土聚水泥的物理力学性能研究

以煤系高岭土为原料,经粉磨、煅烧活化后加入碱性激发剂,在常温常压条件下制备出了土聚水泥.研究了土聚水泥砂浆和混凝土的力学性能及土聚水泥净浆和砂浆的黏结性能.研究表明:煤系高岭土经850℃煅烧-保温2 h,所得的处于无定性状态的偏高岭土经模数为1.2,掺量为9%Na2·nSiO2溶液的激发,在自然养护条件下制备出了具有黏结性能好、早强和高强性能的新型胶凝材料.最后分析了目前国内土聚水泥推广应用存在的主要问题,并结合自身的研究提出了几点建议.     

Physical and mechanical properties of chemically grouted sand

It is generally accepted that only chemical grouts or solutions are available to penetrate and fill narrow joints or soils with very small pore size. Over the last 30 years a few hundreds of different compounds have been used for this purpose showing a wide spectrum of properties. Epoxy resins are among the compounds that are commonly used in building restoration because of their high strength and durability against mechanical or physical erosion. The purpose of this paper is to investigate the improvement of the physical properties (water permeability, porosity and dry unit weight) and mechanical properties (compressive strength, elastic modulus, splitting tensile strength and strength under triaxial stress conditions) of fine sand mixed with a water-soluble two component epoxy resin is, since there is not any published data about the efficiency of such high strength material in ground improvement. The experiments were carried out using different solutions of epoxy resin, which had epoxy resin/water (ER/W) ratio of 2.0, 1.5, 1.0 and 0.5. Cylindrical specimens were prepared by mixing fine sand with an adequate quantity of epoxy resin and were used for compression, splitting tensile and triaxial strength tests. Development of compressive and splitting tensile strength was evaluated from tests at the ages of 3, 7 and 28 days whereas strength under triaxial conditions was determined on specimens cured for 28 days.The results of this study indicate that the epoxy resin solutions, especially the solutions with low water content resulted in higher strength, lower porosity and lower water permeability of the sand, improving significantly the physical and mechanical properties of the fine sand.     

Physical and mechanical properties of mortars without cement

In this study, production of mortars with disposable polyethylene bottles, but without cement, was investigated. The disposable polyethylene bottles were crushed and converted into fiber formation. Then fibers were molten with different types of sands at the temperature range of 180-200 °C. Some physical (e.g. water absorption and abrasion resistance) and some mechanical (e.g. bending strength, compressive strength, toughness) properties of mortars were tested. The results indicated that bending strength and toughness of mortars were improved. Besides, water absorption of mortar was negligible and abrasion was nearly equal to zero.     

Heavy metal contaminants in Red Pandora (Pagellus erythrinus) tissues from the Eastern Aegean Sea, Turkey

Heavy metal contents were investigated in different organ tissues of Red Pandora (Pagellus erythrinus) from the eastern Aegean Sea between May 1996 and July 1998. The concentrations of mercury in the muscle tissue ranged between 16 and 716, in liver 125-5451, in gonad 2.0-1858; cadmium in muscle nd-9.6, in liver 1.4-2245, in gonad nd-192; lead in muscle nd-1397, in liver 112-8311, in gonad nd-2927; zinc in muscle 1352-6693, in liver 2710-78705, in gonad 7273-168655; copper in muscle nd-383, in liver nd-21986, in gonad nd-20499 (microg/kg wet weight). The highest concentrations were generally found in the Southern Aegean Sea. All metal levels in muscle tissues are lower than the limits of European Dietary Standards and Guidelines. The metals ratios between liver and muscle indicated that the liver accumulated higher levels of metals than the muscle tissues. The bioaccumulation factor (BAFs) of metals was measured in muscle, liver and gonads. BAFs among the analysed elements showed the descending orders as Zn>Cu>Cd>Pb for muscle and gonads and Cd>Zn>Cu>Pb for liver.     

Physical equivalent of fragmented clayey soil as a measure of evaluating its mechanical properties (in order of discussion)

Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 21–23, May–June, 1989.     

Influence of weathering on the engineering properties of Harsit granitic rocks (NE Turkey)

Weathering and hydrothermal alteration of the granitic rocks in the Eastern Black Sea Region (NE Turkey) are important phenomena affecting the engineering projects in the region. The study investigated the probable paths of rock-forming mineral transformations due to weathering in the Harsit granitoid rocks, the changes of the major oxides as a consequence of weathering and the effects of weathering on the engineering properties. To identify the changes in the major oxides, the volume concentrations were considered in relation to the dry density. Chemical leaching during weathering was shown to be significant in changing the minerals. It was concluded that the engineering properties of the weathered granitic rocks can be most reliably predicted by P-wave velocity.      

Physical and mechanical properties of rock masses at Stromboli: a dataset for volcano instability evaluation

Stromboli island has a complex geological history with repeated changes in the volcanic activity alternating with destructive events, caldera collapses and flank landslides. The last activity resulted in the creation of the Sciara del Fuoco depression which was modified by the recent 2002–2003 landslide. The variation in lithology, degree of tectonization and disturbance has resulted in the presence of a wide spectrum of geotechnical materials. This paper summarises the physical and mechanical properties of Stromboli’s intact rocks, rock masses and loose deposits, based on field surveys and laboratory tests. A new classification of the rock succession is introduced and four lithotechnical units defined: Lava, Lava-Breccia, Breccia and Pyroclastic deposit. The range of variability in bulk volume, porosity, intact rock compressive strength and geological strength index is presented. The Hoek and Brown’s failure criterion was applied for each lithotechnical unit and the rock mass friction angle, apparent cohesion, tensile and compressive strength, global strength and modulus of deformation calculated in a specified stress range.      

三种常见竹种纤维增强水泥复合材料性能的研究

竹纤维与水泥等无机材料复合制备的加气混凝土,在相同工艺条件下会出现表观密度的下降。以相同表观密度为基准,通过竹纤维复合加气混凝土可以成为增强抗压强度和提高材料的吸音系数的方法之一。研究表明:当慈竹纤维含量达到7.17%时、毛竹纤维含量为5.94%时、绿竹纤维含量为7.93%时,增强效果达到峰值。三种竹纤维中慈竹纤维增强效果最好:抗压强度提高了12.5%;绿竹纤维复合增强抗压强度9.4%;毛竹纤维复合增强7.9%。另一方面,不同竹纤维复合的加气混凝土的吸音系数均有不同程度的提高。     

Cement–clay grouts modified with acrylic resin or methyl methacrylate ester: Physical and mechanical properties

Grouting is a common technical method with many applications, e.g. it is used for soil stabilization and strengthening, for reduction of water ingress to underground facilities or of the water loss through a dam foundation, etc. Grouts comprise several constituents, which are combined in many ways depending on the in situ conditions and the outcome desired. Superplasticizers, accelerators, antifreezers, air-entraining agents and many others are generally used to improve the quality of cement grouts and consequently, their effectiveness on strength (especially bond strength), durability, impermeability and resistance to chemical erosion of the grouted soil or rock mass. A comprehensive laboratory work was carried out in order to study the physical and mechanical properties of grouts prepared by using cement, clay, water in different percentages along with an amount of acrylic resin or methyl methacrylate co-polymer emulsion. Flowability, setting time, bleeding, compressive strength, elastic modulus, shear bond strength, resistance to wet–dry cycles and resistance to sulfate attack of the grouts were determined. The results of this study indicated that the addition of latexes improves significantly the compressive strength, shear bond strength, stability, resistance to wet–dry cycles and resistance to sulfate attack, especially for thick pure cement grouts. This improvement depends on the type of latex.     

高性能纤维增强水泥基复合材料(HPFRCC)的制备及其力学性能研究

采用常规的材料及通用的工艺力法,通过加入不同纤维、降低水胶比、去除粗骨料等方法配制抗压强度接近100 MPa的高性能纤维增强水泥基复合材料,并进行抗压强度、抗折强度、抗拉强度、静力弹性模量等力学性能试验,结果表明:高性能纤维增强水泥基复合材料不但具有较高抗压强度,其韧性及变形能力良好,适应现代工程结构的发展需要。     

混凝土高整体容器(HIC)用密封材料力学性能研究

针对混凝土高整体容器(HIC)用密封材料力学性能进行研究,探讨环氧乳液掺量对混凝土HIC用密封材料抗压强度、抗折强度及拉拔粘结强度的影响规律.研究结果表明:随着聚灰比的增大,混凝土HIC用密封材料的抗压、抗折及拉拔粘结强度均呈先提高后降低的趋势;当聚灰比为2％～8％时,混凝土HIC用密封材料在满足自流平灌注工艺要求的前提下,其力学性能均能符合正在编制的《低、中水平放射性废物高整体容器——混凝土容器》标准要求.并对其机理进行分析.     

无熟料水泥混凝土的物理力学特性

无熟料水泥混凝土(NSC)是用水淬高炉矿渣(GBFS)和激发剂的混合物作为胶凝材料而配制的新型混凝土,其性能取决于GBFS的碱度、化学成分、玻璃化率以及激发剂的种类和数量。为此,以磷石膏作为GBFS的激发剂来配制NSC后,采用与普通水泥混凝土(简称OPC)对比的方法、进行了和易性、强度及其与钢筋黏结强度的试验探讨。结果表明:NSC的和易性优于OPC;早期强度主要来源于钙矾石并接近OPC,长期强度则主要来源于C-S-H水化物且远远超过OPC。     

泡沫(乳化)沥青冷再生混合料力学性能的试验研究

研究了不同水泥剂量、不同养生条件和不同龄期对泡沫(乳化)沥青冷再生混合料劈裂强度和无侧限抗压强度的影响。研究表明,水泥含量对冷再生混合料的强度影响很大,直接影响冷再生混合料早期强度的形成;通过对比不同养生条件和不同龄期下冷再生混合料的强度发展规律,建立了室内养生条件与现场施工之间的关系。     

钢纤维粉煤灰混凝土力学性能试验与分析(Ⅰ)

分别进行了掺入钢纤维、粉煤灰及两种混杂对混凝土抗压性能、抗拉性能增强效果的试验研究.讨论了钢纤维掺量、粉煤灰掺量对混凝土抗压、抗拉性能的影响.试验结果表明:在保证其强度、耐久性、节约材料、降低造价的同时,确定了钢纤维粉煤灰混凝土中合理的钢纤维和粉煤灰掺量;同时表明,钢纤维的掺入对混凝土的强度和变形有明显的改善效果.     

混杂纤维增强高性能混凝土(HFHPC)高温力学性能及微观分析

研究了混杂纤维增强高性能混凝土(HFHPC)与普通混凝土(NC)的高温力学性能,测试了两种混凝土试件在承受常温及200、400、600、800℃高温后的抗压、劈裂抗拉和抗折强度及试件烧失量,采用SEM观察高温后的混凝土微观组织变化。结果表明:混杂纤维可显著提高混凝土的常温及高温力学性能。在所试验温度下的HFHPC混凝土的抗压、劈裂抗拉和抗折强度均高于NC混凝土,且在400℃时,达到最大值。400℃以后,HFHPC混凝土的力学性能随着温度升高而降低,但仍显著高于同温度时NC混凝土的强度值,特别是劈裂抗拉强度的提高尤为明显,至800℃时HFHPC混凝土的抗压、劈裂抗拉、抗折强度分别为同温度时NC混凝土的1.24、4.5和1.61倍。     

麦秸秆的物理力学性能及加筋盐渍土的抗压强度

为研究滨海盐渍土的工程处理新方法,开展了防腐前后的麦秸秆吸水率、抗拉性能和加筋土的无侧限抗压强度试验。在SH胶中浸泡后的麦秸秆吸水率较天然麦秸秆明显降低,SH胶增强了麦秸秆的防腐能力;浸胶干燥后麦秸秆与天然麦秸秆相比、浸胶干燥后再浸水麦秸秆与天然浸水麦秸秆相比,前者的极限拉力和极限延伸率都高于后者,浸胶使麦秸秆的抗拉性能提高。考虑掺加不同加筋长度、不同加筋率、浸胶后呈干燥和湿润状态、不同形状的麦秸秆,测试了加筋滨海盐渍土的无侧限抗压强度。试验证实,石灰+麦秸秆加筋滨海盐渍土的抗压强度较石灰土有较大提高;加筋率0.25%和加筋长度10mm时的麦秸秆加筋土(试样直径50mm)的抗压强度最大;浸胶后呈湿润状态麦秸秆加筋土的抗压强度均高于浸胶后呈干燥状态麦秸秆加筋土的;掺加四等分的片状麦秸秆能更有效地增强加筋土的抗压强度。麦秸秆加筋不仅提高了土体的整体性和抗压强度,还限制了土体的横向变形。     

Biomonitoring of trace elements with lichens in Veneto (NE Italy)

The concentrations of 13 elements in peripheral parts of the epiphytic lichen Xanthoria parietina were measured at 200 stations of Veneto (NE Italy). For each element, two maps are presented, showing, respectively, geographic patterns and deviations from background levels. The results are summarized by a map, showing the joint distribution of elements with concentrations close to Italian backgrounds, and of those strongly deviating from background levels. The results allow selection of high-risk areas for instrumental monitoring.     

Physical reconstruction and mechanical behavior of fractured rock masses

Physical modeling of rock masses containing complex fracture geometries is an important but very challenging task in rock mechanics and rock engineering. In this work, a novel integration of 3D printing and water-soluble casting is presented for the preparation of rock-model specimens with fracture networks, which is similar to the lost-wax casting process. The fracture network is created with water-soluble polyvinyl alcohol (PVA) material by 3D printing. The intact rock matrix is prepared with cement paste. Uniaxial compressive tests combined with the digital image correlation (DIC) technique are conducted to investigate the mechanical properties and failure process of the prepared rock-model specimens. The differentiation rate of the effective variance is defined to recognize the precursory anomalies during the loading process. The mechanical anisotropy is further investigated by a series of rotated models. The results show that the proposed methodology has distinct advantages for replicating rocks with complex fracture geometries in terms of high accuracy for fabricating fracture networks, high repeatability of mechanical properties, and high strength and brittleness of rock matrices. Due to the presence of complex fracture geometries, the nonlinear mechanical responses of the fractured rock-model specimens, including strain-softening and anisotropy, are observed in our experiments.

     

Physical and mechanical properties of coarse-grained alluvial soils from some valleys in the Carpathian and sudety MTS,Poland

The tests described in the paper were made in connection with a large project for hydrotechnical structures in the mountain regions of Poland. The soils considered could be used in the construction of earth-dams. For testing these soils, special, original type, large-dimensioned units were designed and constructed. The author of this paper is co-designer of these pieces of apparatus. Thanks to their application the following physical and mechanical properties of soils were established: compactness, permeability and shear strength. In the paper relations are given between the properties mentioned above and other properties such as: particle size distribution, petrographic composition, degree of roundness, volume density and weight density. The tests were carried out on soils taken from three large river valleys in the Carpathian Mountains and one from the Sudety Mountains.