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考察了3种配合比的钢纤维增强超高性能混凝土/超高性能混凝土(UHPSFRC/UHPC)抗压强度的尺寸效应,分析了试件尺寸、试件形状、养护制度、龄期等因素对抗压强度的影响,探讨了以小尺寸试件替代标准试件测试UHPSFRC/UHPC抗压强度的可行性。研究结果表明:不同尺寸和形状试件的抗压强度存在线性相关性,且强度修正系数宜根据强度等级予以分段考虑;圆柱体试件的抗压强度普遍低于立方体试件;掺与不掺钢纤维对抗压强度尺寸效应影响较大。 相似文献
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Dr.-Ing. Milan Schultz-Cornelius Prof. Dr.-Ing. Matthias Pahn 《Beton- und Stahlbetonbau》2020,115(9):731-739
Influence of moisture on tensile and flexural tensile strength of UHPC Previous studies on material properties of UHPC concentrate on concrete compressive strength. For unreinforced, on bending loaded components, like facades, the flexural tensile strength is the determinative design parameter. With knowledge of the flexural tensile strength the difficult to examine axial tensile strength can be determined. Current design generations for examination of the flexural tensile strength follow on experiences with standard concrete and require a wet storage of the test samples until the examination. Thereby comparable test requirements are created. Own experiments have shown that the flexural tensile strength of wet stored test samples made from UHPC can be about 50 % higher than the strength of dry stored test samples. However, determining the flexural tensile strength on wet stored test samples does not match with the storage conditions of components in practice consequently, subject of the current research is the phenomenon regarding the design of these components. Therefore, this article shows the results of the flexural tensile and surface tensile strength of differently stored prisms and panels to analyse the influence of several moisture and storage conditions. Subsequently, recommendations for the material examination and design are derivated. 相似文献
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早期自收缩是影响超高性能混凝土体积稳定性的重要因素,特别是由粒径较小的风积沙作为骨料的全风积沙超高性能混凝土。试验采用建筑中常用的三种增强纤维,探索纤维种类与掺量对全风积沙超高性能混凝土早期自收缩的抑制规律。通过试验发现,三种纤维对全风积沙超高性能混凝土早期自收缩抑制效果由大到小依次为:PVA纤维玄武岩纤维钢纤维,在一定范围内,纤维的掺量越高,对全风积沙超高性能混凝土早期自收缩抑制效果越好。这一结论为探索增强纤维对全风积沙超高性能混凝土自收缩性能影响的规律提供了参考。 相似文献
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《材料与设计》2015
Ultra-high performance concrete (UHPC) which is characterized by high strength, high ductility and high toughness has been widely applied in modern structure construction. Outstanding mechanical feature of UHPC not only enables strong yet slim structure design but also highlights its potential in protective engineering against extreme loads like impact or explosion. In this research a series of reinforced concrete slabs are tested to determine their response under explosive loading conditions. Concrete materials used in the slab construction are ultra-high strength concrete (UHPC) and normal strength concrete (NSC). In total five slabs are tested including four UHPC slabs with varying reinforcement ratios and one control NSC slab with normal reinforcement. Explosive charges with TNT equivalent weights ranging from 1.0 to 14.0 kg at scaled distances ranging from 0.41 to 3.05 m/kg1/3 are used in the current experiments. Test results verified the effectiveness of UHPC slabs against blast loads. Numerical models are established in LS-DYNA to reproduce the field blast tests on UHPC slabs. The numerical results are compared with the field test data, and the feasibility and validity of the numerical predictions of UHPC slab responses are demonstrated. 相似文献
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王强 《混凝土与水泥制品》2020,(7):12-15
为了研究常温施工和不同养护条件下超高性能混凝土(UHPC)的收缩性能,在实验室模拟现场施工条件进行了UHPC收缩试验,改进了收缩测试方法.试验结果表明,在绝湿养护条件下,掺加CSA膨胀剂比不掺加膨胀剂的UHPC收缩约减小100×10-6,不掺加膨胀剂的UHPC总收缩量为550×10-6;CSA膨胀剂的膨胀作用主要发生在... 相似文献
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Dr. Michael Olipitz 《Beton- und Stahlbetonbau》2023,118(3):201-213
High performance precast elements for building constructions – A contribution to the disruptive change of mineral components Concrete (NPC) is the most commonly used building material worldwide, which also has great development potential in terms of resource and energy efficiency as well as in terms of production, recyclability and durability. A possible further development that sums up this development potential is high-performance precast elements from concrete and steel composit as well as from the material ultra-high-performance concrete (UHPC). When used appropriately to the material, savings of up to 85 % in resources and up to 65 % of GWP (GWP = E = CO2e) can be achieved. With appropriate application, an immediate reduction in resource and GWP- consumption in new buildings would be possible. The high durability of the UHPC material and the use of modular prefabrication in production add to the advantages. We can only meet the stringent requirements of the Intergovernmental Panel on Climate Change (IPCC) via the residual budget available for the industry up to climate neutrality if we are ready to immediately implement measures for resource and climate efficiency with the technologies that are already available. It will sometimes be a major task of politics to quickly implement these requirements for the construction industry through regulations. The embodied energy (PENRT) of our constructed buildings already accounts for approx. 25 % of global CO2e consumption with a strong upward trend and we builders, especially planners and prefabricated part manufacturers, are required to select the material, the structure and the production of components to make an immediate contribution. This report uses innovative high-performance prefabricated structural elements to show the advantages over conventional reinforced concrete construction in terms of recyclability, durability and potential savings in resource and GWP consumption for roof, ceiling and wall elements as well as staircase and balcony elements. Concrete amounts of savings can be specified in t CO2e on the basis of a concrete apartment prototype that is manufactured with these high-performance prefabricated parts. The implementation of existing technologies can lead to significant changes in the construction industry and requires choose, want, courage and repeat on the part of those involved. In this regard, we are all called upon to make a contribution together. 相似文献
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Minghong Qiu Xudong Shao Yanping Zhu Husam H. Hussein Yeping Liu 《Structural Concrete》2023,24(1):703-720
Connections in the assembled precast elements become essential locations for creating structural continuity. However, the construction challenges of conventional steel sleeve connections, such as rebar embedment length, rebar congestion, and formed grout defects (i.e., voids), are still a concern area for researchers and engineers. In this study, a proposed ultrahigh performance concrete (UHPC) grouted sleeve connection was presented for assembled precast elements, which might reduce defects, enhance durability, and accelerate structure construction. The tensile test of grouted sleeve connection with different grouting materials, rebar diameters, and anchoring lengths was conducted to determine an optimal anchoring length used in the flexural design. The precast specimens with the UHPC grouted sleeve connection were tested under flexural load. Also, strain changes in concrete, sleeve, and rebar were reported in tensile and flexural tests. The tensile test results showed two types of failure modes, the rebar rupture and bond failure between rebar and grouting. The recommended rebar anchoring length in the flexural design was six times the rebar diameter. The flexural test results showed that the precast specimen with or without the shear key has a similar failure mode as compared to the cast-in-place specimen, while their average cracking load, yield load, and ultimate load were 27.9%, 11.0%, and 7.4%, respectively, which is less than those of the cast-in-place specimen. Also, the flexural cracking resistance was the highest in the sleeve segment, followed by the joint region and the rebar segment. This study provides a reference for the design of the UHPC grouted sleeve connection for assembled precast elements. 相似文献
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This paper presents an investigation of the age-dependent size effect and fracture characteristics of ultra-high performance concrete (UHPC). The study is based on a unique set of experimental data connecting aging tests for two curing protocols of one size and size effect tests of one age. Both aging and size effect studies are performed on notched three-point bending tests. Experimental data are augmented by state-of-the-art simulations employing a recently developed discrete early-age computational framework. The framework is constructed by coupling a hygro-thermo-chemical (HTC) model and the Lattice Discrete Particle Model (LDPM) through a set of aging functions. The HTC component allows taking into account variable curing conditions and predicts the maturity of concrete. The mechanical component, LDPM, simulates the failure behavior of concrete at the length scale of major heterogeneities. After careful calibration and validation, the mesoscale HTC-LDPM model is uniquely posed to perform predictive simulations. The ultimate flexural strengths from experiments and simulations are analyzed by the cohesive size effect curves (CSEC) method, and the classical size effect law (SEL). The fracture energies obtained by LDPM, CSEC, SEL, and cohesive crack analyses are compared, and an aging formulation for fracture properties is proposed. Based on experiments, simulations, and size-effect analyses, the age-dependence of size effect and the robustness of analytical-size effect methods are evaluated. 相似文献
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《Beton- und Stahlbetonbau》2018,113(7):535-542
Influence of Thermal Treatment on the Strength of Fine‐Grained Ultra‐High Performance Concrete (UHPC/RPC) By means of targeted specific thermal post‐treatment, the bending tensile strength and compressive strength of Ultra‐High Performance Concrete (UHPC) can significantly be increased. In most publications, a pre‐storage time of 1–2 days, a holding temperature of 60–90 °C and a dwell time of 24–48 hours are recommended [1, 2]. Own preliminary investigations on the thermal treatment of fine‐grained UHPC (RPC) at the Institute for Structural Concrete of the University Duisburg‐Essen showed that improved results could be achieved by other variations. Therefore, more detailed investigations were carried out on the pre‐storage time and the holding temperature of two different UHPC mixtures. Furthermore, the influence of protection of the samples against dehydration during the thermal treatment was investigated. The results of these studies are documented and evaluated in this publication. It was found that the treatment temperature has the greatest influence on the compressive strength. The protection of the samples was crucial for the flexural strength. It should also be noted that different thermal treatment regimes led to the best results for the various mixing compositions. 相似文献
