Effect of Straw Mixing Amount on Mechanical Properties of Admixture-adding Hollow Block

The bonding mechanism between straw and concrete was analyzed through testing the compressive strength and flexural strength of hollow block, with different straw amount and different dosage and types of admixtures. The test results show that the mechanical properties of hollow blocks reduced after adding straws, and the more straws was added, the more hollow block density decreased. But adding A12（SO4）3 and CaC12 could improve the dense degree between rice straw and concrete. And when the proportion of straw mixing amount was 10%, the flexural strength of the early strength agent （2% A12（SO4）3, CaC12） added hollow block reached as maximal as 3.1 MPa, while the compressive strength was 9.1 MPa, consisting with the strength grade of common concrete hollow block MU7.5.

Effect of Hole Configuration on Heat Transfer through a Hollow Block Subjected to Solar Flux

In this paper,some effort is provided to optimize the geometry of a concrete hollow brick(used in the construction of building roofs)in order to increase the related thermal resistance,thereby reducing energy consumption.The analysis is conducted for three different configurations of the hollow concrete bricks.Coupling of conduction,natural convection and thermal radiation phenomena is considered.Moreover,the flows are assumed to be laminar and two-dimensional for the whole range of parameters examined.The conservation equations are solved by a finite difference method based on the control volumes approach and the SIMPLE algorithm for velocity-pressure coupling.The results show that the aspect ratio affects neither the nature of the fluid flow nor the number of convective cells.However,the extension of the circulation cells increases with this parameter.Moreover,the cavities with a large aspect ratio lead to significant reductions in the heat transfer through the hollow block,these reductions reaching approximately 14%.

Analysis of Heat Transfer Phenomena inside Concrete Hollow Blocks

During both hot and cold seasons,masonry walls play an important role in the thermal performance between the interior and the exterior of occupied spaces.It is thus essential to analyze the thermal behavior at the hollow block’s level in order to better understand the temperature and heat flux distribution in its structure and potentially limit as much as possible the heat transfer through the block.In this scope,this paper offers an experimental and numerical in-depth analysis of heat transfer phenomena inside a hollow block using a dedicated experimental setup including a well-insulated reference box and several thermocouples and fluxmeters distributed at the boundaries and inside the hollow block.The block was then numerically 3D modelled and simulated using COMSOL Multiphysics under the same conditions,properties,and dimensions as the experimentally tested block.The comparison between the numerical and experimental results provides very satisfactory results with relative difference of less than 4%for the computed thermal resistance.

Coupled Conductive-Convective-Radiative Heat Transfer in Hollow Blocks with Two Air Cells in the Vertical Direction Subjected to an Incident Solar Flux

This work presents the results of a set of steady-state numerical simulations about heat transfer in hollow blocks in the presence of coupled natural convection,conduction and radiation.Blocks with two air cells deep in the vertical direction and three identical cavities in the horizontal direction are considered(typically used for building ceilings).Moreover,their outside horizontal surface is subjected to an incident solar flux and outdoor environment temperature while the inside surface is exposed to typical indoor environment conditions.The flows are considered laminar and two-dimensional over the whole range of parameters examined.The conservation equations are solved by means of a finite difference method based on the control volumes approach,relying on the SIMPLE algorithm for what concerns the coupling of pressure and velocity.The effects of the number of cells in the horizontal direction and the thermal conductivity on the heat transfer through the alveolar structure have been investigated.The results show that the number of holes has a significant impact on the value of the overall heat flux through the considered structure.

Portland Cement-Residues-Polymers Composites and Its Application to the Hollow Blocks Manufacturing

Agricultural wastes and sawdust combined with cement matrix in the manufacture of building elements has been practiced with success in developed countries. In this study, sawdust from wood species (Pinus caribaea and Eucalyptus grandis) and an agricultural waste—rice husk (Oriza sativa) were combined with Portland cement type V (high initial strength), modified by polymer styrene-butadiene (SBR) addition. Hollow blocks produced with Eucalyptus grandis and rice husk residues showed better compressive strength;however, those produced with residues derived from Pinus caribaea presented non-satisfactory results, due to the particle size that was used.

Determination of the inner forms of hollow blocks containing phase-changing material for different climate regions

Hollow blocks are used widely in buildings for their lightweight construction and high thermal resistance charac-teristics.When used with a phase change material(PCM),these blocks can reduce the heating and cooling loads of buildings compared to conventional hollow blocks.However,it is essential that the block inner forms and PCMs should be selected based on climate conditions.In this study,hollow blocks containing PCM in different climate types are thermally analysed.In the first step,ten different formed blocks are thermally analysed.In these blocks,the effects of hollow ratio(HR),inner form,and the number of cavities on heat flux and temperature distribution are investigated.The inner form of the hollow block with the least heat flux is determined in this step.The second step consists of optimization for the PCM melting temperature and layer thickness for the different provinces.The optimization results are evaluated on a building in terms of primary energy consumption and global costs.The best performing locations of the PCMs within the block are defined for all provinces in the last step.The results of the study are discussed in terms of the block surface temperatures and liquid fraction.The best PCM locations are found close to the block’s centerline in hot and warm climates and close to the indoor side in cold climates.

灌孔配筋混凝土模壳砌块基础竖向承载性能试验研究与分析

灌孔配筋混凝土模壳砌块基础具有免支模、整体性好、易施工等优点,为了研究其竖向承载性能和失效破坏模式,通过试验和数值分析研究了配筋方式、试件高度、侧向土压力等因素的影响。结果表明:模壳砌块参与灌孔配筋混凝土模壳砌块基础受力,其在失效破坏时外围剥落、内部横肋可被灌孔混凝土有效约束;内置箍筋能显著提高试件开裂荷载并改善变形性能,但对竖向极限承载力无显著影响,失效时箍筋呈受压屈曲灯笼状外鼓;试件高度增加即高厚比增加,竖向极限承载力小幅下降(最大降幅5.35%);侧向土压力对无箍筋试验组的竖向承载性能无显著影响,但其与内置箍筋会形成双重约束作用并显著改善内置箍筋基础的竖向承载性能。GB/T 50003—2011《砌体结构设计规范》适用于灌孔配筋混凝土模壳砌块基础竖向极限承载力的计算,建立的有限元模型分析结果可靠,可为工程应用或同类研究提供参考。

相变蓄能空心砌块体系热性能测试与构造分析

本研究建立了墙体构件动态热性能测试试验台,采用(PCM)PX-27、RT-27这两种常用的相变材料,与典型混凝土空心砌块相结合的方式进行测试分析。各墙体在我国夏季西(东)向墙、南向墙和北向墙的典型室外综合温度条件下分别进行了测试。结果表明,墙体的中部和内部区域通常是放置PCM的合适位置;只有当相变总潜热足够高时(试验中高于251.93 kJ),墙体的外侧成为PCM的最佳位置。此外,保温层主要决定了墙体热流的平均水平,在一定程度上降低了内表面温度和热流的振幅;PCM不仅对温度和热流振幅有较大程度的衰减,而且显著提高了墙体的延迟时间。

中国现代早期砖拱壳历史遗产之建造组织方式研究——1958年重建工大型空心砌块筒拱厂房设计建造一体化实验回顾

揭示节约“三材”约束条件下,重庆建筑工程学院师生探索设计、施工一体化的快速施工方式,是教学与生产实践结合的一次有益尝试。基于历史文献研究、三维图式、口述采访的工作方法,从设计过程、施工组织、机械工具、人员协调等多方面回顾了1958年重建工师生使用大型空心砌块筒拱技术承建江陵厂厂房的史实。它是新中国早期砖薄壳结构谱系中的重要类型,对当下的建造教学也具有参考价值。

熔纺-选择性溶胀制备嵌段共聚物多通道中空纤维膜

嵌段共聚物的熔纺-选择性溶胀是一种制备中空纤维膜的清洁生产工艺。本文提出构建多通道构型来提升嵌段共聚物中空纤维膜的性能,通过熔纺-拉伸-选择性溶胀,制备了具有3通道和7通道的聚砜/聚乙二醇嵌段共聚物中空纤维膜,研究了通道数、溶胀条件和拉伸行为对中空纤维膜微观结构、渗透性、截留率和耐压性的影响。由于壁厚的相互支撑作用,多通道中空纤维膜的渗透性和耐压性能都比单通道中空纤维膜有所提高,且可通过拉伸和溶胀条件实现膜性能在较大范围内的高效调控。在适当的通道数和拉伸比下,拉伸后的三通道中空纤维膜的通量比单通道中空纤维膜高20倍。此工作对使用清洁方法制备高性能的中空纤维膜具有重要意义。

再生混凝土空心砌块墙体抗压性能试验研究

为分析再生混凝土空心砌块墙体的抗压性能,文中对轴心抗压以及偏心受压条件下再生混凝土的破坏模式、承载特性以及墙体的平面变形进行试验研究。结果表明,轴心受压作用下高厚比7.5的试件比高厚比5.4的试件开裂荷载低14.3%;破坏荷载低7.1%。偏心受压荷载作用下高厚比7.5的试件比轴心受压荷载作用下高厚比5.4的试件开裂荷载低21.4%,破坏荷载低4.1%。相同加载模式下,墙体高厚比越高,其承载荷载越低;偏心荷载作用下墙体的承载性能同样开始降低。

半干法生产磷石膏空心砌块的性能研究

为推进磷石膏的大宗利用,自主研发了半干法用于生产磷石膏空心砌块,对比了半干法与浇注法的工艺,介绍了半干法的工艺、原理及产品性能。研究显示,采用半干法制备的磷石膏空心砌块脱模时的初始含水率为23.06%,远低于浇注法生产的砌块,且第6 d即处于干燥状态;断裂荷载和抗压强度在下线码垛时即符合JC/T 698—2010《石膏砌块》的要求,24 h内线性提高,24~72 h因返潮略有降低,此后至144 h平缓提高并基本稳定。产品应在下线码垛至24 h内或第3 d后装车运送用户,不需要晾晒或烘干;夏季生产在脱模后2 h内应适当喷淋,生产时可适当添加二水石膏(废弃产品粉碎料),应在产品下线第3 d后进行砌筑。

钛石膏空心砌块力学性能试验及水化机理分析

以钛石膏(TG)和脱硫石膏(FGD)作为主要原料制备复合钛石膏,掺加石膏增强剂(GRA),制作钛石膏空心砌块。研究了GRA对复合钛石膏早期强度与凝结时间的影响以及钛石膏空心砌块的力学性能及微观结构。结果表明:当GRA掺量为0.09%,复合钛石膏符合GB/T 9776—2008《建筑石膏》2.0等级要求。按m(TG):m(FGD):m(GRA)=5000:5000:9制备钛石膏空心砌块,断裂荷载平均值为4122 kN,抗压强度平均值为3.1 MPa,表观密度为591 kg/m^(3),软化系数为0.36。钛石膏空心砌块的水化产物主要为棒状的二水石膏晶体,内部非结晶态铁杂质降低了钛石膏空心砌块的强度。

不同条件下再生混凝土掺聚苯颗粒空心砌块力学性能研究

为探究掺聚苯颗粒空心砌块在各条件下的力学性能情况,根据不同配合比分别制作标准空心砌块并测定密度、材料强度,探究空心砌块保温隔热性能。研究结果表明:再生细骨料取代率和聚苯颗粒取代率的提升会导致空心砌块抗压强度降低,但抗压强度水平仍满足非承重墙体要求;掺聚苯颗粒后的再生混凝土密度下降,自重减轻,保温隔热性能提升。综合考虑认为,再生细骨料取代率、粗骨料取代率和聚苯颗粒取代率分别取50%、100%和15%时,材料能够在满足保温隔热性能的基础上保障结构强度。

单因子评价法下的陶粒混凝土空心砌块节能性分析

近年来,建筑行业一直在寻求行业可持续发展的道路上,绿色建筑材料的提出给建筑行业带来了新的发展机遇。目前,对于绿色建筑材料的标准在世界范围内愈发的全面和完善,各地对绿色建筑材料的使用率也稳步上升,更多的建设单位在建筑材料选择上开始选择使用绿色建材,人们对绿色建材的接受程度和认知日益提高。绿色建材的评价体系是评价材料是否满足绿色建材的重要因素,通过对材料的各项指标进行比对、测试等从而确定材料是否达标。本文从绿色建材的发展角度出发,利用单因子评价法对绿色建筑材料陶粒混凝土空心砌块进行节能性分析,根据实际案例的使用情况判别该材料的应用状况,阐述该绿色建材的应用效果,助力绿色建筑的长效发展。

承重型横孔连锁混凝土空心砌块砌体抗压性能研究

砌块结构是常用的建筑结构形式之一.承重型横孔连锁混凝土空心砌块的技术门槛较低,可以在多种建筑施工场景中使用,为了保证其应用后的稳定性,分析了砌体抗压性能.选择QT-250、QH-250、QH-300三种类型砌块作为试件,对照试件的生产尺寸,设定了砌筑砂浆的三种强度类型.采用试压机作为加载受压设备,对砌块砌体进行加压测试,并记录承压数据,以此来分析抗压强度.不同类型试件的抗压强度测试结果表明:不同砌块类型的抗压强度不同,当砂浆强度等级为ER-15、砌块类型为QT-250时,混凝土空心砌体的抗压强度最佳.

方钢管再生混凝土框架-再生空心砌块填充墙抗震性能试验研究

为研究方钢管再生混凝土框架-再生空心砌块填充墙的抗震性能,以有无填充墙为变化参数,进行了2榀框架试件的低周反复加载试验。结果表明:方钢管再生混凝土框架破坏过程为RAC梁破坏→柱脚鼓曲,增设填充墙后,其破坏过程为填充墙破坏→RAC梁破坏→柱脚鼓曲。方钢管再生混凝土框架-再生砌块填充墙试件滞回曲线呈饱满梭形,其在受力过程中经历了弹性、弹塑性及破坏阶段。方钢管再生混凝土框架-再生砌块填充墙试件可满足结构正常使用阶段的变形要求,并具有良好的抗倒塌能力。相较于无填充墙试件,有填充墙试件在正、负向的承载能力分别提升了9.0%与-7.8%,在正、负向的延性系数分别提升了15.6%与35.7%。墙体存在可将框架初始刚度提升1.06倍,但对其残余刚度影响不大。墙体破坏前,其存在可提升框架耗能性能;墙体破坏后,其存在反而会抑制框架耗能性能。

烧结页岩空心砖与加气混凝土砌块碳排放对比

提出了烧结页岩空心砖与加气混凝土砌块生产应用全过程的碳排放计算模型;通过示例分析测算表明,烧结页岩空心砖(1000 kg/m^(3)级)与加气混凝土砌块(B06级)产品生产应用全过程的碳排放量分别为3.4893、2.7924 tCO_(2)/万块标砖,烧结页岩空心砖比加气混凝土砌块碳排放量高24.9%;烧结页岩空心砖碳排放量最大的环节为产品生产,占比87.8%,加气混凝土砌块碳排放量最大的环节为原材料获取,占比75.4%。

混凝土模块井在港口物流园区排水构筑物的应用

港口物流园区工程项目具有施工周期短、施工成本要求低和重载交通流量大等特点,港口物流园区排水构筑物结构一般采用现浇钢筋混凝土结构方案以满足使用要求,但存在工期较长,成本较高等问题,而混凝土模块井结构具有绿色环保、施工周期短、施工成本低等优点,可以解决上述问题。结合港口物流园区工程实例及港区排水构筑物结构设计经验,通过分析混凝土模块井的特点、计算理论及结构体系,对原规范图集的混凝土模块井结构进行灌芯插筋结构改进,提出了适合重载交通条件下港口物流园区排水构筑物的混凝土模块井结构形式。该结构满足港口物流园区重载交通需求,工期及成本也有减少,并总结其施工过程中的关键技术难点,为混凝土模块井在类似工程中的应用提供借鉴。

传热路径嵌入保温材料的空心砌块传热性能与结构强度研究

设计了一种新型的空心砌块,在空心砌块的关键传热路径上嵌入4块60mm×10mm和2块60mm×8mm矩形EPS保温材料,以提高砌块保温性能,并利用有限元数值模拟软件研究嵌入保温材料对空心砌块传热性能和结构强度的影响。结果表明:在空心砌块关键传热路径节点处嵌入保温材料能显著降低砌块的平均传热系数,降低幅度达13.47%;将空心砌块嵌入材料的边角半径从0mm增加到5mm,砌块抗压强度增幅可达4.02%。