A Primary Investigation on Concrete Made from Iron and Steel Slags for Building Ecological Artifical Reefs

A method of orthogonal test was used to optimize the strength of the cementitious material for preparing the concrete of high-strength artifical reefs.The results show that with the ratio of iron slag:steel slag=7:1,and when 10% cement clinker and 10% gypsum of Flue Gas Desulfurization Waste (FGDW) was mixed with 80% iron and steel slags powder,the mixed cementitious material had an optimized strength.The optimized specific surface area are 480 m 2/kg and 550 m 2/kg for iron slag and steel slag powder respectively.The ordinary portland cement can be totally substituted by such a mixed cementitious material with iron and steel slags as its major components in preparing the concrete for building high-strength artificial reefs.A concrete with a compressive strengh over 65MPa can be prepared by using such a mixture as a cementitious material and steel slag grains as its fine and coarse aggregats which have been stubilized by a hot-simmering method. Hydration processes of net slurry were analysized by XRD and SEM methods. The results show that the hydration products in the system are mainly AFt and C-S-H gel. The results also show that the pozzolanic reaction of iron slags could be largely promoted by the coordinations of steel slags,clinker and FGDW.     

Preparation of Cementitious Material Based onAlkali GGBS Manganese Alloy Slag System

Manganese alloy slag is an industrial waste produced from manufacture of manganese alloy. Recent years environment pollution of manganese slag has been becoming heavier and heavier with the development of manganese industry. Aiming to sort out this problem, combination of manganese slag and ground granulated blastfurnace slag (GGBS) were applied to prepare alkali activated cementitious material. Compressive strength and flexural strength of cementitious material prepared with combination of alkali slag manganese slag were measured. And micro structure of hydration production was investigated by scanning electro microscope (SEM). It was shown that the flexural and compressive strength of cementitious material with alkali GGBS manganese slag system were decreased with the increase of replacement of GGBS by manganese slag. The increase of the fineness of manganese slag was favorable for strength improvement of the alkali GGBS manganese slag material. It was concluded that ground manganese slag had hydraulic activity in alkali activated cementitious material and the activity was lower than that of GGBS.     

The Influence on the Strength of Cement Mortars by Emulsified Epoxy

The influence on the strength of cement mortars by adding emulsified epoxy is studied, and epoxy resin polymer cement mortars with excellent performances are made up through modifying ordinary Portland cement with emulsified epoxy and micro-fine slag. The microstructure of the epoxy resin polymer cement materials are studied and their action and mechanism are discussed by means of modern detection measures such as SEM, XRD. The experimental results indicate cement mortars modifying emulsified epoxy and micro-fine slag have higher compressive strength and flexible strength. The series effects of water-reducing, density, pozzolanicity, filling and solidification cross linking through the action together of epoxy organism and micro-fine slag can endow cement-based materials with perfect mechanic performance. The main hydration products in the system are C-S-H gel and micro-crystal hydrated calcium aluminate. When epoxy resin is solidified, the organism is network. No Ca(OH) 2 has been found.     

Sulphate Attack Resistance of the Concrete with Additives and Its Assessment

The influence of three kinds of additives: silica fume,slag and fly ash on the sulphate attack resistance of concrete were studied.The experiment results show that these three kinds of additives can improve sulphate attack resistance of the concrete and the order of their efficiency from high to low is silica fume,slag and fly ash;the development of mortar expansion value is closely related to the degree of sulphate attack resistance of the concrete;integrated assessing two concrete properties: mortar expansion value and compressive strength ratio can more exactly assess the sulphate attack resistance of the concrete.     

Effects of Cement Additives on Properties of CSA Cement from MSWI

Municipal solid waste incineration fly ash (MSWI) was successfully used as raw material in sintering and preparing a calcium sulphoaluminate (CSA) cement clinker in laboratory. The effects of different types and different addition percentages of cement additives on compressive strength and hydration properties were investigated. The results showed that lime (LI) powder / slag (SL) powder was compatible in CSA cement system while the activities of fly ash(FA)/ MSWI was low. Adding these four types of cement additives in CSA cement system respectively, there were negative effects on compressive strengths of hardened cement at early age while LI/SL improved the compressive strength at later age. The performance of combined additives was better, especially, the specimens with 10%LI+10%SL, 10%LI+10%MSWI, and 5%LI+15%SL.     

A Study on Lightweight Aggregate Concrete with High Fluidity

In this paper, the influence of fly ash (FA), blast furnace slag (BS) and silica fume (SF) on the properties of lightweight aggregate concrete (LAC) with high fluidity were studied. Results show that in LAC the effects of composite additives are better than that of single additive. The slump of LAC with apparent density of 1 840 kg/m 3 could reach 267 mm and the spread 650 mm. The 28d strength is 28.8 MPa for LAC with 20% ground FA and 20% BS as additives and the shale ceramsite with bulk density of 503 kg/m 3 and crushing strength 3.1 MPa was used as aggregate. Physical properties of lightweight aggregate have significant effects on durability of the flowing LAC.     

Energy-absorbing Properties and Crushing Flow Stress Equation of Lightweight Foamed Concrete

Lightweight foamed concrete is a new arresting material for arresting overrun aircraft. To reveal its compression properties and mechanism of deformation and destruction, a study on lightweight foamed concrete with different density, 0.21 and 0.31 g/cm 3 respectively, has been carried out. Experiment system include CSS4410 electronic universal testing machine and Dynatup9250 drop-hammer testing machine and VHS8800 high strain rate system. Then, extrusion strength under different indenter area is predicted with a theoretical model, and a crushing flow stress constitutive equation is proposed. The results show that it is characterized by the movement of crushing driving interface during the process of deformation, crush to compaction of the material, and the deformation is notably in local. The compression strength is relevant to density and impact velocity. Moreover, theoretical model can predict the extrusion strength under different indenter area exactly, and the crushing flow stress equation can describe mechanic properties of compression well.     

Compound Effect of Dihydrate Gypsum and Silica Fume on Strength of Steel Slag-Cement Binding Materials

By adding small amount of dihydrate gypsum (CaSO4·2H2O) and silica fume in steel slag-cement system, steel slag-cement binding materials were prepared. And the dosage of CaSO4·2H2O and silica fume on the properties of steel slag-cement binding materials was studied. Hydration properties and paste structure were investigated by SEM and XRD. The results show that both CaSO4·2H2O and silica fume can improve the strength of steel slag-cement binding materials. Compared with single-doped, compound of CaSO4·2H2O and silica fume has much better effect on strength of steel slag-cement binding materials. The optimum proportion of CaSO4·2H2O and silica fume are 1% and 4%, respectively. The 3 d compressive strength is increased by 59.0%, and the 28 d compressive strength is increased by 36.5%. No matter adding CaSO4·2H2O and silica fume or not, the steel slag-cement binding materials have the same hydration products. However, the content of C-S-H gel and AFt crystals is higher, and the content of Ca(OH)2 crystals is lower in steel slag-cement binding materials containing CaSO4·2H2O and silica fume than those in steel slag-cement binding materials without CaSO4·2H2O and silica fume.     

Study on the Seebeck Effect in Steel-slag Concrete

The Seebeck effect of steel slag reinforced concrete was studied in this paper.The effect of steel slag content and curing period on Seebeck effect were focused on especially.The experimental results show that Seebeck effect of steel slag reinforced concrete was discovered,and a good linear relationship was observed between thermoelectric force(TEP)and temperature differential on the specimen;The linear relationship was from enhancing to weakening with increasing steel slag content;As the curing period extends,the Seebeck effect of steel slag reinforced concrete was better,and TEP became steady.     

Preparation Technology of Fiber Toughened Self compacting High strength Concrete

Preparation technology of fiber toughened self compacting high strength concrete was tested by measuring influence of water/binder ratio, sand percentage, and steel fiber content on spread, T500 time , U shape value, and L shape value of fresh concrete. Mechanical properties were analyzed in case of different water/binder ratio, sand percentage, and steel fiber content. The test results show that suitable W/B and sand percentage were necessary to satisfy self compacting performance of the fresh concrete. With the increase of steel fiber content, the compressive strength and flexural strength were improved while workability of fresh concrete was cut down. Steel fiber toughened self compacting high strength concrete was prepared successfully with a strength grade of CF90 and a flexural strength of more than 11.0 MPa.     

冻融环境下钢筋与粉煤灰混凝土的粘结性能

通过对内贴应变片钢筋的直接拔出试验,分析冻融作用下粉煤灰掺量对钢筋与粉煤灰混凝土间粘结性能的影响,得出冻融循环作用对钢筋与粉煤灰混凝土之间粘结性能的影响规律。试验结果表明：钢筋与粉煤灰混凝土的粘结强度随粉煤灰掺量的增加而降低;当粉煤灰掺量一定时,随着冻融循环次数的增加,混凝土强度有所下降,钢筋与粉煤灰混凝土间极限粘结强度降低;当粉煤灰掺量较大,达到40%时,随冻融次数的增加,钢筋粉煤灰混凝土试件极限粘结强度的下降幅度明显减缓,极限粘结强度对应的滑移量增大。表明掺入较多粉煤灰可使试件的冻融损伤现象得到缓解,冻融环境下钢筋混凝土的粘结性能得到提高。     

Computational Model and Influencing Factor Analysis of Reinforced Concrete Walls under Fire

The finite element software ABAQUS is used to calculate the deformation of reinforced concrete walls under fire. The calculated results agree well with previous experimental results. Based on the finite element model, the influences of such parameters as axial load level, lateral load level, height-to-thickness ratio, wall thickness, concrete compressive strength, steel reinforcement yield strength, steel reinforcement ratio and concrete protection thickness on deformation and fire resistance of walls are analyzed systematically. It is found that, under the conditions of big axial load level or wall thickness without lateral load and small height-to-thickness ratio, the reverse deflection of reinforced concrete walls in fire is apt to occur. Within the work range of parameters in common use, the fire resistance of walls decreases with the increase of axial load level, lateral load level, height-to-thickness ratio, steel reinforcement yield strength or steel reinforcement ratio, and increases with the increase of wall thickness or concrete compressive strength.     

Mechanical and Chloride Diffusion Behavior of Kaolinite Clay Modified Cement-Based Material

The effects of kaolinite clay on the microstructure (pore structure, internal structure) and mechanical properties (workability, early-age and long-term flexural strength, chloride diffusion property) of the cementitious composites were tested. It is shown that the addition of clay improves the micro-pore structure in the cement paste and limits the introduction of chloride ions. As a result, it is suggested that the kaolinite clay would act as both filler and accelerator of cement hydration. Compared with the control specimen, the flexural strength of cement paste with 1% kaolinite clay increased by 30.41%, 39.04%, 36.27% and 38.32% at 1, 3, 7 and 90 curing ages, respectively. The 28-day flexural strength increased slightly. It is observed that the clay modified cement mortar has lower chloride diffusion coefficient values compared to the plain mortar, and the 28-day DCl of cement mortar decreased by 53.03% with 5% clay. Compared with the controlled sample, the increase in compressive strength and the reduction in chloride diffusion coefficient of the concrete with 5% clay addition is 28.4% and 18.87% respectively. The chloride diffusion coefficient of concrete decreases with the amount of clay addition exponentially. The 28-day compressive strength increases linearly with the chloride diffusion coefficient of the concrete.     

Experimental Analysis on Axial Compressive Behavior of R- CFTStub Columns with Prestressed Binding Bars

In order to investigate the effect of prestressed binding bars on axial compressive behavior of rectangular concrete-filled tubular (CFT) short columns, five rectangular CFT short columns, three with prestressed binding bars, one with ordinary binding bars, the other with no binding bars, were constructed and tested under axial compressive loads. The binding bars were made up with high-strength bolts. As used for ordinary binding bars, the high-strength bolts were welded to the steel tube before the column was loaded to axial compressive force. As used for prestressed binding bars, the high-strength bolts were first tensed by screwed screw cap down to bring force to prestress the steel tube and its core concrete, then welded to the steel tube before the column was loaded to axial compressive force. Test results indicate that the bearing capacity and ductility of rectangular CFT short columns are increased by setting binding bars. Compared to ordinary binding bars, the prestressed binding bars can decrease the longitudinal displacements corresponding to ultimate strength, but have little effect on the ultimate strength and displacement capacity after ultimate strength of the columns. The longitudinal displacements corresponding to ultimate strength of the columns decrease with the decreasing of space between binding bars. With the same section width and amount of binding bars, the bearing capacity of the columns improves with the increase of section long-broad-ratio, while displacement capacity after ultimate strength decreases with the increase of section long-broad-ratio.     

Quasi -static Mechanical Properties of SFRC under Uni -axial Compression

Using WAW-2000 a multifunction servo-controlled testing machine,uniaxial quasi-static compression experiments for the steel fiber reinforced concrete(SFRC) were conducted with three strain rates.The volume fraction(V_f)of SFRC ranged from 0% to 3%,and the matrix was C50 concrete.The whole stress-strain curves of matrix and SFRC were obtained,and the results showed that with the increase of V_f,the compressive strength increased slowly,while the toughness increase quickly.With the increase of the strain rate,the strength of SFRC increased,but the toughness decreased,and the more the Vf,the less decreasing of the toughness.The results also showed that the elastic modulus and Poisson's ratio of SFRC were not sensitive material parameters,and with the increase of V_f,the former raised slightly and the latter decreased a little,respectively.A well suited numerical expression of the compressive stress-strain curve applicable to SFRC was put forward.     

掺入工业废料的改性生土材料抗压试验

为合理利用废弃材料改善生土材料力学性能,通过在素土中掺入糯米浆、废玻璃渣和橡胶,形成改性土体材料,设计5种配合比方案,制作Φ102 mm×116 mm圆柱体试块。通过对其进行轴心抗压强度试验,对比不同配比试件的试验现象、抗压强度、变形能力、荷载位移曲线,分析不同掺合料的作用机理、研究不同掺料不同掺量对抗压强度的影响规律,提出了玻璃渣和橡胶掺量的合理范围。试验结果表明,在素土中掺入糯米浆能提高素土抗压强度,掺入糯米浆、玻璃渣和橡胶,可提高抗压强度和变形能力,但其抗压强度随玻璃渣和橡胶掺量的增多增至3.12 MPa后下降。     

Properties of Cemented Copper Tailings Backfill with Steel Slag-Blast Furnace Slag-Fluorgypsum-Based Cementation Material

Cement is a traditional tailings cementation material, which causing the high tailings backfill cost. However, the utilization rate of industrial waste residue, such as steel slag and fluorgypsum, is low. So the steel slag-blast furnace slag-fluorgypsum-based cementation materials preparation with industrial waste residue substitutes for cement. As a result, its cementation tailings performances must be studied. According to mortar fluidity and bleeding quantity of tailing cementation slurry at different time and compressive strength change trend at different hydration ages, the performance of steel slag-blast furnace slag-fluorgypsum-based cementation materials is significantly better than P·O42.5 grade cement and two kinds of commonly used cementation agents in China. After soaking for three days, the pH value of these tailings solidification bodies leaching liquid is less than 9.0, which is much lower than the pH values of three kinds of high alkaline tailings cementation materials mentioned before. Leaching liquid fluorine ion concentration is extremely low. With less impact on environment. SEM analysis also show that these tailings solidification bodies mixing with the steel slag-blast furnace slag-fluorgypsum-based cementation materials have relatively dense microstructure.     

冻融损伤对再生混凝土耐久性及与钢筋粘结性能分析

制作掺入引气剂和未掺入引气剂的100%粗骨料取代率的再生混凝土RC1和RC2两组试件以及掺入引气剂和未掺入引气剂的普通混凝土NC1和NC2两组试件,并分别对经过不同次数冻融循环试件的抗压强度、质量损失率、动弹性模量损失率进行研究。结果表明,冻融后各组试件的抗压强度、质量损失率及动弹性模量损失率均降低,对于添加引气剂的NC1和RC1两组试件损失较小,其中RC1组试件在200次冻融后抗压强度损失接近40%,质量损失率达0.5%,动弹性模量损失率38.5%。100%取代率并加入引气剂的ZRC组试件冻融后进行中心拨出实验,发生劈裂破坏和钢筋拔出破坏2种形式。再生粗骨料混凝土与钢筋的极限粘结应力均随冻融次数的增加而降低,200次冻融后极限粘结应力下降33.5,荷载滑移曲线既有上升段也有下降段。     

Preparation of the supplementary cementitious material offerronickel submerged arc furnace slag and its properties

The ferronickel submerged arc furnace slags are stored up more and more, as a result, seriously influenced the sustainable development of the nickel industry. By grinding, the ferronickel submerged arc furnace slag is mechanically activated, then can be used as supplementary cementitious material, thus a comprehensive utilization way of ferronickel submerged arc furnace slag is developed. Using such processed slag to replace cement from 10% to 40% in mass, with the increase of replacing dosage, the water demand of standard consistency of cement paste is lowered, the fluidity of mortar is raised; the compressive strength of mortar is decreased; the flexural strength is increased followed by a decrease after the dosage is above 10%, the ratio of flexural strength to compressive strength is increased. The experimental results indicate that the ferronickel submerged arc furnace slag can be used as supplementary cementitious material and has an increase of flexural strength and effect of plasticizing and water reducing.     

Research on Stability Criterion of Concrete Feature in Different Stress Stage with Lyapunov Exponent

According to the research on whole curves of strain-stress of concrete materials,this paper finds there was an evident features of stages,and the discrete feature of curve is often in strain-softening stage.After data series of test being detected by dynamics of chaos,it presents that system of whole process of strain-stress evolutes from ordered steady state to low chaos state even high chaos state,system after compressive strength which curve of strain-stress is more linear one by one changes from strong ordered steady state to low chaos state;and joint system of concrete before compressive strength normally generates weak chaos state,with increase of uniaxial compressive strength of concrete materials specimens.The LE1 is proposed to be the stability criterion of concrete features in different stress stages,and the LE1 is regarded as the representative value of the system stability degree.The calculation of example shows that the stability criterion defined by the proposed method is consistent with the actual situation.