Showing papers on "Compressive strength published in 2018"
TL;DR: In this paper, an Artificial Neural Network (ANN) was used to predict the compressive strength of recycled aggregate concrete (RAC) using six input features, namely water cement ratio, water absorption, fine aggregate, natural coarse aggregate, recycled coarse aggregate and water-total material ratio.
Abstract: Solid waste in the form of construction debris is one of the major environmental concerns in the world. Over 20 million tons of construction waste materials are generated in Tehran each year. A large amount of these materials can be recycled and reused as recycled aggregate concrete (RAC) for general construction, pavement and a growing number of other works that drive the demand for RAC. This paper aims to predict RAC compressive strength by using Artificial Neural Network (ANN). The training and testing data for ANN model development were prepared using 139 existing sets of data derived from 14 published literature sources. The developed ANN model uses six input features namely water cement ratio, water absorption, fine aggregate, natural coarse aggregate, recycled coarse aggregate, water-total material ratio. The ANN is modelled in MATLAB and applied to predict the compressive strength of RAC given the foregoing input features. The results indicate that the ANN is an efficient model to be used as a tool in order to predict the compressive strength of RAC which is comprised of different types and sources of recycled aggregates.
352 citations
TL;DR: In this paper, the tensile strength and elongation of the UHP-ECC achieved were 20 MPa and 8.7% respectively, which combines the strain-hardening and multiple crack characteristics and the high strength of mortar matrix.
322 citations
TL;DR: In this article, the tensile bond strength of 3D printed geopolymer mortar with respect to printing time gap between layers, nozzle speed and nozzle standoff stance was analyzed and shown that the bond strength is a function of state of interface material between two nearby layers which can be influenced by material strength development rate and 3D printing parameters.
288 citations
TL;DR: In this article, a series of experiments were carried out to measure workability, setting time, compressive strength, splitting tensile strength, flexural strength and dynamic elastic modulus of AAFS concrete.
267 citations
TL;DR: The results showed that the proposed ELM model achieved an adequate level of prediction accuracy, improving MARS, M5 Tree and SVR models, and could be employed as a reliable and accurate data intelligent approach for predicting the compressive strength of foamed concrete.
254 citations
TL;DR: In this paper, the properties of the geopolymer mortars including fresh performance (workability, setting time, and temperature of fresh mortar), physical properties, mechanical properties (compressive strength, tensile strength, elastic properties, flexural performance, bonding behavior, and fracture behavior), durability properties (acid resistance, resistance to elevated temperature, frost resistance, water absorption, and shrinkage properties) and microstructure analysis.
Abstract: Geopolymer mortar refers to the mortar manufactured with sand and geopolymer, which is composed by the base materials containing affluent aluminium and silicon that was activated by adopting alkaline solution to serve as a binder. The investigation of the properties and application of the geopolymer mortar has attracted more and more attention of the researchers and cement based industries because of its sustainability advantages. This study reviews the properties of the geopolymer mortars including fresh performance (workability, setting time, and temperature of fresh mortar), physical properties, mechanical properties (compressive strength, tensile strength, elastic properties, flexural performance, bonding behavior, and fracture behavior), durability properties (acid resistance, resistance to elevated temperature, frost resistance, water absorption, and shrinkage properties) and microstructure analysis. This study also reviews the properties of different types of geopolymer mortars prepared using various source materials as base materials. The current study results indicate that the geopolymer mortar has exhibited significant feasibility and application prospect to be used as an environmental friendly building material, which may be an appropriate replacement to the traditional cement mortar in the future.
242 citations
TL;DR: In this paper, the influence of up to 10% ground granulated blast-furnace slag (GGBS) and silica fume (SF) inclusion within geopolymer blends cured under ambient conditions was investigated in terms of fresh and hardened properties.
Abstract: This study presents the development of fly ash-based geopolymer mixtures for 3D concrete printing. The influence of up to 10% ground granulated blast-furnace slag (GGBS) and silica fume (SF) inclusion within geopolymer blends cured under ambient conditions was investigated in terms of fresh and hardened properties. Evolution of yield stress and thixotropy of the mixtures at different resting times were evaluated. Mechanical performance of the 3D printed components was assessed via compressive strength measurements and compared with casted samples. SF demonstrated a significant influence on fresh properties (e.g. recovery of viscosity), whereas the use of GGBS led to higher early strength development within geopolymer systems. The feasibility of the 3D printing process, during which rheology was controlled, was evaluated by considering extrusion and shape retention parameters. The outcomes of this study led to the printing of a freeform 3D component, shedding light on the 3D printing of sustainable binder systems for various building components.
240 citations
TL;DR: In this paper, the potential of Limestone Calcined Clay Cement (LC3) for use in structural concrete in comparison with Ordinary Portland Cement and fly ash based blended cement (FA30) was described.
235 citations
TL;DR: In this paper, the microstructure and mechanical properties of commercially pure titanium (CP-Ti) gyroid scaffolds with different unit cell sizes and sample orientations were evaluated and the average microhardness of the struts was 2.27 GPa, which is ∼50% higher than that of dense cast CP-Ti.
233 citations
TL;DR: The results show that precipitation strengthening, as one of the main strengthening mechanisms, contributes to a tensile yield strength of ~1.52 GPa at room temperature, which heretofore represents the highest strength reported for an HEA with an appreciable failure strain of ~5.2%.
Abstract: High-entropy alloys (HEAs) are a class of metallic materials that have revolutionized alloy design. They are known for their high compressive strengths, often greater than 1 GPa; however, the tensile strengths of most reported HEAs are limited. Here, we report a strategy for the design and fabrication of HEAs that can achieve ultrahigh tensile strengths. The proposed strategy involves the introduction of a high density of hierarchical intragranular nanoprecipitates. To establish the validity of this strategy, we designed and fabricated a bulk Fe25Co25Ni25Al10Ti15 HEA to consist of a principal face-centered cubic (fcc) phase containing hierarchical intragranular nanoprecipitates. Our results show that precipitation strengthening, as one of the main strengthening mechanisms, contributes to a tensile yield strength (σ0.2) of ~1.86 GPa and an ultimate tensile strength of ~2.52 GPa at room temperature, which heretofore represents the highest strength reported for an HEA with an appreciable failure strain of ~5.2%.
225 citations
TL;DR: In this article, the effect of adding steel fibers with different lengths and diameters on the mechanical properties of concrete for three values of concrete strength was investigated, and the results indicated that the addition of different content and lengths of steel fiber with increasing water-to-cement ratios caused significant change in concrete, with an increase of about 10-25% in compressive strength and about 31-47% in direct tensile strength.
TL;DR: The prediction model based on deep learning exhibits the advantages including higher precision, higher efficiency and higher generalization ability compared with the traditional neural network model, and could be considered as a new method for calculating the strength of recycled concrete.
TL;DR: Estimating the compressive strength of silica fume concrete using the ANN method was considered as a two-objective optimization problem, and an ANN model with just one hidden layer with five neurons and the Pearson correlation coefficient of 0.9617 was chosen as the final ANN model.
TL;DR: In this paper, the strength and durability properties of concrete containing RCA were evaluated by a comprehensive experimental investigation involving nine control mixes, and the test results showed that up to 25% of natural crushed stone aggregates in concrete can be replaced with RCA, without significantly affecting the strength of concrete and that the partial replacement of natural aggregates with aggregate can be recommended in areas of moderate exposure conditions.
Abstract: Recycled concrete aggregates (RCA) sourced from waste concrete are a sustainable alternative to natural crushed stone aggregates. The strength and durability properties of concrete containing RCA were evaluated by a comprehensive experimental investigation involving nine control mixes. The variables considered in the experimental study are water cement ratio, cement content in concrete and percentage replacement of coarse aggregate. The strength properties such as compressive strength, modulus of elasticity, splitting tensile strength and flexural strength are studied. Durability properties such as water absorption, sorptivity, acid attack resistance and chloride permeability are also determined. The test results showed that up to 25% of natural crushed stone aggregates in concrete may be replaced with RCA, without significantly affecting the strength of concrete and that the partial replacement of natural aggregates with RCA can be recommended in areas of moderate exposure conditions. Mathematical models developed in the study can be used for the a priori prediction of the strength parameters of RCA concrete. A mix design methodology using the developed models is proposed to aid practicing engineers to determine the mix proportions of RCA concrete.
TL;DR: In this article, the authors evaluated the application of class F fly ash as a partial replacement of binder in concrete and found that the fly ash concrete exhibited lower water sorptivity and chloride permeability.
TL;DR: An intelligent technique is proposed for predicting the unconfined compressive strength (UCS) of CPB using a combination of the artificial neural network (ANN) and particle swarm optimization (PSO).
TL;DR: In this article, the authors compared the mechanical performance of clayey soil stabilization using volcanic ash (VA) based geopolymer and ordinary Portland cement (OPC) and determined the effects of curing conditions and time.
TL;DR: The dependence of the compressive strength upon dry density, water content, curing conditions, cement type and foaming agents employed in the cement paste is investigated in this paper, where the authors present the first results of an ongoing experimental campaign focused on foamed concrete.
TL;DR: In this article, the authors applied the Fuller Thompson theory and Marson-Percy model in designing cementitious materials for 3D Cementitious Materials Printing (3DCMP), and various gradation methods were adopted in this study.
TL;DR: In this paper, an attempt to use nano SiO2 (NS) and silica fume (SF) modifying cement mortar as a surface protection material (SPM) was made, in order to promote penetration resistance of the whole system.
Abstract: In corrosion environment, corrosion ions can easily penetrate from the surface into the inside of the concrete due to the porous structure of the surface; in this case, concrete can inevitably suffer from the damage. In this study, an attempt to use nano SiO2 (NS) and silica fume (SF) modifying cement mortar as a Surface Protection Material (SPM) was made, in order to promote penetration resistance of the whole system. SPM was coated on the surface of matrix, and then interfacial bond strength between matrix and SPM was measured; shrinkage consistency was also considered; the chloride penetrability of the system was examined as well. To reveal the mechanism, effect of NS and SF on pore structure, Interfacial Transition Zone (ITZ), hydration process, and compressive strength of SPM were investigated. The results show that matrix coated with SPM on the surface has a good integrity, with excellent interfacial bond strength and little difference in shrinkage, and chloride diffusion coefficient of the system was considerably declined, in comparison with the matrix, showing an excellent penetration resistance. The mechanism behind is that SPM, which was modified with SF-NS, shows the excellent impermeability, and this kind of material existing on the surface can noticeably obstruct the chloride ions penetrating into the inside. In cement hydration process, SF and NS can not only consume a large amount of CH to form dense C-S-H, but also exert the grading filling effect, resulting in the decline in porosity, the increase in density, the improvement in microstructure of ITZ, and the enhancement in mechanical performance. The findings can provide useful experience for the design of the cement-based materials servicing in high corrosion environment.
TL;DR: In this article, the effect of fresh biochar and biochar saturated with carbon dioxide a priori on the setting time, mechanical strength and permeability of cement mortar was evaluated, and the experimental results suggested that biochar addition can impart ductility to mortar under flexure, although flexural strength was not significantly influenced.
Abstract: Biochar is widely considered as effective way of sequestering carbon dioxide. The possibility of using it to enhance the mechanical strength and reduce permeability of cement mortar is explored in this study. The effect of fresh biochar and biochar saturated with carbon dioxide a priori on the setting time, mechanical strength and permeability of cement mortar was evaluated. The biochar was prepared from mixed wood saw dust at 300 °C and added to mortar during mixing at 2% by weight of cement. It was found that addition of fresh biochar and saturated biochar reduce initial setting time and significantly improve early compressive strength of mortar. The experimental results suggested that biochar addition can impart ductility to mortar under flexure, although flexural strength was not significantly influenced. Water penetration and sorptivity of mortar was significantly reduced due to addition of biochar, which indicate higher impermeability in biochar added mortar. However, it is found that addition of fresh biochar offers significantly higher mechanical strength and improved permeability compared to biochar saturated with carbon dioxide. These results suggest that biochar has the potential to be successfully deployed as a carbon sequestering admixture in concrete constructions that also provides a way to waste recycling.
TL;DR: In this paper, the micro-structure analyses of the geopolymer specimens and comparison of geopolymers with various binders are presented. But, most of the products revealed a wide hump in the XRD analysis due to the amorphous structure of aluminosilicate, and the results showed that the binders mixed with lower sodium silicate to sodium hydroxide mass ratio of 2.0-2.5 tend to react more efficiently.
TL;DR: In this paper, the effect of alkali activator concentration and curing conditions on consistency and strength of waste clay brick powder-based geopolymer composites was investigated, and it was determined that the microstructure analysis results were consistent with the compressive strength results.
Abstract: The effect of alkali activator concentration and curing conditions on consistency and strength of waste clay brick powder-based geopolymer composites was investigated. For this purpose, geopolymer mortars with twenty different activator concentrations were produced and those mixtures having optimum alkali activator concentration were subjected to different curing conditions. Test results indicated that the optimum alkali activator concentration corresponded to M s (SiO 2 /Na 2 O) ratio of 1.6 and Na 2 O content of 10% by weight of the binder. A maximum compressive strength of 36.2 MPa was achieved by curing at 90 °C, 40% RH for 5 days. In order to characterise the morphology and the structure of the resultant composites, x-ray powder diffraction analysis, thermogravimetric analysis, fourier transform infrared spectroscopy analysis, scanning electron microscopy analysis and micro computed tomography analysis were performed. It was determined that the microstructure analysis results were consistent with the compressive strength results. Denser structure was observed by microstructure analysis in the mixtures having high compressive strength.
17 Jan 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: An equi-atomic WNbMoTaV high entropy alloy (HEA) with a single body-centered cubic structure (BCC) was firstly fabricated by the powder metallurgical process of mechanical alloying (MA) and spark plasma sintering (SPS) as mentioned in this paper.
Abstract: An equi-atomic WNbMoTaV high entropy alloy (HEA) with a single body-centered cubic structure (BCC) was firstly fabricated by the powder metallurgical process of mechanical alloying (MA) and spark plasma sintering (SPS). Mechanical alloying behavior, microstructure and mechanical properties of the WNbMoTaV HEA were studied systematically. During MA, a single BCC phase was formed and the average particle size and crystallite size was refined to 1.83 µm and 66.1 nm, respectively, after 6 h of MA. Afterward, the as-milled powders were subsequently sintered in the temperature range of 1500–1700 °C. The microstructure of the sintered sample exhibits a few micrometer-scale grain size and a homogeneous BCC matrix with a small amount of oxide inclusion originated from oxidation during the powder metallurgical process. The bulk sample of the WNbMoTaV HEA sintered at 1500 °C shows an ultra-high compressive yield strength of 2612 MPa with a failure strain of 8.8% at room temperature, respectively. These mechanical properties of the WNbMoTaV HEA fabricated by the powder metallurgical process were attributed to the combined effects of grain boundary strengthening, substitutional solid solution strengthening, interstitial solid solution strengthening and Orowan strengthening by the oxide inclusions. Through a Hall-Petch analysis, the Hall-Petch coefficient of the WNbMoTaV HEA was derived. The WNbMoTaV HEA fabricated via the powder metallurgical process showed the best compressive yield strength when compared with the other reported refractory HEAs processed with arc-melting and casting.
TL;DR: In this article, the utilization of industrial byproducts such as ground granulated blast furnace slag (GGBS) and rice husk ash (RHA) for the development of sustainable geopolymer concrete was presented and the effect of adding RHA as partial replacement of GGBS on compressive strength, split tensile strength, chloride permeability and sorptivity were investigated up to the age of 90 days.
TL;DR: In this article, the authors compared the fresh and hardened properties of seawater-mixed concretes and found that seawater had a notable effect on the fresh concrete properties.
TL;DR: In this paper, the compressive strengths and microstructures of geopolymer pastes containing waste glass powder and high-calcium fly ash were investigated, and the results indicated that waste glass powders could be used to replace fly ash to produce geopolymers with 7-d compressive strength of 34-48MPa.
TL;DR: In this paper, the compressive strength, geopolymerization process, and microstructure of the geopolymers were characterized in this study, and it was shown that the high alkalinity of red mud contributed to geopolymization, but additional NaOH was necessary to achieve maximum compressive strengths.
TL;DR: In this paper, the authors proposed a strength prediction model integrating boosted regression trees (BRT) and particle swarm optimization (PSO), where the BRT algorithm was used for modelling the non-linear relationship between inputs and outputs and PSO was used to tune BRT hyper-parameters.
TL;DR: In this article, an optimum post-SLM heat treatment scheme at a temperature below the β transus temperature was proposed based on the understanding of microstructure evolution occurring during subtransus treatment and the resultant mechanical properties of the alloy.