阿尔及利亚东西高速公路泥灰岩地质路基设计方案探讨

阿尔及利亚东西高速公路沿线的主要地层为泥灰岩,本文介绍了在泥灰岩这种特殊的地层条件下路基工程常发生的病害设计施工要点及整治措施,对类似地质构造的工程具有参考意义。

Early calcium monocarboaluminate hydrate formation in cement paste:effect of polycarboxylate type admixture

Effects of polycarboxylate type admixture（PCA）on calcium monocarboaluminate hydrate（AFmc）formation in hydrated cement paste containing limestone filler（LF）are investigated by the Fourier transform infrared spectroscopy（FTIR）,the scanning electron microscopy（SEM）,the derivative thermogravimetric（DTG）analysis and the adsorption amount measurement.Experimental results indicate that AFmc forms during the initial hydration period of cement as early as 15 min.It is found that PCA accelerates the early age AFmc formation and enhances cement hydration by promoting C4AF hydration at the early age,and,as a consequence,the iron associated AFmc phase forms more readily.The phenomenon is not observed when PCA is replaced by a naphthalene formaldehyde sulphonate condensate water reducer.Compatibility between PCA and cement is modified due to the presence of AFmc along with ettringite（AFt）,which results in a less adsorption amount of PCA on the surface of cement minerals.As a kind of high-range water reducer,PCA may be the preferred choice for concrete containing LF.

Enhanced photocatalytic performance of cementitious material with TiO_2@Ag modified fly ash micro-aggregates

A TiO2 photocatalyst is coated on the surface of a zeolite fly ash bead（ZFAB） to improve its dispersability and exposure degree in a cement system.The application of Ag particles in TiO2/ZFAB modified cementitious materials is to further enhance the photocatalytic performance.Various Ag@TiO2/ZFAB modified cementitious specimens with different Ag dosages are prepared and the characteristics and photocatalytic performance of the prepared samples are investigated.It is observed that the multi-level pore structure of ZFAB can improve the exposure degree of TiO2 in a cement system and is also useful to enhance the photocatalytic efficiency.With an increment of the amounts of Ag particles in the TiO2/ZFAB modified cementitious samples,the photocatalytic activities increased first and then decreased.The optimal Ag@TiO2/ZFAB modified cementitious sample reveals the maximum reaction rate constant for degrading benzene（9.91×10^-3 min^-1）,which is approximately 3 and 10 times higher than those of TiO2/ZFAB and TiO2 modified samples,respectively.This suggests that suitable Ag particles coupled with a ZFAB carrier could effectively enhance the photocatalytic effects and use of TiO2 in a cement system.Thus,ZFAB as a carrier could provide a potential method for a high efficiency engineering application of TiO2 in the construction field.

Use of Sewage Sludge After Liming as Fertilizer for Maize Growth

The use of sewage sludge on agricultural land provides an alternative for its disposal. Therefore, the aim of the present study was to evaluate the feasibility of using industrial sewage sludge produced in Pakistan, as an agricultural fertilizer. The agricultural soil amended with 250 g kg^-1 sewage sludge with or without lime treatment was used for the growth of the common local grain crop, maize （Zea maize）. The mobility of the trace and toxic metals in the sludge samples was assessed by applying a modified BCR sequential extraction procedure. The single extraction procedure was comprised of the application of a mild extractant （CaCl2） and water, for the estimation of the proportion of easily soluble metal fractions. To check the precision of the analytical results, the concentrations of trace and toxic metals in every step of the sequential extraction procedure were summed up and compared with total metal concentrations. The plant-available metal contents, as indicated by the deionized water and 0.01 mol L^-1 CaCl2 solution extraction fractions and the exchangeable fraction of the sequential extraction, decreased significantly （P 〈 0.05） with lime application because of the reduced metal availability at a higher pH, except in the cases of Cd and Cu, whose mobility was slightly increased. Sludge amendment enhanced the dry weight yield of maize and the increase was more obvious for the soil with lime treatment. Liming the sewage sludge reduced the trace and toxic metal contents in the grain tissues, except Cu and Cd, which were below the permissible limits of these metals. The present experiment demonstrates that liming was an important factor in facilitating the growth of maize in sludge-amended soil.

Ultrasonic attenuation model for measuring particle size and inverse calculation of particle size distribution in mineral slurries

Based on various ultrasonic loss mechanisms, the formula of the cumulative mass percentage of minerals with different particle sizes was given, with which the particle size distribution was integrated into an ultrasonic attenuation model. And then the correlations between the ultrasonic attenuation and the pulp density, and the particle size were obtained. The derived model was combined with the experiment and the analysis of experimental data to determine the inverse model relating ultrasonic attenuation coefficient with size distribution. Finally, an optimization method of inverse parameter, genetic algorithm was applied for particle size distribution. The results of inverse calculation show that the precision of measurement was high.

Effect of Additives on the Morphology of the Hydrated Product and Physical Properties of a Calcium Phosphate Cement

The morphology of a hydrated calcium phosphate cement （CPC） doped with several normally used additives was investigated by scanning electron microscopy （SEM） and the compressive strength of the cement was determined in this study. The hydrated products of CPC without additives was rod-like hydroxyapatite （HA） grains with around 2-5 μm in length and 100 nm in width. The addition of Sr obviously decreased the crystal size of the rod-like grains. CPCs containing carbonate, collagen and gelatin showed flake-like crystal morphology. Crylic acid-containing CPC presented flocculus-like structure. And malic acid-containing CPC exhibited oriented flake-like structure. The X-ray diffraction （XRD） analysis showed that the additives used in this study did not alter the hydration products of the cement. The compressive strength tests indicated that the compressive strength of the cement with rod-like morphology HA crystals was much higher than that of the cement with flake-like morphology HA crystals, and the cement with oriented flake-like morphology HA crystals exhibited the poorest compressive strength.

Incorporating Simulated Zinc Ash by Kaolinite-and Sludge-based Ceramics:Phase Transformation and Product Leachability

Zinc is one of the hazardous metals commonly found in municipal solid waste incineration （MSWI） ash, and this study reveals the stabilization mechanisms when sintering zinc-laden ash and ceramic precursors as a waste-to-resource strategy. Using ZnO to simulate the zinc-laden ash and sintering with kaolinite and mullite ce- ramic precursors, both zinc aluminate spinel （ZnA1204） and willemite （Zn2SiO4） phases were found in the products under the tested thermal conditions. The results also indicate that kaolinite and mullite precursors exhibit different incorporation behavior, and ZnA1204 and Zn2SiO4 were found to be competitive as the Zn-hosting phases in the system. A prolonged leaching test was used to evaluate the leachability of potential product phases in the system. The concentrations of zinc in ZnO and Zn2SiO4 leachates were about two orders of magnitude higher than that in ZnA1204 leachate, indicating the preference of forming ZnA1204 for zinc stabilization. Furthermore, the alumi- num-rich sludge generated from waterworks could be beneficially used as a material resource to stabilize zinc in this study. The X-ray diffraction （XRD） pattern collected from the 1150 ~C and 3-h sintered sample shows the suc- cess of incorporating zinc into the ZnA1204 spinel structure with waterworks sludge precursor. The formation of ZnA1204 indicates a strong potential for employing aluminum- and silicon-based materials to thermally immobilize zinc and achieve the beneficial use of metal-laden MSWI ash.

Effect of textural characteristics on engineering properties of some sedimentary rocks

As it is commonly known,the estimation of physical and mechanical characteristics of rocks is very important issue in various geotechnical projects.The characteristics are mainly influenced by the microfabric-texture features of rocks.In this research,dry unit weight,effective porosity,point load index,Schmidt rebound hardness,uniaxial compressive strength,and texture coefficient were measured with the aim of correlating the physical and mechanical properties to the texture coefficient.For this purpose,a comprehensive laboratory testing program was conducted after collecting twenty sedimentary block samples including nine limestones and eleven mudstones,taken from Kalidromo(central Greece)in accordance with ASTM and ISRM standards.Also,mineralogical and petrographic properties,textural characteristics as well as X-ray diffractions were studied and the obtained results were statistically described and analysed.The maximum and minimum values of the texture coefficient were 0.13 and 0.50,respectively.The highest value was obtained for the rocks with a large amount of grains.Regression analyses were used to investigate the relationships between the texture coefficient and the engineering properties.Thus,empirical equations were developed and because of the good determination coefficients,they showed that all of the engineering properties were well correlated to the texture coefficient.

Consolidation analysis of composite foundation with partially penetrated cement fly-ash gravel(CFG) piles under changing permeable boundary conditions

Based on the double-layered foundation theory, the composite ground with partially penetrated cement fly-ash gravel(CFG) piles was regarded as a double-layered foundation including the surface reinforced area and the underlying untreated stratum. Due to the changing permeability property of CFG piles, the whole consolidation process of the composite ground with CFG piles was divided into two stages, i.e., the early stage(permeable CFG pile bodies) and the later stage(impermeable pile bodies). Then, the consolidation equation of the composite foundation with CFG piles was established by using the Terzaghi one-dimensional consolidation theory. Consequently, the unified formula to calculate the excess pore water pressure was derived with the specific solutions for the consolidation degree of composite ground, reinforced area and underlying stratum under instant load obtained respectively. Finally, combined with a numerical example, influencing rules by main factors(including the replacement rate m, the treatment depth h1, the permeability coefficient Ks1, Kv2 and compression modulus Es1, Es2 of reinforced area and underlying stratum) on the consolidation property of composite ground with CFG piles were discussed in detail. The result shows that the consolidation velocity of underlying stratum is slower than that of the reinforced area. However, the consolidation velocity of underlying stratum is slow at first then fast as a result of the transferring of effective stress to the underlying stratum during the dissipating process of excess pore water pressure.

Lateral displacement of silty clay under cement-fly ash-gravel pile-supported embankments: Analytical consideration and field evidence

Based on back analysis of lateral displacements measured in situ by using the analytical solution, a useful method for estimating stress concentration ratio of geosynthetic-reinforced and pile-supported(GRPS) embankments was proposed. In order to validate the proposed method, a full-scale high-speed railway embankment(HSRE) with four instrumented subsections over medium compressibility silty clay was constructed in three stages. The soil profile, construction procedure and monitoring of settlements and lateral displacements of the four test sections were described. The field deformation analysis results show that 1) the combined reinforcement of CFG piles and geosynthetic layer perform well in terms of reducing lateral displacements; 2) the development of lateral displacements lags behind the increase of fill load, which can be attributed to the vertical load transfer mechanism of the pile foundation; and 3) pile length has a dominant effect on the stress distribution proportion between piles and surrounding soils. The comparison between predicted and experimental results suggests that the proposed analytical solution and the back analysis-based method are capable of reasonably estimating the lateral deformation and the stress concentration ratio, respectively, if the appropriate soil elastic modulus is chosen.

Argillization mechanics of rock from the Xing’anling Group in the Beier depression of the Hailar basin

The reservoir of the Xing'anling Group in the Beier depression of the Hailar basin is loosely cemented with many tuffaceous grains.This causes argillization and collapse of the grain framework of the reservoir sandstones.A detailed study on the characteristics of rocks and minerals was carried out through polarized microscope,X-ray diffraction,X-ray fluorescence,SEM and energy spectrum analysis.The results indicate that the reason for argillization is the abundant pyroclastic,and especially tuffaceous,grains in the reservoir.The alkaline component is relatively high in some strata.These are easily altered to montmorillonite in diagenesis.Na+montmorillonite swells strongly when exposed to water.This is the fundamental reason for the reservoir's argillization and plugging.

Hydration Properties of Calcined Clay Pozzolan and Limestone Mineral Admixtures in Binary and Ternary Cements

This paper investigates the properties of hydrated binary and ternary blended cements using limestone and calcined clay pozzolan as supplementary cementitious materials. The blended cements were hydrated and their phase compositions were evaluated by thermogravimetric and powder X-ray diffraction at 28 days. The morphology of the samples was also determined. The water demand, setting time, compressive and flexural strengths of mortar and concrete samples were determined up to 365 days. The study concluded that the portlandite [Ca（OH）2] content was considerably reduced whilst ettfingite formation were enhanced as a result of admixture reactions. The water demand and setting times of blended cements were lower than OPC with 5% admixture content but higher with increasing content. The mechanical test results also showed that Class 42.5N and 32.5R cements can be produced from the binary and ternary blends containing up to 10% and 20% admixtures, respectively.

Comparative Study on Debris Flow Initiation in Limestone and Sandstone Spoil

Large spoil tips from reconstruction works as a result of the Wenchuan Earthquake in China are new debris flow hazards to the human society.However,there is a lack of detailed comparative study on debris flow initiation in different spoil materials.This paper describes a series of tests and analyses on debris flow characteristics(initiation,scale and mechanism) at six sites with limestone and sandstone materials near the Dujiangyan area.Research shows the limestone spoil contains debris flow prone clay content with high concentration of montmorillonite(highly expandable).In addition,limestone spoil is of such a low permeability that water mainly concentrates in the upper surface layer.Those factors make it easy for the increase of pore water pressure,decline of internal friction and conhesion force,leading to the occurence of large debris flows.In contrast,the sandstone spoil is less problematic and causes no major debris flow threats.Based on our research on the mechanism,the"stereometric drainage"method is sucessfully applied to control limestone spoil debris flows.

Grinding Properties of Abandoned Concrete

The grinding properties of abandoned concrete, which consists primarily of hardened cement, limestone aggregate and river sand, are studied. Theoretical models of grinding are used to explain the experimental observation. The results show that 1) The principle disintegration mechanism of hardened cement and river sand is volumetric grinding, although at later stages grinding of cement becomes difficult because of its flaked structure; 2) The lime- stone grinding process can be divided into two steps. First, volumetric grinding, with an obvious component of surface grinding, followed by primarily surface grinding as the micro-particle content increases; 3) Initially, the principle mechanism of grinding limestone and river sand is volumetric grinding, albeit less efficient grinding than if these components were ground separately, and; 4) After 10 to 20 min of grinding the grinding bottleneck phenomenon ap- pears and after 20 min of grinding the content of micro-particles is large and surface grinding is the main mechanism while the particle size of the mixture is smaller than that of separately ground river sand and cement but bigger than that of separately ground limestone.

Injectable Premixed Cement of Nanoapatite and Polyamide Composite

A new type of injectable premixed bone cement consisting of nano hydroxyapatite (n HA) and polyamide 66(PA66) composite is investigated. This cement can be handled as paste and easily shaped, which can set in air, in physiological saline solution and in blood. The setting time, injectability and compressive strength of the cement largely depend on the ratio of liquid to powder (L/P). Moreover, the content of n HA in composite also affects the compressive strength and injectability of the cement. The premixed composite cement can remain stable in the package for a long period and harden only after delivery to the defects site. The results suggest that injectable premixed cement has a reasonable setting time, reasonable viscosity for injecting, excellent washout resistance and high mechanical strength, which can be developed for root canal filling, sealing and various bone defects augmentation.

Cemented backfill technology based on phosphorous gypsum

Physical-chemical properties of phosphorous gypsum, proportion and cemented mechanism of slurry with gypsum as aggregate were studied to remove the harms of gypsum pile, combining with difficult problems of excessive mined-out gobs, enormous ore body under roadway and low recovery ratio of Yongshaba Mine, Kaiyang Phosphor Mine Group, Guizhou Province, China. An appropriate backfill system and craflwork were designed, using shattering milling method to crush gypsum, double-axles mixing and strong activation mixing way to mix slurry, cemented slurry and mullock backfill alternately process. The results show that gypsum is fit for backfilling afterwards by adding fly ash, though it is not an ideal aggregate for fine granule and coagulate retardation. The suggested dosage （the mass ratio of cement to fly ash to gypsum） is 1：1：6-1：1：8 with mass fraction of solid materials 60%-63%. Slurry is transported in suspend state with non-plastic strength, and then in concretion state after backfilling. The application to mine shows the technology is feasible, and gypsum utilization ratio is up to 100%. Transportation and backfill effect is very good for paste-like slurry and drenching cemented slurry into mullock, and the compressive strength and recovery ratio are 2.0 MPa and 82.6%, respectively, with the maximum subsidence of surface only 1.307 mm. Furthermore, the investment of system is about 7 × 10^6 yuan （RMB）, only 1/10 of that of traditional paste backfill system.

Effects of Limestone Powder on Rheological Properties of Cement - Fly Ash Mortar

This article studies the effects of limestone powder on rheological properties of cement - fly ash mortar with RHEOLAB QC type rotation viscometer. The Bingham fluid model is introduced to fit the yielding stress and plastic viscosity of the mortar. The POWER LAW fluid model is introduced to fit the rheological index of the mortar. The results show that, adding limestone powder and fly ash to the cement mortar significantly decreases the yield stress of the mortar, changes the plastic viscosity of the mortar, increases the rheological index, decreases the degree of shear thinning of the mortar, and thereby improves the mortar＇ s workability. In the case of cement - fly ash mortar, with the increase of limestone powder content, both the yield stress and plastic viscosity of the mortar increase. When the limestone powder content is not higher than 14%, the increase of yield stress is not significant. When the limestone powder content is lower than 8%, the increase of plastic viscosity is not significant. When the content of limestone powder is higher than 22%, the rheological index of the mortar decreases and the degree of shear thinning increases. The effects of limestone powder＇ s packing density, shape and size, specific surface area, and fluid volume, are found to be the four major factors responsible for the changes ofrheological properties of the mortar.

Annual precipitation gray forecast in disaster year of Chedaren debris flow

The Chedaren ravine belongs to high-prone areas of debris flow in Jilin Province, which threaten the local people＇ s life and security seriously. The authors used the residual correction theory to amend the GM （ 1, 1 ） model and forecast annual precipitation in disaster year of the Chedaren ravine ; it provides scientific foundation for early warning of debris flow disaster in the rainy season based on weather forecast. The prediction resuits show that annual precipitation is 724.7 mm in 2009 ; the region will probably occur large-scale debris flow during the rainy season.

Phytoavailability of Copper, Zinc and Cadmium in Sewage Sludge-Amended Calcareous Soils

The toxicity of trace elements （TEs）, such as copper （Cu）, zinc （Zn）, and cadmium （Cd）, often restrict land application of sewage sludge （SS） and there was little information about soil-plant transfer of TEs in SS from field experiments in China. In this study pot and field experiments were carried out for 2 years to investigate the phytoavailability of TEs in calcareous soils amended with SS. The results of the pot experiment showed that the phytoavailability of Zn and Cu in the SS was equal to 53.4%-80.9% and 54.8%-91.1% of corresponding water-soluble metal salts, respectively. The results from the field experiment showed that the contents of total Zn, Cu, and Cd in the soils increased linearly with SS application rates. With increasing SS application rates, the contents of Zn and Cu in the wheat grains initially increased and then reached a plateau, while there was no significant change of Cd content in the maize grains. The bioconcentration factors of the metals in the grains of wheat and maize were found to he in the order of Zn 〉 Cu 〉 Cd, but for the straw the order was Cd 〉 Cu 〉 Zn. It was also found that wheat grains could accumulate more metals compared with maize grains. The results will be helpful in developing the critical loads of sewage sludge applied to calcareous soils.