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

In recent years, a very important environmental issue all over the world is the disposal of waste tyres. Rubber from waste tyres can be used to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). CRC can improve ductility, damping ratio, and energy dissipation, which are the most important parameters in concrete structures resisting earthquakes. However, CRC can have lower compressive strength when compared with conventional concrete. This paper presents an empirical model able to predict CRC compressive strength. The proposed model is verified using 148 different CRC mixes and compared to two previous models. The proposed model resulted in CRC strength predictions with only 10.7% mean error. The proposed model reduced the mean error in the predictions by 24.6% compared to the nearest predictions by previous models. This paper can aid structural designers who are considering using CRC as a promising alternative to conventional concrete in seismic zones.

Prediction of crumb rubber concrete strength

This chapter investigates the accuracy of the height-to-thickness ratio (h/t) correction factors presented in the ASTM standard (ASTM C1314-03) and in other international standards using numerical finite element analysis. The FEM is calibrated with experimental results, and then a parametric study is performed to examine the effect of size on the strength of masonry prisms. Calibration of masonry material provided in this chapter is then used in developing finite element models of PT-MWs presented in Chap. 5.

Effect of Dimensions on the Compressive Strength of Concrete Masonry Prisms

Three alkali-activated mortars (AAM), or what is called geopolymer, mix with different fly ashes sources were tested during the study. X-ray fluorescence was carried out on AAM samples to determine their chemical composition. Flowability and setting times of the AAMs were tested. Compressive strength was analyzed for five different temperatures of 30, 40, 55, 70, and 85 °C under five different time intervals of 4, 8, 16, 24, and 48 h. The compressive strength results indicate that the calcium content and ratio of silica to alumina played a pivotal role in the optimum curing conditions for each of AAMs.

Effect of Curing Temperatures on Zero-Cement Alkali-Activated Mortars

Analytical Modeling of the Main Characteristics of Crumb Rubber Concrete

Note: 10 pagesCD ROM Reference IMAC-CONF-2004-016 Record created on 2007-06-13, modified on 2016-08-08

/pdf/static-cyclic-tests-on-urm-wall-before-and-after-ot6a23mt92.pdf

Mohamed A. ElGawady

Papers

Prediction of crumb rubber concrete strength

Effect of Dimensions on the Compressive Strength of Concrete Masonry Prisms

Effect of Curing Temperatures on Zero-Cement Alkali-Activated Mortars

Analytical Modeling of the Main Characteristics of Crumb Rubber Concrete

Static Cyclic Tests on URM Wall before and after Retrofitting with Composites