Behavior of high performance artificial lightweight aggregate concrete reinforced with hybrid fibers

In this investigation, sustainable High Performance Lightweight Aggregate Concrete (HPLWAC) containing recycled crushed clay brick from construction and demolition waste 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 crushed brick lightweight aggregate concrete mix with compressive strength of 41.2MPa, oven dry density of 1930 kg/m3 at 28 days were prepared. The Fibers used including, macro hooked steel fiber with aspect ratio 60 (type S1), macro crimped plastic fiber (P) with aspect ratio 63, micro steel fiber with aspect ratio 65 (type S), and micro polypropylene fiber (PP) with aspect ratio 667. Six HPLWAC mixes were prepared including, one plain concrete mix (without fiber), two mono fiber reinforced concrete mixes ( reinforced with either steel fiber type S or plastic fiber with 0.75% volume fraction), two double hybrid fiber reinforced concrete mixes (0.5% steel fiber type S +0.25% polypropylene fiber and 0.5% plastic fiber + 0.25% steel fiber type S), and one 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, splitting tensile strength, flexural strength and absorption) were studied. In general mono and hybrid (double and triple) fiber reinforced HPLWAC specimens give significant increases in splitting tensile strength and flexural strength compared with plain HPLWAC specimens. The percentages increase in splitting tensile strength for specimens with mono steel fiber are 55.8%, 65.9%, 82% and 91.9%, while for specimens with mono plastic fiber the percentages increase are 34%, 45.5%, 61.5% and 71.2% 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 percentages increase in splitting tensile strength for triple hybrid fiber reinforced specimens are 57.2%, 68.6%, 87.5% and 101.8%, while the percentages increase in flexure strength are 84%, 95.6%, 6665% and 7.67% 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.

This investigation aims to study some properties of high strength lightweight aggregate concrete (HSLWAC) reinforcedwith mono and hybrid fibers in different dimensions and types. High strengthporcelinite lightweight aggregate concretemix with compressive strength 41 MPa at 28 day age was prepared. The fibers used included macro hooked steel fiber with aspect ratio 100 (type S1), macro hooked steel fiber with aspect ratio 60 (type S2), micro polypropylene fiber (pp)and micro carbon fiber (CF). Eight HSLWAC mixes were prepared including, one plain concrete mix (without fibers), three mono (single) fiber reinforced concrete mixes (with 0.5% volume fraction of steel fiber type S1, 1% volume fraction of steel fiber type S1and 0.25% volume fraction of CF) and four double hybrid fiber reinforced concretes mixes [0.5% steel fiber type S1 +0.5% steel fiber S2 mix (HSF1), 0.75% steel fiber S1+ 0.25% steel fiber type S2mix ( HSF2), 0.75% steel fiber type S1+ 0.25% pp mix (HSPPF) and 0.75% steel fiber type S1+ 0.25% CF mix (HSCF)]. Fresh properties (workability and fresh density) and hardened properties (oven dry density, compressive strength, splitting tensile strength, flexural strength and thermal conductivity) of HSLWAC were studied. Generally mono and hybrid fiber reinforced HSLWAC specimens show significant increase in splitting tensile strength and flexural strength in comparison with plain HSLWAC specimen. All hybrid fiber HSLWAC specimens show significant increase in splitting tensile strength and flexural strength compared to concrete specimens reinforced with 1% volume fraction of mono steel fiber type S1. The percentage of increase in splitting tensile strength for hybrid fiber reinforced specimens prepared from HSLWAC mixes HSF1, HSF2, HSPPF and HSCF is 316.6%, 361.1%, 377.7% and 433.3%, while the percentage of increase in flexural strength is 29.43%, 59.89%, 26.56% and 64.58% respectively relative to the plain specimens.

This paper presents an experimental work to study the effect of dune sand as an alternative to sand on the mechanical properties of hybrid fiber reinforced concrete. 24 concrete mixes were prepared, 6 of them without fibers and containing different proportions of dune sand, and 18 concrete mixes with the same proportions of dune sand but containing long and short single and hybrid steel fibers. For the purpose of studying the properties of hybrid concrete, including measuring the workability of fresh concrete, examining the compressive strength, dry density, split tensile strength, Flexural strength, ultrasonic pulse velocity testing, water absorption of hardened concrete. The main parameters were the proportions of dune sand (20 %, 40 %, 60 %, 80 %, and 100 %) in addition to the ratio 0 % without dune sand. Two types of steel fibers were used: straight steel fibers (short) with a length of 13 mm and hook end steel fibers (long) with a length of 50 mm, It is added to concrete (single or hybrid) with a total volume ratio of 1 % of the concrete volume. The tests that were conducted showed that sand dunes affect the compressive strength, especially when the percentage increased by more than 40 %, where the compressive strength of concrete decreases by 39 % when the replacement ratio reaches 100 %, but it improves with the addition of single or hybrid fibers. Also, the workability from high to medium level decreases by 30 % with increasing dune sand content, the addition of steel fibers along with dune sand significantly reduced the workability. The tensile and flexural strength decreases with the increase in the sand dune rate, but at a lower rate than the compressive strength, which was 29.3 %, 21.1 % for splitting and flexural tensile strength, respectively. The addition of steel fibers improved the mechanical properties of the hybrid concrete, which can compensate for most of the lost strength due to the increase in sand dunes ratios. The study also showed that the use of long fibers (hook end) gives better results than straight fibers. But in the case of using hybrid fibers, we can get an improvement in the mechanical properties more than using one type of fiber.

Traditional concrete, made from binding material, fine aggregate, coarse aggregate, and water, often suffers from low tensile strength and susceptibility to cracking. Microscopic cracks can develop before any significant load is applied, making the structure vulnerable to damage. Fiber reinforced concrete (FRC) tackles these issues by adding different types of fibers, like steel, glass, and polypropylene, to enhance strength and flexibility. This study aims to find the best mix for Steel Fiber Reinforced Concrete (SFRC) and Hybrid Fiber Reinforced Concrete (HFRC) of M25 grade. Compressive strength, split tensile strength, flexural strength, Young's modulus, and ultrasonic pulse velocity tests are conducted to see how well the fibers work to prevent cracks and boost strength. Results have showed that SFRC with 1.5% steel fiber content significantly improve compressive strength, split tensile strength, and flexural strength compared to normal concrete. Similarly, HFRC mix of steel, glass, and polypropylene fibers, performs well, showing a notable increase in split tensile and flexural strength. The percentage increase in strength highlights how effective fiber reinforcement can be, with HFRC showing better results in some aspects compared to SFRC. Furthermore, both SFRC and HFRC are stiffer than normal concrete, indicating better overall structural integrity. Our comparison suggests that incorporating a blend of fibers, as seen in HFRC, can provide even better results, particularly in enhancing split tensile and flexural strength, showing promise for future reinforced concrete applications.

This paper presents the result of the regression modeling of the strength properties of hybrid fiber reinforced concrete made with polypropylene fiber (PPF) and alkali resistant glass fibre (ARGF). The fibres were added to grade 25 concrete at different proportion of 0.5%, 1.0%, 1.5% and 2.0% of volume of concrete. A total of sixty three cubes samples were tested for compressive strength, twenty four cylindrical samples for split tensile strength and twenty four beam samples for flexural strength. Maximum compressive strength was attained at 1.5% fibre volume with hybrid fibre ratio of 80% ARGF and 20% PPF, maximum split tensile strength was attained at 1.0% fibre volume with hybrid fibre ratio of 80% ARGF and 20% PPF. The beam samples attained its maximum flexural strength at 1.0% fibre volume with hybrid fibre ratio of 60% ARGF and 40% PPF. Empirical expressions were established by using multiple regression analysis to predict the compressive, split tensile and flexural strengths of the hybrid fibre reinforced concrete made with PPF and ARGF. The predicted values compared favourably with the experimental results from all specimens.Keywords: alkali resistant glass fibre, compressive strength, flexural strength, hybrid fibre concrete, polypropylene fibre, regression modeling. reinforced concrete, split tensile strength

The effect of trio-fiber reinforcement on the properties of self-compacting fly ash concrete

The purpose of this investigation is to study the effect of inclusion steel fiber on microstructure and some properties of lightweight geopolymer concrete. Lightweight geopolymer concrete containing, Fly Ash, alkaline liquids (mixture of sodium hydroxide and sodium silicate solutions) and steel fibers were produced. Mixtures were prepared with, alkaline liquid to fly ash ratio of 0.4, sodium silicate: sodium hydroxide solutions of 2.5, using artificial local lightweight aggregate and steel fiber in volume fractions of 0.25%, and 0.5% with aspect ratio of 60. Reference lightweight geopolymer concrete not containing steel fiber was also prepared. Properties studied including, density, compressive strength, ultrasonic pulse velocity, splitting tensile strength, and flexural strength; also the microstructure of lightweight geopolymer concrete was investigated. Steel fibers increase the splitting and flexural tensile strength. Specimens with steel fiber volume fraction of 0.5% achieved increase in flexural strength of 6.3% relative to specimens without steel fiber at 28 day age.

Several common high elastic modulus fibers (steel fibers, basalt fibers, polyvinyl alcohol fibers) and low elastic modulus fibers (polypropylene fiber) are incorporated into the concrete, and its cube compressive strength, splitting tensile strength and flexural strength are studied. The test result and analysis demonstrate that single fiber and hybrid fiber will improve the integrity of the concrete at failure. The mechanical properties of hybrid steel fiber-polypropylene fiber reinforced concrete are excellent, and the cube compressive strength, splitting tensile strength and flexural strength respectively increase than plain concrete by 6.4%, 3.7%, 11.4%. Doped single basalt fiber or polypropylene fiber and basalt fibers hybrid has little effect on the mechanical properties of concrete. Polyvinyl alcohol fiber and polypropylene fiber hybrid exhibit ‘negative confounding effect’ on concrete, its splitting tensile and flexural strength respectively are reduced by 17.8% and 12.9% than the single-doped polyvinyl alcohol fiber concrete.

This study aims to detect the mechanical properties of lightweight aggregate moderate strength concrete (LWAMSC) reinforced with single and hybrid fibers in various types and sizes. Moderate strength pumice lightweight aggregate concrete mix with compressive strength 40 MPa at 28 day age with silica fume and superplastizier was used. The fibers used include macro hooked steel fiber with aspect ratio 80, steel fiber with aspect ratio 60, and polypropylene fiber (P.P.F). Two groups of (LWAMSC) mixes were made with reference concrete mix (without fibers). The first group of mixes were substituted three (LWAMSC) mixes with different single fiber including, concrete mix reinforced with Polypropylene (P.P.F) about 0.75 % volume fraction (P1), concrete mix reinforced with macro hooked steel fiber type SF1 with volume fraction 0.75% mix (M1) and concrete mix reinforced with macro hooked steel fiber type SF1 volume fraction 1.5% mix (M2). The second group of fiber reinforcement (0.75% steel fiber type (SF1) + 0.75% steel fiber (SF2) mix (H1), (1% steel fiber (FS1)+ 0. 5% steel fiber type (SF2) mix (H2)),and finaly (1% steel fiber type (SF1)+0.5% PPF mix (H3)). Dry density, strengths of compressive, splitting tensile, and flexural of (LWAMSC) were examined. generally single and hybrid reinforcement fiber of (LWAMSC) show important increase at flexural strength and splitting tensile strength in comparison with reference concrete.The results also show that, the optimum added proportion of fiber steel type (SF1) was (1.0%) and with (0.5%) steel fiber type (SF2) that portion raised the strengths of compressive, flexural, and splitting tensile around (4.34%), (52.93%), and (297%) respectively comparison with control mixture.

Engineering and research challenges include exhausting traditional construction resources and disposing of garbage. In order to solve these issues, industrial or agricultural waste is being extensively studied as a construction material alternative. Primary wastes in our country are Fly Ash (FA) and Coconut Shell (CS). They can cause major waste disposal concerns if mismanaged. This study is a feasibility study on employing FA (an industrial waste) as binder and coconut shell (an agricultural waste) as coarse aggregates. The composite obtained by incorporating waste materials is reinforced with hybrid fibres to enhance its mechanical performance. The work undertaken comprises four distinct phases, the first phase evaluates reference mix with conventional materials. FA is utilized as SCM in concrete in the second phase. In the third phase, Coconut Shell Aggregate (CSA) is used to partially replace Natural Coarse Aggregate (NCA). In the final phase, fibres in different proportions of polypropylene and steel fibres are included to Coconut Shell Aggregate Concrete (CSAC). The findings demonstrate that replacing up to 20% of cement with FA enhances compressive, split tensile and flexural strengths by 8.1%, 5.9%, and 7.8%, respectively. The use of CSA, while slightly reducing strength parameters compared to NCA. The incorporation of 1% steel fibers (SF) significantly enhanced the mechanical properties of CSA-based concrete, achieving increases of 11.9%, 33.0%, and 30.7% in compressive, split tensile, and flexural strengths, respectively. Adding 0.2% polypropylene fibers (PPF) to SF further amplified these strengths by 3.5%, 13.5%, and 15.6%, respectively and decrease the brittleness and improve the post-peak toughness. Advanced statistical method response surface method and artificial neural network (ANN) modeling using MATLAB proved highly effective for predicting compressive strength, with ANN showing superior accuracy compared to the response surface method. The results indicate that hybrid fibre reinforced coconut shell aggregate concrete (HFRCSAC) mixture has significant potential for use in civil engineering applications.

This study conducted an experimental investigation to evaluate the splitting tensile strength of ultra-high performance concrete (UHPC) and UHPC reinforced concrete (UHPFRC) incorporating different fibre types including copper-coated and hooked-end steel fibres, basalt fibres, polyvinyl alcohol fibres, polypropylene fibres, and hybrid fibres. The experimental results indicated the average splitting tensile strength ranges from 7.09 to 17.08 MPa, corresponding to fibre contents between 0% and 2%. In general, steel fibres enhance the splitting tensile strength of UHPC more significantly than synthetic fibres. The strength enhancement is more pronounced when the fibre content is increased from 1% to 2%. Under splitting tensile loading, all fibre-reinforced specimens exhibited ductile failure, retaining their original shape with varying degrees of cracking, while plain UHPC specimens performed brittle failure with splitting into two halves. Typical failure patterns and crack propagation stages are proposed for UHPC and UHPFRC. Furthermore, the experimental results demonstrated the use of hybrid fibres, achieved by partially substituting synthetic fibres with steel fibres, significantly enhances the splitting tensile strength. Finally, this study compiles formulae for predicting the splitting tensile strength from international standards and previous models. A comparison between the predicted and experimental splitting tensile strengths was conducted to confirm the suitability of the collected formulae.

The properties of foamed concrete reinforced with carbon fibres and hybrid fibres of carbon with polypropylene fibres has been studied. Various volumetric fractions of carbon fibres (0.5, 1 and 1.5%), hybrid fibres of carbon fibres (CF) with polypropylene fibres (PPF) as (1% CF + 0.5% PPF) & (0.5% CF + 1% PPF), also the mono polypropylene fibres as 1.5% PPF were used to reinforce foamed concrete mix. Fresh and hardened properties of all mixes included flowability, density, absorption, compressive strength, splitting tensile strength, and flexural strengths has been tested. Results showed that inclusion of carbon fibres up to 1% volumetric fraction may increase the compressive strength by about 36% higher than that of control mix. Whereas, the use of 1.5% carbon fibres exhibit significant increase in splitting and flexural tensile strengths by about 47 and 114%, respectively, compared to the reference mix. On the other hand, the hybridization of 1% CF + 0.5% PPF increased the splitting tensile strength and flexural strengths by 53% and 114%, respectively, compared with plain foamed concrete mix.

In this study, high strength concrete of 75 MPa compressive strength was investigated. The experimental program was designed to study the effect of fibers and hybrid fibers (steel and polypropylene fibers) on the fresh (workability and wet density) and hardened properties (compressive strength, splitting strength, flexural strength and dry density) of high strength concrete. Results show that decreases in slump flow of all concrete mixtures containing steel, polypropylene and hybrid fibers compared with control mix (0% fiber). Hybrid high strength concrete with steel and polypropylene fibers showed superior compressive, splitting, flexural strengths over the others concrete without or with single fibers content. The test results indicate that the maximum increase in compressive and flexural strengths are obtains with the hybridization ratio (70%steel + 30% polypropylene) and were equal to 14.54% and 23.34% respectively, compared with the control mix. While, the maximum increase in splitting tensile strength with (100% steel fiber + 0 polypropylene) is 21.19%. KEYWORDS: High strength concrete, Fibers, Hybrid fibers high strength concrete, Mechanical properties.

There is a need to investigate the flexural behavior and mechanical properties of super high-performance concrete (SHPC) for a better understanding of its response to compression, tension, and bending. Super-high-performance concrete (SHPC) lies between high-performance concrete (HPC) and ultra-high-performance concrete (UHPC) in strength, durability, and workability and is suitable for sustainable buildings. This paper presents an extensive experimental and analytical study to investigate the effect of the hybridization of micro-polypropylene and macro-steel fibers on the flexural behavior and mechanical properties of super-high-performance concrete (SHPC). The hybridization of both micro-PP fibers and macro-hooked-end ST fibers gathers the benefits of their advantages and offsets their disadvantages. Three types of fibers (micro polypropylene fibers (PP), macro hooked-end steel fiber (ST), and hybrid fiber (PP + ST)) with different fiber content up to 2% were tested to study their effect on the following: (a) the workability of fresh concrete, (b) concrete compressive strength, (c) splitting tensile strength, (d) flexural behavior, including flexural tensile strength and toughness, and (e) the optimum percentage of each of the two fibers, PP and ST, in the hybrid to get the maximum structural and economic benefits of hybridization. Based upon the experimental results and using a statistical program, formulae to calculate both the tensile splitting strength (fsp) and the flexural tensile strength in the form of the modulus of rupture (fctr) were obtained. These formulae were able to predict accurately both the splitting tensile strength and modulus of rupture for SHPC with each of the three types of fibers used in this research. Also, they were in very good agreement with the values corresponding to different experimental results of other research, which means the ability to use these equations more generally. In addition, the prediction of the additional ultimate moment provided for all fibers was investigated. This research confirms the structural and the economical efficiency of hybridization in the behavior of SHPC. It was found that the optimum percentage of the fiber volume content for the hybrid of ST and PP is 1%; 0.5% for each of the two kinds.