects of fiber strength,tensile strength,diameter and dosage on the mechanical properties of concrete were studied,which included compressive strength,flexural strength,flexural toughness,impact resistance,and crack reduction coefficient.The results show that the recycled car-bon fibers can improve the compressive and flexural strength of concrete,and effectively enhance the flexural toughness and impact resistance of concrete.To ensure the fluidity of concrete,it is recommended that the content of recycled carbon fiber does not exceed 1.0%.The flexural toughness of carbon fiber reinforced concrete is more than 20%higher than that of the benchmark concrete.The crack control effect of fine carbon fibers is slightly better than that of coarse fibers.SEM analysis results show that there exists a close interfacial bond between the recycled carbon fiber and concrete matrix,which can effectively play the role of bridging and im-prove the properties of concrete.

Abstract:A metakaolin fly ash based geopolymer was prepared using metakaolin and fly ash as cementitious materials,and sodium silicate and NaOH as alkali activators.Orthogonal experimental design was used to study the effects of modulus,water-solid ratio,and solid content of sodium silicate on its mechanical properties and dry density.The mechanism of alkali activators was analyzed and explored by SEM,XRD and other microscopic methods.The results show that the influencing factors of the 28 d compressive strength of geopolymer from large to small are water-solid ratio,sodium silicate modulus and solid content,and the optimal parameters of alkali activator are water glass modulus 1.0,water-solid ratio 0.48 and solid content 36%,at this time,the 28 d compressive strength of geopolymer reaches 33.5 MPa and the dry density is 1.6 g/cm3.XRD analysis show that there is a"steamed bread peak"in geopolymer at 15°～40°,forming a cementitious structure with amorphous structure.

Abstract:This study investigates the feasibility of employing a composite admixture comprising sodium polyacrylate(PAAS)and citric acid(CA)for the repair of macroscopic cracks in cement mortar,as well as their synergistic effects.The results indicate that PAAS exhibits excellent water absorption and swelling capacity,enabling effective macroscopic crack repair.Furthermore,citric acid serves as an efficient auxiliary additive,facilitating the repair process by promoting calcium carbonate(CaCO3)precipitation and retarding cement hydration,thereby ensuring complete crack closure.The repair mechanism of this theory was further verified through optical microscopy and scanning electron microscopy testing methods.