蒸压加气混凝土砌块墙体裂缝的防治

介绍了蒸压加气混凝土砌块的特性，施工准备及施工工艺，分析了蒸压加气混凝土砌块墙体裂缝产生的原因，提出了有效防治墙体裂缝的措施，需从设计和施工两个方面入手，才能确保砌块墙体的施工质量。     

谈蒸压加气混凝土自保温墙体工程质量监督要点

针对当前蒸压加气混凝土砌块自保温墙体工程设计、施工及质量监督管理中存在的问题,结合工程质量监督工作实践,进行了分析和讨论,研究了推进质量监督模式向动态监督方式转变的必要性,并提出做好蒸压加气混凝土砌块自保温墙体工程质量监督的工作要点.     

基于鱼刺图分析法的加气混凝土砌块生产实践

加气混凝土砌块作为一种新型墙体材料,在生产过程中受到人员、设备、原料、制度和环境的影响,通过运用鱼刺图分析法,对影响加气混凝土砌块生产的五大要素,即"人、机、物、法、环",查找分析生产过程控制点,对产品质量进行持续改进。     

新型墙体材料在建筑中的应用

发展新型墙体材料和推广节能建筑，其中混凝土小型空心砌块和加气混凝砌块土已广泛用于工业及民用建筑，它们具有轻质高强、保温隔音好等特点，作为承重或非承重的结构材料和保温材料，对建筑节能、节约土地、利用废料等方面具有显著的效果。     

干法脱硫灰在加气混凝土砌块中的开发与应用

根据公司产的脱硫灰具有的胶凝性、颗粒细、密度轻等特性提出了将其应用于加气混凝土砌块的设想,通过实验和工业化生产实践,表明了将干法脱硫灰应用于加气保温砌块是完全可行的。目前,加气混凝土砌块是公司产的脱硫灰的主要应用途径之一,该技术的使用既为梅钢创造了效益,又践行了绿色经营的理念。     

利用选金尾矿生产系列硅酸盐墙体材料的工艺技术研究

本文对以选矿金尾矿为主要原料，生产蒸压标准砖，榫式砖，空心砌块，加气砌块等硅酸盐墙体材料的生产工艺流程和工艺参数进行了全面论述和详细讨论。     

浅谈采用新型砌块墙体裂缝产生的原因及其防治措施

用新型砌块砌筑的墙体产生裂缝,是我国墙体材料革新后产生的一种新的质量通病,已引起人们的重视,本文就墙体产生裂缝的原因及防治措施进行分析和探讨.     

加气混凝土表面吸放湿性对墙面开裂的影响

加气混凝土填充墙具有节能、廉价等优点,同时它的墙体普遍存在开裂现象.作者结合自身的工作实践,从加气混凝土表面吸放湿性阐述砌体开裂的原因,并提出施工控制的防裂措施.     

混凝土砌体墙体施工的质量控制

混凝土小型空心砌块是一种新型墙体材料,随着国家对墙体改革的要求,砌块的施工正在迅速地在建筑业发展,由于砌块建筑适应性强,施工方便,对建筑物的平面和空间变化无严格要求,能够满足建筑变化的需要.而且空心砌块制作工艺简单,可以因地制宜,充分利用本地区材料.     

地下室墙裂缝成因及其防治

高层建筑地下室的渗漏总是施工中的一种通病 ,而地下室外墙是最易发生渗漏的部位 .根据多年的施工经验 ,将地下室渗漏成因及其防治总结如下 .1　裂缝的成因( 1 )墙体外墙混凝土浇筑后 ,由于水化热升温冷却后收缩 ,而墙体受地基混凝土底板外部结构的约束 ,使墙体混凝土内部出现较大拉应力而导致墙体裂缝出现 .( 2 )混凝土内部的毛细孔裂缝 .( 3)外加剂的掺量不够及养护不及时 .( 4)墙体钢筋间距太大 ,不利于限制裂缝产生 .( 5)施工中未采用低水化热水泥 .2　裂缝的防治( 1 )地下室墙体施工中 ,在底板和墙板上设置贯通的后浇带作为临时收缩缝 …     

Machine Vision-Based Concrete Surface Quality Assessment

Manually inspecting concrete surface defects (e.g., cracks and air pockets) is not always reliable. Also, it is labor-intensive. In order to overcome these limitations, automated inspection using image processing techniques was proposed. However, the current work can only detect defects in an image without the ability of evaluating them. This paper presents a novel approach for automatically assessing the impact of two common surface defects (i.e., air pockets and discoloration). These two defects are first located using the developed detection methods. Their attributes, such as the number of air pockets and the area of discoloration regions, are then retrieved to calculate defects’ visual impact ratios (VIRs). The appropriate threshold values for these VIRs are selected through a manual rating survey. This way, for a given concrete surface image, its quality in terms of air pockets and discoloration can be automatically measured by judging whether their VIRs are below the threshold values or not. The method presented in this paper was implemented in C++ and a database of concrete surface images was tested to validate its performance.     

Radon penetration of concrete slab cracks, joints, pipe penetrations, and sealants

Radon movement through 12 test slabs with different cracks, pipe penetrations, cold joints, masonry blocks, sealants, and tensile stresses characterized the importance of these anomalous structural domains. Diffusive and advective radon transport were measured with steady-state air pressure differences controlled throughout the deltaP = 0 to 60 Pa range. Diffusion coefficients (deltaP = 0) initially averaged 6.5 x 10(-8) m2 s(-1) among nine slabs with only 8% standard deviation, but increased due to drying by 0.16% per day over a 2-y period to an average of 2.0 x 10(-7) m2 s(-1). An asphalt coating reduced diffusion sixfold but an acrylic surface sealant had no effect. Diffusion was 42 times higher in solid masonry blocks than in concrete and was not affected by small cracks. Advective transport (deltaP < or = 60 Pa) was negligible for the slabs (10(-16) m2 permeability), pipe penetrations, and caulked gaps, but was significant for cracks, disturbed pipe penetrations, cold joints, masonry blocks, and concrete under tensile stress. Crack areas calculated to be as small as 10(-7) m2 significantly increased radon advection. Algebraic expressions predict air velocity and effective crack width from enhanced radon transport and air pressures. Masonry blocks, open cracks, and slab cold joints enhance radon penetration but stressed slabs, undisturbed pipe penetrations, and sealed cracks may not.     

浅谈现浇混凝土楼板裂缝在施工过程中的控制

现浇混凝土楼板经常出现裂缝，造成裂缝原因很多，裂缝形成多种多样，本文介绍了裂缝的存在的形式，产生原因，以及在设计施工，原材料控制中采取减少或避免楼板产生裂缝的措施。     

如何预防水泥混凝土路面的裂缝和断板

介绍了水泥混凝土路面几种常见裂缝类型,并进行了简要的原因分析,提出了预防水泥混凝土路面裂缝(或断板)的措施。     

Modeling Cracking in Shell-Type Reinforced Concrete Structures

A three-dimensional (3D) hypoelastic material model for modeling material properties of cracked reinforced concrete is proposed. Material properties of multidirectionally cracked reinforced concrete are represented by the material properties of intact concrete and a number of uniaxially cracked concrete with their coupling solids. Cracking effects due to multiple nonorthogonal cracks are traced in each uniaxially cracked concrete. Tension softening and aggregate interlock occurring at the crack interface as well as tension stiffening and compression softening initiated in concrete between cracks due to multiple nonorthogonal cracks are all incorporated explicitly. RC panels under in-plane loading and RC slab under pure torsion have been analyzed. The developed 3D hypoelastic material model has been proved to be efficient and effective in modeling the material behaviors of cracked reinforced concrete in shell-type RC structures. The deformational response, the ultimate strength, and failure mode can be captured reasonably well.     

Field Investigations of Cracking on Concrete Pavements

This paper presents the results of several investigations to identify the underlying causes of longitudinal cracking problems in Portland cement concrete (PCC) pavement. Longitudinal cracking is not intended and detrimental to the long-term performance of PCC pavement. Longitudinal cracking problems in five projects were thoroughly investigated and the findings indicate that longitudinal cracking was caused by: (1) late or shallow saw cutting of longitudinal joints; (2) inadequate base support under the concrete slab; and (3) the use of high coefficient of thermal expansion (CTE) aggregates. When the longitudinal cracks were caused by late or shallow saw cutting of longitudinal joints, cracks developed at a very early stage. However, when there was adequate base support, the longitudinal cracks remained relatively tight even after decades of truck trafficking. Another cause of longitudinal cracking was inadequate base support, and cracking due to this mechanism normally progressed to rather wide cracks. Some cracks were as wide as 57?mm. Evaluations of base support by dynamic cone penetrometer in areas where longitudinal cracks were observed indicate quite weak subbase in both full-depth repaired areas and surrounding areas. This implies that the current requirements for the subbase preparation for the full-depth repair are not adequate. Another cause of longitudinal cracking was due to the use of high CTE aggregate in concrete. Large volume changes in concrete when coarse aggregate with high CTE is used could cause excessive stresses in concrete and result in longitudinal cracking. To prevent longitudinal cracking, attention should be exercised to the selection of concrete materials (concrete with low CTE) and the quality of the construction (timely and sufficient saw cutting and proper selection and compaction of subbase material).     

浅谈温度对混凝土裂缝的影响及预防措施

通过多年的现场观察并查阅有关混凝土内部应力方面的专著,对混凝土温度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施等进行阐述。     

硫酸盐侵蚀作用下纤维锂渣混凝土裂缝的分形特征

为探究新型混凝土受硫酸盐侵蚀后的力学性能,采用质量分数为5%的硫酸盐溶液全浸泡加速侵蚀法,对11组聚丙烯纤维混凝土（PC）试块、11组聚丙烯纤维锂渣混凝土（PLiC）试块、8根PC大偏心受压柱和8根PLiC大偏心受压柱进行侵蚀试验,得到了不同侵蚀时间下混凝土的力学性能。基于分形理论分析了试块及构件破坏时表面裂缝分布的分形特征,详细讨论了试块及构件表面裂缝分形维数与其侵蚀时间、抗压强度、极限承载力之间的关系。研究表明,PC和PLiC立方体抗压强度随侵蚀天数先增加后降低,在120 d达到最大;试块及构件破坏时表面裂缝分布具有分形特征,试块表面裂缝分形维数随侵蚀天数的增加呈现先增加后减少再增加的规律,随试块抗压强度的提高而减少;PC及PLiC混凝土大偏心柱极限承载力随侵蚀天数的增加先增加后减少,锂渣的掺入可以提高聚丙烯纤维混凝土柱的抗硫酸盐侵蚀能力,构件破坏时表面裂缝分形维数随硫酸盐侵蚀天数呈现震荡上升的趋势;因此混凝土表面裂缝的分形特征可作为判定构件损伤程度的指标之一,可为今后对在役混凝土结构承载力和寿命预测提供参考。      

75t／h电站锅炉制粉系统三次风带粉原因

从旋风分离器的设计,制造,制粉系统的运行及煤粉的特性四个角度探讨75t/h锅炉的制粉系统三次风带粉问题,为解决同类型问题提供一些依据和借鉴。     

Effect of Untreated Surface Disbonds on Performance of FRP-Retrofitted Concrete Beams

Retrofitting concrete structures with externally bonded fiber-reinforced polymer (FRP) laminates has become an increasingly common practice. Disbonds at the concrete-FRP interface, if left untreated, may adversely affect the performance of the retrofitted system. Disbonds in the form of surface voids and cracks are the subject of this paper. Voids may occur due to poor compaction or defective formwork, or in the form of air entrapment between resin and FRP laminate during application. Cracks, on the other hand, generally result from loading. This study is comprised of a detailed experimental program and a nonlinear finite-element analysis. In the experiments, surface cracks were simulated by cutting slits in concrete, herein termed as surface cuts. The study shows that leaving surface disbonds untreated, within the considered range of disbond variables, does not have a significant impact on the overall structural performance. A threshold of 12.7 mm for void diameter was deemed conservative for structural performance. On the other hand, 38 mm spacing was considered an appropriate threshold for epoxy injection in crack widths between 0.25 and 0.8 mm. Hence, conservative thresholds in current practice may be revised accordingly, unless considered necessary to avoid environmental effects.