Petrophysical behaviour and durability of the Miocene sandstones used in the architectural heritage of Tunisia (Roman aqueduct of Oued Miliane and Uthina Roman site)

In the present work, the relationship between intrinsic factors, mechanical properties and durability of Miocene sandstones used in the architectural heritage of Tunisia, specifically in the Roman aqueduct of Oued Miliane and Uthina site, are studied. The petrographic study and the characterisation of porous network have been carried out using optical microscopy, mercury intrusion porosimetry and laser scanner confocal microscopy (LSCM). The hygric behaviour has also been determined from water absorption under vacuum, drying, capillary water absorption and water vapour permeability. The mechanical properties have been assessed from compressive strength and abrasion tests. Rock durability has been evaluated from salt crystallization (sodium sulphate) accelerated aging tests. The results show good hygric behaviour characterised by a high evaporation rate and almost no retention of water; due to the macroporous character of the rock and the good connectivity of the pore network. Because of the poor lithification, the stone has a very low mechanical strength which makes it very vulnerable to the salt crystallization effects. The absence of chemically unstable minerals preserves the rock from chemical alteration. The durability of the building stone is mainly conditioned by salt loading of the monument.     

Water absorption process effect on strength of Ayazini tuff,such as the uniaxial compressive strength (UCS), flexural strength and freeze and thaw effect

Tuffs have been used as a construction material possibly since ancient times. In Afyonkarahisar, Turkey, there are numerous buildings constructed by tuff. Tuff has been a local construction material, during the Roman, Seljuk and Ottoman periods. Even though tuffs have relatively low durability and low strength values compared to marble, etc., they have survived with no major deterioration failures on many historical buildings. It has also been preferred because of its high porous texture, lightweight and easy shaping and process properties in the building sector. Naturally, it would be easily affected by water and humidity because of its porous structure. However, having this kind of structure leads to poor durability properties due to keeping water in it. The main objective of this study was to evaluate the physical and mechanical properties of the tuff quarried from the region and possible water effect, which may lead to degradation of its strength and durability of the material, thereby shortening the life span of the building structure used. Samples, which were tested after exposing to water and the freeze and thaw effects, were measured at a certain time. In this study, uniaxial compressive strength and flexural strength tests were conducted on test samples. The test results indicate that water may deteriorate the tuff’s strength properties and durability of the materials in due time.     

Geotechnical characterisation of lateritic soils from south-western Nigeria as materials for cost-effective and energy-efficient building bricks

Lateritic soils which have been described as highly weathered tropical or subtropical residual soils were studied with an attempt to establish its suitability or otherwise as sustainable material in building bricks and housing development that will meet the present challenge of sustaining the environment without costing too much and maintaining a high standard of strength, durability and aesthetics. Index properties of the tested lateritic soils revealed them as mostly well graded, comprising both cohesive (silt and clay) and cohesionless (sand and gravel) soil fraction. The geotechnical analyses on the studied lateritic soil revealed a strong compressive strength with a relatively sound dry density which could guarantee a good durability in resulting bricks made from these soil materials. Further test on the strength and durability of the compressed earth bricks (CEBs) made from these lateritic soils revealed a brick with compressive strength ranging between 6.33 and 15.57 MPa which is considered to be of good strength coupled with its sound durability strength established over a period of more than one year under a complete cycle of weather and seasonal conditions. In conclusion, lateritic soils from the study area were found to be suitable as materials for bricks (CEB) with good compressive and durability strength which qualifies them as sustainable and cost-effective materials for low-cost housing development.     

Assessment of Durability and Weathering State of Some Igneous and Metamorphic Rocks Using Micropetrographic Index and Rock Durability Indicators: A Case Study

Weathering and durability are the key factors of the rock in the suitability and usefulness of different construction materials, building materials and engineering structures. A single test never predicts the entire factor for suitability of rock stone and aggregate in different uses. Thus, variety of physical, mechanical and chemical tests and indices of rocks are widely used to estimate and evaluate the rocks for the suitability of the required purpose. In all the cases, knowledge of durability and weathering properties are the most important along with the strength of the rock. Micropetrographic index and rock durability indicators (dynamic and static) are the one of the best methods to evaluate the rock for weathering and durability. To estimate these indices, variety of tests are performed such as petrographic examination test, point load index, sulfate soundness test, water absorption test, modified aggregate impact value test and test for specific gravity. Slake durability index and impact strength index tests were also performed for correlation with static and dynamic rock durability indicators due to its application and usefulness in the durability and strength of the rock materials. Micropetrographic index was obtained by petrographic examination test and correlated with all the physical and mechanical properties used for find out the durability indicators. The present study is to express the usefulness of these three indices in the classification of weathering and durability classes and estimation of durability indices by slake durability index, impact strength index and micropetrographic index.     

Durability Characterization of Marls from the Region of Dalmatia,Croatia

Durability is one of the most important engineering properties of weak and clay-bearing rocks. Weathering can induce a rapid change in rock material from initial properties to soil-like properties. The sensitivity of a rock type against weatherability is usually described by a durability parameter, such as the slake durability index. However, marl resistance is not detected satisfactorily by the durability indices by using slake durability test as suggested by ISRM for two wetting–drying cycles. The results of this study are obtained from samples of compact or laminated eocene marls from region of Dalmatia, Croatia. The samples were subjected to 4 cycles of slake durability, point load tests, determination of dry density, determination of carbonate content and absorption of water. The scatter of data suggests that strength probably has no influence on the durability of marls. On the other hand a separate group of marl samples have a second-cycle slake durability index higher than approximately 85%, and the durability of these samples is classified as “medium-high” to “high”, although the visual inspection of samples after testing, suggests that they should have “medium” to “low” durability classification. According to obtained results these samples of marl fulfil the criterions for the durability classification: a carbonate content lower than approximately 65%, a dry density lower than 2.4 Mg/m³, and values of water absorption higher than 5%.     

Factors affecting the durability of selected weak and clay-bearing rocks from Turkey, with particular emphasis on the influence of the number of drying and wetting cycles

Weathering can induce a rapid change of rock material from initial rock-like properties to soil-like properties. The resistance of a rock to short-term weathering is described through a durability parameter called the slake durability index. As durability is an important engineering parameter, particularly for weak and clay-bearing rocks, it was assessed by a number of tests. The main purpose of this study is to assess the influence of the number of drying and wetting cycles and controls of mineralogical composition and strength on durability. For this purpose, 141 samples of different types of weak and clay-bearing rocks were selected from different parts of Turkey, and relationships between the above-mentioned rock characteristics were statistically investigated. The samples were subjected to multiple-cycle slake durability testing, X-ray diffraction (XRD) analysis and uniaxial compression testing. In addition, to assess the influence of mineralogical composition on durability, the mineral contents of the original material and the material passing from the drum of the slake durability apparatus after each cycle were also determined by XRD. The results indicate that the type and amount of clay minerals are the main factors influencing the variations of the slake durability index in all samples. The durability of the clay-bearing rocks studied correlates best with the amount of expandable clay minerals. A strong relationship between the uniaxial compressive strength and the fourth-cycle slake durability index is found only for the marls among the rock types studied. Assessment of gradation results of the spoil pile materials consisting of clay-bearing rocks also reveals that the increase in percentage of fines in old piles is indicative of material degradation, as is evident by multiple-cycle slaking. It is emphasized that two-cycle conventional slake durability testing did not appear to offer an acceptable indication of the durability of weak and clay-bearing rocks when compared with multiple-cyclic wetting and drying. Comments on the performance of the test are made that aim to make the testing process and interpretation of the results more reliable.     

The effect of pH and salty solutions on durability of sandstones of the Aghajari Formation in Khouzestan province,southwest of Iran

Slake durability of rocks is a vital engineering geological property of rock materials that has an important role in the promotion of slope stability, evaluation of rock materials, as well as the estimation of stone degradability. This parameter is related to such factors as mineralogy, physical characteristics of rocks, and the environmental conditions. A major part of south and southwestern Iran embraces the Aghajari Formation whose sandstones are used to form the foundations for some structures in Khouzestan province where they are being extensively used as aggregate(s). In this paper, tests of mineralogical examinations, physical properties, and slake durability of sandstones from Ahwaz and Haftkel anticlines were administered in order to assess the durability and degradability of these rocks. The rock durability of each type was evaluated to be up to 15 cycles in acidic and alkaline watery environments and salt aqueous solutions. The results showed that durability of sandstones under study is related to their petrographical and physical characteristics. The durability index of the sandstone samples was decreased by pH reduction and by increasing the concentration of aqueous solutions. The durability index of Ahwaz samples, too, was decreased in basic solutions while this index increased for Haftkel sandstones with the increase in the pH of solutions. Also, the obtained results illustrated that durability index decreased with the increase in the number of cycles. Based on the results, all sandstones show that the durability in sodium sulfate solution is much lower than that for the sodium chloride. Moreover, the slake durability index of the sandstones is decreased with an increase in the concentration of aqueous solutions. As a final statement, the Ahwaz sandstones show lower resistance to weathering processes than Haftkel sandstones; therefore, the use of rocks as building stones is not recommended here.     

Estimation of Durability Aspects of Al Masjid Al-Haram Marble,Makkah City,Saudi Arabia

The durability is a measure of the rock’s ability to resist degradation during its working life. Rock durability is greatly related to the mineralogical composition of rocks, rock texture (crystal interlocking, crystal shape and size), and the nature of fluids that are in contact with rock. Marbles have been among the most important building materials since ancient times. The main aim of this study is to evaluate the durability of Al Masjid Al-Haram marble and Ordinary white marble “Carrara” (M₁ and M₂) and develop some correlations among the physical and mechanical properties such as P-wave velocity, slake durability index, dry uniaxial compressive strength (UCS_Dry), abrasion resistance, point load index, impact strength index, Brazilian tensile strength, and Shore hardness. After testing and the evaluation of the test results, strong statistical correlations were found between P-wave velocity and other rock properties. Statistical correlations between the UCS_Dry other tests were also carried out. The coefficients of regressions (R²) range from 0.6177 to 0.997. The study shows that the UCS_Dry values of M1 and M2 have positive relationship with P wave velocities. Concluding remark is that the rocks tested in the study have good durability characteristics and can be reliably used for construction projects. On the other hand, the derived empirical equations can be used for the estimation purposes for similar rock types.     

城市地下混凝土结构耐久性评估方法及工程应用分析

及时开展城市地下混凝土结构耐久性评估是确保长期稳定和安全、降低维修成本和践行绿色建筑理念的重要环节。按照技术合理、经济可行、现场容易操作的工作原则,提出一种简化的城市地下混凝土结构耐久性评估方法,包括评估程序、耐久性等级划分、耐久性调查和典型环境耐久性评估。该方法能够快速评估城市地下混凝土结构耐久性,并划分耐久性等级,为城市地下混凝土结构维修和养护提供参考。耐久性评估简化方法案例应用分析表明,该方法得到的结果与工程实际相符,具有良好的可操作性,评价结论容易得到,预测计算结果可有效指导城市地下结构维护。     

Engineering characteristics of road aggregates from northern Pakistan and the development of a toughness index

This paper summarizes an extensive series of common durability, shape and strength tests carried out on road aggregates from quarries in northern Pakistan by Sharif et al. at the University of Engineering and Technology, Taxila. The data from these standard tests have been correlated for a particular aggregate type to show the close relationship between these measured physical characteristics. The paper outlines how, once these relationships have been established for a particular aggregate source, it is feasible to simplify the testing or quality assurance regime and monitor only some of these characteristics to assess the overall quality of the aggregate. The physical characteristics have then been combined into a linear relationship, using coefficients estimated from the extensive data set in the paper, to give a single characteristic for an aggregate type known as the Toughness Index (TI). The TI is therefore based on the main strength and durability characteristics of the aggregates and can be used as an indicator of the overall quality of the aggregate.     

新型高分子材料固沙抗冻性能试验研究

抗冻性反映固沙剂在低温环境下固沙的耐久性能。以新型高分子材料SH进行固沙,就其固沙后固沙体的抗冻、融特性进行了室内两种不同周期的冻、融循环试验。结果表明,冻、融循环对SH固沙性能均有劣化趋势。但冻、融速率较慢时,抗冻性较稳定。SH抗冻性优于其它同类化学固沙剂,显示其抗冻性良好。有机材料在冻、融过程中一段时间内出现强度增加的机理尚不清楚,建议进一步研究。     

Characterization of natural stone material used in the Nordic eastern urban and costal environment

The report analyses the main properties pertaining to the durability of Finnish granitoid rocks, based upon extensive field and laboratory data collected during the past ten years. Commercial materials have been tested and compared along ten years of production and their frost resistance assessed according to European standards. Laboratory tests have been coupled with non-destructive methods most used on site assessment as ultra-pulse velocity and Schmidt hammer in order to compare the results of commercial materials with materials on construction site. Evaluation of durability has included petrographic analysis, crack density, and for site exposed material, chemical analysis, to understand the environmental effects on it. The material has generally maintained its original properties. It has natural heterogeneity, and it presents higher interlocked cracking network on the surface of the exposed materials. Site samples in some cases have shown chemical changes due to environmental actions.     

酸碱环境对水泥土抗剪强度影响的试验研究

以水泥土处于复杂环境中的安全性和耐久性为研究背景,对酸碱环境下水泥土进行了固结不排水剪切试验,得到了水泥土应力偏差（σ₁-σ₃）与轴向应变（ε）关系曲线和抗剪强度指标,研究了酸碱度对水泥土抗剪强度的影响.试验结果表明,随着围压、水泥掺量、pH值的增加,水泥土的抗剪强度逐步增加;水泥土的黏聚力、内摩擦角随着水泥掺量及酸碱度pH值的增大而逐渐增加;得到了不同酸碱度环境下水泥土的抗剪强度方程.其研究结果对在水泥土工程中的安全性和耐久性设计具有一定的指导意义和参考价值.     

活性MgO−粉煤灰固化淤泥耐久性研究

将绿色环保活性MgO?粉煤灰材料引入淤泥固化,采用系列室内模拟试验,深入研究冻融、浸水和干湿等复杂气候环境下活性MgO?粉煤灰固化淤泥试样的外观形貌和强度特征,明确外界环境干扰诱使固化淤泥性能演化的内在规律。结果表明：活性MgO?粉煤灰固化淤泥具有良好的抗冻融、抗干湿及水稳性,且活性MgO?粉煤灰掺量及MgO/粉煤灰配比提高可进一步改善活性MgO?粉煤灰固化淤泥试样的耐久性能。冻融、浸水和干湿等复杂环境显著劣化固化淤泥抗压强度,其强度水平均低于同龄期标准养护试样。固化淤泥试样无侧限抗压强度随冻融循环次数增加而逐渐降低,随浸水时间增加先降低后趋于稳定,随干湿循环次数增加呈降低的趋势。基于所得试验结果,提出了活性MgO?粉煤灰固化淤泥耐久性演变的内在微观机制模型。     

锚杆耐久性研究回顾与探讨

锚杆的耐久性问题是岩土锚固技术中重要但相对薄弱的研究环节。本文回顾了国内关于锚杆耐久性问题所取得的主要研究成果,总结了影响锚杆耐久性不良的主要因素,并指出当前针对锚杆耐久性问题可以重点研究的几个方向。     

部分优化处理宝石颜色稳定性研究

选用市场上常见的紫红色、橙色、粉色、绿色、黑色处理珍珠,粉橙色、金黄色铍扩散蓝宝石,充胶翡翠作为研究对象,通过设计耐久性实验,对样品颜色的稳定性进行了研究。结果显示,充胶翡翠和铍扩散蓝宝石在日晒、盐雾及人工汗液中均表现出了良好的颜色稳定性;处理珍珠在盐雾环境中表现出了较好的稳定性,在模拟日光照射试验中褪色明显,而经过人工汗液腐蚀,其颜色表现出了较差的稳定性。对样品颜色稳定性的研究,可以为优化处理宝石的市场准入提供一定的依据。     

Slake durability and mineralogical properties of some pyroclastic and sedimentary rocks

Slake durability of rocks is an important property of rock-mass and rock-materials in geotechnical practice. The slake durability of rocks is closely related to their mineralogical composition. In this paper, mineralogical examinations and slake durability tests for argillaceous clastic rocks, especially pyroclastic rocks, sandstones and mudstones of Neogene Tertiary age from Japan, were performed in order to assess the slake durability and rock alteration process of these rocks as well as to understand the relationship between mineralogy and durability.The mineral composition and textural features of the rocks were studied by means of optical microscopy (OM), X-ray diffractometry (XRD), electron microprobe analysis (EPMA), and scanning electron microscopy (SEM). In addition, the slake durability test was carried out by using the standard testing method of ISRM [Int. J. Rock Mech. Min. Sci. 16 (1979) 148] in distilled water and in the aqueous solutions with dissolved electrolytes of NaCl and CaCl₂.The pyroclastic rocks and tuffaceous sandstone, rich in di-octahedral and tri-octahedral Fe smectite, respectively, show distinctively different slaking behaviors. The pyroclastic rocks show relatively high slaking (Id₂=55.5% and Id₁₀=10.5%) than the tuffaceous sandstone (Id₂=94.1% and Id₁₀=87.8%, refer to text for Id₂ and Id₁₀). This difference in the slake durability observed in these rocks is due to the microscopic occurrences of smectite present in the interspaces between the particles (pyroclastic rocks) and zeolite cementing the interspaces (tuffaceous sandstone) as alteration minerals. In addition, the durability results of tuffaceous sandstone show that the slake durability decreases as the degree of weathering increases (weathered material Id₂=88.7% and Id₁₀=65.3%). Furthermore, two mudstones of Miocene and Pliocene ages, having different clay mineral compositions (smectite vs. illite+chlorite), show the lowest and the highest slake durability among the tested clastic rocks. Hard mudstone shows the highest (Id₂=98.1% and Id₁₀=95.5%) while the soft mudstone shows the lowest (Id₂=33.9% and Id₆=0.4%.) slake durability. Thus, the slake durability of pyroclastic and sedimentary rocks is greatly affected by their mineral composition and texture, and is closely related to their alteration history. Slake durability is also affected by the kind of dissolved electrolyte and its concentration in the aqueous solution, providing some useful information for geotechnical practice.     

Determination and Application of the Sharp Degradation Point of Concrete under Environmental Actions

INTRODUCTIONMany experi mental results have indicated thatthe deterioration process of concrete can be dividedinto two stages—the nondestructive stage (stage 1)and the destructive stage (stage 2) ,as shownin Fig.1 ( Wu, 2002 ; Rostam, 1993) . When concrete issubjected to environmental actions ,the inner energyit gains is al most balanced by the released energywhen crackingin stage 1 , while in stage 2 the innerenergy is greater than that released. There are fewremarkable degradation phe…     

固化铅污染土的干湿循环耐久性试验研究

在商用高岭土、膨润土与商业黄砂混合物中加入硝酸铅溶液,添加水泥和石灰两种固化剂,采用室内压实制样方法获得固化的铅污染土试样。进行干、湿循环试验,测试固化体的质量损失和无侧限抗压强度等参数随干、湿循环次数的变化规律,评价固化铅污染土的干、湿耐久性。测试结果表明,本试验8种配比的试样都满足干、湿循环的要求;黏土矿物为膨润土的试样干、湿循环耐久性比黏土矿物为高岭土的试样要差;水泥固化土的干、湿循环耐久性要略优于石灰固化土;加入 8 000 mg/kg的铅可略增大土体的抗干、湿循环耐久性。水泥和石灰固化/稳定化重金属污染土时,土体中含水率是保证加固效果的关键参数之一。土体中含水率应能满足固化剂充分水化、水解、火山灰和碳酸化反应之需要。