Shrinkage and impact strength of fibre-reinforced artificial lightweight aggregate concrete

Abstract

A sustainable High-Performance Lightweight Aggregate Concrete (HPLWAC) that uses artificial aggregate as part of its coarse ingredients (LWA) as well as being reinforced with single, double, and triple hybrid fibres in many forms, and aspect ratios (l/d) was developed. HPLWAC with a compressive strength of 47MPa and an oven-dry density equal to 1828 kg/m3 at 28 days, was made using various fibres: steel fibres with hooked ends (S1), plastic fibre (P), micro steel fibre (S), and polypropylene fibre (PP). In addition, four mixes of each type of HPLWAC were considered: reference concrete mix, single-fibre reinforced concrete mix, double-hybrid concrete mix, and triple-hybrid concrete mix. Concrete specimens reinforced with the triple hybrid fibre (MAH5) withstood the maximum number of the blows to ultimate failure and first crack. The increments of rate of increase in impact resistance to ultimate failure were 1275, 977, 950, and 862 % at 7, 28, 60, and 90 days compared with the reference concrete. The drying shrinkage related to the concrete sample reinforced with single plastic fibres was reduced in comparison to the reference concrete. The percentage reductions in drying shrinkage of the single fibre (MAP) concrete specimen were 30.54 %, 20.23%, 16.12%, 14.38 %, 14.26 %, and 12.14% at 7, 14, 28, 60, 90, and 180 days respectively. The hybrid fibre-reinforced samples (MAH4 and MAH5) indicated a reduction in drying shrinkage in comparison to the samples reinforced with single plastic fibre (MAP). The percentage decreases in the drying shrinkage for (MAH5) were 58.3%, 40.6 %, 32.7% 26.4%, 252%, and 19.5% at 7, 14, 28, 60, 90, and 180 days, respectively in comparison with the reduced e reference specimen (MAR). SEM indicated that all the specimens of HPLWAC had thick and dense cement pastes with elevated C-S-H content and reduced porosity indicating that high-strength was obtained for such specimens.