This paper presents a rhetorical discussion on the subject of fiber-reinforced concrete, FRC. It is intended as an overview of the types of commercially available FRCs and how they work. It discusses commonly applied terminology and models of mechanical behavior that form a basis for understanding material performance without presenting mathematical details. Historical review is intended to help build a background for what is currently understood about FRC rather than as historical reporting. References from both early and contemporary authors are included as a means of tying the subject together along a time line.

Fiber-reinforced concrete: An overview after 30 years of development

Strength properties of nylon- and polypropylene-fiber-reinforced concretes

Steel-fiber reinforced concrete is increasingly being used day by day as a structural material. The complete stress–strain curve of the material in compression is needed for the analysis and design of structures. In this experimental investigation, an attempt has been made to generate the complete stress–strain curve experimentally for steel-fiber reinforced concrete for compressive strength ranging from 30 to 50 MPa. Round crimped fibers with three volume fractions of 0.5%, 0.75% and 1.0% (39, 59, and 78 kg/m3) and for two aspect ratios of 55 and 82 are considered. The effect of fiber addition to concrete on some of the major parameters namely peak stress, strain at peak stress, the toughness of concrete and the nature of the stress–strain curve is studied. A simple analytical model is proposed to generate both the ascending and descending portions of the stress–strain curve. There exists a good correlation between the experimental results and those calculated based on the analytical model. Equations are also proposed to quantify the effect of fiber on compressive strength, strain at peak stress and the toughness of concrete in terms of fiber reinforcing parameter.

Stress-strain curves for steel-fiber reinforced concrete under compression

This paper presents the results of an experimental program designed to assess the durability of sisal and coconut fibres exposed to alkaline solutions of calcium and sodium hydroxide. In addition, the durability and microstructure of the cement mortar composites reinforced with these fibres aged under tap water, exposed to controlled cycles of wetting and drying, as well as to the open air weathering have been studied. The possibility of biological attack of fibres was investigated by conditioning them in tap water for 420 days. It was found that sisal and coconut fibres kept in a calcium hydroxide solution of pH 12 completely lost their flexibility and strength after 300 days. The composites manufactured with short sisal or short coconut fibres and ordinary Portland cement `OPC' matrix presented a significant reduction in toughness after six months of exposure to the open air weathering or after being submitted to cycles of wetting and drying. The embrittlement of the composites can be mainly associated with the mineralization of the fibres due to the migration of hydration products, especially calcium hydroxide, to the fibre lumen, walls and voids.

Durability of alkali-sensitive sisal and coconut fibres in cement mortar composites

The primary concern for vegetable fibre reinforced mortar composites (VFRMC) is the durability of the fibres in the alkaline environment of cement. The composites may undergo a reduction in strength and toughness as a result of weakening of the fibres by a combination of alkali attack and mineralisation through the migration of hydration products to lumens and spaces. This paper presents several approaches used to improve the durability performance of VFRMCs incorporating sisal and coconut fibres. These include carbonation of the matrix in a CO2-rich environment; the immersion of fibres in slurried silica fume prior to incorporation in the ordinary Portland cement (OPC) matrix; partial replacement of OPC matrix by undensified silica fume or blast-furnace slag and a combination of fibre immersion in slurried silica fume and cement replacement. The durability of the modified VFRMC was studied by determining the effects of ageing in water, exposure to cycles of wetting and drying and open air weathering on the microstructures and flexural behaviour of the composites. Immersion of natural fibres in a silica fume slurry before their addition to cement-based composites was found to be an effective means of reducing embrittlement of the composite in the environments studied. Early cure of composites in a CO2-rich environment and the partial replacement of OPC by undensified silica fume were also efficient approaches in obtaining a composite of improved durability. The use of slag as a partial cement replacement had no effect on reducing the embrittlement of the composite. © 2002 Published by Elsevier Science Ltd.

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Claire G. Ball

Papers

Measurement of Properties of Fiber Reinforced Concrete