Recycled aggregate from C&D waste & its use in concrete – A breakthrough towards sustainability in construction sector: A review

Recent advances in understanding the role of supplementary cementitious materials in concrete

Graphene oxide (GO) is the product of chemical exfoliation of graphite. Due to its good dispersibility in water, high aspect ratio and excellent mechanical properties, GO is a potential candidate for use as nanoreinforcements in cement-based materials. In this paper, GO was used to enhance the mechanical properties of ordinary Portland cement paste. The introduction of 0.05 wt% GO can increase the GO-cement composite compressive strength by 15-33% and the flexural strength by 41-59%, respectively. Scanning electron microscope imaging of the GO-cement composite shows the high crack tortuosity, indicating that the two-dimensional GO sheet may form a barrier to crack propagation. Consequently, the GO-cement composite shows a broader stress-strain curve within the post-peak zone, leading to a less sudden failure. The addition of GO also increases the surface area of the GO-cement composite. This is attributed to increasing the production of calcium silicate hydrate. The results obtained in this investigation suggest that GO has potential for being used as nano-reinforcements in cement-based composite materials.

Mechanical properties and microstructure of a graphene oxide-cement composite

Analysis and performance of oil well cement with 30 years of CO2 exposure from the SACROC Unit, West Texas, USA

The rheological or flow properties of concrete in general and of high performance concrete (HPC) in particular, are important because many factors such as ease of placement, consolidation, durability, and strength depend on the flow properties. Concrete that is not properly consolidated may have defects, such as honeycombs, air voids, and aggregate segregation. Such an important performance attribute has triggered the design of numerous test methods. Generally, the flow behavior of concrete approximates that of a Bingham fluid. Therefore, at least two parameters, yield stress and viscosity, are necessary to characterize the flow. Nevertheless, most methods measure only one parameter. Predictions of the flow properties of concrete from its composition or from the properties of its components are not easy. No general model exists, although some attempts have been made. This paper gives an overview of the flow properties of a fluid or a suspension, followed by a critical review of the most commonly used concrete rheology tests. Par ticular attention is given to tests that could be used for HPC. Tentative definitions of terms such as workability, consistency, and rheological parameters are provided. An overview of the most promising tests and models for cement paste is given.

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Measurement of the Rheological Properties of High Performance Concrete: State of the Art Report

This updated, definitive reference book on concrete technology covers the fundamentals and detailed information on freshly mixed and hardened concrete for Canada The properties of concrete as needed in concrete construction are presented, including strength and durability All concrete ingredients are reviewed for their optimal use in designing and proportioning concrete mixtures Applicable standards from the American Society for Testing and Materials, Canadian Standards Association and American Concrete Institute are referred to extensively Individual chapters address: (1) fundamentals of concrete; (2) Portland, blended and other hydraulic cements; (3) fly ash, slag, silica fume and natural pozzolans; (4) mixing water; (5) aggregates for concrete; (6) admixtures for concrete; (7) fibers; (8) air-entrained concrete; (9) designing and proportioning normal concrete mixtures; (10) batching, mixing, transporting and handling concrete; (11) placing and finishing concrete; (12) curing concrete; (13) hot weather concreting; (14) cold-weather concreting; (15) volume changes of concrete; (16) control tests for concrete; (17) high-performance concrete; and (18) special types of concrete

Beatrix Kerkhoff

Papers

Design and Control of Concrete Mixtures