关键参数对水泥浆体干燥收缩的影响外文文献翻译、中英文翻译

XXXXX设计(XX)外文资料翻译院 系专业学生姓名班级学号外文出处Cement and Concrete Research附件：1.外文资料翻译译文（约3000汉字）； 2.外文资料原文(与课题相关的1万印刷符号左右)。指导教师评语：指导教师签名：年月日关键参数对水泥浆体干燥收缩的影响摘要干燥收缩是一个混凝土结构破坏的主要原因。材料的收缩通常阻碍由内部或外部克制以及张应力作用。这些应力可能超出拉伸强度，引起混凝土的裂纹。对应力分布在材料而引起的“真正”自由收缩形变。这篇论文将陈述有关的结果来评价形变的情况，并获得更好地了解混凝土的干燥收缩行为的研究。收缩测试在水泥浆体中进行。不同的关键影响参数为：相对湿度，试样尺寸，水灰比，水泥含量。结果表明，在48%到100%相对湿度，水泥浆体的收缩成反比相对湿度。水泥砂浆的最终收缩量测量在5050400-mm试件并不是有很多不同于“真正”收缩测量的4832-mm试件。因此，在试件的实验中，存在的一个湿度比的下降从而在很大程度上影响最终收缩应变。水灰比在(0.35-0.50)内范围发现对干燥收缩影响最小。然而，水泥的含量却被认为是最重要的影响因素。关键词:水泥浆体;混凝土;干燥;湿度;收缩1.简介干燥收缩和低抗拉强度，是大多数硅酸盐水泥混凝土的不利特性1。收缩通常导致裂纹，即使它可能不影响结构完整性，但会影响混凝土的耐久性2。这是对混凝土尤其是在重叠出和砂不同等级的情况下，干燥的地方会出现从一面起到阻碍和收缩并由外部和内部一起约束3,4。外部限制是由于连接之间修复层和重叠情况的旧水泥混凝土，同时，对等级一样的砂，限制来自与摩擦路基与板自重。内部约束是由于湿度梯度在混凝土中的存在，直到在与周围环境测湿达到平衡。局部收缩直接关系到湿度的大小，因此，收缩变形梯度存在于整个干燥过程。因此，在拉伸应力最终可能克服混凝土的拉伸强度而造成的物质和开裂和剥落5。为了提高混凝土的设计上强度和等级，材料的要求被定性更为准确。目前，实践（如，国际机场理事会，行政首长协调会）给予相当不错的模型来预测一个收缩变形6，但这些模型不适合在某些情况下，例如，计算的压力所导致收缩渐变。而“真正的“收缩率的测定对混凝土应变（即元素的大小无关）作为局部湿度的功能是用于此目的至关重要。这项研究是一个关于部分在薄壁混凝土耐久性的修复，进行评估自由的胶凝材料收缩变形，并阐述了某些基本参数的影响对干燥收缩影响。收缩试验，进行了水泥浆体，混凝土。研究参数分别为：相对湿度，试样尺寸，水灰比，水泥量。2.测试方法为了获得更好的收缩现象的认识并评价“真正的”自由收缩变形，更重要的是要考虑的关键参数影响，如标本的大小和相对湿度。对干燥收缩测量，进行了两不同大小的标本：4832毫米和5050400毫米棱镜。较小的试件进行了足够的研究以获得约束梯度自由收缩。这是在以往的研究表明7,8中关于厚度在13毫米水泥浆体试件不同影响平衡的收缩。 在较小的试件进行了收缩试验，相对湿度在三个级别（48%，75%和92）。这些值的范围从一般的最低发生的温和气候条件下（50），以此来接近完全饱和的条件（100）。对较大的试件，在所有测试48的相对湿度。在两个W/ C比值被选定（0.35和0.50）下，一般认为是比较大的变化范围，从而得到高到正常质量的胶凝材料。 为了表示浆体量之间的关系（或者来说，集料量），并最终导致收缩，对水泥浆体、混凝土进行了研究。在有混凝土的情况下，胶砂比分别为1和2，水灰比在混凝土分别为0.30和0.35。粗骨料砂率（在混凝土）维持在1.5不变，以减少参数的数目。3 混合物的组成及实验程序3.1混合物所有混合物都是用相同的普通硅酸盐水泥。化学成分和水泥物理性能见表1。使用的花岗岩砂的细度模量为2.46，其分级如表2所示。最大标称尺寸为10毫米的石灰岩碎石用作粗骨料。对于与W/ C的0.35，这一比例的混凝土外加剂（含有33的固体和单位重量为1.1）一般用在3.8毫升/公斤，以使其水泥用量可提供稳定可操作性。该混合物的比例和新的混合物如表3（水泥浆体和砂浆）和表4（混凝土）。混合物之空气含量测定按美国ASTM C138重量测试方法。水泥和砂在10L的垂直轴砂浆搅拌机。混凝土混合物在一批次100L的锅搅拌机。所有的混合物是指在相同顺序下放入搅拌机。水泥首先加入，水渐渐地增加，直到获得均匀的糊状。此时的沙和水泥至少2分钟后才能混合。对于混凝土混合物，所有的（水泥，沙子）粗骨料，加入搅拌机后，水（含高效减水剂）其后逐步添加并至少持续15分钟。3.2实验步骤 对于每一个混合物，五个样本（2个100 200毫米气瓶和三个50 50 400毫米模具）分成两层模具进行振动。对于水泥浆体和砂浆，另外的250322575毫米模具，是进行小试样（43832毫米）在（在固化期）为自收缩测量。 24小时后，所有的试件拆模并放在室温下养护28天。养护是为确保有关条件不能使其干燥。 28天抗压强度的试验根据试件的强度值做成圆柱形图，一般要求为ASTM的C39。这些测试的结果列于表3和4。 在28天后，5050400毫米模具被放置 在温度（23）和相对相对湿度（48）恒定的养护室中。在不同的养护龄期，对长度变化和质量的变化进行测定。28天龄期后，将4832毫米的试件，用来测量自由收缩变形的试件放置在干燥饱和三盐溶液器中。据对化学平衡的定律9，饱和食盐在一个固定的温度能提供了一个恒湿的封闭的环境。在这个实验中，三盐（碳酸钠，氯化钠和碳酸钾）是用来提供三种不同的湿度在干燥器的（92%，75%和48）。将一个真空器引入这些干燥器，以避免在测试期间碳化。 由于试件的体积非常小，并不可避免的干燥器的相对湿度变化，通常的测量设备无法使用。对于一个光应变系统，在允许长度测量从干燥器外部变化就可以利用。这个装置，有引伸和自准直仪组成，根据光反射原理工作。把引伸安装在试件上使其放置了两个镜子，其中一个是固定的，另外可以旋转（菱形）。该长度变化的测量条件为自准直仪，它是阅读分光仪，其灵敏度为独立的量具的距离所决定。这个反射仪由两个反射镜的光形成图像出现在自准直仪视野中。在位于图像中心是一个菱形旋转功能所造成的试样变形。图一简图展示了如何从自准直光来反映在固定镜子菱形回自准直仪，来形成图像。4.试验结果4.1收缩4832毫米标本4832毫米水泥浆体和砂浆试件干燥收缩如下图.2。在每个图中，作为时间函数的收缩体现出这三个实验显示出的湿度水平。每条曲线表示的平均价获得到了两个试件。如图2的结果，表明干燥速度极为快，经过1天的干燥收缩一般占60的最终收缩或更多。在所有情况下，一个给定的砂浆的W/ C比减少从0.50至0.35导致略低收缩。正如设想，干燥收缩率降低非常显与水泥量。从相对湿度为48，减少到平均约3200毫米/米至950毫米/米的砂浆总的胶灰比为2.0。从中可以进一步看出，在图2中收缩还是相当显着，在相对湿度为92而“最终“线性收缩率相对增加与相对湿度在92%和48的下降。4.2收缩5050400毫米标本如图3给出的干燥收缩试验结果5050400毫米的试件，砂浆和48相对湿度混凝土。每条曲线在四个图上代表了三个平均结果的试件。 “最终”收缩测量范围在平均约600毫米/米四个混凝土和3000毫米/米的水泥浆体。从图3可以得到，对干燥速率慢得多为5050400毫米以上较小的试件。即使经过500天，测湿平衡还没有完全达到。此外，试件的W/ C比对一般的影响对这些较大的试件更明显，相比与它与较小的试件。水泥量的效果是相似的，随着薄试件观而变化。5讨论5.1 W / C比 总体而言，影响干燥的W / C比对浆体和水泥砂浆试样的情况不同，并可以在收缩值范围测定（瓦特/ 5 0.35和0.50），在（图2）中可以观察到相对小。从早先进行的收缩数据8,10-12，可以得出W/ C对浆料和水泥砂浆产生重大影响。严格的比较是不同，由于实验的差异和材料不同。例如，实验由皮克特10在0.35和0.50 W / C比浆料和水泥砂浆进行了超过40年的大试件（19.0325.4毫米截面）实验，从而作出的推测粗水泥和不使用任何塑化外加剂。在其他研究8,11,12，在W/ C比实验范围高（0.54和0.60），甚至更高的W / C比，研究发现其效果在较大的浆体和水泥砂浆试件（图3）中水的扩散率降低水泥水化与W/ C比。因此，影响干燥收缩的大小和速度可能有共同的放大值，期间的差异将获两个瓦/ C比值。这种影响仍然相当小，但并在具体实验（图3B和三维），它不会明显出现。这种W/ C比的影响也会减少，对于不同的研究人员在砂浆的试件13和混凝土14-16的实验中。 虽然目前的研究还没有定论，使得W/ C比的影响力对干燥水泥基材料收缩还不确定，使得这样的研究在符合条件的限制下可能不那么重要。这是可能再次为限定w/ C的范围和条件，即一些是在W/取决于几个因素收缩率及影响（孔径分布，总孔隙率，弹性模量，蠕变，水扩散等）可能有这样一种方式，相反个别效果整体效果是相当小。这是重要的，因为最常见的混凝土混合物属于实际范围控制的W / C比内。 值得一提的是砂浆收缩模型与混凝土的收缩一般会随预期这种W/ C比减少。在实际的情况下W/ C比只考虑效果明确模型是关系到体积计算的制约所提供的未水化水泥颗粒，预测主要依赖于实际的收缩实验测定水泥净浆试件。事实上，这种关系对实验数据是最真实可用模型。令人惊讶的是有关W/ C比影响水泥浆体收缩后的数据是相当稀缺。5.2 尺寸效应 最终的两个水泥收缩试件原料和四个获得这两个试件砂浆大小在实验如表5所示。试样的大小使干燥速率的影响强烈，可以从表中的最终变形看出。因此，对于较大规模在这项研究中使用，可以看来，湿度梯度没有大的影响在对最终的收缩。在湿度梯度场的没一个浆料明显的：在第一天干燥，裂纹图案覆盖整个表面在所有清晰可见5050400毫米的标试件。因此，可以看来，表面裂缝是发生在早期阶段干燥收缩，往往会降低整体现象或“明显“收缩3，可能会逐渐接近干燥。在干燥过程结束时，试件变形然后很接近自由收缩变形。这个过程实际上是通过光学显微镜上观察从1至3毫米7薄试件得出的。5.3 相对湿度 收缩率和相对湿度为同时的关系时，可以提出了浆体和砂浆图4。数据在此图显示了测试结果，获得4832毫米的试件和数据代表收缩分数在48相对湿度测量的收缩。对于浆体，可以看出，几乎增加收缩线性关系，在相对湿度下降为100%和48。在砂浆为48%至75的相对湿度低情况时，那么它在75%至100的增长相对湿度范围将对W/ C比的影响力似乎非常小。5.4浆体量 由于水泥浆体的收缩是水泥浆体是主要特征，这一点在图5可以显示出来，相对收缩，关于浆体量对于两个W/ C比值的影响。收缩数据从上执行相应的测试所得的较大的试件得到，并在来表示的分数应变测量水泥净浆试件。 如图所示的曲线五清楚地表明了抑制聚集效应，结果与弹性理论曲线吻合较好，是凸或凹取决于弹性模量（和相对值泊松系数水泥净浆和聚合）11。有趣的是注意到，“最终”混凝土的收缩总体积含量通常位于65至75，约等于15%至25整洁的水泥浆体的收缩。图5还清楚地表明了这对关系的影响的W / C比体积收缩和浆体是非常小。 浆体量之间的关系的内容及“最终”减少（单位体积）如图所示6所示。这些数据再次对应了从测试所得的进行了较大的试件。他们清楚地表明该材料的数量，每单位重量的损失是直接成比例的两个瓦/ C比值浆体量：在比重较高导致更高的减少，只是由于自由水含量越高。5.5干缩对比减少 在图7中干燥收缩是针对减少所有的混合物策的实验。这些数据也对应从测试所得的进行了较大试件。对于与W/ C的0.35比所有的混合物，收缩率约成正比的水分流失。在W/ C的0.50混合物的情况下，水失去了早期干燥收缩小阶段的原因，因为这些水主要来自大型毛细管孔隙17。随后，该曲线的斜率变为约等于到W/ C的0.35混合物。 应当指出，动态收缩暴露于不同的试件减少薄曲线相对湿度将提供进一步的评价在短暂的水分梯度的潜在影响。在另一项实验中提出这样的测量8结果表明，在收缩2.3毫米厚的测量试件，没有发生显着影响的梯度，因此，测量反映了真正的材料收缩。不过，与实验在这项研究中用于安装长度的测定上薄试样的变化，这是无法估量他们在测试的重量的变化。朗读6 结论 结果表明，对于试样尺寸在本实验研究范围（4832和5050400毫米），这个参数对收缩率有明显的影响，但对“最终”的收缩量影响不大。他实验还表明，在湿度48%至100之间，干燥收缩率约反比与相对湿度。对于那些水灰比在0.35到0.5时，在这个比值其相对较少收缩影响减少。此外，测试结果证实在胶凝材料的收缩幅度与浆体量成正比。Influence of key parameters on drying shrinkage of cementitious materialsAbstract Drying shrinkage can be a major cause of the deterioration of concrete structures. The contraction of the material is normally hindered by either internal or external restraints and tensile stresses are induced. These stresses may exceed the tensile strength and cause concrete to crack. The evaluation of the stress distribution in the material requires the knowledge of the “real” free shrinkage deformation. This paper presents the results of a study performed to evaluate this deformation and obtain a better understanding of the behavior of concrete under drying conditions. Shrinkage tests were carried out on cement pastes, mortars, and concretes. The influences of different key parameters were evaluated: relative humidity, specimen size, water/cement ratio, and paste volume. The results indicate that between 48 and 100% relative humidity, the shrinkage of cement paste is approximately inversely proportional to relative humidity. Results also show that the ultimate shrinkage of pastes and mortars measured on 50350 400-mm specimens does not differ much from the “real” shrinkage measured on 4832-mm specimens. Thus, for the specimen dimensions investigated in this study, the existence of a humidity gradient did not affect to a large extent the ultimate shrinkage strain. The influence of the water/cement ratio, within the range investigated (0.350.50), was found to be relatively small. Conversely, paste volume was observed to have a very strong influence. 1999 Elsevier Science Ltd. All rights reserved. Keywords: Cement paste; Concrete; Drying; Humidity; Shrinkage1. Introduction Drying shrinkage, together with its low tensile strength, is probably the most disadvantageous property of Portland cement concrete 1. Shrinkage generally leads to cracking and, even though it may not affect the structural integrity, durability problems are generally increased 2. This is particularly true in the case of concrete overlays and slabs on grade where drying occurs from one face only and shrinkage is hindered by external and internal restraints 3,4. The external restraint is due to the bond between the repair layer and the old concrete in the case of overlays, while, for slabs on grade, it comes from the friction with the subgrade and the slab self-weight. The internal restraint is caused by the humidity gradient that exists in concrete until the hygrometric equilibrium with the surroundings is reached. Local shrinkage is directly related to pore humidity; there-fore, a gradient of shrinkage deformation exists throughout the drying process. Tensile stresses are thus induced in the concrete and may eventually overcome the tensile strength of the material and cause cracking and debonding of over-lays 5.To improve the design of concrete overlays and slabs on grade, the material behavior under drying has to be characterized more precisely. Presently, codes of practice (e.g., ACI, CEB) give fairly good models to predict shrinkage as a global deformation 6, but these models are unsuitable in some cases, for instance, to compute the stresses induced by a shrinkage gradient. The determination of the “real” shrink-age strain of concrete (i.e. independent of the element size) as a function of local humidity is essential for this purpose. This study, which is part of a research program on the durability of thin concrete repairs, was performed to evaluate the free shrinkage deformation of cementitious materials and to characterize the influence of certain basic parameterson this deformation. Shrinkage tests were carried out on cement pastes, mortars, and concretes. The parameters studied were: relative humidity, specimen size, water/cement (W/C) ratio, and paste volume. 2. Test program To obtain a better understanding of the shrinkage phenomenon and to evaluate the “real” free shrinkage deformation, it is important to take into account the influence of key parameters such as the size of specimens and the relative humidity.Drying shrinkage measurements were carried out on twodifferent sizes of specimens: 4832-mm and 5050400-mm prisms. The smaller specimens were considered thin enough to obtain approximately gradient-free shrink-age. It was shown in previous studies 7,8 that the thickness of cement paste specimens in the range of 1 to 3 mm does not affect equilibrium shrinkage.The shrinkage tests on the smaller specimens were per-formed at three relative humidity levels (48, 75, and 92%). These values range from the minimum occurring generally in moderate climates to close to full saturation conditions (100%). The larger specimens were all tested at 48% relative humidity.The two W/C ratios that were selected (0.35 and 0.50) were considered to cover fairly well the range from high- to normal-quality cementitious materials.In order to characterize the relation between paste volume (or, conversely, aggregate content) and ultimate shrinkage, cement pastes, mortars, and concretes were investigated. In the case of mortars, the sand/cement weight ratios chosen were 1 and 2, respectively. The paste volume fractions of the concretes were 0.30 and 0.35. The coarse aggregate to sand ratio (in concretes) was kept constant at 1.5 to reduce the number of parameters. 3. Mixture composition and experimental procedures3.1. Mixtures All mixtures were made with the same Canadian (Type 10) normal Portland cement. The chemical composition and physical properties of this cement are given in Table 1. A granitic sand having a modulus of fineness of 2.46 was used; its grading is shown in Table 2. A 10-mm maximum nominal size crushed limestone was used as coarse aggregate. For the concrete mixtures with a W/C ratio of 0.35, a melamine-based super plasticizing admixture (containing 33% solids and having a unit weight of 1.1) was used at a dosage of 3.8mL/kg of cement to provide a satisfactory workability. The mixture proportions and the properties of the fresh mixtures are given in Table 3 (cement pastes and mortars) and Table 4 (concretes). The air content of the mixtures was determined according to the ASTM C138 gravimetric test method.Cement pastes and mortars were batched in a 10-L vertical axis mortar mixer. Concrete mixtures were batched in a 100-L pan mixer. All mixtures were batched at atmospheric pressure and the constituents were always introduced into the mixer following the same sequence. The cement wasfirst introduced and the water was progressively added until a homogeneous paste was obtained. The sand was then added and the mortars were mixed for at least 2 min. For the concrete mixtures, all the dry constituents (cement, sand, and coarse aggregates) were first introduced in the mixer.The water (containing the super plasticizer) was then progressively added and mixing continued for at least 15 min.3.2. Experimental proceduresFor each mixture, five specimens (two 100200-mm cylinders and three 5050400-mm prisms) were cast into molds in two layers consolidated by vibration. For the cement pastes and mortars, an additional 25022575-mm prism was cast from which small specimens (4832 mm) were sawed (during the curing period) for the free shrinkage measurements. After 24 h, all the specimens were demolded and cured in lime-saturated water at ambient temperature (23) for 28 days prior to testing. Care was taken to ensure that the specimens were never allowed to dry. The 28-day compressive strength tests were carried out on the cylindrical specimens according to the requirements of ASTM C39. The results of these tests are given in Tables 3 and 4. At 28 days, the 5050400-mm prisms were placed in a room at a constant temperature (23) and a constant relative humidity level (48%). At different time intervals, the length change and the mass of the specimens were measured. After the curing period, the 4832 mm prisms used to evaluate the free shrinkage deformations were placed in three desiccators over three saturated salt solutions. According to the laws of chemical equilibrium 9, a saturated salt solution at a fixed temperature gives a constant humidity level in a closed space. In this study, three salts。 were used to provide three different humidity levels (92, 75, and 48%) in the desiccators. A vacuum was introduced into these desiccators to avoid carbonation during the testing period.Because of the very small size of the specimens and to avoid undesirable relative humidity variations in the desiccators, usual measuring devices could not be used. An optical strain gage system allowing the measurement of length change from outside of the desiccators was thus used. This device, composed of an extensometer and an autocollimator, works upon the principle of light reflection. The extensometer mounted on the specimen incorporates two mirrors, one of which is fixed and the other can rotate (lozenge). The length change is measured with the autocollimator, which is a reading auto collimating telescope whose sensitivity is in-dependent of the distance from the gage. The reflection of light by the two mirrors causes an image to appear in the autocollimator field of view. The position of the image on the reticule scale is a function of the lozenge rotation caused by the specimen deformation. Fig. 1 displays a simplified diagram showing how light coming from the autocollimator is reflected by the lozenge to the fixed mirror and back to the autocollimator to form an image. The resolution of the devices used in this study.4. Test results4.1. Shrinkage of 4832-mm specimensThe results of the drying shrinkage tests on the 4832-mm specimens of paste and mortar are presented in Fig. On each graph, the shrinkage as a function of time is shown for the three humidity levels investigated. Each curve represents the average value obtained for two specimens. The results in Fig. 2 clearly show that the rate of drying is extremely rapid. After 1 day, the recorded value generally represents 60% or more of the “ultimate” shrinkage. In all cases, for a given paste content the reduction of the W/C ratio from 0.50 to 0.35 resulted in a slightly lower shrinkage. As expected, drying shrinkage decreases very significantly with the paste volume. At 48% relative humidity, it de-creases from an average of approximately 3200 for the pastes to 950m/m for the mortars with an aggregate/ cement ratio of 2.0. It can further be seen in Fig. 2 that shrinkage is still quite significant at 92% relative humidity and that the “ultimate” shrinkage increases relatively linearly with a decrease in relative humidity between 92 and 48%.4.2. Shrinkage of 5050400-mm specimens Fig. 3 presents the results of the drying shrinkage tests performed on the 5050400-mm specimens of paste, mortar, and concrete at 48% relative humidity. Each curve on the four graphs represents the average result for three specimens. The “ultimate” shrinkage measured ranges between an average of approximately 600m/m for the four concretes to 3000m/m for the cement pastes.It is quite evident from Fig. 3 that the rate of drying is much slower for the 5050400-mm specimens than for the smaller specimens. Even after 500 days, hygrometric equilibrium has not been completely reached. In addition, the influence of the W/C ratio generally appears to be a little more pronounced for these larger specimens than it is with the smaller ones. The effect of paste volume, however, appears to be similar to that observed with the thin specimens.5. Discussion5.1. W/C ratio Overall, the influence of the W/C ratio upon drying shrinkage of the thin paste and mortar specimens, for a given paste content and within the range of values investigated (W/C0.35 and 0.50), is observed to be relatively small (Fig. 2). Shrinkage data from earlier investigations8,1012 indicate a more significant influence of the W/C ratio for pastes and mortars. Strict comparisons are hazardous however, because of miscellaneous differences in experimental procedures and materials. For example, the experiments by Pickett 10 on 0.35 and 0.50 W/C ratio pastes and mortars were conducted over 40 years ago on larger specimens (19.025.4-mm cross-section) made with pre