Lightweight Concrete Material Research Articles

軽量気泡コンクリート材を利用したセシウムイオン交換材料の開発

軽量気泡コンクリート材を利用したセシウムイオン交換材料の開発

Reinforced concrete beams with lightweight concrete infill

In structural design, an ideal situation in material saving is to reduce the weight of the structure without having to compromise on its strength and serviceability. A new lightweight sandwich reinforced concrete section has been developed with a novel use of lightweight concrete as infill material. The section, namely LSRC section, is suitable for use as beam or slab members. Experimental investigations into the strength of beams with LSRC section shows promising results under both flexural and shear tests. Based on the test results, the flexural capacity of LSRC beams was found to be almost identical to the capacity of the equivalent solid beam. The shear capacity of the LSRC beams was expectedly reduced due to the low compressive strength of the lightweight concrete infill material. ANSYS 12.1 was employed to develop three dimensional nonlinear finite element models of LSRC beams and was verified against the experimental results. Key words: Lightweight concrete, composite section, sandwich section, ANSYS.

Methods of determination of liquid transfer coefficient in building materials

At present there is no unified, widely recognized method of estimation of the dependency between the liquid transfer coefficient and the moisture content in material. It is possible to determine such relation by several methods requiring long-term and laborious experimental research, expensive apparatus and complex calculating procedures. The original method of determination of the liquid transfer coefficient in building materials is presented in this work. This method is limited to obtaining experimental data of the kinetics of one-way capillary water uptake by specimens and calculations based on the suggested model. Accuracy of the given method was confirmed using experimental results of capillary absorption process of lightweight concrete and ceramic material. Since the suggested method is theoretically grounded and its accuracy is comparable with other known methods and at the same time it is less laborious and cost-consuming, it can be recommended for practical application.

A Qualitative Study of Green Building Indexes Rating of Lightweight Foam Concrete

Green building index is considered as the rating tool for evaluating the siting, design and performance of buildings and infrastructures based on worldwide acceptable six main criteria’s It was invented after the Kyoto protocol, Japan, on 11 th of December 1997 and the adoption in Marrakesh in 2001 by the United Nations and her subcommittee. It was developed in the built environment industry by the Government support of each country to combat the issue of green house gas emission. Carbon dioxide is acclaimed as one of the main greenhouse gas emission which is mainly through the activities of human race in the world resulting into global warming hence the effort to make the environment lighter enough to inhabit. Construction industry was assessed through studies to be contributing 5% of the world total carbon dioxide emitted through cement production. It was also claimed that a tonne of concrete produces carbon dioxide in the range of 0.05 to 0.13 tonnes. Foam concrete being a new innovative green technology material for sustainable building and civil construction needs to fulfill the criteria’s of this rating tools for it to be considered as sustainable materials. This paper study the assessment of this lightweight concrete material in view of green building index criteria’s and the result are hereby analyze and concluded that foam concrete can be effectively used as sustainable material for building and civil engineering construction.

The acoustic behavior of concrete resonators incorporating absorbing materials

Acoustic resonators are a common engineering solution providing sound absorption in intermediate frequencies. They are used in many acoustic applications where noise absorption is required, such as outdoor barriers. Outdoor noise barriers face aggressive weather conditions and so their design has to reconcile durability and absorption. This compromise may be achieved by making use of materials such as standard and lightweight concrete. The work described in this paper analyzes the acoustic behavior of concrete resonator shapes using an experimental approach. The resonant frequency of resonators of different dimensions and the sound absorption they provide are determined. In addition, lightweight concrete resonator-like structures are analyzed, and their acoustic absorption is characterized. Mixed devices that incorporate both standard concrete, lightweight concrete (with expanded clay) and porous materials, arranged in different configurations, are also analyzed so as to define higher performance solutions.

Equilibrium isotherms and kinetics studies for the sorption of fluoride on light weight concrete materials

The sorption kinetics of F − on light-weight concrete materials have been investigated at different pHs, agitation rates and temperatures of solution. The pseudo second-order kinetic model was successfully applied in the removal of fluoride ions from synthetic solution. The optimum values of k ads for pH (6.9), temperatures (333 K) and agitation rate (235 rpm) were obtained as 0.300, 0.255 and 0.147 g mg −1 min −1, respectively. The equilibrium time of sorption studies using jar tests was defined as 60 min. The surface area of light weight concrete was 22 m 2 g −1. The experimental results have been analyzed using Freundlich, Langmuir, Brunauer, Emet and Teller (BET) and Dubinin–Radushkevich (D–R) sorption isotherm models. From D–R sorption isotherm, the mean energy of sorption was defined as 8.68 kJ mol −1. The sorption activation energy ( E a) was calculated using Arhenius equation. Thermodynamic parameters such as Δ H°, Δ S° and Δ G° were calculated from the slope and intercept of linear plot of ln K D against (1/ T). The Δ H° and Δ G° values of fluoride sorption on light weight concrete materials show endothermic heat of sorption. But negative free energy value, indicating that the process of fluoride sorption is favored at high temperatures.

Sludge Ash as Lightweight Concrete Material

Sludge is an inevitable by‐product of wastewater treatment. Its abundance poses disposal problems that can be drastically reduced if sludge can be converted for economical uses in construction as substitute materials. Digested and dewatered sludge, after incineration at a high temperature, yields a hard, cellular, porous mass with low unit weight. This hardened mass of sludge ash can be crushed to smaller‐sized aggregates, which, when graded in suitable proportions, manifest the basic attributes required of lightweight aggregates. When used as aggregates in the production of lightweight concrete, experimental results show that the resulting concrete satisfies the physical requirements of a lightweight concrete in terms of unit weight, strength, heat‐insulating properties, and fire resistance, thus indicating that sludge ash could be a potential source of suitable lightweight aggregates.

Performance characteristics of an apparatus based on the curve-fitting method for measuring thermal properties at cryogenic temperatures

This paper describes the performance characteristics of a new test apparatus and the measured results using the apparatus. It has been developed on the basis of Harmathy's curve-fitting method to measure, in a short time, the physical properties of the nonmetallic materials for a cryogenic storage tank. The apparatus has been used to measure the heat capacity, thermal conductivity, and thermal diffusivity of the materials at the same time in the temperature range of approximately −180°C to +50°C. With this apparatus the thermal conductivity can be measured over a wide range of approximately 0.01 kcal m −1 h −1°C −1 to 10 kcal m −1 h −1°C −1 in the range of −180°C to +50°C. The materials investigated were structural materials such as concrete, wood, frozen soil, and autoclaved lightweight concrete (ALC) and such insulation materials as calcium silicate, phenolic foam, and polyurethane foam.