Durability of similar self-compacting concrete batches produced in two different EU laboratories

The present study intends to evaluate the sensitivity of self-compacting concrete (SCC) mixtures, cast in two different laboratories of the European Union, with a focus on rheological parameters, mechanical characteristics and durability properties. Six SCC mixtures with different water-to-binder ratios and silica fume levels of cement replacement and two normally vibrated concrete (NVC) mixtures have been compared. It has been found that the reproducibility of similar mixtures is possible, when using different constituent materials that conform to the European Standards. Comparable rheological, mechanical and durability properties can be achieved. Open porosity and sorptivity appear to be more sensitive than chloride penetrability. © 2012 Elsevier Ltd. All rights reserved.

Reproducibility of self-compacting concrete batches between two different EU laboratories

Self Compacting Concrete (SCC) offers a wide variety of advantages during casting. Considering the worldwide uniformity of guidelines concerning the composition and casting instructions for the production of fresh SCC, there is a need to explore the reproducibility of similar self-compacting concrete batches between different countries. In the present study, the fresh properties of similar SCC batches produced in two different laboratories of the European Union are being compared and evaluated.

Durability performance of self-compacting concrete

Although self compacting concrete (SCC) is currently used in many countries, there is a fundamental lack of the intrinsic durability of the material itself. This article presents the outcomes from a research program on principal indicators that define the durability of SCC (sorptivity, porosity and chloride ion permeability) and compares these indicators with the corresponding parameters of conventional concrete. The results show, for the first time, that there is a correlation between the various durability indicators for the specific filler additives used in the mix designs incorporated in this paper. Such a correlation may be used to assess the durability of SCC without the need to rely on time consuming artificial weathering experimental procedures. © 2012 Elsevier Ltd. All rights reserved.

Performance of joints in reinforced concrete slabs for two-way spanning action

A series of tests on filigree slab joints was performed with the aim of assessing whether such joints can be reliably used in the construction of two-way spanning reinforced concrete slabs. The test results were compared with code requirements. Adequate joint performance is shown to be achievable when the joints are appropriately detailed. Further research is recommended for the formulation of a more generic understanding when the design parameters are varied from those studied in this work.

Determination of the rheological parameters of self-compacting concrete matrix using slump flow test

The classification of a concrete mixture as self-compacting (SCC) is performed by a series of empirical characterization tests that have been designed to assess not only the flowability of the mixture but also its segregation resistance and filling ability. The objective of the present work is to correlate the rheological parameters of SCC matrix, yield stress and plastic viscosity, to slump flow measurements. The focus of the slump flow test investigation was centered on the fully yielded flow regime and an empirical model relating the yield stress to material and flow parameters is proposed. Our experimental data revealed that the time for a spread of 500 mm which is used in engineering practice as reference for measurement parameters, is an arbitrary choice. Our findings indicate that the non-dimensional final spread is linearly related to the non-dimensional yield-stress. Finally, there are strong indications that the non-dimensional viscosity of the mixture is associated with the non-dimensional final spread as well as the stopping time of the slump flow; this experimental data set suggests an exponential decay of the final spread and stopping time with viscosity. © Appl. Rheol.

MgO expansive cement and concrete in China: Past, present and future

Uniquely, China employs MgO already contained in cement clinker or as an expansive additive to compensate for the thermal shrinkage of mass concrete, particularly dam concrete, with almost 40 years' experience in both research activities and industrial applications. Compensating shrinkage with expansion produced by MgO has been proved to effectively prevent thermal cracking of mass concrete, and reduce the cost of temperature control measures and speed up the construction process. Moreover, the expansion properties of MgO could be designed flexibly, through adjusting its microstructure by changing the calcination conditions (calcining temperature and residence time). The collective knowledge and experience of MgO expansive cement and concrete is worthy of sharing with relevant engineers and researchers globally but dissemination has been hindered as most of the relevant literature is published in Chinese. This paper reviews the history, state-of-the-art progress and future research needs in the field of MgO expansive cement and concrete. © 2013 Elsevier Ltd.

Achievements and challenges in machine vision-based inspection of large concrete structures

Large concrete structures need to be inspected in order to assess their current physical and functional state, to predict future conditions, to support investment planning and decision making, and to allocate limited maintenance and rehabilitation resources. Current procedures in condition and safety assessment of large concrete structures are performed manually leading to subjective and unreliable results, costly and time-consuming data collection, and safety issues. To address these limitations, automated machine vision-based inspection procedures have increasingly been proposed by the research community. This paper presents current achievements and open challenges in vision-based inspection of large concrete structures. First, the general concept of Building Information Modeling is introduced. Then, vision-based 3D reconstruction and as-built spatial modeling of concrete civil infrastructure are presented. Following that, the focus is set on structural member recognition as well as on concrete damage detection and assessment exemplified for concrete columns. Although some challenges are still under investigation, it can be concluded that vision-based inspection methods have significantly improved over the last 10 years, and now, as-built spatial modeling as well as damage detection and assessment of large concrete structures have the potential to be fully automated.

On a Certain Algebraic Property of Block Ciphers

This is a study on a certain group theoretic property of the set of encryption functions of a block cipher. We have shown how to construct a subset which has this property in a given symmetric group by a computer algebra software GAP4.2 (Groups, Algorithms, and Programming, Version 4.2). These observations on group structures of block ciphers suggest us that we may be able to set a trapdoor based on meet-in-the-middle attack on block ciphers.

linear cryptanalysis of nush block cipher

IEEE Computer Society

Design for an IO block array in a tile-based FPGA

A design for an IO block array in a tile-based FPGA is presented.Corresponding with the characteristics of the FPGA, each IO cell is composed of a signal path, local routing pool and configurable input/output buffers.Shared programmable registers in the signal path can be configured for the function of JTAG, without specific boundary scan registers/latches, saving layout area.The local routing pool increases the flexibility of routing and the routability of the whole FPGA.An auxiliary power supply is adopted to increase the performance of the IO buffers at different configured IO standards.The organization of the IO block array is described in an architecture description file, from which the array layout can be accomplished through use of an automated layout assembly tool.This design strategy facilitates the design of FPGAs with different capacities or architectures in an FPGA family series.The bond-out schemes of the same FPGA chip in different packages are also considered.The layout is based on SMIC 0.13μm logic 1P8M salicide 1.2/2.5 V CMOS technology.Our performance is comparable with commercial SRAM-based FPGAs which use a similar process.

Comparison of aggregation behaviors between branched and linear block polyethers: MesoDyn simulation study

The comparison of aggregation behaviors between the branched block polyether T1107 (polyether A) and linear polyether (EO)(60)(PO)(40)(EO)(60) (polyether B) in aqueous solution are investigated by the MesoDyn simulation. Polyether A forms micelles at lower concentration and has a smaller aggregation number than B. Both the polyethers show the time-dependent micellar growth behaviors. The spherical micelles appear and then change to rod-like micelles with time evolution in the 10 vol% solution of polyether A. The micellar cluster appears and changes to pseudo-spherical micelles with time evolution in the 20 vol% solution of polyether A. However, the spherical micelles appear and change to micellar cluster with time evolution in the 20 vol% polyether B solution. The shear can induce the micellar transition of both block polyethers. When the shear rate is 1x10(5) s(-1), the shear can induce the sphere-to-rod transition of both polyethers at the concentration of 10 and 20 vol%. When the shear rate is lower than 1x10(5) s(-1), the huge micelles and micellar clusters can be formed in the 10 and 20 vol% polyether A systems under the shear, while the huge micelles are formed and then disaggregated with the time evolution in the 20 vol% polyether B system.