Influence of Ca(OH)2 on Strength of Low Proportional Cemented Soil

Laboratory experimental research is performed by strengthing three different types of soil with low proportional cement to test the unconfined compressive strength of such cemented soil under different dosages of Ca(OH)2 and the different ages. The variation rules and causes of the unconfined compressive strength of these three types of age-different cemented soil with increasing the dosage of Ca(OH)2 are analyzed. The results shows that the intensity of red clay cement improves most obviously with Ca(OH)2 content increased, followed by silty clay, and sand is the weakest. The reason is that the fineness of the soil affect the strength of the cement greatly. The finer the soil, the more clay minerals in soil. The increase in Ca(OH)2 content promotes the ion exchange and the occurrence of volcanic ash, which improves the strength of cemented soil. Among the three types of soil in this experiment, the fineness of red clay particles is the best, so the intensity of red clay cement improves most obviously with Ca(OH)2 content increased.     

污水环境对水泥土力学性能的影响试验研究

由于多数地下水泥土工程直接与地下腐蚀性介质环境接触,必将导致水泥土材料的逐步劣化甚至失效破坏。以某市区工地附近明渠排放的污水作为侵蚀性介质,制作了不同水泥掺量的水泥土试件,通过对比试验,研究了污水环境和清水环境下不同水泥掺量、不同龄期的水泥土抗压强度和抗剪强度。结果表明,在污水或清水环境下,相同水泥掺量水泥土30 d龄期的抗压强度几乎相等,随着龄期的增加其抗压强度均逐步增大,但污水环境下其抗压强度增长的幅度明显小于清水环境,90 d后清水环境的水泥土抗压强度不再增长,而污水环境的抗压强度开始降低;污水环境和清水环境下的水泥土内摩擦角和黏聚力随龄期、水泥掺量的增加均逐步增大,污水环境下龄期90 d后的内摩擦角和黏聚力均开始降低。     

Strength and Microstructure of Sulphoaluminate Cement Containing Ultra- Fine CaCO3

The existence of ettringite in sulphoaluminate cement hardened paste is mainly in the form of pole-like crystal,which causes unfavorable effect on the cement.In this paper the strength and microstructure of the sulphoaluminate cement containing ultra-fine CaCO_3 weze discussed.Experimet results show that the strength of sulphoaluminate cement was obviously improved by adding 3% of ultra-fine CaCO_3.After curing for 28d,the compressive strength of cement paste and mortar is 100.6MPa and 94.1MPa respectively,and the bending strength of the mortar reached 12.5MPa.SEM study on hardened paste of sulphoaluminate cement containing ultra-fine CaCO_3 showed that its structure was dense and homogeneous,there was hardly any massive crystall detected.     

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 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.     

Effects of Stone Powder on Wet Packing Density of Cement and Performances of Concrete

The amount of limestone powder, which is a by product of manufactured fine aggregate, is larger and larger with the increase of manufactured fine aggregate. Environment will be severely polluted if the powder is improperly used. The effects of limestone powder on workability, compressive strength, and impermeability of concrete were studied when cement is substituted for the mass proportion of 0, 10, 15, 20 percent with it. The results show that the performances of concrete are better improved when the percentage of limestone powder is about 10 percent. The wet packing density of mixture of limestone powder and cement was measured, and it shows that the degree of density was biggest when limestone powder is 10 percent. This shows that the best mixing proportion of limestone powder and cement may be determined through measuring the change of compactness of mixture of limestone powder and cement.     

Experimental Investigation of Stabilized Soft Soil by New GSC

Soft clay is stabilized by desulphurization gypsum and steel slag-slag blended cementitious materials (GSC), which can not only reuse industrial waste and decrease second pollution, but also can conserve mineral resources and protect natural ecology. The variation of unconfined compressive strength of the clay improved by GSC with different mixing ratios and water-GSC ratio and ages was studied through the laboratory experiments. The long-term strength of stabilized soil is predicted with GSC by quasi-water-GSC ratio. The results show that the more the mixing ratios is, the better the stabilized effect of soft soil is. With increase of curing period, the strength increasing of GSC-soil is consistent with cement-soil, and it has lower strength in the early stage. When mixing ratios of GSC is more than those of cement by 3%, if the water-GSC ratio is less than those of cement, it has the higher strength than cement-soil, after 28 days. The results show that GSC stabilized soil is feasible and it can meet the demand of cure strength.     

STUDY ON THE LOW TEMPERATURE CALCINATION AND THE BEHAVIOUR OF STEEL SLAG COLOUR CLINKER CEMENT

The colourcd clinker cement which fired directly from kiln has the advantages of low cost,bright colour and good colour durability.This paper studies the possibility of using calcium flouridc and gypsum combined mineralizer to calcine the col-outed clindcr cement at low temperature.Different methods such as X-ray diffraction ana ysis,scanning electron microscopy,infrared spectra analysis,combined water content chemical asysis,compressive strength test and so on arc used to study the clinder minerals,the colour,the physical and mechanics properties and behaviour of the coloured clinker cement which made both with high quality raw materials and with electric furnace reduced slag additive.     

多浓度营养盐处理对微生物胶结砂土均匀性与强度的影响

采用二次注入菌液方式，制备不同浓度营养盐处理的MICP （微生物诱导碳酸钙沉淀）胶结砂样。选用巴氏芽孢杆菌作为固化细菌，采用单一浓度（0.5、1.0 mol/L）和多浓度相结合（前期采用0.5 mol/L，后期采用1.0 mol/L）的处理方式注射营养盐（尿素/氯化钙混合液），研究多浓度营养盐结合处理方式对微生物固化砂土强度及均匀性的影响。基于试验测试分析了固化砂土试样不同区间段的强度、弹性模量以及碳酸钙含量。试验结果表明，多浓度营养盐处理方式对固化砂土试样的强度及碳酸钙含量有明显影响；多浓度营养盐结合处理方式能够保证试样有较好的均匀性条件下获得较高强度及弹性模量。基于多浓度营养盐处理方式，探讨分析了影响试样强度和均匀性的基本因素。     

建筑垃圾细料生产流动化回填材料的性能

以灰砂比0.03、0.05和0.08,粉砂比0、0.05、0.1、0.15和0.2为设计参数,对建筑垃圾回填材料进行设计。通过试验对回填材料的流动性(流动度、泌水率)、无侧限抗压强度以及应力应变曲线、本构关系模型和弹性模量等进行研究。研究结果表明:回填材料的流动度受水固比影响较大,两者接近线性关系;流动度在200~250 mm范围,泌水率在4%~8%之间;回填材料抗压强度与灰砂比和水固比之间存在很好的幂指数关系;回填材料应力应变曲线形状与普通混凝土的相似,在此基础上提出回填材料的本构关系模型;回填材料无侧限抗压强度与弹性模量之间存在很好的指数关系。     

Recycling Technology of Aged Asphalt Pavement

Firstly,the current development of the technologies for recycling of reclaimed asphalt pavement(RAP) in China and abroad is introduced in this study.The theoretic evidence is supplied for the feasibility and means of the recycling technology for RAP by analyzing the aged asphalt recycling mechanism.On the basis of it,a series of recycling processes for RAP are stated in detail,including the performance assessment of RAP,mix design and construction techniques of recycling asphalt mixture.The traits and actual example of different construction techniques for RAP supplied a good consultation for its reasonable choice.All of them would play a role in the research,application and spread of the recycling technologies for RAP in China.     

自制硅酸盐对传统糯米灰浆性能的影响

采用灰浆性能表征和扫描电镜（SEM）、X射线衍射（XRD）、红外光谱（FTIR）等技术手段，探讨了自制硅酸盐对糯米灰浆的影响及作用机理。结果表明：自制硅酸盐对糯米灰浆的表面硬度、抗压强度、耐冻融性和耐水性均有一定程度的改善。6%自制硅酸盐糯米灰浆的综合性能最佳，其66 d抗压强度高达1.41 MPa，耐冻融性较之空白样品提高了133%，耐水性能提高了43.8%。改性糯米灰浆耐水性等性能的提高，可能与灰浆中水化硅酸钙的生成有关。     

污泥与城市生活垃圾混填的力学特性及稳定性

工业污水和生活污水排放量日益增多,污水处理厂污泥产量日趋加大,污泥填埋关键技术问题已成为当今环境工程以及环境岩土工程的热点问题之一。污泥和垃圾混合填埋在其他国家已得到应用,但由于目前中国关于污泥及其城市生活垃圾混合样的基础性室内试验成果不多,对污泥与城市垃圾混合样的工程力学特性及其混合填埋的适宜比例等不甚了解,从而导致中国污泥垃圾混合填埋工程事故频繁发生。对不同配比的污泥与城市生活垃圾混合样进行了固结压缩实验、三轴固结不排水实验、无侧限抗压强度实验,得出污泥与城市生活垃圾混合样的工程力学特性;同时,用ANSYS数值模拟方法,对不同配合比的污泥城市生活垃圾混合填埋边坡的稳定性进行分析,从而对污泥与城市生活垃圾混合填埋的适宜配合比及其稳定安全问题提出理论支撑。     

Fabrication and Formation Mechanism of FoamedIron Slag-Steel Slag Concrete

In order to achieve the comprehensive utilization of iron slag and steel slag, foamed concrete were prepared by adding small amount of gypsum, lime and clinker in steel slag-iron slag system and using aluminum powder as foaming agent,. The three-day, seven-day and twenty-eight-day bulk density and compressive strength of foamed concrete with the different ratio of the main raw materials were researched. Furthermore, in order to research the hydration mechanism and microstructure of foamed concrete, the XRD and SEM images of the three productions of foamed concrete were analyzed. The results showed that the coordination of the dosage of steel slag and iron slag was better when the former was 30% and the latter was 45%, Meanwhile, the compressive strength was 5.1 MPa, the bulk density was 625 kg/m 3; Ettringite and C-S-H gel synergies generated in steel slag-iron slag system. Besides, hydration activity of steel slag was obviously lower than that of iron slag.     

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.     

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.     

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.     

再生混凝土抗碳化性能试验研究及理论分析

通过快速碳化试验,以再生骨料掺量、水灰比、水泥用量、原始混凝土强度和矿物掺合料为影响因素,对再生混凝土的碳化性能进行研究。试验结果表明：再生混凝土的碳化深度随水灰比、再生骨料掺量的增加而减小,随原始混凝土强度的增大和水泥用量的增加而增大,适量添加矿物掺和料能降低再生混凝土的碳化深度,提升其抗碳化性能。在已有的普通混凝土碳化模型研究基础上,结合本试验和中国其他学者的试验数据,建立了再生混凝土碳化深度预测模型,模型预测结果与试验值吻合较好。     

不同黑杨无性系及树干高度木材顺纹抗压强度研究

为探明黑杨无性系间及个体木材顺纹抗压强度的变异情况,进一步拓宽黑杨木材开发利用途径,笔者对15年生的5个黑杨无性系的生长性状以及木材顺纹抗压强度进行测定分析。结果表明：不同黑杨无性系间木材顺纹抗压强度存在极显著差异,无性系内不同树干高度木材顺纹抗压强度差异显著。供试各无性系木材顺纹抗压强度均达到41 MPa 以上,无性系83 的木材顺纹抗压强度最大,为48.44 MPa;无性系69 的木材顺纹抗压强度最小,为41.06 MPa。各无性系木材顺纹压力强度沿树干高度变化基本一致,都是随着树干高度的增加木材顺纹抗压强度呈逐渐增加的趋势,但无性系内木材顺纹抗压强度在不同树干高度上的变异差异显著。黑杨无性系木材顺纹抗压强度与胸径呈负相关,与树高呈正相关,但均未达到显著水平;与单株材积基本不相关,相关系数仅为0.106。     

氯氧镁水泥混凝土中钢筋的腐蚀与防护试验研究

结合氯氧镁水泥混凝土耐水性，研究氯氧镁水泥混凝土中钢筋的腐蚀与防护，试验变量包括钢筋种类、混凝土保护层厚度和腐蚀龄期等。钢筋种类包括裸露钢筋和美加力涂层钢筋；混凝土保护层厚度包括25、50 mm；腐蚀龄期包括60、120、180、240、300、360 d。试验采用自来水长期浸泡至试块2/3处，并采用扫描电子显微镜（SEM）和能谱仪（EDS）对腐蚀后的钢筋微观结构和化学元素组成进行分析，研究钢筋的腐蚀机理。结果表明，通过软化系数分析，氯氧镁水泥混凝土的软化系数处于0.78～0.87，说明试验设计的氯氧镁水泥混凝土可用于干燥地区、受潮较轻地区或次要建筑结构。通过极化曲线及其电化学参数分析，裸露钢筋腐蚀速率为美加力涂层钢筋腐蚀速率的40～80倍，说明涂层防腐效果明显。