The review outlines modern trends in theoretical developments, novel designs and modern applications of sandwich structures. The most recent work published at the time of writing of this review is considered, older sources are listed only on as-needed basis. The review begins with the discussion on the analytical models and methods of analysis of sandwich structures as well as representative problems utilizing or comparing these models. Novel designs of sandwich structures is further elucidated concentrating on miscellaneous cores, introduction of nanotubes and smart materials in the elements of a sandwich structure as well as using functionally graded designs. Examples of problems experienced by developers and designers of sandwich structures, including typical damage, response under miscellaneous loads, environmental effects and fire are considered. Sample applications of sandwich structures included in the review concentrate on aerospace, civil and marine engineering, electronics and biomedical areas. Finally, the authors suggest a list of areas where they envision a pressing need in further research.

Review of current trends in research and applications of sandwich structures

Disposal of waste tire rubber has become a major environmental issue in all parts of the world. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. It was estimated that almost 1000 million tires end their service life every year and out of that, more than 50% are discarded to landfills or garbage without any treatment. By the year 2030, there would be 5000 million tires to be discarded on a regular basis. Tire burning, which was the easiest and cheapest method of disposal, causes serious fire hazards. Temperature in that area rises and the poisonous smoke with uncontrolled emissions of potentially harmful compounds is very dangerous to humans, animals and plants. The residue powder left after burning pollutes the soil. One of the possible solutions for the use of waste tire rubber is to incorporate into cement concrete. This paper presents an overview of some of the research published regarding the fresh and hardened properties of rubberized concrete. Studies show that there is a promising future for the use of waste tire rubber as a partial substitute for aggregate in cement concrete. It was noticed from literatures that workable concrete mixtures can be made with scrap tire rubber and it is possible to make light weight rubber aggregate concrete for some special purposes. Rubberized concrete shows high resistance to freeze-thaw, acid attack and chloride ion penetration. Use of silica fume in rubberized concrete enables to achieve high strength and high resistance to sulfate, acid and chloride environments.

A comprehensive review on the applications of waste tire rubber in cement concrete

Seismic Design and Retrofit of Bridges

Workability and mechanical properties of alkali-activated fly ash-slag concrete cured at ambient temperature

Waste tyres and their accumulation is a global environmental concern; they are not biodegradable, and, globally, an estimated 1.5 billion are generated annually. Waste tyres in landfill and stockpiles are renowned for leaching toxic chemicals into the surrounding environment, acting as breeding grounds for mosquitoes, and fuelling inextinguishable fires. The properties of waste tyre rubber and engineering applications have been previously reported in a range of publications with respect to the environmental, economic, and technical factors. This study compiles and reviews this research with a focus on geotechnical engineering applications, such as earthworks and infrastructure construction. The applications of waste rubber in construction materials includes cementitious concrete, asphalt concrete, and granular materials for earth structures. Crumb rubber, when used as a sand replacement in flowable concrete fill, improved ductility and strength-to-weight ratio. A 40 MPa concrete mix with 0.6% rubber crumb content exhibited optimal strength and air entrainment capabilities, displaying minimal damage after 56 freeze/thaw cycles. Rubber, as a partial replacement for aggregate in road base and sub-base layers, adversely affected the California Bearing Ratio (CBR) of the graded aggregate base course. Rubber-soil mixtures as the interface of foundation and structure yielded a 60–70 % reduction in vertical and horizontal ground accelerations when subjected to earthquake simulation modelling. There is concern regarding the toxicity of waste rubber incorporated products due to leachates of heavy metals and other chemicals common in tyres. Further comprehensive studies in this area are needed. Leachate studies should be conducted under different pH and liquid to solid ratios.

Recycling waste rubber tyres in construction materials and associated environmental considerations: A review

Note: CD ROM Reference IMAC-CONF-2006-031 Record created on 2007-06-13, modified on 2016-08-08

Seismic behavior of URM walls retrofitted using Shotcrete

1School of Natural and Built Environments, University of South Australia, Adelaide, SA, Australia 2Department of Civil and Environmental Engineering, The University of Auckland, Auckland, New Zealand 3Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO, USA 4Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong

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Resilient civil infrastructure under dynamic loadings 2020

The effect of the water to fly ash (W/FA), alkali activators to fly ash (Alk/FA), and curing regimes on the workability and compressive strength of the alkali-activated mortar (AAM) was studied. Three high calcium fly ashes (FAs) having different chemical compositions were used. Sodium hydroxide (SH) and sodium silicate (SS) were used as the alkali activators. The two alkali activators were mixed together at ratio of 1.0. Two curing regimes, elevated heat curing in an electric oven at 70°C for 24 hr and ambient curing at 23 ± 2°C, were applied. The water to fly ash (W/FA) ratios were 0.350, 0.375, and 0.400. However, the alkali activators to fly ash (Alk/FA) ratios were 0.250, 0.275 and 0.300. The results revealed that the workability and the compressive strength of the oven cured specimens were decreased with increasing the calcium content of FA in the mixture. However, the compressive strength of the specimens that cured under the ambient temperature increased with increasing the calcium content. The workability increased with increasing the W/FA and decreasing the Alk/FA. The compressive strength based on both curing regimes decreased with increasing the W/FA. The optimum Alk/FA was 0.275 with W/FA of 0.400.

Influence of Water, Alkali Activators, and Curing Regime on the Workability and Compressive Strength of the Alkali Activated Mortar

Note: 8 pagesCD ROM Reference IMAC-CONF-2003-010 Record created on 2007-06-13, modified on 2016-08-08

Mohamed A. ElGawady

Papers

Seismic behavior of URM walls retrofitted using Shotcrete

Resilient civil infrastructure under dynamic loadings 2020

Influence of Water, Alkali Activators, and Curing Regime on the Workability and Compressive Strength of the Alkali Activated Mortar

Dynamic in-plane tests on URM

Effects of Footing Connections of Precast Hollow-Core Composite Columns