In this investigation, sustainable High Performance Lightweight Aggregate Concrete (HPLWAC) containing artificial aggregate as coarse lightweight aggregate (LWA) and reinforced with mono fiber, double and triple hybrid fibers in different types and aspect ratios were produced. High performance artificial lightweight aggregate concrete mix with compressive strength of 47 MPa, oven dry density of 1828 kg/m3 at 28 days was prepared. The Fibers used included, macro hooked steel fiber with aspect ratio of 60 (type S1), macro crimped plastic fiber (P) with aspect ratio of 63, micro steel fiber with aspect ratio of 65 (type S), and micro polypropylene fiber (PP) with aspect ratio of 667. Four HPLWAC mixes were prepared including, one plain concrete mix (without fiber), one mono fiber reinforced concrete mixes (reinforced with plastic fiber with 0.75% volume fraction), one double hybrid fiber reinforced concrete mixes (0.5% plastic fiber + 0.25% steel fiber type S), and a mix with triple hybrid fiber (0.25% steel fiber type S1+ 0.25% polypropylene fiber + 0.25% steel fiber type S). Fresh (workability and fresh density) and hardened concrete properties (oven dry density, compressive strength, ultrasonic pulse velocity, splitting tensile strength, flexural strength, static modules of elasticity, thermal conductively, and water absorption) were studied. Generally, mono and hybrid (double and triple) fiber reinforced HPLWAC specimens give a significant increase in splitting tensile strength and flexural strength compared with plain HPLWAC specimens. The percentage increases in splitting tensile strength for specimens with mono plastic fiber are, 20.8%, 31.9%, 36.4% and 41%, while the percentage increases in flexure strength are 19.5%, 37%, 33.9% and 34.2% at 7, 28, 60, 90 days age respectively relative to the plain concrete. The maximum splitting tensile and flexure strengths were recorded for triple hybrid fiber reinforced HPLWAC specimens. The percentage increases in splitting tensile strength for triple hybrid fiber reinforced specimens are 19.5%, 37%, 33.9% and 34.2%, while the percentage increases in flexure strength are 50.5%, 62.4. %, 66.8% and 62.2% at 7, 28, 60 and 90 days age respectively relative to the plain concrete specimens.
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.
High strength concrete has strength significantly beyond what is used in normal practice. According to American Concrete Institute (ACI), high strength concrete revised the definition to cover mixtures with specified design strength of 55 MPa or more. The main objective of this investigation is to study the effect of using different supplementary cementitious materials in binary blends on mechanical properties of high strength concrete.The experimental work includes three stages: firstly, preparation of cementitious materials (metakaolin and pumice) from local materials, second involves conducting several trial mixes to choose the best of superplasticizer that satisfies the required properties and to specify the optimum water content which is designed in laboratory by 0.3 W/Cm ratio, to achieve workability with (60-80mm) slump and the best compressive strength which was 64.6 at 28 days.Thirdly carrying out tests to find out the compressive strength, splitting tensile strength, modulus of rupture, on binary concretes including mixes containing silica fume as cement replacement at percentages of 8%, 10% and 15%, mixes containing metakaolin as cement replacement levels of 10%, 15%, and 20% and mixes containing pumice at cement replacement of 10%, 15%, and 20%.These properies were measured at ages ranging from7 days to 180 days.The results indicate that the silica fume performs better than other supplementary cementitious materials (metakaolin or pumice) in terms of the compressive strength, splitting tensile strength and modulus of rupture development at ages of 7,28,60,90and180 days where the average percentage of increase when using 8%,10% and 15% of silica fume was about (19%,23% and 18.7%) ,respectively, while when using 10%,15% and 20% metakaolin the average percentage of increase was (10%,12.6% and 4%) respectively, also when using 10%,15% and 20% of pumice the average percentage of increase was (2.6%, 6% and 1.5%), respectively.
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