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含CAD图纸+文档 艺术 水泥 护栏 葫芦 成型 设计 机械 部分 CAD 图纸 文档

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压缩包内含有CAD图纸和说明书,均可直接下载获得文件，所见所得，电脑查看更方便。Q 197216396 或 11970985

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毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 1次指导， 20*年 2 月 27 日教师指导意见及指导内容：1.交外文翻译（与专业有关的外文资料）汉字3000左右（含译文与原文），外文。翻译语句的准确程度把握不够。2.安排本次毕业设计有关题目，选题。3.题目：艺术水泥护栏葫芦瓶成型机设计4.参照任务书要求，拟开题报告初稿。学生任务完成情况、需要解决的问题及下一步工作方案等：1.完成毕业设计开题报告和外文翻译。2.开题报告内容不够完善，字间行距未修改，外文字体未设置标准，内容部分缺少研究时可能出现的问题。3.外文翻译图表部分在中文里未体现出来，翻译未达到流畅，需改进。4.下一步完善开题报告和外文翻译，成型机传动装置数据分析。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 7次指导， 20* 年 4 月 17 日教师指导意见及指导内容：继续拆绘零件图。学生任务完成情况、需要解决的问题及下一步工作方案等：1.对上周内容进行修改并交老师，进行完善。2.对论文格式进行完善和修改。3.初步完成轴的设计计算和校核。4.在完成过程中遇到了意料之外的问题，尚未解决。5.完成成型机总图和部分零件图。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 3次指导， 20* 年 3 月 13 日教师指导意见及指导内容：1. 开题报告层次基本可以，调整语句与格式。2. 重点分析好解决问题的方案。3. 下一步进入葫芦瓶成型机的方案考虑。学生任务完成情况、需要解决的问题及下一步工作方案等：1.完成开题报告和外文翻译，并打印出来。2.根据指导老师意见修改总体方案设计，确定成型机传动机构。3.查阅资料，初步完成电气控制原理图、传动机构、轴的设计。4在完成行数内容的时候出现了一些疑点。5.下一步继续完成传动、轴等设计计算未完成部分。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 9次指导， 20* 年 4月 24 日教师指导意见及指导内容：手工绘图中存在一些小问题，如标注错误、配合等需要完善。学生任务完成情况、需要解决的问题及下一步工作方案等：1.继续绘制手工图。 2.并着手完善毕业设计说明书。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 2次指导， 20* 年 3 月 6 日教师指导意见及指导内容：1. 交外文翻译，个别地方翻译语句的准确度不够。2. 开题报告层次基本可以。3. 细化一下解决问题的方案。4. 按要求完成开题报告初稿。学生任务完成情况、需要解决的问题及下一步工作方案等：1. 完善上次的开题报告和外文翻译，格式内容达标。2. 完成了毕业论文的总体方案设计。3. 总体方案设计过程中遇到的一些待解决问题，考虑一些传动机构的问题。4. 下一步需完成方案设计和轴、传动机构的设计计算。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 5次指导， 20* 年 3月 27 日教师指导意见及指导内容：成型机结构安排合理。学生任务完成情况、需要解决的问题及下一步工作方案等：1.对上周内容进行修改并交老师检查，再进行修改。2.对论文格式进行完善和修改。3.初步完成轴的设计计算和校核。4.在完成上述问题时遇到了待解决的问题。5.拟定成型机设计草图。注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 8次指导， 20* 年 4月 17日教师指导意见及指导内容：总装图和零件图修改基本完成，修改好读书报告。学生任务完成情况、需要解决的问题及下一步工作方案等：1.进一步完善总装图和零件图。 2.开始着手手工绘图。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 6次指导， 20*年 4月 3 日教师指导意见及指导内容：先绘制成型机装配图，然后拆装成型机零件图，完成对各零件图的绘制。学生任务完成情况、需要解决的问题及下一步工作方案等：1.对上周内容进行修改并交老师对其指导，然后进行完善。2.对论文行文和格式进行完善和修改。3.初步完成轴的设计计算和校核。4.在完成上述内容的过程中出现很多意料之外的问题，待解决。5.完成成型机总图及部分零件图。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 11次指导， 20*年 5月 8 日教师指导意见及指导内容：图纸、设计说明书基本完成，但一些细节问题还是存在，等待修改。学生任务完成情况、需要解决的问题及下一步工作方案等：1.进一步完善图纸、毕业设计说明书。 2.主要修改设计说明书的格式。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 13次指导， 20* 年 2 月 22 日教师指导意见及指导内容：最终要完成图纸、论文修改，并打印出来。学生任务完成情况、需要解决的问题及下一步工作方案等：整理图纸、论文，准备答辩 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 12次指导， 20* 年 5月15 日教师指导意见及指导内容：图纸、毕业设计修改完成，开始为毕业答辩作准备。学生任务完成情况、需要解决的问题及下一步工作方案等：1.最终完成图纸和毕业设计说明书。2.开始着手于毕业答辩。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 10次指导， 20*年 5月 1 日教师指导意见及指导内容：毕业设计中的字体、格式与要求不太符合，需要进一步修改和完善。学生任务完成情况、需要解决的问题及下一步工作方案等：1.完成手工绘制图。 2.继续修改和完善设计说明书。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 14次指导， 20*年 5 月 29 日教师指导意见及指导内容：检查了打印好的图纸和论文，签字无需再打印，审阅一下图纸中的小错误，准备答辩。学生任务完成情况、需要解决的问题及下一步工作方案等：1.将图纸、论文打印并装订成册2.为6.2号的答辩作最后的准备工作。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 毕业设计（论文）指导情况记录表（本表由学生按指导情况如实填写并由指导教师签字认可）第 4次指导， 20* 年 3月 20 日教师指导意见及指导内容：1. 要在工艺方案基础上，重点考虑成型机结构，初步完成成型机设计计算。2. 成型机的总体外形尺寸的选择，拟定成型机草图。学生任务完成情况、需要解决的问题及下一步工作方案等：1.对上周内容进行修改并交老师指导，再进行修改。2.对论文格式进行完善和修改。3.初步完成轴的设计计算和校核。4.在完成上述问题时遇到了待解决的问题。5.拟定成型机设计草图。 注：此页可根据需要自行复制，每指导一次，填写一次，不受页数限制。指导教师签名： 任务书题 目艺术水泥护栏葫芦瓶成型机设计(机械部分设计）论文时间20*年2月25日至 20*年6月14日课题的主要内容及要求(含技术要求、图表要求等)为了更好地完成艺术水泥护栏的设计，必须以下面几点为依据：1.艺术水泥护栏是围栏的创新产品，造型精美、古朴大方，对围墙、阳台、回廊等建筑物具有明显的装饰作用，更是铁艺、不锈钢、PVC围栏的更新替代产品。具有抗风雨雪冻强度高，永不生锈无污染，使用寿命长，维护方便，不易被盗以及造价低的优点。2.主要构件罗纹柱、葫芦瓶等花式立柱使用钢筋水泥材料，为中空结构形式，一般用模具成型，为提高材料紧实度和增加表面花纹的立体感，可采用离心旋转和真空吸水的工艺方法，由成型机实现。3.葫芦瓶规格：1151620。4.生产率：80100根/天。课题的实施的方法、步骤及工作量要求1.查阅有关资料和设计手册，了解国家或行业对艺术水泥护栏葫芦瓶成型机设计的要求等；2.确定设计方案，完成艺术水泥护栏葫芦瓶成型机设计的总装配图及零件图，完成图纸工作量累计3张零号图纸以上（葫芦瓶成型机装配图、真空罐部件图、部分零件图、电气控制系统原理图）；3.完成外文翻译汉字5000字以上；4.完成毕业设计说明书（1万汉字以上）。指定参考文献 1机械工程手册编委会编.机械工程手册.第二版.北京：机械工业出版社，1995.2纪名刚等主编.机械设计M.北京：高等教育出版社，2001.3刘鸿文主编.材料力学.第四版.高等教育出版社，2004.4陆玉等编著.机械设计课程设计M.北京：机械工业出版社，1999.05（第三版）5王春香等.机械设计基础（多媒体CAI教学教材）M.北京：地震出版社，2004.6林清安.ProPENGINEER2000i2零件设计基础篇（上、下）M.北京：清华大学出版社，2001.7黄圣杰等.ProPENGINEER2001高级开发实例M.北京：电子工业出版社，2002.8濮良贵，纪名刚.机械设计.北京：高等教育出版社，1997.9成大先.机械设计的错误与禁忌.北京：化学工业出版社，1997.10吴永贵，丁亚军.机械设计.上海：复旦大学出版社，1996.11何达，朱红军主编.CAXA2005基础及应用教程M.北京：电子工业出版社.12陈立德.机械设计基础课程设计指导书M.北京：高等教育出版社，2003.13黄观尧，刘保河.机械制造工艺基础M.天津：天津大学出版社，2003.14黄鸿元，林锡榕.SolidWorks2001入门与实践M.北京：北京大学出版社，2003.15王大康.机械设计综合课程设计M.北京：机械工业出版社，2003.毕业设计(论文)进度计划(以周为单位) 第 1 周（20*年2月25日-20*年3月3日）：检查寒假外文翻译情况，下达具体毕业设计任务，指导学生撰写开题报告，熟悉设计内容，查阅有关资料第 2 周第 3 周（20*年3月4日-20*年3月17日）：参观实验室或有关厂家，增加感性认识，方案论证并确定设计方案，完成电气控制系统原理图、电动机选择及有关传动机构、轴的设计计算第 4 周第 5 周（20*年3月18日-20*年3月31日）：完成葫芦瓶成型机装配图第 6 周第 7 周（20*年4月1日-20*年4月14日）：完成真空罐部件图和部分零件图第 8 周（20*年4月9日-20*年4月21日）：提交第1-8周的指导记录表和已做的毕业设计内容，由指导老师初审后上交学院第 9 周第 13 周（20*年4月22日-20*年5月26日）：在指导老师指导下修改并完成设计，完成相关设计图纸，同时撰写毕业设计说明书，并提交指导老师初审第 14 周第 16 周（20*年5月27日-20*年6月14日）：修改毕业设计图纸及说明书，完成后参加毕业答辩备注注：表格栏高不够可自行增加。此表由指导教师在毕业设计（论文）工作开始前填写，每位毕业生两份，一份发给学生，一份交院（系）留存。毕业设计(论文)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 presumably coarser cements and without using any plasticizing admixture. In the other studies 8,11,12, the W/C ratio range investigated is higher (W/C 0.40 and 0.60).The slightly more pronounced effect of the W/C ratio ob-served on larger paste and mortar specimens (Fig. 3) is presumably due to the fact that the rate of water diffusion from hydrated cement paste decreases with the W/C ratio. Hence, the influence of the size and rate of drying may together amplify the difference between the values obtained for the two W/C ratios. The effect remains quite moderate though and, in the case of concrete (Figs. 3b and 3d), it does not appear significant. A mitigated effect of the W/C ratio has also been observed by different investigators in the case of mortar 13 and concrete 1416. While it should not be inferred from the results of the present study that W/C ratio has no influence on the drying shrinkage of cement-based materials, it does appear that within the limits and conditions met in the present study it might not be as important as it is often considered to be. It is possible, again for the given W/C range and conditions, that some of the several factors that are dependent on the W/C ratio and that affect shrinkage (pore size distribution, total porosity, modulus of elasticity, creep, water diffusion, etc.) might have opposite individual effects in such a way that the overall effect is rather small. This is important because most usual concrete mixtures fall within the actual range of interest in term of W/C ratio.It is worth mentioning that shrinkage models for mortar and concrete generally predict a decrease in shrinkage with a reduction of the W/C ratio. It is the case, for instance, in the constitutive model developed by Hansen 12. However, the only effect of the W/C ratio considered explicitly in that model is related to the calculation of the restraining volume provided by the unhydrated cement particles, and the pre-diction relies mostly on the actual shrinkage measured experimentally on cement paste specimens. In fact, such a dependence on experimental data is true for most available models. Unfortunately and surprisingly, reliable and well-documented data regarding the effect of the W/C ratio upon shrinkage of cement paste are rather scarce.5.2. Size effect The “ultimate” shrinkage strains of the two cement pastes and of the four mortars obtained for the two specimen sizes investigated are shown in Table 5. Even though the rate of drying is strongly affected by the size of the specimen, it can be seen from this table that the “ultimate” de-formation does not differ much from one specimen size to the other. Thus, for the larger size used in this study, it seems that the humidity gradient did not have a large influence on the “ultimate” strain. The presence of a humidity gradient was evident on both pastes: during the first days of drying, a crack pattern covering the whole surface was clearly visible on all 5050400-mm specimens. It thus appears that skin cracks, which occur in the early stages of drying and tend to reduce the overall observed or “apparent” shrinkage 3, may gradually close as drying proceeds inward. At the end of the drying process, the global deformation is then quite close to the free shrinkage strain. Sucha process was actually observed by optical microscopy on thin specimens ranging from 1 to 3 mm 7.As mentioned earlier, the size effect may be slightly more pronounced for the materials with a W/C ratio of 0.35. Again, this is probably simply related to the lower porosity, hence the slower rate of drying, of the cement pastes having a lower W/C ratio.5.3. Relative humidityThe relation between shrinkage and relative humidity for both pastes and mortars is presented in Fig. 4. The data shown in this figure were obtained from tests on 4832-mm specimens and the shrinkage data represent the fraction of the shrinkage measured at 48% relative humidity. For the pastes, it can be seen that the shrinkage increases al-most linearly with a decrease in relative humidity between 100 and 48%. In the case of the mortars, the behavior is slightly different: the slope between 48 and 75% relative humidity is lower and then it increases in the 75 to 100% relative humidity range. The influence of the W/C ratio appears to be very small.5.4. Paste volumeSince shrinkage is a cement paste-related phenomenon, the paste volume is a dominant feature. This is illustrated in Fig. 5 where relative shrinkage is plotted against paste volume for the two W/C ratios investigated. The shrinkage data correspond to those obtained from the tests performed on the larger specimens and are expressed in terms of the fraction of the strain measured on the cement paste specimens. The curves shown in Fig. 5 clearly demonstrate the re-straining effect of aggregates. The results agree well with the elastic theory; whether the curve is convex or concave depends on the relative values of the elastic modulus (and Poissons coefficient) for cement paste and aggregates 11.It is interesting to note that the “ultimate” shrinkage of concrete, for which the aggregate volume content usually lies between 65 and 75%, is approximately equal to 15 to 25% of the neat cement paste shrinkage. Fig. 5 also shows clearly that the influence of the W/C ratio on the relationship between shrinkage and paste volume is extremely small.The relationship between paste volume content and “ultimate” weight loss (per unit volume) is shown in Fig. 6. These data again correspond to those obtained from the tests carried out on the larger specimens. They clearly demonstrate that the weight loss per unit volume of material is directly proportional to the paste volume for both W/C ratios: the higher ratio leads to a higher weight loss, simply due to the higher free water content.5.5. Drying shrinkage vs. weight lossIn Fig. 7, drying shrinkage is plotted against weight loss for all mixtures investigated. These data also correspond to those obtained from the tests carried out on the larger specimens only. For all mixtures with a W/C ratio of 0.35, shrinkage is approximately proportional to the loss of water. In the case of the 0.50 mixtures, the water lost in the early stages of drying causes little shrinkage, since this water mainly comes from the large capillary pores 17. After-ward, the slope of the curves becomes approximately equal to that of the 0.35 mixtures.It should be pointed out that the dynamic shrinkage weight loss curves of the thin specimens exposed to different relative humidities would have provided a further evaluation of the potential effect of the transient moisture gradients. Such measurements made in another investigation 8 showed that the measurement of shrinkage on 2.3-mm thick specimens were not influenced significantly by the occurrence of gradients and, thus, the measurements reflected the true material shrinkage. Unfortunately, with the experimental setup used in this study for the determination of length change on the thin specimens, it was not possible to mea-sure their weight change during the tests.朗读 6. Conclusions The test results presented in this paper show that for the range of specimen sizes investigated in this study (4832 and 5050400 mm), this parameter significantly influences the rate of shrinkage, but has little effect on the “ultimate” shrinkage deformation that is measured. They also indicate that in the 48 to 100% range, drying shrinkage is approximately inversely proportional to the relative humidity of the surrounding atmosphere. For those mixtures made with ordinary Portland cement at W/C ratios of 0.35 and 0.50, the value of this ratio was found to have relatively little influence on shrinkage. In addition, the test results con-firm that the magnitude of shrinkage in cementitious materials is directly proportional to the paste volume content.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