Showing papers on "Flexural strength published in 2021"
TL;DR: In this article, the state-of-the-art technologies for developing UHPC mixtures with improved properties are reviewed, including the typical ingredients (e.g., binders, aggregates, chemical admixtures, and fibers).
Abstract: Ultra-high-performance concrete (UHPC) is a type of cement-based composite for new construction and/or restoration of existing structures to extend service life. UHPC features superior workability, mechanical properties, and durability compared with conventional concrete. However, some challenges limit the wider application of UHPC, such as low workability for large-volume production, high autogenous shrinkage, insufficient flexural/tensile properties, and unpredictable durability after concrete cracking. Therefore, this paper reviews the state-of-the-art technologies for developing UHPC mixtures with improved properties. This review covers the following aspects: (1) the existing design methodologies; (2) the typical ingredients (e.g., binders, aggregates, chemical admixtures, and fibers) for preparation of UHPC and the underlying working principals; (3) the technologies for improving and controlling key properties (e.g., workability, autogenous shrinkage, compressive performance, tensile/flexural properties, and durability); and (4) the representative successful applications. This review is expected to advance the fundamental knowledge of UHPC and promote further research and applications of UHPC.
187 citations
TL;DR: The water-to-cement ratio and silica fume content were the most influential factors in the prediction of compressive strength of SFRC, whereas the silicafume and fiber volume fraction most strongly influenced the flexural strength.
140 citations
TL;DR: In this paper, the authors investigated employing recycled concrete aggregate (RCA) and pozzolanic additives as a partial replacement (PR) of natural coarse aggregate (NCA), and Portland cement, respectively.
126 citations
110 citations
TL;DR: In this paper, the effects of various printing parameters including nozzle temperature, platform temperature, printing speed and layer thickness on the mechanical properties (including tensile strength, flexural strength and impact strength) were surveyed.
105 citations
TL;DR: In this article, the effect of seven different types of nano rice husk ash (NRHA) on the mechanical, ultrasonic pulse velocity, and durability of ultra-high-performance concrete (UHPC), whereby two different scenarios were applied.
99 citations
TL;DR: In this paper, the effect of high temperatures on lightweight geopolymer concrete and lightweight ordinary concrete made of natural pumice and lightweight expanded clay aggregate (LECA) with the addition of trapped air was examined.
88 citations
TL;DR: In this article, the authors investigated the effect of glass fiber and polypropylene fiber on the mechanical and microstructural properties of concrete as a function of the water/binder ratio and fiber content.
84 citations
TL;DR: In this paper, the authors present a comprehensive review on the workability and mechanical properties of fiber reinforced recycled aggregate concrete (FRAC) and highlight the most promising and feasible strength enhancement methods for the FRAC mainly using steel fiber, polypropylene fiber (PPF), basalt fiber (BF), and glass fiber (GF).
83 citations
TL;DR: In this paper, the influence of nano-SiO2 and nano-CaCO3 on mechanical properties of ultra-high performance concrete (UHPC) made with 2% steel fibers was investigated.
Abstract: The unique physical and chemical properties of nano-particles can enhance the nature of cement-based materials at the micro-scale and nano-scale levels, leading to improved properties. To uncover the strengthening mechanism associated with various types of nano-particles, a laboratory investigation was undertaken to evaluate and compare the influence of nano-SiO2 and nano-CaCO3 on mechanical properties of ultra-high performance concrete (UHPC) made with 2% steel fibers. Each type of nano-particle was incorporated at four contents, and the mini-slump flow of the UHPC was maintained at 240–260 mm. The microstructure of the matrix and the fiber-matrix interface of UHPC, as well as the features of hydration products were characterized using advanced techniques, such as electron microscopy (SEM), X-ray diffraction (XRD), differential thermal gravimetric (DTG) analyses, 3D micro-tomography, and mercury intrusion porosimetry (MIP). Test results indicate that both the fiber-matrix strength and mechanical strength of UHPC increased with the increase of nano-SiO2 and nano-CaCO3 until threshold limits of 1% and 3.2%, respectively. The 28-d fiber-matrix bond, compressive, and flexural strengths of the optimal UHPC mixtures made with 3.2% nano-CaCO3 were approximately 40%, 10%, and 20%, respectively, greater than those of the reference mixture. These strength values were higher than those of UHPC made with 1% nano-SiO2. When used below these optimal nano-material contents, the filler and nucleation effects related of the nano-SiO2 and nano-CaCO3 promoted the strength development through improved density and homogeneity with optimized structure of hydration products, as indicated by SEM observation and DTG analysis. Beyond these limits, additional use of nano-materials resulted in increased volume of air voids and capillary pores and weak interfacial zones due to the agglomeration of nano-particles, which hindered strength development.
81 citations
TL;DR: In this paper, the application of geopolymer tiles in conditions of high temperature and saturation was evaluated in order to understand how fires and rains modify the performance of these materials, and the results showed that due to the non-formation of polysialate networks in an effective way, formulations 3.50 and 4.00 showed a high drop in properties, differently from formulations 2.25, 2.50, and 3.00.
TL;DR: In this article, the authors developed a novel ultra-high ductile concrete (UHDC) for 3D concrete printing, which was modified using crumb rubber to possess high ductility, and a series of mechanical tests including uniaxial tensile test, compressive test, flexural test and double shear test, were carried out to investigate the anisotropic-mechanical properties of the printed UHDC.
Abstract: This study developed a novel ultra-high ductile concrete (UHDC) for 3D concrete printing, which was modified using crumb rubber to possess high ductility. Flowability tests were conducted to determine optimal open time range for continuous printing. A series of mechanical tests, including uniaxial tensile test, compressive test, flexural test and double shear test, were carried out to investigate the anisotropic-mechanical properties of the printed UHDC. The results indicate that the tensile strength, flexural strength and shear strength of the printed specimens were slightly lower than those of mold-cast specimens, while reverse tendency was observed in compressive strength. It is of interest that the deformability and energy dissipation of the printed UHDC at some directions are higher than those of mold-cast UHDC. Additionally, it is found that the printed UHDC performed minimal anisotropy in flexural strength, but significant anisotropy in flexural deformability, compressive and flexural energy dissipation capacity.
TL;DR: In this article, the effects of combined application of calcium silicate hydrate seed-Polycarboxylate (C-S-Hs-PCE) and sodium sulfate (SS) on the hydration kinetics and mechanical properties of cement paste were evaluated.
TL;DR: In this paper, the effects of water absorption on the mechanical properties of hybrid phenol formaldehyde (PF) composite fabricated with Areca Fine Fibres (AFFs) and Calotropis Gigantea Fibre (CGF).
Abstract: This investigation is carried out to understand the effects of water absorption on the mechanical properties of hybrid phenol formaldehyde (PF) composite fabricated with Areca Fine Fibres (AFFs) and Calotropis Gigantea Fibre (CGF). Hybrid CGF/AFF/PF composites were manufactured using the hand layup technique at varying weight percentages of fibre reinforcement (25, 35 and 45%). Hybrid composite having 35 wt.% showed better mechanical properties (tensile strength ca. 59 MPa, flexural strength ca. 73 MPa and impact strength 1.43 kJ/m2) under wet and dry conditions as compared to the other hybrid composites. In general, the inclusion of the fibres enhanced the mechanical properties of neat PF. Increase in the fibre content increased the water absorption, however, after 120 h of immersion, all the composites attained an equilibrium state.
TL;DR: In this article, a group of spore-forming bacterium related with gen Bacillus subtilis M9 was selected for cultivation at elevated pH solution to develop novel bacteria-based self-healing concrete by microbial induced calcium carbonate precipitation mechanism.
TL;DR: In this article, a cement-free geopolymer concrete (GPC) mix is prepared using locally produced fly ash with varying NaOH concentrations (8−M−16M), Na2SiO3/NaOH ratios (1.5−2.5) and alkaline activator to fly ash (AA/FA) ratios (0.4−0.6) to investigate the influence of AL on the mechanical properties of GPC cured at ambient temperatures.
TL;DR: In this article, the physical and mechanical properties of a SBA-based geopolymer with various percentages of (PP)(PP) fibers were evaluated through the experiments and discussed in detail.
Abstract: Recently, the lightweight geopolymer production from wastes got adamant attention for sustainable and green building construction. But lower flexure and the tensile strength limit its wider application in the construction industry. This study was intended to prepare sugarcane bagasse ash (SBA) based geopolymer reinforced with (PP) (PP) fibers. The physical and mechanical properties of geopolymers with various percentages of (PP) (PP) fibers were evaluated through the experiments and discussed in detail. The addition of (PP) fibers resulted in enhanced flexural and tensile strength. Results assert that by limiting the content of (PP) fibers to 1%, not only improve in the flexural properties but also enhance the compressive strength by providing denser microstructure. This study concludes that the use of (SBA) composite reinforced with (PP) fibers can provide alternative ways to achieve sustainability by utilizing the wastes which mainly cause environmental degradation during landfilling.
TL;DR: In this paper, the effect of self-curing concretes on the engineering properties of normal strength concrete (NSC) and high-strength concrete (HSC) was investigated.
TL;DR: In this article, the effects of interfacial bond properties on the anisotropic mechanical behavior of 3D printed concrete were explored, and one finite element (FE) model which fully considered the interfacer bond properties with the traction-separation law was established and verified by the experimental results.
Abstract: This study aims to explore effects of interfacial bond properties on the anisotropic mechanical behavior of 3D printed concrete. One finite element (FE) model which fully considered the interfacial bond properties with the traction-separation law was established and verified by the experimental results. The influence of nozzle dimensions, interfacial bond strength and concrete properties on the compressive and flexural strengths was analyzed. The results show that the horizontal shear deformation between printed filaments leads to the strength reduction for the 3D printed specimen under compression, and the tensile strength at the mid-span determines the flexural strength of 3D printed specimen. The compressive strength is relatively lower while the flexural strength is much higher for the specimens loaded in Y and Z directions. The simulation shows that the number of interfaces, the tensile and shear properties of the interface between printed filaments contribute the variation of anisotropy under compression and flexure.
TL;DR: In this article, a series of experiments were carried out to study the effect of fiber content (1.0, 1.5% and 2.0% by volume fraction) on workability and mechanical-anisotropic properties of the UHDC.
TL;DR: In this paper, the micro carbon fiber (CF) was used to enhance the mechanical properties of fly ash geopolymer containing fine recycled concrete aggregate (RCA), where natural river sand was replaced with RCA at 0, 50, and 100% by volume.
Abstract: In this study, the micro carbon fiber (CF) was used to enhance the mechanical properties of fly ash geopolymer containing fine recycled concrete aggregate (RCA). Natural river sand was replaced with RCA at 0, 50, and 100% by volume. The CF was used as additive material by incorporating into the mixture at 0, 0.1, 0.2, and 0.3% by weight of fly ash. The results showed that the CF enhanced the mechanical properties of geopolymer containing RCA through the increased nucleation sites for geopolymerization reaction and the bridging effect of the fiber. For the mix with 100% RCA, the incorporation of 0.2% CF resulted geopolymer mortar with higher compressive and splitting tensile strengths . For the flexural strength and surface abrasion resistance , best results were obtained with the use of 50%RCA with significant improvement in both flexural strength and surface abrasion resistance. The incorporation of CF thus increases the use of recycled fine aggregate without resort to natural fine aggregate .
TL;DR: An overview on fiber alignment and its effect on mechanical properties of UHPC is presented in this paper, where the changes in flow patterns of mixture and the assistance of electromagnetic field during casting can lead to a higher improvement in fiber orientation (up to 80%) compared to other fiber alignment methods.
TL;DR: The role of sintering temperature on the relative density, microstructure and mechanical characteristics of as-sintered specimens were studied in this paper, and the role of produced in-situ phases on the grain growth also studied using SEM fractographs.
Abstract: Ti–10 wt% Mo–1 wt% B4C composite samples were SPSed under the circumstances of 5 min dwell time, 50 MPa external pressure and sintering temperatures of 1150 °C, 1300 °C and 1450 °C. The role of sintering temperature on the relative density, microstructure and mechanical characteristics of as-sintered specimens were studied. Near fully dense relative density was obtained for the samples sintered at 1450 °C. The best mechanical properties including UTS, elongation, bending strength and micro/macro hardness were achieved for the composites SPSed at the highest temperature. The XRD results and also microscopic photographs disclosed the formation of TiB + TiC in-situ phases. However, there was not any evidence for chemical reaction between Mo and other phases. The role of produced in-situ phases on the grain growth also studied using SEM fractographs.
TL;DR: In this paper, the effects of basalt fibres on the workability of fresh self-compacting concrete (SCC) were measured using slump flow, J-ring flow, V-funnel flow and L-box height ratio.
TL;DR: In this article, the effect of using glass powder alongside polypropylene fibers was investigated in different compression and flexural beam specimens, and the best rate for glass is 25% which causes an increase in the compressive and Flexural strengths of the concrete.
TL;DR: In this paper, the effect of the concentration of sodium hydroxide (NaOH) and substitution of GGBFS with pozzolans such as natural zeolite (NZ) and silica fume (SF) on the mechanical properties of GPC was investigated experimentally.
Abstract: Geopolymer concrete (GPC), usually produced via the activation of the cementitious nature of industrial by-products (IBPs) such as ground granulated blast furnace slag (GGBFS) and fly ash (FA), has potential to be used as a replacement for conventional portland concretes (CPCs). In this study, the effect of the concentration of sodium hydroxide (NaOH) and substitution of GGBFS with pozzolans such as natural zeolite (NZ) and silica fume (SF) on the mechanical properties of GPC was investigated experimentally. For this purpose, the compressive, flexural, and tensile strengths of various GPC mixes were measured. GPC mixes were prepared with various concentrations (i.e., 4, 6, and 8 M) of sodium hydroxide as well as GGBFS substitution (i.e., 5, 10, 15, 20, 25, and 30 wt%) with NZ and SF. Furthermore, the response surface method (RSM) was employed to achieve the optimum values of the design variables to maximize the compressive, flexural, and tensile strengths of pozzolanic GGBFS-based GPC. Overall, the results showed that with increasing NaOH concentration, the compressive strength was decreased while the maximum flexural and tensile strengths were obtained when the concentration of NaOH was 6 M compared with 4 and 8 M. In addition, the utilization of NZ improved the compressive, flexural, and tensile strengths of GGBFS-based GPC by about 4%, 6%, and 20%, respectively, at 10 wt% replacement. Moreover, the substitution of GGBFS with SF could improve the compressive, flexural, and tensile strengths of GPC up to 30%, 20%, and 25%, respectively, at 30 wt% substitution. Besides, the optimization results demonstrated that by substituting GGBFS with 60.29 kg (i.e., 15.9%) of NZ and using 5.28 M NaOH the optimal trinary conditions in terms of the compressive, flexural, and tensile strength values could be achieved. The optimal conditions could also be obtained by substituting GGBFS with 113.79 kg (i.e., 30.0%) of SF and using 6.19 M NaOH.
TL;DR: In this paper, the effects of the stacking sequence of kenaf and jute fibers on the tensile and flexural properties of the hybrid composites were analyzed, and the authors proposed a method to analyze the effect of stacking sequence on tensile properties.
Abstract: The aim of this study to analyze the effects of the stacking sequence of kenaf and jute fibers on the tensile and flexural properties of the kenaf/jute hybrid composites. Kenaf/jute/kenaf (...
TL;DR: In this article, a fly ash-steel slag-based geopolymer mortar was studied for recycling solid wastes and developing a sustainable alternative to Ordinary Portland Cement (OPC).
TL;DR: In this paper, the static and dynamic mechanical properties of an eco-friendly natural cellulosic fiber reinforced epoxy composites were evaluated using morphological and single fiber pullout studies.
Abstract: The purpose of this present research work is to assess the static and dynamic mechanical properties of an eco-friendly natural cellulosic fiber (Phoenix sp.) reinforced epoxy composites. The cellulosic fiber was isolated from Phoenix sp. plant petioles, and it was treated with various concentrations of sodium hydroxide (5, 10, 15 and 20%) solution. The impact of treatments on tensile, flexural, impact and dynamic mechanical properties of the fabricated composite was explored and optimized. Moreover, the mechanically tested samples were subjected to morphological analysis to predict the failure mechanisms. The outcomes revealed that the treated fibers had good interfacial bonding with epoxy matrix (confirmed through morphological and single fiber pull-out studies), reduced the failure mechanisms (fiber pull-outs and fiber debonding) and exhibited good static and dynamic mechanical properties of composite materials than untreated fiber composites. It is concluded that composites fabricated using 15% of sodium hydroxide treated fiber could be used to manufacture automotive panels and other lightweight industrial products.