共查询到20条相似文献,搜索用时 62 毫秒
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混凝土膨胀剂具有补偿混凝土干燥收缩的效果,但在实际地下室防水混凝土工程中使用效果不甚理想,存在掺加膨胀剂后地下室底板和外墙仍然出现混凝土开裂渗漏的现象.本文从设计和施工两个方面提出了全面、有效的解决措施. 相似文献
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在混凝土拌合物中掺加适量的膨胀剂来补偿其收缩,是防止或减小混凝土产生裂缝的有效方法之一,因此,使用范围不断扩大,促进了建筑工程设计和施工技术的进步和发展.与此同时,随着混凝土膨胀剂用量的不断增加,应用效果不佳、使用失败的工程时有发生,造成混凝土结构渗漏和开裂的质量事故也屡见不鲜,因而使得有人对混凝土膨胀剂的补偿收缩作用产生了怀疑,甚至有人在工程中拒绝使用。 相似文献
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采用单轴固结试验和三轴剪切试验对饱和、湿润、风干以及烘干的藤森粘土进行了应力-应变特性研究。在试验过程中,进行了不同轴向应力水平下的恒应变率加载试验、蠕变试验以及卸载与重复加载试验。局部变形测量传感器(LDT)被用于三轴剪切试验中的轴向变形测量以提高小应变测量的精度。试验结果表明,不同含水率与饱和度的藤森粘土在单轴固结试验与三轴剪切试验条件下都表现出明显的粘塑性。它们的加载速率效应、蠕变效应都相似;而且在蠕变结束后的一小段邻域内藤森粘土的强度有明显的提高。笔者提出用参数β来描述藤森粘土的粘性。对试验结果的计算分析表明,在单轴和三轴试验条件下不同含水率与饱和度的藤森粘土的β值介于0.034到0.064之间;而且,含水率高的藤森粘土的β值大于含水率低的藤森粘土的β值,单轴试验条件下的β值大于三轴试验条件下的β值。 相似文献
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During childhood, playgrounds have a great impact on development of children. Not only do well designed playgrounds help children fast problem solving ability but also increase their social interactive relationships. User surveys are sources of data to aid for planning, designing and management processing of playgrounds. The aim of this study was to investigate the characteristics of the playground users in districts which have different socio-economical structures in Erzurum. The study focuses on users of three different playgrounds, who belong to poor-middle-high income family groups. To identify the characteristics of playground users of three districts, a questionnaire survey was performed. Results were evaluated using Chi Square (χ2) Correlation Test. 相似文献
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S. Mahmood Sadat Noori Kumars Ebrahimi Abdol‐Majid Liaghat Abdol‐Hossein Hoorfar 《Water and Environment Journal》2013,27(1):10-19
The main aim of this study has been to assess the spatially variability of groundwater level at different climatic periods. The study area is Saveh‐Nobaran aquifer in Iran. First, using two drought indices, different climatic periods in the region including wet, normal and dry during 1993–2003 were recognized. Second, with the use of measured elevations of the water table, experimental semivariograms (spherical, exponential and Gaussian) were constructed that characterize the spatial variability of the measured groundwater levels. Groundwater levels were interpolated by four different geostatistical methods. RMSE, MAE and R 2 were calculated to determine the best method. The R 2 coefficient obtained from kriging, cokriging, TPSS and IDW methods were 0.95, 0.97, 0.89 and 0.83, respectively. Cokriging method was used to create groundwater‐level maps, including maximum, average and minimum water levels for each climatic period. The results obtained from geostatistical analysis showed that groundwater depth varies spatially in different climatic conditions. 相似文献
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探讨了水泥量、标准砖类型在不同养护条件下对瓷砖胶拉拔强度的影响,结果表明,在3种养护条件下,瓷砖胶的拉拔强度并未随水泥量的增加而增大,水泥量在30%~35%时试验结果比较理想.欧洲进口标准砖的测试结果偏差比较小,且测试结果远高于国产的标准砖:国产的标准砖自身相比,处理过的测试结果也比未处理的高很多. 相似文献
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2007年12月分别在内蒙古自治区和山西省砷中毒病区采集砷中毒病人家庭压井水水样33份,采用离子色谱氢化物发生原子荧光法对33份水样在现场即刻测量iAs(Ⅲ)和iAs(Ⅴ)含量,水样于-20℃保存10d后在实验室进行了相应检测;采用配对t检验分析不同时间的测量结果。对2008年7月在内蒙古采集的10份水样逐日测量了冷冻和室温条件下iAs(Ⅲ)和iAs(Ⅴ)含量变化情况。结果表明,iAs(Ⅲ)含量现场即刻和10d后测量结果差别有统计学意义(t=6.291,P〈0.001),10d后测量比现场即刻测量平均降低53.78 μg/L,95%CI为36.36~71.19μg/L;iAs(Ⅴ)现场即刻和10d后测量结果差别有统计学意义(t=-4.327,P〈0.001),10d后的测量结果比现场即刻测量平均增加23.75μg/L,95%CI为9.47~26.31μg/L;总砷现场即刻和10d后测量结果差别无统计学意义(t=0.806,P=0.426)。逐日测量结果表明iAs(Ⅲ)含量逐渐降低,iAs(Ⅴ)含量逐渐升高。水体基质不同及采样、运输和保存样品的过程会造成iAs(m)被氧化为iAs(Ⅴ),导致不能精确测量不同价态砷暴露水平,因此现场即刻测量砷可以更为准确地测量砷价态暴露水平。 相似文献
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通过使用(5-160)kV X射线标准化辐射场和标准铅片对三种不同规格的实心砖在(70-150)kV管电压条件下的铅当量进行了研究。结果显示:实心砖的铅当量随着管电压的增加出现先增加后减小的变化趋势,在管电压为90kV时,铅当量达到最大;实心砖的表观密度越大,比铅当量也越大。 相似文献
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《Construction and Building Materials》2000,14(5):253-259
The incompatibility between cement and chemical admixtures has increased over the last decade. Specifications calling for the use of admixtures in concrete often results in strange occurrences, i.e. rapid set, retardation, accelerated stiffening, etc. This paper presents the observations of a study on the effect of different superplasticizers with respect to the setting behavior and compressive strength. The hydration behavior of different cements at different time intervals (1, 3, 7, 28 and 360 days) in the presence of superplasticizers has also been analyzed by differential thermal analysis (DTA). The 33 grade ordinary Portland cement has shown retardation with naphthalene-based superplasticizer at the recommended dose (2%) of manufacturer, where as 43 grade OPC has shown retardation with blended polymer-based superplasticizer. Portland Slag Cement and 53 grade OPC has been found to be compatible with all the superplasticizers studied in the present investigation. 相似文献