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Showing papers on "Compressive strength published in 2021"


Journal ArticleDOI
TL;DR: In this paper, the authors provide a comprehensive review on recycled aggregate (RA) and recycled aggregate concrete (RAC) regarding their history, recycling, reuse and manufacture process, inherent defects (e.g. existing of additional interfacial transition zones in RAC), and materials properties.
Abstract: Using recycled aggregate s from construction and demolition waste can preserve natural aggregate resources, reduce demand of landfill, and contribute to sustainable built environment. This study provides a comprehensive review on recycled aggregate (RA) and recycled aggregate concrete (RAC) regarding their history, recycling, reuse and manufacture process, inherent defects (e.g. existing of additional interfacial transition zones in RAC), and materials properties. Specifically, these properties of RAC include fresh concrete workability, physical and chemical properties (i.e. density, carbonation depth, and chloride ion penetration), mechanical properties (i.e. compressive, flexural, and splitting tensile strength as well as elastic modulus), and long-term performance (i.e. freezing-thawing resistance, alkali-silica reaction resistance, creep, and dry shrinkage). On top of that, methods for improving RAC mechanical properties and long-term performance are summarized and categorized into three groups, i.e. (1) reduction of recycled aggregate porosity, (2) reduction of old mortar layer on recycled aggregate surface, and (3) property improvement without recycled aggregate modification (i.e. different concrete mixing design and addition of fibre reinforcement). Next, current regression-based models and artificial intelligence models on the prediction of compressive strength, modulus, and compressive stress-strain curves of RAC are reviewed and the ir limitations of those models are discussed. Furthermore, the state-of-the-art RAC applications are presented. Additionally, challenges of RAC application are reviewed taking China as an example. The link between material from CDW and EU green policy are discussed by analysing the previous research projects funded by European Commission. Finally, future perspectives of RAC research focus are discussed, i.e. development of “green” treatment methods on recycled aggregate s , further direction on nanoparticle application in RAC, and the establishment of database for RAC strength prediction.

213 citations


Journal ArticleDOI
TL;DR: The developed ANN model has been introduced as the best predictive technique for solving problem of the compressive strength of mortars and an ambitious attempt to reveal the nature of mortar materials has been made.
Abstract: Despite the extensive use of mortars materials in constructions over the last decades, there is not yet a reliable and robust method, available in the literature, which can estimate its strength based on its mix parameters. This limitation is due to the highly nonlinear relation between the mortar’s compressive strength and the mixed components. In this paper, the application of artificial intelligence techniques toward the prediction of the compressive strength of cement-based mortar materials with or without metakaolin has been investigated. Specifically, surrogate models (such as artificial neural network, ANN and adaptive neuro-fuzzy inference system, ANFIS models) have been developed to the prediction of the compressive strength of mortars trained using experimental data available in the literature. The comparison of the derived results with the experimental findings demonstrates the ability of both ANN and ANFIS models to approximate the compressive strength of mortars in a reliable and robust manner. Although ANFIS was able to obtain higher performance prediction to estimate the compressive strength of mortars compared to ANN model, it was found through the verification process of some other additional data, the ANFIS model has overfitted the data. Therefore, the developed ANN model has been introduced as the best predictive technique for solving problem of the compressive strength of mortars. Furthermore, using the optimum developed model an ambitious attempt to reveal the nature of mortar materials has been made.

187 citations


Journal ArticleDOI
TL;DR: In this paper, an Artificial Neural Network (ANN) was proposed to predict the compressive strength of pozzolanic GPC based on ground granulated blast-furnace slag.

158 citations


Journal ArticleDOI
TL;DR: Findings demonstrated that the proposed ICA-XGBoost model performed better than the other models in estimating compressive strength of recycled aggregate concrete, and can be used in construction engineering in order to ensure adequate mechanical performance of the recycled aggregatecrete and allow its safe use for building purposes.
Abstract: Recycled aggregate concrete is used as an alternative material in construction engineering, aiming to environmental protection and sustainable development. However, the compressive strength of this concrete material is considered as a crucial parameter and an important concern for construction engineers regarding its application. In the present work, the 28-days compressive strength of recycled aggregate concrete is investigated through four artificial intelligence techniques based on a meta-heuristic search of sociopolitical algorithm (i.e. ICA) and XGBoost, called the ICA-XGBoost model. Based on performance indices, the optimum among these developed models proved to be ICA-XGBoost model. Namely, findings demonstrated that the proposed ICA-XGBoost model performed better than the other models (i.e. ICA-ANN, ICA-SVR, and ICA-ANFIS models) in estimating compressive strength of recycled aggregate concrete. The suggested model can be used in construction engineering in order to ensure adequate mechanical performance of the recycled aggregate concrete and allow its safe use for building purposes.

155 citations


Journal ArticleDOI
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


Journal ArticleDOI
TL;DR: In this paper, the influence of steam curing on mechanical as well as microscopic performances of metakaolin (MK) contained UHPC matrix was investigated at various steam curing regimes with variable curing temperatures and durations.

133 citations


Journal ArticleDOI
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


Journal ArticleDOI
TL;DR: In this article, the effect of mix proportioning on fresh, hardened and durability properties of fly ash and fly ash-slag geopolymer mortar is discussed. But, the main focus of this paper is on the quality of the mortar.

109 citations


Journal ArticleDOI
TL;DR: In this paper, a 50-60% (TiC+TiB2)/Al composites were fabricated in Al-Ti-B4C system via a one-step method of reaction and densification, and their interface bonding and mechanical properties were compared with those of in-situ TiC/Al composite.
Abstract: As interfaces play a more important role in high-volume-fraction ceramic/metal composites because of containing more hetero-phase interfaces, it is a great challenge to control the interfaces in such composites to balance their strength and plasticity and to obtain high performances. In this work, 50–60 vol% (TiC + TiB2)/Al composites were fabricated in Al–Ti–B4C system via a one-step method of reaction and densification, and their interface bonding and mechanical properties were compared with those of in-situ TiC/Al composites. Apparently, the defects, such as interfacial discontinuity, macro-pores, coarsening and agglomeration of particles, caused by increased ceramic content in the TiC/Al composites, are eliminated in the (TiC + TiB2)/Al composites using Al–Ti–B4C system. The 60 vol% (TiC + TiB2)/Al composite exhibits significantly enhanced mechanical properties, i.e. 70.5%, 60.7% and 69.8% respectively higher yield strength, ultimate compressive strength and plastic strain than 60 vol% TiC/Al composite. Such enhanced mechanical properties are attributed to the improvement in interface bonding strength and therefore the increase in the energy dissipation of crack propagation. The formation of enhanced interface in the (TiC + TiB2)/Al composites results from the reduction in the reaction heat in the Al–Ti–B4C system, improved crystallographic match and improved adhesion work between ceramic particles and matrix. This work may provide a new idea for the design and control of interfaces in high-volume-fraction ceramic-metal composites.

108 citations


Journal ArticleDOI
TL;DR: In this paper, the shredded face mask (SFM) was added to the recycled concrete aggregate (RCA) for road base and subbase applications to increase the strength and stiffness.

106 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented a data-driven approach to the shear strength of reinforced concrete beams and incorporated the largest database compilation of 507 experimental data, including the ratio of shear span to effective depth, concrete compressive strength, longitudinal reinforcement ratio, volume fraction, aspect ratio, and type of fiber.

Journal ArticleDOI
TL;DR: In this article, an Artificial Neural Network (ANN) was used to predict the compressive strength of the fiber reinforced geopolymer concrete based on three different input conditions, including the molarity of alkaline solution, utilization of Ground Granulated Blast Furnace Slag and glass fiber.

Journal ArticleDOI
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.

Journal ArticleDOI
TL;DR: In this article, the compressive strength of fly ash residual from thermal industries has been used in the production of FA-based geopolymer concrete (FGPC) to avoid time-consuming and costly experimental procedures, soft computing techniques, namely, random forest regression (RFR) and gene expression programming (GEP), are used in order to develop an empirical model for the prediction of compressive strengths.
Abstract: Fly ash (FA) is a residual from thermal industries that has been effectively utilized in the production of FA-based geopolymer concrete (FGPC). To avoid time-consuming and costly experimental procedures, soft computing techniques, namely, random forest regression (RFR) and gene expression programming (GEP), are used in this study to develop an empirical model for the prediction of compressive strength of FGPC. A widespread, reliable, and consistent database of compressive strength of FGPC is set up via a comprehensive literature review. The database consists of 298 compressive strength data points. The influential parameters that are considered as input variables for modelling are curing temperature , curing time , age of the specimen , the molarity of NaOH solution , percent SiO2 solids to water ratio in sodium silicate (Na2SiO3) solution, percent volume of total aggregate (), fine aggregate to the total aggregate ratio , sodium oxide (Na2O) to water ratio in Na2SiO3 solution, alkali or activator to the FA ratio , Na2SiO3 to NaOH ratio , percent plasticizer (), and extra water added as percent FA . RFR is an ensemble algorithm and gives outburst performance as compared to GEP. However, GEP proposed an empirical expression that can be used to estimate the compressive strength of FGPC. The accuracy and performance of both models are evaluated via statistical error checks, and external validation is considered. The proposed GEP equation is used for sensitivity analysis and parametric study and then compared with nonlinear and linear regression expressions.

Journal ArticleDOI
TL;DR: In this paper, a dual mechanism of direct reaction and precipitation has been put forward to describe the formation of the TiB phase, which can be mainly attributed to Hall-Petch strengthening and load-bearing transformation strengthening.
Abstract: In-situ TiB reinforced titanium matrix composites (TMCs) were fabricated by selective laser melting (SLM) of ball-milled Ti6Al4V–TiB2 powders. Optimized SLM processing and stress relief annealing were applied to obtain crack-free and fully dense composites. TiB reinforcement is mainly present in the form of whisker clusters and exhibits a quasi-continuous distribution in TMC1 (2 vol%TiB) while a full-continuous distribution in TMC2 (5 vol%TiB). The distribution of TiB whisker clusters in primary β-Ti grain is not consistent with the complete dissolution mechanism proposed previously. As a result, a dual mechanism of direct reaction and precipitation has been put forward to describe the formation of TiB phase. The microhardness, compressive strength and tensile strength of TMC1 are improved by 14%, 36%, 25% respectively, compared with those of Ti6Al4V alloy. These enhancements can be mainly attributed to Hall-Petch strengthening and load-bearing transformation strengthening. The fracture surface of TMC1 after tensile testing shows a mixture of regions of cleavage facets with regions of small dimples.

Journal ArticleDOI
TL;DR: In this paper, the compressive strength of slag with D50 − 3.1μm activated by 4% Na2O-E of NS reached 36.2MPa and 77.3MPa at 28-d and 90-d age.

Journal ArticleDOI
TL;DR: In this article, a novel structural-functional integrated concrete (MPCM-UHPC) with excellent mechanical properties and thermal storage capacity was developed by incorporating microencapsulated phase change material (mPCM) into ultra-high performance concrete.

Journal ArticleDOI
TL;DR: In this paper, the relationship between compressive strength and internal crack formation (e.g., crack width and volume) of cement-fiber-tailings matrix composites (CFTMC) using an industrial computed tomography system and scanning electron microscopy.
Abstract: This paper deals the relationship between compressive strength and internal crack formation (e.g., crack width and volume) of cement-fiber-tailings matrix composites (CFTMC) using an industrial computed tomography system and scanning electron microscopy. Two types of fibers (polypropylene PP and polyacrylonitrile PAN) were used to manufacture CFTMC with a constant cement-to-tailings ratio, solid content and curing time of 1:6, 75 wt% and 14 days, respectively. The results showed that strength gaining of CFTMC increased remarkably with fiber additions which effectively improve its toughness. When compared to samples without fibers, the compressive strength of CFTMC was the highest because of the reduced interconnection between pores and high particle packing density. The internal structure analysis showed that the maximum crack widths of CFTMC increased when the fiber content increased from 0.3 to 0.6 wt%, regardless of fiber type, growing the crack volumes of samples. The failure pattern of all CFTMC samples was mainly tensile, shear and mixed failure (tensile/shear), and a high strength value accompanies with a big volume of crack. At last, the findings of this study may offer a key reference for fiber-reinforced backfills, which can lift their strength, stability and integrity behavior under extreme conditions, such as rock burst, squeezing ground, blast or seismic event.

Journal ArticleDOI
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.

Journal ArticleDOI
TL;DR: In this paper, a green foamed concrete based on river sediment-metakaolin blends was proposed. But the results showed that the results were not as good as the results obtained for the traditional Portland concrete with a similar density.

Journal ArticleDOI
TL;DR: In this paper, the impact of temperature exposure (up to 1000°C) on the microstructure and the mechanical properties of the geopolymer mortars was evaluated. And the results showed that the mortar with no slag addition yielded better performances at high temperature.

Journal ArticleDOI
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).

Journal ArticleDOI
01 Aug 2021-Silicon
TL;DR: In this paper, the effect of nano-silica and silica fume (SF) on workability, setting time, compressive strength and microstructural properties of fly ash-ground granulated blast furnace slag (FA-GGBFS) based geopolymer concrete (GPC) is investigated.
Abstract: In this study, the effect of nano-silica (NS) and silica fume (SF) on workability, setting time, compressive strength and microstructural properties of fly ash-ground granulated blast furnace slag (FA-GGBFS) based geopolymer concrete (GPC) is investigated. Five mixtures of each containing 0.5%, 1.0%, 1.5%, 2.0% and 2.5% NS and SF are prepared for this investigation. The optimum GPC mixture with NS resulted in compressive strength of 63 MPa and the SF modified GPC achieved a compressive strength of 59.59 MPa after 28 days of outdoor temperature curing (Avg. temp. 31.4℃). The hardened concrete samples are analyzed through X-ray diffraction (XRD), X-ray fluorescence (XRF), field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), and petrographic examination, for the better understanding of geopolymer mineralogy, mechanism and microstructure. Results indicate that both NS and SF facilitated a higher degree of geopolymerization, leading to the densification of the geopolymer matrix which led to the improvement of the properties of FA-GGBFS based GPC.

Journal ArticleDOI
TL;DR: In this article, a comprehensive review was carried out on the influence of recycled plastic fibers (RPFs), recycled carpet fibers (RCFs) and recycled steel fibers (RSFs) on the fresh, mechanical and ductility properties of concrete.
Abstract: Municipal solid waste materials are growing worldwide due to human consumption. Nowadays, a different type of goods on large-scale is produced in the factories which is going to generate numerous amount of solid waste materials in the near future. Therefore, the management of these solid waste materials is a great concern around the world. Inadequate landfill, environmental pollution and its financial burden on relevant authorities, recycling and utilization of waste materials have a significant impact compared to disposing them. Studies have been done to reuse of waste materials as one of the elements of concrete composites. Each of the elements gives the concrete strength; however, the reuse of these wastes not only makes the concrete economical and sustainable, but also helps in decreasing environmental pollution. There are a number of different types of waste materials such as plastics, carpets, steels, tires, glass, and several types of ashes. In this paper, a comprehensive review was carried out on the influence of recycled plastic fibers (RPFs), recycled carpet fibers (RCFs) and recycled steel fibers (RSFs) on the fresh, mechanical and ductility properties of concrete. The previous studies were investigated to highlight the effects of these waste product fibers on the most important concrete properties such as slump, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity, energy absorption, ductility, and toughness. In this regard, more than 200 published papers were collected, and then the methods of preparation and properties of these recycled fibers (RF) were reviewed and analyzed. Moreover, empirical models using mechanical properties were also developed. As a result, RPFs, RCFs and RSFs could be used safely in concrete composites due to it is satisfactory fresh, physical and mechanical properties.

Journal ArticleDOI
TL;DR: In this article, the compressive strength and elastic modulus of compressed RAC and treated RAC incorporating 10-20% of CR in replacement of coarse aggregates are quite close to traditional concrete specimens without CR.
Abstract: The inferior performance of eco-friendly concrete owing to the addition of waste materials is a big hurdle in its practical adaptation. This study focuses on developing eco-friendly and green concrete, having performance similar to normal aggregate concrete (NAC). For this purpose, two waste products, including recycled aggregates (RA) and waste tire chipped rubber (CR), were used during the study. Furthermore, green concrete was also manufactured using RA treated through techniques such as lime immersion with carbonation and acetic acid immersion with mechanical rubbing. To achieve the strength of green concrete similar to NAC, an innovative concrete casting approach was followed. Green concrete specimens were cast and then compressed in the fresh state using specially designed molds. Results show that the compressive strength of recycled aggregate concrete (RAC) incorporating 20% CR in replacement of coarse aggregates is noticed 49% lower than NAC. However, the compressive strength and elastic modulus of compressed RAC and treated RAC incorporating 10-20% of CR in replacement of coarse aggregates are quite close to traditional concrete specimens without CR. No such method is available in the current literature through which green concrete incorporating RA and CR can achieve properties similar to NAC. Furthermore, the cost comparison and cement strength contribution index calculated in this study also show the industrial application potential of the new casting approach. Therefore, the developed concrete casting approach promotes the efficient utilization of RA and CR in the production of precast concrete members resulting in eco-friendly and sustainable construction.

Journal ArticleDOI
TL;DR: In this article, a review on the production of supplemental-cementing-materials (SCMs), their economic returns, environmental and durability impacts, the conceptual model for geopolymerization, durability affecting factors, and function and long-term durability properties of geocrete is presented.

Journal ArticleDOI
TL;DR: In this paper, the influence of different FA fineness, UFA content (30-70%), and curing regimes on the compressive strength and microstructure of steam-cured high volume fly ash cement composites were studied.

Journal ArticleDOI
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.

Journal ArticleDOI
TL;DR: In this article, the effects of adding fine grains and sintering additives on the stereolithography additive manufactured Al2O3 ceramic lattice structures with high precise and high compressive strength were investigated.

Journal ArticleDOI
TL;DR: A new type of Mg-Zn-Y-Nd alloy for degradable orthopedic implants was developed in this paper, where the Zn and Y content was adjusted and their influences on the microstructures and mechanical behaviors were discussed in depth.