Delayed ettringite formation (DEF) in mortars of white cement

In this study white cement CEM I-52.5 and white limestone cement CEM II-LL, A and B, with 15% and 25% limestone substitution, were studied. The way delayed ettringite forms, due to exposure to high temperatures (50 °C) and external sulphate attacks, was examined in the mortar samples.The mortars were immersed at 50 °C for 180 days in: (a) a saturated Ca(OH)₂ solution and (b) a 5% Na₂SO₄ solution. During the experiment’s duration, the mortar samples were being observed visually on a regular basis while their expansion was estimated on a weekly basis by measuring the change of length with a micrometer. At the end of the experiment, the mortar samples’ compressive strength was determined and the deterioration products were identified through means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDAX), Thermogravimetry (TG) and Infra-Red Spectroscopy (FT-IR).Concluding it is evident that the amount of ettringite is proportional to the C₃A content of cement. Sulphates amount in cement is the controlling factor for heat induced ettringite formation since when they are consumed the reaction stops. On the other hand in the case of external sulphate attack another important controlling factor is the compressive strength of the cement; the higher compressive strength the lower the risk of expansion. Finally, in the case of external sulphate attack, limestone, when added to cement, was proved to enhance the durability against sulphates attack when compared to a cement of the same class.     

Long-term evolution of delayed ettringite and gypsum in Portland cement mortars under sulfate erosion

The magnitude evolution of ettringite and gypsum in hydrated Portland cement mortars due to sulfate attack was detected by X-ray powder diffraction. The influences of sulfate concentration and water-to-cement ratio on the evolution of ettringite and gypsum were investigated. Experimental results show that the magnitude of ettringite formation in sodium sulfate solution follows a three-stage process, namely, the ‘penetration period’, ‘enhance period of strength’, and ‘macro-crack period’. The cracking of concrete materials is mainly attributed to the effect of ettringite. The gypsum formations occurred in two stages, the ‘latent period’ and the ‘accelerated period’. The gypsum formation including ettringite formation was relative to the linear expansion of mortars to some extend. Both water-to-cement ratio and sulfate concentration play important roles in the evolution of ettringite and gypsum.     

Performance of limestone cement mortars in a high sulfates environment

With the aim of studying the influence of cement composition on resistance in high sulfates environment, standard mortars have been produced using ordinary Portland cement (CEM I – 32.5) and limestone cement with 35% limestone (CEM II/B-LL – 32.5). The pore size distribution of the cement pastes was measured. The mortars were immersed in a 5% Na₂SO₄ solution at 20 °C for 1.5 years and the caused deterioration was been visually observed at a regular basis. Furthermore, the mortars expansion was being estimated by measuring the change of length. At the end of the experiment the compressive strength of the mortars was measured. The deterioration products of the mortars have been identified by means of X-ray diffraction, optical microscopy and environmental scanning electron microscopy. The limestone cement based mortar presented cracking that started at the age of 6 months and continued throughout the experiment. It also displayed high expansion after 250 days of immersion in a 5% Na₂SO₄ caused, as proved using the analytical techniques, by the formation of gypsum and ettringite. Concluding, the cement with 35% limestone did not perform as well as ordinary Portland cement under the most aggressive laboratory conditions. Hence, it is obvious that the addition of limestone in the cement leads to a totally different behaviour than Portland cement with respect to the resistance in high sulfates environment.     

铁路高地热隧道衬砌混凝土延迟钙矾石生成风险分析

在分析DEF的产生和破坏作用机制的基础上,根据铁路高地热隧道施工过程中温度的变化条件,分别对隧道初支和二衬混凝土或砂浆试件进行DEF加速模拟试验。试验结果表明,采用符合现行铁路混凝土技术标准要求的原材料,并对配制参数进行合理控制的前提下,混凝土或砂浆试件的膨胀率均低于0.04%的安全限值。说明铁路高地热隧道衬砌混凝土产生DEF破坏的风险很低,高地热环境对混凝土耐久性的影响较小。     

新型环氧树脂乳液改性水泥砂浆性能的研究

研究了环氧树脂乳液对水泥砂浆力学性能的影响，耐酸碱性的影响。采用电子扫描显微镜（SEM）分析了环氧胶乳网络结构与水泥砂浆的作用机理，以及环氧树脂乳液水泥砂浆微观结构形态。     

Effect of under water storage on bridge formation by water-soluble polymers in cement mortars

Polymer film formation in cement mortars modified with small amounts of water-soluble polymers (1% of the cement mass) is studied. A major contribution of the polymer films to the mechanical strength is found. Polymer bridges are detected between the layered Ca(OH)₂ crystals, on top of the cement hydrates at the air void surfaces and intermingled with the cement hydrates. Because water-soluble polymer films are highly sensitive to moisture and water, the effect of under water storage on the bridge formation is important towards the practical applications. A serious decrease of the flexural and splitting tensile strength is observed during intensive storage at high relative humidity or under water. The polymer bridges are leached under water and deposed in free spaces of the cement matrix upon subsequent drying.     

提高试验室温、湿度控制水平适应水泥胶砂强度检验方法(ISO)要求

自2001年4月1日起强制实施的GB/T 17671-1999<水泥胶砂强度检验方法(ISO法)>,对试验室温、湿度控制条件提出了更严格要求.为什么要规定这种严格要求,怎么样达到这种严格要求,是广大水泥试验室关心的问题,现就此简述如下.     

Influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars

Mortar is the material responsible for the distribution of stresses in masonry structures. The knowledge about the fresh and hardened properties of mortar is fundamental to ensure a good performance of masonry walls. Water/cement ratio and aggregates grading are among several variables that influence physical and mechanical behaviour of mortars. An experimental program is presented in order to evaluate the influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars. Eighteen compositions of mortar are prepared using three relations cement:lime:sand, two types of sand and three water/cement ratios. Specimens are analyzed through flow table test, compressive and flexural strength tests. Results indicate that the increase of water/cement ratio reduces the values of hardened properties and increases the workability. Besides, sands grading has no influence in compressive strength. On the other hand, significant differences in deformation capacity of mortars were verified with the variation of the type of sand. Finally, some correlations are presented among hardened properties and the compressive strength.     

Waste gypsum–blast furnace slag cement in mortars with granulated slag and silica sand as aggregates

The performance and water resistance of binders 30–50% blast furnace slag and hemihydrate from waste gypsum were investigated. Mortars of various aggregate:binder ratios were prepared with granulated BFS and silica sand. The cements with 50% slag were the best in terms of strength; higher aggregate loads reduced the strength. The solidification of mortars by the formation of an initial gypsum framework was indicated by the very fast setting, low 1 day strength and high non-evaporable water. Further strength development was due to the slag reactions. The microstructures of polished samples were dense and conformed by gypsum crystals surrounded by C–S–H. The use of BFS sand was more efficient, in terms of strength, than silica sand; this was due to the participation of the slag aggregate in the hydration reactions, improving the bonding in the interfacial zone. The lower density of the former makes them potentially more insulating efficient.     

Bioaccumulation profiles of S-labelled sodium alkylpoly(oxyethylene) sulfates in carp (Cyprinus carpio)

The uptake, distribution and elimination of two labelled surfactants, ³⁵S-labelled sodium dodecyltri(oxyethylene) sulfate (³⁵S-C12-AES(3)) and ³⁵S-labelled sodium dodecylpenta(oxyethylene) sulfate (³⁵S-C12-AES(5)) were investigated in carp (Cyprinus carpio) exposed to concentrations of 0.3–0.6 mg l⁻¹, using whole-body autoradiography and the liquid scintillation counting method. ³⁵S-Radioactivity was first rapidly absorbed by the gills and skin and transferred to other organs and tissues. After 24 h-exposure, there was a comparatively high accumulation of ³⁵S-radioactivity in the gills, hepatopancreas, gall bladder, intestinal content, and nasal and oral cavity. The distribution patterns of ³⁵S-radioactivity derived from ³⁵S-C12-AES(3) and ³⁵S-C12-AES(5) in tissues and organs were similar. The whole-body concentration factors of ³⁵S-radioactivity in fish exposed to ³⁵S-C12-AES(3) and ³⁵S-C12-AES(5) for 72 hr were 18 and 4.7, respectively. In surfactant-free water, the absorbed ³⁵S-radioactivity was eliminated more rapidly from the fish body exposed to ³⁵S-C12-AES(3) than ³⁵S-C12-AES(5). It was eliminated relatively fast from gills and hepatopancreas, but elimination from gall bladder was rather slow.     

Investigation of the physico-chemical and microscopic properties of Ottoman mortars from Erzurum (Turkey)

Ottoman mortar is the long-established binding material used for centuries and there are many historical buildings as evidence of its use by Ottomans in Erzurum (Eastern Turkey). The physico-chemical and microscopic properties of the Ottoman mortars in Erzurum have been studied in detail as part of an investigation of the mineral raw materials present in the territory of Turkey. For this purpose, SEM, XRD and EDS analyses of six main types of mortars were carried out showing the presence of organic fibers and calcite, quartz and muscovite minerals. The chemical analyses of the specimens showed that higher SiO₂ + Al₂O₃ + Fe₂O₃ contents yielded in higher values of hydraulicity and cementation indices. A significant result of this investigation was that mortars with higher hydraulicity and cementation indices had higher compressive strengths. Most probably this is the main reason why historical Ottoman buildings were resistant against serious earthquakes.     

水泥基复合材料中SO3与Al2O3含量对钙矾石及膨胀性能影响的研究

本文通过水泥基复合材料水泥，膨胀剂，粉煤灰，引气剂，高效减水剂中SO3与Al2O3含量对钙矾石及混凝土膨胀性能的影响进行了研究，指出了SO3与Al2O3及其比值对膨胀性能影响的重要性，试图使人们在使用补偿收缩混凝土前事先确定膨胀量，再根据膨胀量去确定水泥基复合材料中的SO3与Al2O3含量，从而达到由定性到定量的转变。     

Optmization of calculation method for determination of composition of hardened mortars of Portland cement and hydrated lime made in laboratory

This work presents a reviewed method for determining the composition of cement- and lime-based mortars and discusses the results obtained from the chemical characterization of Portland cement and hydrated lime mortars, which are currently being used in Brazil. It aims to assess the reproducibility level of the calculated proportion based on the figures of the chemical analysis of hardened mortars, while considering the nominal compositions established by the dosage. As the study was made with materials of known compositions the results permit suggesting the use of correction factor or adjustment to the calculation of the mix proportion, so that results very near the real dosage of materials can be obtained. The method of calculation can be applied to the mix proportion determination of new and historical mortars.     

Small-Scale Test Protocol for Firefighting Foams DEF(AUST)5706: Effect of Bubble Size Distribution and Expansion Ratio

The experimental program described in this paper sought to assess the suitability of the small scale DEF(AUST)5706 standard for measuring the suppression and burnback performance of Class B foams on pool fires. DEF(AUST)5706 is an Australian Defence standard mandatory for use by the Australian Navy, Army and Air Force. The test protocol required the measurement of the 3/4 control, extinguishment and 1/3 burnback times for a circular pan of aviation gasoline (AVGAS 100/130), 0.28 m² in surface area. The test program involved compressed-air foams (CAF) and aspirated foams of two expansion ratios, and employed two AFFF formulations: a 6% telomer concentrate and, to obtain base-line measurements, 3% PFOS FC-600 concentrate which was manufactured by the 3 M company prior to the PFOS phase out. At lower expansion (7:1), the aspirated and compressed-air foams demonstrated similar fire control performance, whilst more expanded (9:1) CAF was generally more efficient at extinguishing, but less efficient in controlling the fire. CAF formed a better seal over the fuel surface and at the hot pan walls, and these foams performed noticeably better than aspirated foam against fuel re-ignition. The paper links these observations with the underlying distributions of bubble sizes, which were measured and fitted to modified Rosin/Rammler cumulative volume distribution functions. We propose that a modified version of DEF(AUST)5706 be adopted as a universal small-scale test protocol.     

浅谈白水泥厂立磨常见故障及处理对策

立磨在水泥生产中,被广泛用于生料的粉磨工艺,主要优点是产量高、磨耗小,由于带进产品的铁含量低,因而特别适合粉磨白水泥的生料。我厂(前身广州市建材一厂)在1995年安装使用MLY—14立磨用于白水泥生产,经过几年的实践,总结了一些使用经验,使初期较多出现的问题逐步得到解决,效果较为满意。现就立磨在白水泥生产中常见的几个问题及对它的改革谈几点体会:1 解决立磨生产过程中常见的几个问题1.1漏风问题立磨的粉磨原理是由辊子对物料进行压碎和辗磨。当物料经给料器送入磨腔落到磨盘上,旋转着的磨盘把物料带到辊子底下,在辊子自身的重力和…     

Bioaccumulation profiles of 35S-labelled sodium alkylpoly(oxyethylene) sulfates in carp (Cyprinus carpio)

The uptake, distribution and elimination of two labelled surfactants, ³⁵S-labelled sodium dodecyltri(oxyethylene) sulfate (³⁵S-C12-AES(3)) and ³⁵S-labelled sodium dodecylpenta(oxyethylene) sulfate (³⁵S-C12-AES(5)) were investigated in carp (Cyprinus carpio) exposed to concentrations of 0.3–0.6 mg l^?1, using whole-body autoradiography and the liquid scintillation counting method. ³⁵S-Radioactivity was first rapidly absorbed by the gills and skin and transferred to other organs and tissues. After 24 h-exposure, there was a comparatively high accumulation of ³⁵S-radioactivity in the gills, hepatopancreas, gall bladder, intestinal content, and nasal and oral cavity. The distribution patterns of ³⁵S-radioactivity derived from ³⁵S-C12-AES(3) and ³⁵S-C12-AES(5) in tissues and organs were similar. The whole-body concentration factors of ³⁵S-radioactivity in fish exposed to ³⁵S-C12-AES(3) and ³⁵S-C12-AES(5) for 72 hr were 18 and 4.7, respectively. In surfactant-free water, the absorbed ³⁵S-radioactivity was eliminated more rapidly from the fish body exposed to ³⁵S-C12-AES(3) than ³⁵S-C12-AES(5). It was eliminated relatively fast from gills and hepatopancreas, but elimination from gall bladder was rather slow.     

Effect of temperature on porosity and on chloride diffusion in cement pastes

This paper is related to the effect of temperature upon the diffusive properties and the microstructural features of cementitious materials. Our experimental studies aim at linking the transport properties to the porosity and the cracks network of the microstructure.

The studied materials were three cement pastes having different water to cement (W/C) ratios (W/C = 0.35, 0.45 and 0.60). Rise of temperature in concrete structures was simulated by heating at different temperatures (45 °C, 80 °C and 105 °C). Evolution of microstructure was essentially characterized by mercury intrusion porosimetry (MIP). Diffusion tests in non-steady-state regime were carried out in order to characterize the diffusive properties. Apparent diffusion coefficients were determined from colorimetric method to follow the ingress of chloride and an analytical solution of Fick’s second law.

Our results showed that rise of temperature induced macroscopic cracking network and modification of pore size distribution. As a consequence, the transport properties were modified by thermal treatment. These modifications were mostly explained by the increase of capillary porosity.     

水泥企业如何实施顾客满意的监视与测量

追求顾客满意,争取超越顾客期望是以顾客为中心原则的明确要求,也是企业实施持续改进的不竭动力.ISO/FDIS 9001:2000版标准8.2.1中明确规定组织应监视顾客对组织是否满足其要求的感知的有关信息,获取和利用这些信息的方法应予以确定.