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.     

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.     

Relationship between porosity and chloride diffusivity in cement-based composite materials

For investigating the effect of porosity in cement-based composite materials on diffusion coefficient of chloride ion, a series of mortar specimens with different water-cement ratios, different volume fractions and different diameters and graduation of aggregates are cast, and then chloride diffusivity of mortar specimens are measured by steady-state electric acceleration method and pore structure parameters of corresponding samples are obtained by mercury intrusion porosimetry. At the same time, the pore size distributions are visualized by X-ray micro-focus computer tomography. The results show that porous interfacial transition zones between aggregate and bulk cement paste significantly change the distribution of pore structure in hardened cement paste, and the smaller water-cement ratio is, the more significant the effect of interfacial transition zones on pore structures of hardened cement paste is. A good correlation between the total porosity, capillary porosity and the diffusion coefficient of chloride ion in cement-based composite materials has been determined and the continuous pore diameter is linearly related to the diffusion coefficient of those. Furthermore, the larger the continuous pore diameter is, the larger the value of chloride diffusivity is.     

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.     

Experiment And Study On Microstructure of Superfine- sand High Strength Concretes

A high strength concrete with 28 day strength up to 80 MPa from superfine sand with fineness modulus of 0.56 is obtained.It has a permeability resistance of 4.0 MPa and small shrinkage creep.Experiment and study were carried out on its pore structure,hydration products and microhardness of transient area in cement paste and aggregate interface. The essence for high strength of such concrete was revealed.     

Influence of Macromolecule-type Retarders on the Hydration and Microstructure of Hardened Paste

Influence of one macromolecule-type retarder bone glue on the setting time, strength, ion concentration in liquid phase and supersaturation degree, crystal morphology of dehydrate and microstructure of hardened paste of building gypsum is investigated. Furthermore, internal cause of strength loss of building gypsum with addition of retarder is analyzed, The results indicate that bone glue could retard the hydration of building gypsum markedly, but its negative influence on the strength of building gypsum is far lower than that of low molecule-type retarders. Bone glue has a minor effect on crystal morphology of dehydrate and porosity of hardened paste, but it causes the large crystal size and coarsening of pore size distribution of hardened gypsum paste, which is the very intrinsic reason of strength loss of building gypsum.     

Performance of synthesized polycarboxylic grinding aid

Hydrolyzed polymaleic anhydride (HPMA) and polyethylene glycol monomethyl ether(MPEG) synthesized a kind of polycarboxylic grinding aid, the esterification was prompted by the mechanical force during the process of cement grinding. The effects on cement grinding and mortar property were tested from HPMA, MPEG, the mixture of HPMA and MPEG, and the resultant of HPMA and MPEG. The results showed that the mixture of HPMA and MPEG and the resultant of HPMA and MPEG had better grinding performance than HPMA and MPEG, and which can improve the fluidity and early strength of cement mortar. Laser Raman spectrum tests showed that the resultant of HPMA and MPEG had a similar Raman shift spectrum with the mixture of HPMA and MPEG, when they were adsorbed on the cement particle surface after co-grinding.     

Investigation on EPS Surface Modification and EPS Thermal Insulation Mortar''s Weather-resisting and Crack-resisting

The surface of EPS is of hydrophobic nature, which can not wet binding material. As in the freshly mixed mortar, EPS particle is not affined with cement paste and has a low bulk density, which will be apt to make EPS particle buoy, and lead to the segregation of mortar, the decrease of water retentivity and affect its workability. When pretreated, the surface of EPS can be changed into that of hydrophilic nature, and be wetted by freshly mixed silicate paste. The technology channel of EPS surface modification is that select proper high-molecular binder and coupling agent, prepare polymer silicate binding material of low water-cement ratio, and utilize the double effect of binder and coupling agent to form silicate grout of hydrophilic nature on the surface of EPS, by composite binding material wrapping the surface of EPS. A new thermal insulating mortar with good properties of thermal engineering, weather-resisting and crack-resisting can be made by modified EPS as light aggregate and cement as binder, modification with fiber and polymer. This new type of insulating mortar can be used as outer thermal insulation of outside wall, which breaks the limitation of traditional insulating mortar only as interior insulation. It has been widely used in the building energy-saving model project.     

Study on the Exterior Wall External Thermal Insulating Mortar Made from Waste Expanded Polystyrene(EPS)

The surface of modified EPS can be changed from the character of water-repellent to hydrophilic,and be wetted by freshly mixed portland cement paste.A new thermal insulating mortar with good properties of workability,thermal insulation,climate-resisting and crack-resisting can be made modified EPS as light aggregate and cement as binder,and modified with fiber and polymer.This new type of insulating mortar can be used as exterior wall thermal insulation,which breaks the limitation of traditional insulating mortar only as interior insulation.It has been widely used in civil engineering.     

Experiment Research of Adhesive and Shearing Strength between the Concrete Member Poured with Special-shaped Steel Form and the Cement Mortar on its Surface

This paper systematically presents the experiment about the adhesive and shearing strengthbetween the concrete member poured with two kinds of steel form and the cement mortar on the membersurface. By the comparison of three groups of experiments, this paper draws a conlusion tha the adhesive and shearing strentgh between concrete member and cement mortar could be considerably increased if the special-shaped steel form was applied.     

Cementation Effect with Cement during Cold In Place Recycling System of Asphalt Pavement

Different kinds of structures of RAP and different contents of cement were prepared. By means of standard compaction test, unconfined compressive strength, water stability, modulus and SEM test, the cementation effect with cement was studied. It was shown that the maximum dry density of RAP mixture rose from 1.91g/cm3 to 2.00g/cm3 with the increase of cement content when A/S was 0.4. The maximum dry density of RAP mixture would rise when adding more asphalt. The unconfined compressive strength rose from 1.48MPa to 2.63 MPa and then down to 2.28MPa when cement content was 6%. The best property could be got when A/S was 0.4 and the cement content was 6% with 9.5% water. The compressive strength of RAP mixture declined after it was cured in water for 24 h, but it had the same tendency with those of which had not been maintained in water. And it is also found that RAP does not obtain better stabilities in high temperature with modular test. From SEM test, it is shown that ettringite and C S H interlace and form the netted structure, and the aggregate would be enwrapped to increase the strength.     

Experimental Study on Flexural Behavior of Reinforced Concrete Beams Strengthened With Ferrocement Mortar

Experimental research on flexural behavior of the different grade RC beams strengthened with ferrocement mortar through six RC beams is carried out. The matching of original component concrete to the composite mortar strength rank is studied and its influence on bending strength, the crack-resisting capacity and the bending stiffness of RC beams is analyzed. Based on plane cross-section assumption and the experimental results, the formulas of the theoretical ultimate strength capacity and stiffness are brought forward. The calculated results fit well with the experimental results, to provide a theoretical reference for actual engineering designs.     

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。     

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.     

Preparation of Porous Hardened Cement Paste Synthetic Filter Material and Phosphorus Removal from Wastewater by Adsorption

Taking cement as primary raw material, a porous hardened cement paste synthetic filter material was prepared by steam curing in a reaction kettle. The optimum process combination condition of the filter material was determined. By orthogonal experiment, the optimal combinations of technical conditions were determined: water-solid ratio is 0.25, and pore-forming agent/cement equals to 0.3 with steaming temperature at 180°C in the reaction kettle for 4 h. Effects of pH value, dosing quantity and the initial concentration of phosphorus on phosphorus removal by using the filter materials which prepared under the optimal conditions were tested. The results show that the phosphorus removal rate reaches all above 95.3% and the highest one is 99.8% when the initial concentration of phosphorus is 5~10 mg·L -1. When the amount of filter material is added 2.5 g/100 mL, under the experimental condition of pH neutral, the top phosphorus removal rate reaches 89.6% when the concentration is 50 mg·L -1. The analysis of adsorption kinetic process shows that the pseudo-second-order kinetic is fitted to the adsorption characteristics of filter material and the adsorption rate is controlled by the intra-particle diffusion.     

Drying shrinkage characteristics of alkali slag cement mortar

The drying shrinkage characteristics of alkali slag cement mortar from the view of irreversibility are studied. It is found that the shrinkage of alkali slag cement mortar water curing after drying is significantly greater than that of OPC mortar which is cured under the same conditions. The drying shrinkage (14 d) of alkali slag cement mortar activated with NaOH solution and water glass is respectively 5.5 and 2.2 times of those of OPC mortar. Moreover, the majority of drying shrinkage of alkali slag cement mortar is irreversible, and the proportion of this part is up to 86%(activated with water glass) and 68%(activated with NaOH solution).     

地下水强酸盐复合腐蚀环境下不同矿物掺合料对水泥砂浆耐腐蚀性能的影响

模拟了贵州地区地下水强酸盐复合腐蚀环境,系统研究了粉煤灰、矿渣粉和硅灰3种矿物掺合料单掺与复掺对水泥砂浆耐腐蚀性能,如耐蚀系数、质量变化率、氯离子相对扩散系数的影响规律,并探讨了地下水强酸盐复合腐蚀环境下水泥砂浆的腐蚀机理。结果表明,与基准砂浆相比,单掺与复掺矿物掺合料均提高了砂浆的耐蚀系数,降低了砂浆后期氯离子相对扩散系数,但增大了砂浆质量损失率。这3项指标从不同角度反映了地下水复合腐蚀环境下水泥砂浆的耐腐蚀性能。     

Dry mixed Superfine Sand Mortar for Bonding Ceramic Tile

By modification with water retentive agents and organic bonding admixtures, one dry mixed superfine sand mortar used as ceramic tile bonding was prepared with good workability, adhesive capacity and climate resistance. The test results indicate that this mortar has excellent anti sagging characteristics, with slippage of less than 2mm, sufficient open time and bonding strength over 1 MPa after being open for 20 minutes. These traits provide the needed qualities for thin construction of ceramic tile bonding. By adding polypropylene fiber, a flexible mortar was prepared with superior crack resistance for use as a ceramic tile bonding agent. The preparation mechanism, method and performance are introduced in detail.     

AN EXPERIMENTAL STUDY ON CEMENT MORTAR SPBCIMENS WITN A CENTRAL SLITS UNDBR UNIAXIAL COMPRESSION

The cement mortar specimens with a central slits are tested under uniaxial com-pression.The test results show that tensile cracks initiate,as a rule near the tip and may propagatesteady for a certain length.Mean while shear fructures appear and propagate slowly to the failurestate in the zone of compressive stress concentration. So the fracture strength of rock under compres-sion might be differentiated into the initial tensile strength,the peak strength and residual strength.     

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。