再生骨料透水混凝土体积法配比设计关键参数的优化选择

以再生骨料配制的透水生态混凝土为研究对象,用体积法进行配合比设计并调整不同的配比参数,研究保证再生骨料配制透水生态混凝土透水性和强度的最佳配比参数,并比较再生骨料与天然骨料配比设计中参数选择的异同。     

高强抗磨混凝土配制技术研究

以不同掺合料品种、不同骨料级配、不同水胶比条件下,测试混凝土的强度及抗磨性能。通过试验研究发现：混凝土水胶比控制在0．25以下,混凝土中掺加硅粉、膨胀剂,并将骨料最大粒径减小到20mm以下,混凝土具有优异的抗磨性。可使山区性河道,泄水建筑物混凝土磨损减少,增加建筑物的使用年限。     

邢东矿-980m外水仓钢管混凝土支架支护技术应用

针对邢东矿-980 m外水仓由于埋深大,地压显现明显,巷道变形量大的特点,使用钢管混凝土支架进行二次支护,并联合锚喷及后期浅层注浆构建巷道围岩承压环,有效地控制了围岩的变形,保证了巷道长期稳定,为深井巷道支护形式的选择提供了参考。     

煤矸石混凝土空心砌块性能实验研究

以辽宁阜新矿区所产废渣自燃煤矸石为骨料,添加适当粉煤灰,配制混凝土空心砌块.依据均匀设计理论设计实验方案,研究不同配合比情况下煤矸石混凝土空心砌块的表观密度、吸水率、相对含水率、软化系数、碳化系数、抗冻性和抗压强度等性能指标.通过回归分析,得到抗压强度方程.利用BP神经网络预测出煤矸石混凝土砌块抗压强度,预测结果与实验结果吻合较好.实验与计算结果表明,采用煤矸石配制混凝土砌块,强度达到建材使用标准,能降低工程造价,且可以有效治理环境污染,工艺先进,值得大力推广使用.     

粗纤度PVA纤维混凝土力学性能试验分析

将粗纤度聚乙烯醇(PVA)纤维加入混凝土中,采用搅拌试验方法分析PVA纤维在混凝土中的分散性;对比不同纤维体积分数下PVA纤维混凝土的坍落度分析其可施工性;对比不同纤维体积分数PVA纤维混凝土的抗压、抗弯拉及劈裂抗拉强度和破坏状态来探索其综合力学性能。试验结果表明:PVA纤维在混凝土搅拌过程中分布较均匀不易结团;相对素混凝土,PVA纤维混凝土的坍落度略有下降;抗压强度无明显提高,抗弯拉及劈裂抗拉强度随着纤维体积分数增加呈二次函数增大。     

Gradientenbetontechnologie

The technology of graded concrete – From the development of concrete mixtures and the conceptual design to the automatized manufacturing In accordance with the principle form follows force, the DFG Priority Programme (SPP) 1542 – Leicht Bauen mit Beton – focuses on energy efficient building elements which are designed specifically for desired operational demands. This concept is a specific adaption of the component's inner structure and works in parallel to the optimization of its outer shape which is often limited due to the outer geometry of slabs, walls and supporting pillars. The technology of graded concrete provides an innovative possibility to adapt the inner structure of a concrete component in order to meet defined static and structural‐physical requirements. The challenging demands imposed by the technology of graded concrete require a holistic approach including the development of the concrete mixtures, the design of the building components and finally the automatized manufacturing. In collaboration between the departments ILEK, IWB and ISYS of the University of Stuttgart a complete process chain for the manufacturing of functionally graded concrete components was realized. This approach for concrete results in fully recyclable building elements with significant savings in mass and energy.     

Tragverhalten von geschichteten Deckenelementen aus Normal‐ und Porenleichtbeton

Load bearing behaviour of layered ceiling elements made of regular and porous lightweight concrete Lightweight and efficiently bearing steel reinforced elements may be achieved through the application of regular and porous concrete in a three‐layer cross‐section. While exterior layers of higher strength carry bending moments, a lightweight core layer material holds up to shear stresses. In order to quantify the potential of this construction method, the bearing behaviour of 18 layered ceiling elements with six different geometries was investigated. The goals were both to identify different failure modes, as well as evaluate the suitability of commonly used calculation procedures. The following paper shows that an optimal usage of cross‐sections of ceiling elements can already achieved by using concrete with strengths between 5 MN/m² and 20 MN/m². The efficiently bearing elements are characterized by the fact, that both the concrete, the reinforcing steel and the layer's interface are highly stressed both under pressure and tension. The tested specimens showed both a tensile bending and interface failure with a partly very high utilization of the flexural compressive zone.     

Sonderlösungen bei der brandschutztechnischen Bewertung von Konstruktionsdetails

Special‐purpose solutions in the fire‐protective evaluation of construction details Very often components or construction details in existing buildings but also in new buildings cannot be evaluated with regard to its fire resistance ability considering established technical building regulations. There are no regulations for the evaluation of such components or construction details as these specific construction details have not been evaluated by a certified test authority. However, these components and construction details very often can be classified in fire resistance classes e. g. by evaluating fire tests, with regard to DIN 4102‐4, on the basis of similar proof of usability or only by pragmatic considerations. Since introducing the technical approval of the fire protection Eurocodes more often engineering methods of fire protection are used based on these Eurocodes by using temperature assessment in order to secure the evaluation results. Within this essay we show methods and ways of fire‐protective evaluation for components and construction details. The approach of proof including dimensions of possible upgrade measurements if necessary are being illustrated by examples of use out of practical experience. At the same time different materials such as steel, concrete and wood will be treated with different fire‐proof products. The essay is to explain ways of evaluation of components and construction details involving fire‐proof requirements including upgrade measurements also especially for existing buildings.     

Messtechnische Herausforderungen bei der Analyse von hochdynamischen Aufprallbeanspruchungen

Metrological challenges analyzing high dynamic impact on reinforced slabs The comprehension of high dynamic impact processes on reinforced concrete structures is of essential importance for the dimensioning of structures regarding exceptional loading scenarios like airplane impacts. Since, for high strain rates in comparison with quasi‐static conditions an altered material behavior appears, an adequate methodology and application of appropriate measurement is required to assess the structural behavior of building components. The present paper describes the metrological methodology and the challenges of the experimental investigations of reinforced concrete slabs under impact with loading periods of only a few μs or ms. The determination of time history curves of impact velocities, bearing forces, displacements and the determination of sound wave velocities inside the structure requires an appropriate high sampling rate with the signal recording. The results lately lead to a holistic assessment of the structural behavior and the damage phenomena of such processes.