Tensile Strength Characteristics of GFRP Bars in Concrete Beams with Work Cracks under Sustained Loading and Severe Environments

To investigate the effect of different environmental conditions of GFRP bars in concrete beams with work cracks subjected to sustained loads, the beams were exposed in indoor, freeze/thaw cycles and immersed in alkaline solution at elevated temperature. The bars were carefully extracted from the beams and tested in order to evaluate residual tensile properties. The results show that the tensile strength decreased significantly in the highly aggressive conditions but not in the natural conditions. The effect of GFRP bars casting in concrete beams demonstrated approximately 2.5% decrease of tensile strength caused by pore water environment in concrete beams on basis of those of the original bars. The effect of sustained loading plus work cracks demonstrated about 10.5% tensile strength decrease on basis of those of the bars only casted in concrete beams. The effect of environments under sustained loading plus work cracks demonstrated about 17% tensile strength decrease caused by a saturated solution of Ca（OH）2 and 60-2 ℃ tap water （pH=12-13） and about 8% tensile strength decrease caused by freezing and thawing cycle （F/T）, both on basis of those of the bars of the indoor beams only under sustained loading plus work cracks. The results demonstrate the effects of the tensile strengths under different environmental conditions of GFRP bars in concrete beams with work cracks subjected to sustained loads.

Developing Sustainable High Strength Concrete Mixtures Using Local Materials and Recycled Concrete

This study presents the development of high strength concrete (HSC) that has been made more sustainable by using both local materials from central Texas and recycled concrete aggregate (RCA), which has also been obtained locally. The developed mixtures were proportioned with local constituents to increase the sustainable impact of the material by reducing emissions due to shipping as well as to make HSC more affordable to a wider variety of applications. The specific constituents were: limestone, dolomite, manufactured sand (limestone), locally available Type I/II cement, silica fume, and recycled concrete aggregate, which was obtained from a local recycler which obtains their product from local demolition. Multiple variables were investigated, such as the aggregate type and size, concrete age (7, 14, and 28-days), the curing regimen, and the water-to-cement ratio (w/c) to optimize a HSC mixture that used local materials. This systematic development revealed that heat curing the specimens in a water bath at 50℃ (122oF) after demolding and then dry curing at 200℃ (392oF) two days before testing with a w/c of 0.28 at 28-days produced the highest compressive strengths. Once an optimum HSC mixture was identified a partial replacement of the coarse aggregate with RCA was completed at 10%, 20%, and 30%. The results showed a loss in compressive strength with an increase in RCA replacement percentages, with the highest strength being approximately 93.0 MPa (13,484 psi) at 28-days for the 10% RCA replacement. The lowest strength obtained from an RCA-HSC mixture was approximately 72.9 (MPa) (10,576 psi) at 7-days. The compressive strengths obtained from the HSC mixtures containing RCA developed in this study are comparable to HSC strengths presented in the literature. Developing this innovative material with local materials and RCA ultimately produces a novel sustainable construction material, reduces the costs, and produces mechanical performance similar to prepackaged, commercially, available construction building materials.

中国地理学者“可持续”研究的文献分析(1994—2021)

地理学研究可持续发展旨在构建人与自然命运共同体,实现人类社会的永续发展.该文依托CNKI数据库、读秀资源库以及Web of Science数据库,限定主题词为“可持续”“可持续发展”和“可持续性”,采用CiteSpace软件对1994—2021年中国地理学者“可持续”研究的核心力量、重点区域与重要领域进行文献计量分析,结果表明:1)中国地理学者“可持续”研究的过程可分为快速兴起(1994—2001年)、稳定发展(2002—2011年)和整固深化(2012—2021年)三个阶段.2)中国开展“可持续”研究的地理学者多达624位,主要是自然地理学者和人文地理学者,研究机构多达258个,主要是中国科学院所属地理单位,机构间合作具有空间邻近性,机构空间分布具有东、中、西梯度分异性;中国地理学者“可持续”研究的对象区域以地方行政区域为主,服务国家重大区域发展战略的特色鲜明.3)中国地理学者“可持续”研究的重点领域有资源可持续利用、生态环境保护与建设、农业可持续发展、旅游可持续发展、可持续发展教育、可持续发展伦理、消除贫困与可持续生计、区域人地关系协调、城市可持续发展、农村可持续发展、区域可持续发展战略、区域可持续发展评价等.4)未来中国地理学者的“可持续”研究应在可持续发展专业人才培养、可持续发展理论体系完善、可持续发展研究领域拓展、可持续发展服务能力提升等方面下功夫.

持续荷载作用对GFRP筋-海工混凝土黏结性能的影响

为研究持续荷载作用下GFRP筋与海工混凝土间的黏结性能,设计制作了16个GFRP筋-海工混凝土梁式黏结性能试件,在不同持续荷载等级(0%P_(u),25%P_(u),45%P_(u),65%P_(u))作用下进行了为期120 d的持载试验。对持载过程中GFRP筋-海工混凝土间的瞬时滑移及时变滑移进行了测试分析,并建立不同持载等级作用下的GFRP筋-海工混凝土间时变滑移模型;对比分析了持续荷载作用下GFRP筋与混凝土和普通钢筋与混凝土间的滑移量大小及变化规律。试验结果表明:瞬时滑移量随着持载等级的提高而增大,加载端滑移量大于自由端滑移量;时变滑移量随时间呈非线性增长,前期增长较快,后期滑移量逐渐趋于稳定;两种筋材与混凝土间的时变滑移变化规律相似,但GFRP筋与混凝土间的滑移量要远大于普通钢筋与混凝土间的滑移量。

Studies on Strength and Related Properties of Concrete Incorporating Aggregates from Demolished Wastes: Part 1—A Global Perspective

The present study addresses the global concern of sustainability in building and construction engineering and how to an extent the use of demolished aggregate wastes in concrete production contributes towards ameliorating or minimizing the problem. The influence of demolished aggregate waste on the mechanical strength and stiffness of concrete are examined from the standpoint of the compressive, split tensile and flexural strengths as well as the modulus of elasticity of the concrete. In this respect the research carried out by previous investigators are noted. It is observed that in the Southern African region in general and Botswana in particular there is a paucity of studies on the subject, and consequently, it is concluded that further investigations need to be conducted utilizing aggregates derived from local wastes or sources.

高性能混凝土在交通工程中的应用

高性能混凝土(HPC)正重新定义交通工程的质量和可靠性标准。在北京大兴国际机场和上海杨浦大桥等关键项目中,HPC不仅证明了自身作为一种革命性材料的价值,而且展示了其在提升工程结构强度、耐久性和环境适应性方面的显著优势。这些特性不仅降低了长期维护成本,还为现代交通基础设施的设计和建设提供了新的可能性,推动了整个行业向着更经济、环保和可持续的方向发展。HPC的成功应用案例突出了其在应对现代工程挑战中的关键作用,预示着其在未来建筑材料领域的广泛应用前景。

Developing High Strength Pervious Concrete Mixtures with Local Materials

This study focuses on developing pervious concrete mixtures that have higher compressive strengths than conventional pervious concrete. This study also focuses on producing high strength pervious concrete that is also made with locally available materials. The study focused on four aspects of pervious concrete to produce high compressive strengths. These parameters were the effect of the coarse aggregate (type and size), the compaction of the test specimens, the effect of the w/c along with superplasticizers, and lastly the effect of silica fume. This study was completed parametrically in order to isolate each variable in order to see its individual affect. Once an optimum performance was obtained from one variable the best performing mixture was used for the next variable testing. This method allowed for the highest performing mixture to be obtained from each of the investigated variables. The results showed that high strength pervious concrete made with local aggregates, without polymers, and without fibers can be produced in the range of 15.44 MPa - 21.63 MPa. A porosity range 19.1% - 32.9% with a percolation rate range of 5.8 mm/s - 1.9 mm/s was also achieved, with a porosity of 19.4% and percolation rate of 2.6 mm/s for the highest performing mixture.

Study on Comparison between Enzyme Wash and Bleach Wash (Traditional vs. Sustainable Washing Machine) the Physical and Color Fastness to Rubbing Properties of Denim Garments

This study focuses on comparison between Enzyme Wash and Bleach Wash (Traditional vs. Sustainable Washing Machine) the physical and color fastness to rubbing properties of denim garments. For this experiment indigo dyed cotton denim garments (trousers) were chosen which were 98% cotton and 2% spandex and processed by enzyme with the concentration of 2 g/l, and the temperature of 45°C. In another work, enzyme treated denim garments were used for bleach wash with the concentration of 2 g/l, temperature 45°C and those samples have been processed by traditional and sustainable washing machine. After completing process, the sample properties have been compared like rubbing, tearing and tensile properties. After comparing result the color fastness to rubbing of enzyme wash was poor in traditional and sustainable machine and tensile strength, tearing strength properties down in traditional machine but the color fastness to rubbing of bleach wash was good in sustainable machine than traditional machine and a little bit lesser tensile and tearing properties in sustainable process.

Sustainable Construction—High Performance Concrete Containing Limestone Dust as Filler

Massive amounts of limestone waste are produced by the stone processing industry worldwide. Generally, it is believed that 60% to 70% of the stone is wasted in processing in the form of fragments, powder and slurry out of which around 30% is in the form of fine powder [1]. This waste has no beneficial usage and poses environmental hazards. Use of this waste product in the construction industry can largely reduce the amount of waste to be disposed off by the local municipalities in addition to reducing large burden on the environment. Some basic research on use of limestone dust as cement/ concrete filler?has?been carried out in the recent past but high strength/ high performance concretes have not been investigated yet [2] [3]. The concrete industry is among the largest consumer of raw materials worldwide and has been investigated for use of various types of waste materials like crushed brick, rice husk and straw ash as either aggregates for concrete or as partial cement substitutes. Use of limestone dust as filler material in concrete can consume a huge amount of this waste material which has to be disposed off otherwise, creating large burden on the environment. This experimental study aimed at evaluating the properties of high performance concretes made from Portland cement, natural aggregates and sand. Limestone dust was added by replacing sand in the percentages of 10% and 20%. Wide ranging investigations covering most aspects of mechanical behavior and permeability were carried out for various mixes for compressive strengths of 60?N/mm2, 80?N/mm2 and 100?N/mm2. Compressive strengths of concrete specimen with partial replacement of sand with 10% and 20% limestone dust as filler material for 60?N/mm2, 80N/mm2 and 100?N/mm2 were observed to be higher by about 4% to 12% than the control specimen. Flexural strengths were also observed to be higher by 12%?-?13%. Higher elastic moduli and reduced permeability were observed along with better sulphate and acid resistance. Better strengths and improved durability of such high-performance concretes make it a more acceptable material for major construction projects.

弯曲荷载作用下混凝土碳化和力学性能研究

通过混凝土四点弯曲持荷碳化试验,研究了不同持荷水平对混凝土碳化深度的影响规律,建立了考虑持荷作用的混凝土碳化深度预测模型。同时分析了荷载与碳化共同作用下混凝土抗折强度的变化规律,并基于混凝土内部孔结构特征来探讨抗折强度变化的内在机理。试验结果表明:混凝土受拉区的碳化深度随持荷水平的增加而增加,受压区的碳化深度随持荷水平的增加而减小。在持荷水平相同时,碳化时间为7 d时,碳化深度的增长速率相对较快,之后碳化深度增长的速率逐渐变缓。荷载与碳化共同作用下,混凝土抗折强度随碳化时间的增长,首先会有一定程度的下降,然后又逐渐增加。持续荷载会使混凝土内部孔隙粗化,降低混凝土的抗折强度。碳化会使混凝土内部孔结构细化,从而提高混凝土的抗折强度。

日本人口安全问题对其未来走势的影响及应对举措

日本人口减少及人口结构的重大变化使日本面临严重的人口安全问题。日本人口安全问题的基本特征为日本人口减少及少子老龄化趋势严重、生产年龄人口及劳动力严重短缺、人口过疏地区及限界村落急剧增加。日本人口安全问题已对日本国家财政及国民生活带来沉重负担,国内政局受“银发民主主义”影响趋于保守,自卫队兵员及国防安全受到影响,综合国力及国际影响力越来越削弱。日本正在通过“老龄社会对策”及“少子化社会对策”增加人口数量,改善人口年龄结构,增强人口综合素质,保障日本人口安全。同时,还力求通过采取一系列综合举措,如社会保障与税收一体化改革、构建地域综合照护体系等措施,完善社会保障制度,建设地域共生社会,缓解人口安全问题及其对未来走势的影响。

持续荷载作用下砂浆裂缝的自修复性能及其评价指标

以高吸水树脂为自修复剂,以表面裂缝愈合率(γ)和强度恢复率(η)为砂浆裂缝自修复性能的评价指标,对比研究了预裂龄期为7 d和28 d时,不同持续荷载作用对砂浆裂缝自修复性能的影响。结果表明:相较预裂龄期为28 d的砂浆组,预裂龄期为7 d的砂浆组自修复效果较好;持续压荷载下,砂浆裂缝的自修复效果较好,其η比不受荷载作用的试件分别增大3.2%(7 d预裂龄期)和9.3%(28 d预裂龄期);持续弯曲荷载和持续扭荷载作用不利于砂浆的自修复,其中持续弯曲荷载的不利影响较为显著,持续弯曲荷载作用下,其η比不受荷载作用的试件分别低43.5%(7 d预裂龄期)和47.3%(28 d预裂龄期)。微观测试表明,砂浆裂缝中的自修复产物主要是碳酸钙,且主要集中在裂缝开口位置附近,因此采用γ作为自修复评价指标有可能高估自修复效果。

加强能源公司ESG管理,打造企业新型竞争力

在实现2℃和1.5℃温控目标的全球共识下,应对气候变化成为最重要的ESG议题。由于石油、煤炭等化石能源被认为是全球变暖的最主要因素之一,所以在所有行业中,石油等化石能源上市公司面临的ESG压力巨大。我国能源公司需要加深对ESG的认识,将其作为价值管理的工具,在企业发展中运用好ESG,应对发展风险、把握战略机遇,在行业发展中抢得先机,打造新发展阶段企业新型竞争力。

亚鲁杰伊油田低温防窜水泥浆体系研究与应用

环空带压是北极地区亚鲁杰伊油田固井长期存在的一大技术难题,为此开发了适用于极地地区低温固井防窜水泥浆,该水泥浆体系具有稳定性高、流动性好、低失水、高触变、短过渡和高早强度等技术特点。现场应用1.40 g/cm^(3)漂珠低密度水泥浆作领浆,加入0.75%降失水剂RC012-04、3.0%低温促凝早强剂ALE、5%纳米增强剂RC090-01和0.40%分散剂Plast-A,水泥浆失水量为14 mL,稠化时间为188 min,浆体SPN值为1.13,水泥石的24 h抗压强度和界面胶结强度分别为9.6 MPa和3.63 MPa;1.85 g/cm^(3)尾浆中加入0.75%降失水剂RC012-04、5%纳米增强剂RC090-01、0.25%防气窜剂RC21-09、3.0%低温促凝早强剂ALE和0.40%分散剂Plast-A,水泥浆失水量为12 mL,稠化时间为132 min,浆体SPN值为0.77,24 h水泥石的抗压强度和胶结强度分别为16.5 MPa和5.15 MPa。现场应用了22口井,固井质量的优质率从65.0%提升至88.5%,合格率从85%上升到100%,交井后,环空带压率从50%降至5%以下,低温防气窜水泥浆体系在亚鲁杰伊油田取得了良好的现场应用效果。

景德镇陶瓷企业竞争力分析与可持续发展研究

景德镇陶瓷企业在市场经济的大环境中缺乏竞争力,这是由于企业规模小,实力弱,管理水平不高等原因造成的。本文在分析这些因素的基础上,针对性地提出实现景德镇陶瓷企业可持续发展的对策。

硝苯地平-海藻酸钠缓释片的制备和性能研究

目的制备硝苯地平-海藻酸钠缓释片,考察海藻酸钠的含量对其抗张强度、体外释放性能和稳定性的影响。方法以直接压片法制备硝苯地平-海藻酸钠缓释片;在海藻酸钠含量为60、100、140mg的条件下,测定其厚度和抗张强度;建立硝苯地平的体外分析方法,测定硝苯地平-海藻酸钠缓释片在人工胃液(前2h)和人工肠液(后22h)中的释放曲线,考察片剂的稳定性,并探讨海藻酸钠含量对片剂释放性能和稳定性的影响。结果海藻酸钠含量为60、100、140mg片剂的抗张强度依次为2.86、2.71、2.67 MPa,无显著性差异。在胃液环境中释放2h后,3种片剂累积释放率依次为60.3%、46.7%、35.6%,随海藻酸钠含量升高而降低(P<0.05)。在肠液环境中释放10h后,3种片剂累积释放率依次为86.5%、74.6%和61.6%,随海藻酸钠含量升高而下降(P<0.05)。释放24h后3种片剂累积释放率达到98.3%、91.3%、85.6%,片剂3的释放率比片剂1和2降低(P<0.05)。片剂对高湿、高温环境稳定性强,但对光的稳定性弱。结论硝苯地平-海藻酸钠缓释片的厚度和抗张性能与海藻酸钠含量无关,海藻酸钠能够降低其在胃液中的突释效应,提高其在肠液环境中的缓释性能和对光的稳定性。

钢筋混凝土梁加固时的既有荷载对其抗弯性能的影响

模拟实际构件的加固及受力过程,对梁在承受不同荷载作用时外贴CFRP加固进行了抗弯试验和理论分析。试件包括16根外贴CFRP加固梁和2根对比梁。试验参数为:纵筋配筋率、CFRP加固量、粘贴纤维布时持载大小。论文对持载的大小对梁的抗弯性能的影响进行了详细的分析。试验和分析结果表明:采用CFRP加固的钢筋混凝土梁的刚度较普通钢筋混凝土梁的刚度都有明显提高,纤维布对以抗弯为主的构件具有增强刚度、控制挠度的作用。纤维加固时梁所持荷载的大小,对梁的刚度有较大影响,特别是对屈服阶段的刚度影响较大;但对梁的屈服荷载及极限承载力影响较小,可以忽略其影响。论文的试验现象及分析结果都有新颖之处,对相应规范的编制及工程应用有较高的参考价值。

我国体育设施建设现状与发展研究

采用文献资料法、分析法和综合法对我国体育设施建设的现状与发展进行了详细的研究。结果表明:体育设施是我国体育事业发展的重要物质基础,加快发展我国体育设施建设,必须借鉴国外发达国家体育场馆建设的设计理念和先进的科技成果、重视体育建筑工艺设计;尽快完善我国体育设施标准化的制定、管理和实施工作;以文化的力量推动我国体育建筑设施的创新和可持续快速发展。

混凝土在持续荷载下的强度

通过比较混凝土在持续荷载的损伤与疲劳损伤的联系,假定在持续荷载下混凝土的损伤速率和应变增长速率成正比;分析了混凝土在持续荷载下的变形行为和损伤机理,及混凝土在不同荷载历史情况下的破坏边界面;建立了荷载水平和临界损伤应变之间的关系;研究了不同荷载水平下混凝土的真实强度以及不同强度混凝土在持续荷载下的性能。与试验结果对比,建立的模型可以较好地反映混凝土在持续荷载下的性能。

贵州省食用菌产业现状与可持续性发展分析

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