Abstract
Structural lightweight aggregate concrete (SLWAC) is an alternative building material to normal-weight one, due to its ability to reach a relatively high compressive strength at still significantly lower density. Nevertheless, the application of lightweight aggregate instead of normal-weight one to concrete must result in deterioration of some characteristics of the composite. One of the methods of improving SLWAC properties is incorporation of fibers into concrete. This paper focuses on the influence of steel fibres on modification of properties of structural lightweight concrete with sintered fly ash aggregate. Two different concrete mixtures, producing various levels of matured composite density and compressive strength, were modified with three dosages of fibers: 30, 45 and 60 kg/m3. The applied amounts did not result in significant deterioration of the rheological parameters of concrete mixtures. Despite relatively low volume content of fibres, a considerable increase of flexural and tensile splitting strength was observed. Fibres also improved concrete shrinkage as well as post-peak deformability in uni-axial compression. The effect of steel addition on compressive strength proved to be dependent on specimen type. Nevertheless, it was not as crucial as in the case of the above characteristics. However, the modulus of elasticity of SLWAC was not affected by fibre addition. Santrauka Konstrukcinis su lengvaisiais užpildais betonas (SLWAC) yra normalaus svorio statybinių medžiagų alternatyva, turinti mažesnį tankį ir gebėjimą pasiekti gana didelį gniuždomąjį stiprį. Nepaisant to, lengvieji užpildai, naudojami vietoj normalaus svorio užpildų, realiai gali pabloginti kai kurias kompozito savybes. Vienas iš lengvojo betono SLWAC savybių tobulinimo būdų yra plieninių fibrų įterpimas į betono sudėtį. Šiame darbe aptariamas plieninių fibrų poveikis konstrukcinio lengvojo betono su lakiaisiais pelenais savybėms. Tikslui pasiekti buvo parinktos pagal tankį ir gniuždomąjį stiprį dvi skirtingos betono sudėtys su skirtingais (30, 45 ir 60 kg/m3) plieninių fibrų tankiais. Paruošti bandiniai buvo naudoti gniuždomajam stipriui ir kitoms savybėms nustatyti. Tyrimų rezultatai parodė, kad plieninių fibrų priedas nepablogino reologinių betono mišinio rodiklių. Nepaisant palyginti mažo fibrų kiekio, labai padidėjo bandinių lenkiamasis ir tempiamasis stipris. Fibros taip pat pagerino deformacines betono savybes. Gauto kompozito gniuždomasis stipris iš dalies priklausė nuo naudojamų plieninių fibrų charakteristikų. Tačiau plieninių fibrų priedas nepakeitė SLWAC tamprumo modulio.
Highlights
Structural lightweight aggregate concrete (SLWAC) is a versatile building material which has been used in building engineering since Roman times
It must be noted that increasing compressive strength and durability of SLWAC does not involve proportional improvement of the other mechanical and physical properties
In comparison to normal weight concrete of a given compressive strength, lightweight aggregate concrete is characterized by higher shrinkage, higher brittleness, lower shear, flexural and tensile strength, lower modulus of elasticity and lower fracture parameters (Chandra and Berntsson 2003; Clarke 1993; Domagała 2006)
Summary
Structural lightweight aggregate concrete (SLWAC) is a versatile building material which has been used in building engineering since Roman times. Journal of Civil Engineering and Management, 2011, 17(1): 36–44 even better than in the case of normal weight concrete of the same strength level It seems that from among all types of fibres steel ones are the most effective additives to modify mechanical properties of lightweight concrete at a rational concrete cost. Most research carried out on this subject (Kayali et al 2003; Chen and Liu 2005, 2004; Gao et al 1997; Balendran et al 2002; Campione and Miragla 2001) indicates that, using steel fibres, it is possible to enhance fracture parameters, shear and flexural as well as tensile strength Such characteristics of SLWAC as shrinkage, compressive strength, modulus of elasticity and stress-strain relationship are in some cases affected by steel fibres, yet in others there is no such effect.
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