Iron tailings powder (ITP) is a kind of solid waste, which pollutes the environment, without any treatment. The application of ITP in cement concrete is a good choice. In this study, the influence of ITP on the flowability, compressive strength, chloride ion permeability and the attenuation of the performance of cement concrete during freeze–thaw cycle (F-T) damage are investigated. An X-ray diffraction, an analysis of the pores and a scanning electron microscope (SEM) are obtained to analyze the mechanism of cement concrete’s performance. The results show that the addition of ITP can decrease the flowability of fresh cement concrete. Cement concrete with a 7% ITP to mass ratio of the total aggregate shows the highest compressive strength and the minimum chloride ion permeability. The relative dynamic modulus of the elasticity of the specimens with 7% ITP during the F-T is the highest. The corresponding mass loss rate is the lowest. The mercury intrusion analysis results show that the pore volume of the specimens with 7% ITP is the lowest. The SEM results confirm that the specimens with 7% ITP show the densest microstructures.
2023年11月9-10日,中国混凝土与水泥制品协会水泥混凝土管涵分会第二次会员代表大会暨行业技术交流会在山东青岛召开.来自行业企业、地方协会的领导、专家及媒体代表等近400人参加了会议.大家集聚一堂,为管涵行业高质量发展建言献策;共商共讨,为分会健康发展谋篇布局.
Sand is one of the main raw materials for concrete preparation,and its mechanical properties and structural stress response state are related to the strength and stability of concrete structure.Therefore,it is of great practical significance to study the basic mechanical properties and structural stress response state of sea sand concrete.In this paper,the control variable method is adopted to determine that other components of the concrete structure are completely consistent,only the type of mixing sand is changed,and the workability,compressive strength and elastic modulus changes of ordinary river sand concrete and sea sand concrete are compared,and the actual mechanical characteristic parameters obtained by analysis are combined.Midas finite element analysis software is used to establish the finite element analysis model of concrete column compression,and the numerical simulation of concrete column compression process is carried out to study the influence of river sand and sea sand on the stress,displacement,deformation and critical load of concrete column.The results show that the sea sand has an effect on the workability,compressive strength and elastic modulus of concrete,especially on the sea sand concrete with strength of C30 and C20.The slump decreases about 31.1%on average,the strength decreases about 10.9%on average,and the elastic modulus increases 17.8%and 5.3%respectively.Under the action of vertical load,the displacement and deformation of sea sand concrete column are larger,and the critical coefficient of buckling load of the main structure is reduced by 19.3%compared with that of ordinary concrete column.
说她"年少",是因为这是一家刚成立8年,十分"年轻"的企业.青岛环球重工科技有限公司(以下简称"环球重工")成立于2015年,是青岛环球集团旗下的全资子公司.公司牢牢锚定"为新型绿色建筑构件制造企业提供智能制造系统解决方案"这一宗旨,现已发展为集盾构管片模具、风电混塔模具、装配式地铁站模具、轨道板模具、智慧梁场模具、整体箱涵模具及各类自动化生产线制造销售于一体的工程装备制造公司.
The industrial sector is the main field of carbon emissions in China,and the building materials industry is an important basic industry for China's national economy and social development.It is also a key industry for energy consumption and carbon emissions in the industrial sector.Under the"carbon peaking and carbon neutrality"goals,accelerating low-carbon transformation is the responsibility of the building materials industry for the dual carbon work.Promoting the greening of building materials has become a trend,and green buildings and green building materials continue to develop.Among them,green certification is an important certification evaluation method for the future mortar industry,the research and promotion of green certification work directly affect the future green development direction of China's mortar industry.This article focuses on the development process of green certification for mortar products,starting from the relevant policies of green certification in China,analyzes and explores the current status and future development trends of green certification work for mortar products.
Special mortar is a type of mortar mainly suitable for special requirements such as insulation,sound absorption,waterproofing,corrosion resistance,radiation protection,decoration,and bonding.Due to its special performance requirements,there is a high requirement for the fineness of sand,river sand or washed sand is often used for drying.However,with the deepening of green environmental protection concepts,more demand has been put forward for ultra-fine mechanism sand to reduce the damage to natural resources and carbon emissions of sand source products.This article mainly introduces the preparation method of special mortar with ultra-fine machine-made sand.Based on actual projects,using ultra-fine machine-made sand as the main raw material and modern manufacturing technology,it deeply studies the process of preparing special mortar with ultra-fine machine-made sand.After experimental verification,the prepared ultra-fine machine-made sand fully meets the performance requirements of special mortar.The research results provide certain reference and guidance for improving the construction quality and efficiency of the construction industry.
Vertical grinding has gradually become one of the mainstream production methods for preparing cement,but it is not clear whether the effect of the vertical grinding method on the emphasis and durability of concrete made from cement.This paper studies the particle size distribution,hydration heat release,and microstructure of concrete prepared by testing the strength and durability of vertical mill cement and roller ball mill combined grinding cement.The results show that the proportion of vertical grinding cement with particle size less than 3 μm is relatively small,and the hydration rate is slow in the early stage,resulting in its early strength being slightly lower than that of roller ball mill combined grinding cement.The interfacial transition zone of the two types of cement concrete is dense and has good durability.The properties of vertical grinding cement are basically consistent with the strength and durability of roller ball grinding cement combined with pulverized cement.
In order to determine the effect of limestone powder dosage on the properties of permeable concrete,this paper conducts experimental studies on the permeability coefficient,compressive strength,flexural strength,and frost resistance of permeable concrete with different limestone powder dosages,and analyzes the changes in the performance of permeable concrete.The results show that when the content of limestone powder is less than 10%,the permeability coefficient of permeable concrete does not change much,the compressive strength has a certain increase,the flexural strength slightly decreases,and the loss rate of concrete quality and compressive strength after freeze-thaw is relatively small;when the content of limestone powder exceeds 10%,it will have a significant negative impact on the performance of permeable concrete.Therefore,in the actual preparation process of permeable concrete,the amount of limestone powder should be controlled to ensure the stability of the performance of permeable concrete.
This paper takes a shield tunnel project in Nanjing as a background,establishes a three-dimensional solid discontinuous contact shield tunnel segment finite element model considering concrete plastic damage by the strata structure method,studies the mechanical properties of polyformaldehyde fiber reinforced concrete shield tunnel segments under the action of surrounding rock pressure and structural weight,and compares with the results of ordinary concrete segments.The results show that the stress and deformation characteristics of fiber reinforced concrete segments and ordinary concrete segments under the action of surrounding rock pressure and self-weight of their own structure are the same,but the values are smaller.The circumferential tensile strain of fiber concrete segments is reduced by 14.6%,the maximum tensile strain of steel cages is reduced by 3.9%,and the stress value of each joint is reduced by 6%～13%,which shows better crack resistance.
This paper adopts a combination of experimental and numerical simulation methods to study the static and impact dynamics performance of steel slag concrete.In the experimental section,four concrete specimens with different steel slag contents(0%,25%,35%,45%)were prepared and their compressive and tensile strength were tested.In the numerical simulation section,a three-dimensional finite element model of steel slag concrete was established,and the RHT constitutive model was used to describe the nonlinear constitutive relationship of concrete,simulating the SHPB impact dynamic response of concrete under different steel slag dosages.The results show that an increase in the amount of steel slag can lead to a downward trend in the static and impact dynamic properties of concrete;when the steel slag content is 25%,the impact state and parameters of concrete are closest to those of concrete with a steel slag content of 0%,and it has high impact resistance;when the steel slag content is 45%,the peak impact stress of concrete is the lowest,exhibiting the characteristic of complete damage.
"十年很短,我们只争朝夕;十年很长,行业高速发展.这十年,我们一路追光,也身披万丈光芒,广厦千万、山河锦绣、世界舞台,都能看见成长的砂浆、奋进的砂浆."2023年12月13日,由中国建筑材料联合会预拌砂浆分会主办的"全国预拌砂浆行业大会暨协会十周年"在北京召开,以"十年勤 再前进"为主题,共话十年,共享理念,共商融合."全国预拌砂浆行业大会"受到行业内外的广泛关注与支持,出席大会的嘉宾涵盖预拌砂浆生产、装备制造、原材料供应、科研院所及高校、施工、房地产、装饰装修等上下游产业链.
This paper taking Baotou aggregate project 22 m inner diameter column supported silo as an example,on the basis of PKPM calculation,SAP2000,Midas Gen and YJK software are used to check and compare the results.The research method is to conduct modal analysis of the model under the horizontal seismic force in the area with seismic fortification intensity of 6 degrees,and compares the displacement response,shear weight ratio and anti-lateral stiffness of the silo structure in four kinds of software.The results show that the overall torsional stiffness of the reinforced concrete silo structure is weak,and the seismic balance of the corner column should be enhanced in the structure layout.The lateral stiffness of the supporting column under the bin is weak.The lateral stiffness of the silo wall is much higher than that of the supporting column and more uniform,and there is a sudden change in stiffness between the silo floor and the silo wall.
初冬时节,北方已树木萧萧,冷风入怀,然而岭南却暖风习习,草木青青.12月9日,由中国混凝土与水泥制品协会、中国水利学会、中国水利水电勘察设计协会共同主办的"大口径长距离输水管材高质量发展研讨会"在广东湛江举行.国内混凝土输水管材行业协会学会、研究设计院、国内大型水利工程业主单位及混凝土管材头部企业的专家、学者、企业领导人等齐聚广东湛江,共同聚焦大口径长距离输水管材高质量发展.
金隅混凝土集团首次应收账款ABS发行获得圆满成功,此次发行为上交所混凝土行业首单ABS!金隅集团混凝土应收账款资产支持专项计划于11月29日簿记完成,产品规模5.50亿元,其中优先级资产支持证券规模5.225亿元、次级0.275亿元.本期ABS发行的优先级票面利率为3.35％,次级票面利率为6％,均低于同期可比市场案例发行利率水平,取得了良好的发行结果,体现了资本市场对金隅集团及金隅混凝土集团的充分认可.
With the design and construction of high-rise buildings with large spans and special functional requirements,concrete is developing towards higher strength,durability,and reliability.In this context,ultra-high performance concrete(UHPC)has emerged as the times require.Due to its ability to improve the environment,increase economic benefits,solve difficult engineering problems,and possess excellent mechanical and durability properties,it has become a hot research topic for scholars.This article provides a detailed explanation of the research and application progress of UHPC based on its basic design principles,excellent physical properties,environmental performance,establishment of relevant standards,and engineering applications.At the same time,it proposes the development trend and research focus of UHPC:firstly,it is to optimize the mix design and raw material selection of UHPC,reduce the viscosity of its slurry,and replace some existing UHPC raw materials with low-cost solid waste to reduce the cost of UHPC;secondly,it is to study reasonable maintenance methods to reduce the high energy consumption and high cost of existing maintenance methods,while promoting the hydration process of unhydrated cement;thirdly,the development of steel wire(steel bar)mesh skeleton reinforcement for UHPC and low fiber or even no fiber UHPC can not only reduce the cost of UHPC,but also improve the flexural and compressive strength of UHPC;fourthly,it is to develop durability standards based on the characteristics of UHPC,provide guidance and suggestions for further promotion and application of UHPC in the future.
The groundwater in karst areas is abundant,the soil is soft,and the geological conditions are complex,tunnel construction in karst strata greatly increases the risk and difficulty of tunnel construction due to the presence of groundwater and karst caves,which can easily lead to engineering accidents and even geological disasters.This paper takes the Zhongshan Tunnel in the Yingde section of the Guangle Expressway as an example and formulates an overall strategy for tunnels under complex geological conditions,which includes"advanced support,initial support strengthening,combined waterproofing and drainage,monitoring strengthening,reasonable deformation,timely closure,and closely following the inverted arch secondary lining".Regarding the karst cavities that appear in front of the tunnel face and above the arch during the construction process,it uses a backfilling to treat the karst caves,and summarizes the effective treatment measures in actual tunnel construction,provides guidance and reference for future construction of karst tunnels.
This study prepares low alkali lightweight porous concrete using lightweight aggregate shale ceramsite 900 grade and slag sulfoaluminate cement under different mix design,and conducts experimental analysis on properties such as porosity,unit weight,compressive strength,and flexural strength through mix ratio tests.The results show that in different mix ratios,the larger the design porosity,the closer the measured effective porosity is to the design value;under a porosity design of 20%to 30%,the unit weight of lightweight porous concrete is only about 0.5 times that of ordinary concrete.The maximum 28 d compressive strength and 28 d flexural strength of porous concrete prepared in this experiment can reach 17.7 MPa and 2.1 MPa,respectively.The compressive strength and flexural strength of porous concrete decrease with the increase of porosity.
With the continuous improvement of people's requirements for building quality and construction efficiency,prefabricated buildings have become an important development direction in the modern construction industry.To meet people's needs,high-performance prefabricated concrete exterior wall panels have become an important component for achieving building assembly,industrialization,and energy conservation.This paper elaborates on the research on the integration and application technology of high-performance precast concrete exterior wall panels.Based on the integration and application technology,and with key manufacturing technologies of precast concrete exterior wall panels as the research content,a high-performance precast concrete exterior wall panel component system with diversified decoration and functional integration is formed,and it is promotes and applies in industrial buildings,industrial factories,and residential buildings.In practical engineering applications,the integration of different finishes of prefabricated concrete exterior wall panels meets the needs of different architectural styles and environmental conditions,not only improving the durability of the finishes,but also enhancing the safety of their use;prefabricated concrete exterior wall panels effectively improve the insulation performance of buildings by selecting appropriate insulation materials and designing sandwich insulation wall panels;by using new materials for door and window integration,the airtightness,waterproofing,and durability of doors and windows can be effectively improved.
研究了普通搅拌工艺、净浆裹石搅拌工艺和基于剪切稀化的低粘度净浆裹石搅拌工艺对不同强度等级混凝土坍落度、倒置坍落度筒排空时间、压力泌水率及7 d和28 d抗压强度的影响.结果表明:基于剪切稀化效应,采用低粘度净浆裹石搅拌工艺更有利于提升C40、C50、C60混凝土拌合物的工作性能和力学性能,并且随着混凝土强度等级的提高,其性能改善更明显.相比于普通搅拌工艺,低粘度净浆裹石搅拌工艺可使C40、C50、C60混凝土坍落度分别提高12、14、15 mm;倒置坍落度排空时间分别减少2.1、2.6、3.2 s;28 d抗压强度分别提高2.7、4.6、10.1 MPa.
本文阐述了传统钢梁防火板安装过程中存在的问题,分析了H型钢梁防火板组合连接件技术的特点及施工工艺,总结了其在实际应用中的优点.在实际工程项目中,通过预先焊接在H型钢梁上的Z型及L型卡件与防火板进行连接,可有效减少施工现场的焊接工序,提升施工进度,并且相较于传统安装方式,操作更加方便快捷,减少了高空作业的时间,保障了施工人员的安全.
