建议尽快制定各种回弹仪检定规程

一、回弹仪最大的生产国、使用国理应有完善的检定规程 按检测对象不同,回弹仪分为高强回弹仪、混凝土回弹仪、测砖回弹仪、砂浆回弹仪等。20世纪60年代我国开始生产、使用标称能量为2.207J的用于检测混凝土抗压强度的回弹仪,随后又相继开发出了用于检测黏土砖、砌体砂浆抗压强度和高强混凝土抗压强度的专用回弹仪。     

橡胶骨料碱性砂浆孔结构与抗压性能非线性回归模型

废旧轮胎的弃置会导致诸多环境问题，而粉碎制得的橡胶粉可在建筑砂浆中替代细骨料。砂浆中橡胶骨料的掺量和粒径是橡胶混凝土强度的主要影响因素，利用碱激发矿渣材料可替代普通硅酸盐水泥，提升砂浆的环境友好性。研究多因素耦合作用对橡胶骨料砂浆抗压性能的影响，通过测试砂浆的抗压强度，对试验结果进行显著性分析及多元非线性回归，建立了多因素与砂浆抗压强度的多元非线性回归模型。对砂浆试样进行细观孔隙测量和SEM表征，探究橡胶骨料对砂浆抗压强度的劣化机制。结果表明：砂浆中橡胶骨料掺量的提升会造成砂浆抗压强度的下降，40vol%骨料替代率下碱激发类砂浆抗压强度均值相比对照组降低了49.93%，硅酸盐类降低了66.62%；在碱激发类砂浆的高碱性环境下，使用0.38 mm粒径橡胶骨料的砂浆抗压强度均值为对照组的69.65%，取得试验组中最优值；而在硅酸盐类砂浆的低碱性环境中，随着橡胶骨料粒径的减小，砂浆抗压强度均值由对照组的61.46%降至37.98%。     

贯入仪的保养与调修

砌筑砂浆的抗压强度是影响砌体强度的重要因素．在建筑工程施工中．由于对砌体砂浆的质量不够重视．发生建筑事故的现象时有发生。因此．必须对砌体中的砂浆强度进行检测。保证贯人法检测混凝土强度准确度的前提是确定贯入深度与砌体砂浆的回归方程。精确的贯入深度需要精确的贯入力。     

两种乳胶粉对三元胶凝体系饰面砂浆性能的影响

研究了乙烯-醋酸乙烯共聚物(乳胶粉A)及乙烯-醋酸乙烯-丙烯酸酯三元共聚物(乳胶粉B)对铝酸盐水泥-硅酸盐水泥-半水石膏三元体系饰面砂浆抗泛白性、耐沾污性、吸水性及力学性能的影响。结果表明,乳胶粉B对各项性能的作用效果均优于乳胶粉A。乳胶粉B掺量为0~6%时砂浆7d泛白等级为0级;适当掺量的乳胶粉B能改善砂浆的耐沾污性,在其掺量大于等于12%时,砂浆的耐沾污性优于未掺乳胶粉的砂浆;乳胶粉A的掺量为3%~9%时,乳胶粉B掺量为3%~15%时可改善砂浆的吸水性;乳胶粉A能提高砂浆抗折强度及拉伸粘结强度,但会降低砂浆的抗压强度,而乳胶粉B能同时提高砂浆的抗折强度、抗压强度及拉伸粘结强度。     

气瓶安全与检验问答(十)

问 :气瓶不再允许改装使用了吗 ?答 :据国家质量技术监督局 2 0 0 0年 1 2月 31日颁发、 2 0 0 1年 7月 1日生效的《气瓶安全监察规程》第 1 7条规定 :“气瓶必须专用。只允许充装与钢印标记一致的介质 ,不得改装使用。”把原规程第61条规定的“对少数尚有使用价值的气瓶 ,允许改装后降压使用”删去。同时还把原规程第 58条第 5款“气瓶改装”的职责删去。由此可见国家已不再允许气瓶改装使用了。这项规定非常符合国内在用气瓶的使用状况 ,随意进行气瓶改装之风一日不刹 ,由此引发的气瓶爆炸事故就一日得不到扼制。问 :有关部门在检查我公司…     

碱矿渣陶粒混凝土砌块砌体受压本构关系

为考察碱矿渣陶粒混凝土砌块砌体的受压本构关系及基本力学性能,完成了126个用碱矿渣陶砂砂浆和碱矿渣陶粒混凝土砌块砌筑的砌体试件的轴心抗压试验。研究结果表明:当砌块抗压强度和砌筑砂浆抗压强度相同时,由于碱矿渣陶砂砂浆收缩大,该类砌体的峰值压应变、极限压应变均低于普通混凝土砌块砌体。建立了以砌体抗压强度、砌块抗压强度和砌筑砂浆抗压强度为自变量的这类新型砌体峰值压应变、极限压应变以及弹性模量计算公式。     

钢纤维砂浆空心砖砌体抗压强度试验研究

本文通过对１８个空心砖砌体抗压试件的试验研究,对比了普通砂浆砌筑的抗压试件、钢纤维砂浆砌筑的抗压试件和用两种砂浆一定间一皮砌筑的抗压试件的抗压强度和破坏形态的异同,表明用钢纤维砂浆砌筑的体抗压强度可提高约１５％。     

计量检定规程的法律地位

《计量法》第十条明确规定 :计量检定必须按照国家计量检定系统表进行。计量检定必须执行计量检定规程。所以计量检定规程是计量检定人员开展计量检定工作的主要依据 ,检定规程的有效性直接关系到检定数据是否具有法律效力。但是目前我们执行的水表检定规程却出现了真空。1 985年发布实施的水表及其试验装置ＪＪＧ1 62 -85检定规程 ,原是水表和水表试验装置二合一的规程 ,现在为了进一步完善检定行为 ,已经把水表和水表试验装置分开 ,水表试验装置归入新规程ＪＪＧ1 64-2 0 0 0液体流量标准装置。检定规程ＪＪＧ1 64-2 0 0 0已于 2 0 0 0年 …     

砂浆力学性能与其断口分形维数关系的研究

对4种不同配比、3种不同养护期的砂浆的抗压性能差异性进行了检测;用投影覆盖法编程计算了砂浆断面的表面分形维数,并考察了它与抗压强度之间的关系。结果表明,不同的配比、不同的养护期均会对砂浆的抗压强度产生影响,由实验结果分析得出最优配比和最优养护期;砂浆断口的分形维数介于2.7~3,相关系数均大于0.9,分形维数与抗压强度呈正相关关系,验证了用分形理论分析建筑砂浆力学性能的可行性。     

经表面处理的钢纤维在砂浆中耐蚀性的研究

将国产新型钢纤维进行无机复合表面处理（A处理）或高分子化合物表面处理（B处理），使砂浆中的钢纤维耐氯离子腐蚀的能力在不同的PH值环境下均得到明显提高。其中A处理的钢纤维在砂浆中耐蚀性最佳，大约是未处理钢纤维在砂浆中耐蚀时间的2．9～3．4倍；B处理的钢纤维在砂浆中的耐蚀性次之，大约是未处理钢纤维在砂浆中耐蚀时间的1．5～2．O倍。表面防蚀处理还增加了钢纤维砂浆的抗折、抗压强度，从而为国产新型钢纤维增强砂浆在含氯离子等的腐蚀环境中的应用创造了条件。     

集料-基体协调性对混凝土强度影响的试验研究

研究了集料-基体两相协调性对混凝土强度的影响.试验研究了碎石、钢、砂浆、陶粒和加气混凝土5种强度差异较大的集料在3种不同强度等级基体下的混凝土抗压强度及其发展规律.研究结果表明粗集料和砂浆基体对混凝土抗压强度影响十分显著.在基体强度一定时,粗集料强度达到一定程度后再增加对提高混凝土强度作用不大;当集料强度比基体强度低时,单纯通过增大基体强度来提高混凝土强度效果不明显;集料与基体的差异对强度发展规律和混凝土绝对强度有很大影响.只有在两者相互协调的基础上,才能充分发挥集料和基体的作用.     

Variation in mechanical properties of natural and recycled aggregate concrete as related to the strength of their binding mortar

Experimental work was performed to study the effect of binding mortar strength on the mechanical properties of recycled natural aggregate concrete mixes as well as reference corresponding natural aggregate concrete mixes. The moduli of elasticity of both NAC and RAC were found to be higher than that of corresponding mortar by about 40% and 10% respectively, for all compressive strengths investigated. It was possible to reach compressive strength for RAC of 53.5 MPa. The ratios of compressive strength of NAC or RAC to that of mortar varied between (1.05–1.56) and (1.02–1.26) respectively, these ratios decreased with the increase in compressive strength. Also from the results of compressive strength, it was found that the ratios cylinder/cube compressive strengths of RAC and mortar were smaller than those of NAC. The ranges of values obtained were (0.71–0.84) and (0.69–0.75) for RAC and mortar respectively, while for NAC this ratio ranged between (0.81–0.92), these values were obtained for compressive strengths ranging between 15 to 55 MPa. It was found that it is better to relate the cylinder/cube strength ratio to the modulus of elasticity of the concrete or mortar rather than to its compressive strength. The flexural strength showed an opposite trend, the ratios of NAC and RAC to that of mortar ranged between (0.72–0.95)% and (0.61–0.80)% respectively. These ratios increased with the decrease in compressive strength of mortars. On the other hand, the splitting tensile strength of NAC was higher than that of RAC and mortar for all strength levels investigated. The ratio of NAC to mortar splitting tensile strength ranged between (1.13–1.69), while this ratio for RAC ranged between (0.87–1.36). Finally, several regressions were developed that can relate the mechanical properties of the three materials investigated.     

聚合物水泥砂浆的力学性能

本文采用美国产 MTS试验机 ,分别研究了掺聚醋酸乙烯水泥砂浆的轴拉和轴压应力 -应变关系及抗弯性能。试验结果表明 ,随着聚醋酸乙烯的掺入 ,砂浆的轴压强度和弹性模量显著下降 ,但极限应变却明显增大 ;砂浆的轴拉强度和抗弯强度均略有提高 ,而极限应变、拉压强度比和弯压强度比则显著增加。因此 ,掺入聚醋酸乙烯能有效改善砂浆的变形力学性能。根据 12年龄期的粘结抗弯强度试验结果 ,聚醋酸乙烯砂浆不但具有优良的粘结性能 ,还具有良好的耐久性 ,可广泛用于新老混凝土的粘结、修补及结构加固中的钢板粘贴和表面粉刷等。     

再生橡胶颗粒对自流平砂浆力学性能影响的试验研究

分别研究了再生橡胶颗粒掺量、颗粒粒径及乳化沥青复合对自流平砂浆力学强度、折压比等力学性能参数的影响规律;提出了再生橡胶颗粒在水泥基材料体系中的三大作用效应,并分析了相应的影响机理。结果表明,再生橡胶颗粒掺量、颗粒粒径对自流平砂浆的抗折强度、抗压强度以及折压比存在较为显著的影响,当橡胶颗粒等量取代骨料体积15%时,体系的折压比达到最大,且橡胶颗粒与乳化沥青复掺后可进一步显著提高试件的折压比;与普通振捣密实成型砂浆体系相比,橡胶颗粒对自流平砂浆力学强度的影响未有明显的不同。     

Influence of shear bond strength on compressive strength and stress–strain characteristics of masonry

The paper is focused on shear bond strength–masonry compressive strength relationships and the influence of bond strength on stress–strain characteristics of masonry using soil–cement blocks and cement–lime mortar. Methods of enhancing shear bond strength of masonry couplets without altering the strength and modulus of masonry unit and the mortar are discussed in detail. Application of surface coatings and manipulation of surface texture of the masonry unit resulted in 3–4 times increase in shear bond strength. After adopting various bond enhancing techniques masonry prism strength and stress–strain relations were obtained for the three cases of masonry unit modulus to mortar modulus ratio of one, less than one and greater than one. Major conclusions of this extensive experimental study are: (1) when the masonry unit modulus is less than that of the mortar, masonry compressive strength increases as the bond strength increases and the relationship between masonry compressive strength and the bond strength is linear and (2) shear bond strength influences modulus of masonry depending upon relative stiffness of the masonry unit and mortar.     

聚乙烯醇纤维增强偏高岭土-水硬石灰砂浆材料性能的研究

针对偏高岭土-水硬石灰砂浆材料抗拉强度低、极限延伸率小、性脆的问题,为了提高其韧性和稳定性,增强其抗裂能力,设计并制备了聚乙烯醇(PVA)纤维掺杂偏高岭土-水硬石灰砂浆材料,开展了PVA纤维不同掺量、不同长度下偏高岭土-水硬石灰砂浆材料收缩率、波速、抗压强度、抗折强度及劈裂抗拉强度的试验研究,通过扫描电镜观察分析了PVA纤维在偏高岭土-水硬石灰砂浆材料中的微观作用机理。结果表明:PVA纤维改变了偏高岭土-水硬石灰砂浆的收缩率和内部结构。试样的抗折强度和劈裂抗拉强度随着纤维增加而增大,抗压强度会在纤维长度一定时随着掺量的增多而降低。PVA纤维对砂浆材料整体性有明显改善,受压后仍能够保持着较好的原样性,纤维和砂浆基体之间产生了机械铆合作用,具有较好黏结性。     

低强度砂浆灌孔砌块砌体抗压性能试验研究

为了研究低强度砂浆对灌孔砌块砌体抗压性能的影响, 该文通过9 个采用石灰砂浆砌筑的灌孔砌块砌体的抗压试验, 对其抗压破坏形态、开裂荷载、极限荷载及变形能力进行了分析, 提出了适用于砂浆强度很低的灌孔砌块砌体的抗压强度计算公式。分析表明:低强度砂浆砌块砌体的初裂荷载与极限荷载之比较小, 而开裂荷载过低将会对砌体房屋的耐久性产生不利影响, 因此, 该文认为在进行灌孔砌块砌体的设计和施工时, 砂浆的强度应得到保证, 不能过低。     

Effect of strain rate and saturation on uniaxial dynamic compressive behaviours of mortar

The effect of moisture content on the compressive mechanical behaviours of cement mortar under different high strain rates is studied in this paper. The rapid impact testing, i.e. the strain rates of 80, 100, 150, 200 and 250 s^? 1 by Split Hopkinson pressure bar, on number of specimens with special water/cement ratio of 0.50 and saturations as 0%, 25%, 50%, 75% and 100%, respectively, was executed. The dynamic compressive behaviours were analysed in terms of the maximum stresses, elastic modulus, critical strain at maximum stresses and ultimate strains at failure. Results indicated that similarity existed in the shape of strain–stress curves of mortars with different moisture subjected to different strain rates of impact loading, i.e. the upward section presented bilinear characteristics, while the descending stage was almost linear. As strain rate increases, the dynamic compressive strength, elastic modulus and critical strain at maximum stress increase which can be ascribed to the dynamic fracture effect and the microscope inertia effect. Besides, it was shown that desiccation provokes an increase in mortar strength and deformation behaviour of the studied mortar with different saturation caused by capillary depression and microcracking. Drying effect has to be considered in modelling of the coupling between desiccation and mechanical behaviour of the mortar. Finally, the multi-parametric statistical analysis of water content and strain rate on the mechanical behaviours of cement mortar subjected to dynamic loading is detailed.