Salt transport and storage parameters of renovation plasters and their possible effects on restored buildings’ walls

Three systems of brown coat-renovation plasters for restoration of building structures damaged by moisture and salt efflorescence are analyzed, and their properties are compared with reference lime plaster. In the experimental part, measurement of bulk density, matrix density, open porosity, pore distribution curves, chloride binding isotherms, moisture and chloride concentration profiles is performed. The obtained data are used in the calculations of moisture dependent moisture diffusivity and concentration dependent chloride diffusion coefficient. The experimental and computational results show that all three systems can have beneficial influence on the restored building structures but they should be used with caution, taking into account the properties of the material of load bearing wall and the conditions for water and salt transport in the wall including their possible sources after reconstruction. The measured water and salt transport and storage parameters may contribute to the improvements in service life assessment if they are used as input parameters in computational modeling of water and salt transport and accumulation in the load bearing wall-renovation plaster system.     

The use of brick–lime plasters and their relevance to climatic conditions of historic bath buildings

Brick–lime mortars and plasters have been widely used as water-proof materials in aqueducts, bridges and cisterns since early Hellenistic time. In this study, the characteristics of brick–lime plasters used in some Ottoman bath buildings were investigated in order to understand their relevance as plasters in hot and humid environmental conditions of the baths. For this purpose, basic physical properties, raw material compositions, mineralogical, microstructural and hydraulic properties of brick–lime plasters of some historic bath buildings in ?zmir (Turkey) were determined by XRD, SEM-EDX, AFM and chemical analyses. The results indicated that their survival without loosing their strength and adhesion in hot and humid conditions of the baths was explained by their hydraulic characters due to the consciously use of porous and pozzolanic crushed bricks as aggregate in the manufacturing of plasters.     

NaCl crystallization in restoration plasters

Salt crystallization is one of the most recurrent causes of damage in building materials. In this paper a study of NaCl crystallization in restoration plasters is presented. The morphology of the salt crystals, the location of salt crystallization and the decay patterns are investigated and related to the properties of the plaster and of the substrate/plaster combination. The research has been part of a European research program COMPASS.Based on ESEM observations from laboratory and field samples it is shown that moisture transport is one of the most important factors determining the location of salt crystallization. In particular, the presence of a water repellent strongly influences the location of salt accumulation. Depending on the effectiveness of the water repellent, salt will accumulate either at the substrate/plaster interface (salt blocking plasters) or in the inner layer of the plaster (salt accumulating plasters). The transport can be influenced by the pore system and by chemical admixtures like water repellents. Furthermore, it is discussed that salt is usually not found in cracks. It is suggested that a mechanism of differential dilation of zones with high and low salt content may be responsible for the damage.     

利用磷石制造建筑石膏的研究

通过水洗净化法、石灰水中和法、生石灰中和法等多种方法对磷石膏加以处理,试图探讨不经水洗制造性能良好的建筑石膏的途径,研究结果表明,生石灰中和法工艺简单,可制成一级建筑石膏。     

Effects of the climatic conditions of the southeastern Brazil on degradation the fibers of coir-geotextile: Evaluation of mechanical and structural properties

In tropical countries where rainfall rates are high, and especially in deforested areas in the Atlantic Rainforest and Cerrado in southeastern Brazil, water is the dominant driving force of erosion. The most common method used to restore degraded tropical lands is to plant nursery-raised tree seedlings, but this method is not always practical and a variety of newer reforestation techniques have become available. Biodegradable coir geotextiles combined with native seeds can be used to restore degraded forest areas. The effects of the climatic conditions during a seasonal cycle of rain and drought were evaluated on the structural and mechanical properties of coir geotextile fibers that were treated, or not, with lime. Analyses of the tensile strength of coir fibers showed that after 12 months of exposure untreated fiber had retained 23% and treated fiber 19% of their initial strength. Two principal factors were considered in evaluating the structural properties of the coir fibers after environmental exposure: (i) initial cellulose retention and its stability after lime-treatment; (ii) lignin degradation and/or its loss to the environment. The structural changes seen by thermogravimetry (TGA) and Fourier Transforms in Infrared spectroscopy (FTIR) analyses explained the changes seen in coir mechanical properties. The greater cellulose contents of fiber structures treated with lime explained their greater tensile strength and high Young's modulus measures after the first three months of exposure in local weather conditions. Considering that lime treatment improved coir fiber properties, lime applications are indicated when coir geotextiles are to be used in acidic Brazilian Cerrado soils.     

古建筑修复用熟石灰性能优化及机理研究

研究了矿渣、循环流化床锅炉燃烧脱硫灰(CFBC脱硫灰)和硅灰对熟石灰性能的影响及作用机理,并与理想的古建筑修复材料——强度等级为NHL2的天然水硬性石灰(简写为NHL2)进行性能对比,探讨了改性熟石灰用于古建筑修复的合理性.结果表明:由于火山灰反应及对熟石灰微观结构的影响,矿渣、CFBC脱硫灰和硅灰均可明显改善熟石灰的力学性能、防水性和耐候性;与NHL2相比,掺矿渣的熟石灰力学性能、防水性、耐候性和柔性均有所提高,掺CFBC脱硫灰的熟石灰性能优势较小,掺硅灰的熟石灰抗压强度和耐候性能较好,但防水性和柔性较差.在古建筑修复中,可利用质量分数为20%的矿渣作为熟石灰的添加剂.     

影响石灰改良下蜀黏土工程性质的几个因素分析

试验研究表明,石灰改良下蜀黏土具有水稳性好、强度高、压缩性低的良好工程性质,可作为高速铁路路基填料,但其工程性质受多个因素的影响。结合室内试验,对石灰掺入量、压实系数、含水量、干湿循环、龄期等对石灰改良下蜀黏土作为填料的工程性质的影响进行了分析,给出石灰改良下蜀黏土用作高速铁路路基填料的合理建议。     

Rechnerischer Nachweis der Randverformungen bei Wärmedämmverbundsystemen (WDVS) mit Holzfaserdämmplatten und großer Dämmdicke bis ca. 200 mm

Numerical analysis of edge deformations in external thermal insulation compound systems with wood‐fibre insulating boards and large insulation thickness up to approx. 200 mm. In Germany, external thermal insulation compound systems (ETICS) with wooden fibreboards are regulated by approvals. So far, the thickness of the thermal insulation was limited to 120 mm, however, some companies wanted to be free to use thicker thermal insulation. Therefore, it seemed to be necessary to have a closer look on tensions and deformations of the system. This article comprises methods for the assessment of system deforma tions of ETICS with mechanical fixed wooden fibreboards. Due to the complexity of the topic, this article is structured as following: – hygric and thermal expansion of the thermal insulation, and – hygric and thermal expansion of the rendering plane‐parallel to the surface. The article concludes that it is not necessary to regard additional requirements for thermal insulation material with larger thickness than 120 mm. The calculated deformation of approx. 1,8 mm during a loading condition “primal shrinkage and temperature change” of a theoretically endless ETICS will generate to micro cracks, which are uncritical in general. Furthermore, this article provides options for more precise calculations of deformations of ETICS.     

高庙子膨润土热膨胀特性试验研究

采用DIL806热膨胀仪,通过室内试验系统研究了不同影响因素对高庙子压实膨润土样品热膨胀性能的影响,获得了膨润土样品热膨胀系数随干密度、升温速率、含水率和环境气氛等条件的变化规律.试验结果表明:膨润土样品的热膨胀系数随着干密度的增大而增大;样品热膨胀系数随初始含水率的升高而降低;高含水率的膨润土样品,其热膨胀系数随升温...     

Chemical resistance of pozzolanic plaster for earthen walls

Earth is an economical and ancient construction material. Historical earthen architecture is a heritage that must be handed over to the next generations but experience shows that these historical structures do not stand up well against the destructive action of rain. In this study, fly ash, powdered brick, hydrated lime and water were mixed to develop a pozzolanic plaster for use in conservation of earthen walls. Chemical durability, such as sulfate, salt and acid resistance of this pozzolanic plaster also was investigated. The chemical compounds employed in these tests were 2000 and 5000 ppm sodium sulfate and ammonium nitrate solutions for sulfate and salt attack. Also, the acidic media were with 1%, 5% and 10% concentrations of sulfuric acid and hydrochloric acid. All test results indicated that incorporation of fly ash in pozzolanic plaster provides a satisfactory resistance to aggressive chemicals such as sulfate, salts and acids. The developed plaster seems to be a suitable material for preservation of earthen walls since it has adequate mechanical and chemical properties in comparison with soil.     

Flue gas desulfurization gypsum: Study of basic mechanical,hydric and thermal properties

Flue gas desulfurization (FGD) gypsum is a waste material produced in desulfurization of flue gases in power stations and heating plants in high amounts. However, the industrial use of FGD gypsum is insufficient considering the amount of its production. Nowadays, it is mostly used for the production of gypsum plasterboards only, and the rest is deposited at waste disposal sites. Calcined gypsum as a low-energy material can be produced with advantage from the waste FGD gypsum by its dehydration at the temperatures of 110–150 °C. The solid structure of calcined gypsum can then be created by reverse hydration. Due to the very low price and large availability of FGD gypsum, the material has a good potential for applications in building structures, possibly also as a material of load-bearing structures. One of the reasons for the neglect of the material by building industry is the almost complete lack of knowledge of its properties. In this paper, the measurements of basic mechanical, thermal and hydric parameters, namely compressive strength, bending strength, thermal resistance, frost resistance, moisture diffusivity, water vapor diffusion coefficient, sorption isotherms, water retention curve, thermal conductivity, volumetric heat capacity, and linear thermal expansion coefficient, of hardened flue gas desulfurization gypsum are presented.     

Effect of cracks on hygric and thermal characteristics of concrete

The effect of cracks on the moisture and heat transport and storage properties, basic physical properties and compressive strength of six different types of high performance concrete is analyzed in the paper. The cracks in the material specimens are randomly distributed, imposed by thermal treatment. Experimental results show that the presence of cracks affects all hygric and thermal parameters except for the specific heat capacity in quite a significant way. Also, the effects of microsilica addition and of the size and presence of aggregates are important. The liquid water transport is influenced by cracks, microsilica and aggregates in the most remarkable way, together with the compressive strength. Water vapor transport parameters, water sorption parameters, thermal conductivity and open porosity are also subject of significant changes and can indicate the damage induced by cracks with a sufficient sensitivity.     

加气混凝土湿物理性质的测定

分析建筑围护结构的热湿过程有着重要意义,而材料的物理性质是完成分析必不可少的参数。对中国常用多孔建筑材料而言,其湿物理性质并不完备。在20~25℃下,依据ISO和ASTM标准,通过平衡吸放湿实验、压力平板实验、蒸汽渗透实验、毛细吸水实验和真空饱和实验,对中国产B07级加气混凝土进行了测试,得到了包括等温吸放湿曲线、保水曲线、蒸汽渗透系数、液态水扩散系数、吸水系数、毛细饱和含湿量和真空饱和含湿量在内的所有湿物理性质。     

复合改性耐水砂浆的合理配比和性能

为改善砌体抹面砂浆的耐水性和耐久性,采用矿物掺和料和有机聚合物防水剂克汰对普通水泥砂浆进行复合改性.以矿粉、粉煤灰、硅灰、克汰掺量为影响因素,以体积质量、软化系数、力学性能和吸水率为指标,进行对比试验研究.结果表明,复合改性砂浆的性能比普通砂浆有明显提高,当掺入5%硅粉、15%粉煤灰、10%矿粉和7 L/m3克汰时,28 d抗压强度提高16.88%、28 d抗折强度提高19.36%、28 d的24 h吸水率降低48.2%.     

透辉石-叶腊石-粘土系统陶瓷的相组成和性能

研究了透辉石-叶腊石-粘土系统陶瓷中，透辉石、叶腊石、石英和粘土含量对烧成后陶瓷的晶相组成、吸水率、收缩率、抗折强度和热性能的影响．用XRD，SEM分析了陶瓷的晶相组成和形貌．根据测定的陶瓷热膨胀曲线，用Excel软件计算了陶瓷的热膨胀系数．实验证明，减少透辉石含量，增加石英含量，可使产物相中顽火辉石量减少，石英和莫来石相增加，从而提高陶瓷强度，降低热膨胀系数；适当调整透辉石和叶腊石的比例，可以增加产物相中微斜长石含量，得到满意的陶瓷热膨胀系数。     

膨胀土石灰改良室内试验研究

通过对采取的代表性弱膨胀土和中等膨胀土试样进行石灰改良前后的室内试验研究,得到膨胀土改良前后的土性变化规律,试验研究结果表明膨胀土填料经石灰改良后,其粘粉粒含量减小、塑性指数降低、胀缩性降低、力学强度提高、压缩性减小、水理性增强,填料的工程性质大大改善,可用于高速铁路路基填筑.     

无机添加剂对糯米灰浆性能影响及机理研究

采用扫描电镜（SEM）和X射线衍射（XRD）等分析技术,探讨了硫酸铝、明矾和工业石膏对糯米灰浆性能的影响及作用机理.结果显示：硫酸铝对于改善糯米灰浆的力学性能、耐冻融性和耐水性均有较大帮助;明矾对糯米灰浆的改善主要表现在力学性能方面;工业石膏对糯米灰浆在力学性能和耐候性方面均未有明显改善;3种添加剂对减缓和减少糯米灰浆收缩均表现出良好的效果.在实际应用中,建议采用一定比例的硫酸铝作为糯米灰浆的添加剂.     

桐油灰浆材料的物理性能与显微结构

采用扫描电镜、X射线衍射、傅里叶变换红外光谱等技术手段,初步探讨了桐油灰浆的材料配方和理化性能,为其在古代建筑、船舶等文化遗产保护中的应用提供理论依据.结果显示,用Ca(OH)2和熟桐油制备的桐油灰浆综合性能最佳,其90d抗压强度和剪切强度较普通石灰浆分别提高了72%和245%,吸水系数仅为普通石灰浆的1/620,抗氯离子侵蚀能力和耐冻融循环等性能均大大改善;该桐油灰浆的优良性能源于桐油的强固化能力以及桐油与Ca(OH)2反应形成的致密结构.     

Waste gypsum from intermediate dye industries for production of building materials

Paper presents the studies on characterization, beneficiation and utilization of H-acid gypsum, a waste material produced by the neutralization of free sulphuric acid collected during the formation of intermediate dyes. The waste gypsum contains impurity of organic matter like nitro compounds, naphthalene etc. The removal of impurities and improvement in colour was carried out by scrubbing with water, centrifuging and drying. The beneficiated H-acid gypsum was calcined to form β-hemihydrate plaster. The plaster was tested and evaluated for engineering properties such as compressive strength, bulk density, water absorption and porosity. These properties suggest the use of beneficiated H-acid gypsum for making building and ceramic grade plasters and for casting building blocks, board and cementitious binder. Data showed that cementitious binder of low water absorption (9.5%) and adequate compressive strength (19.6 MPa at 28 days) can be produced for use as construction material. The use of waste gypsum will definitely benefit environment and sustainable development.