scholarly journals Effect of Size of Coarse Aggregate on Mechanical Properties of Metakaolin-Based Geopolymer Concrete and Ordinary Concrete

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3316
Author(s):  
Hamed Fazli ◽  
Dongming Yan ◽  
Yajun Zhang ◽  
Qiang Zeng
Keyword(s):  
Mechanical Properties ◽  
Coarse Aggregate ◽  
Mercury Intrusion Porosimetry ◽  
Experimental Studies ◽  
Aggregate Size ◽  
Promising Alternative ◽  
X Ray ◽  
Ordinary Concrete ◽  
Eds Analysis ◽  
Geopolymer Binder

Geopolymer binders are a promising alternative to ordinary Portland cement (OPC) because they can significantly reduce CO2 emissions. However, to apply geopolymer in concrete, it is critical to understand the compatibility between the coarse aggregate and the geopolymer binder. Experimental studies were conducted to explore the effect of the size of the coarse aggregate on the mechanical properties and microstructure of a metakaolin-based geopolymer (MKGP) concrete and ordinary concrete. Three coarse aggregate size grades (5–10 mm, 10–16 mm, and 16–20 mm) were adopted to prepare the specimens. The microstructure of the concretes was investigated with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) and mercury intrusion porosimetry (MIP). Results showed an opposite coarse aggregate size effect between OPC and MKGP specimens in terms of compressive strength. SEM/EDS analysis indicated that the MKGP concrete has a weaker microstructure compared to OPC concrete induced by a higher porosity. The differences in mechanical properties and pore structure between the MKGP and OPC concrete are attributed to the greatly differing shrinkages triggered by the large surface area and penny-shaped particles of metakaolin. The findings in this work help tailor the mechanical properties and microstructure of MKGP concrete for future engineering applications.

Experimental Study on Mechanical Properties of Fine Aggregate Concrete Made after Wet-Sieving Coarse Aggregate

2010 ◽  
Vol 168-170 ◽  
pp. 2200-2203 ◽  
Author(s):  
Shun Bo Zhao ◽  
Na Liang ◽  
Li Xin Liu ◽  
Li Sun ◽  
Su Yang
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Coarse Aggregate ◽  
Fine Aggregate ◽  
Concrete Wall ◽  
Aggregate Concrete ◽  
Structural Wall ◽  
Ordinary Concrete ◽  
Reinforced Composite ◽  
Wet Sieving

The validity of the wet-sieving concrete technique for building the reinforced composite concrete wall are demonstrated in the paper. The fine aggregate concrete made by ordinary concrete passing the sieve with square mash of 15 mm was cast for the surface layer, the recomposed concrete mixed by the residual concrete stayed on the sieve with the ordinary concrete was cast for the reinforced concrete structural wall. The mechanical properties such as the cubic and compressive strengths, the elastic modulus and the splitting and flexural tensile strengths of the fine aggregate concrete, the recomposed concrete and the ordinary concrete were tested and analyzed. The results show that the elastic modulus and splitting tensile strength of fine aggregate concrete reduce in some extent compared with that of ordinary concrete, the mechanical properties of recomposed concrete are almost the same as that of ordinary concrete.

Analysis and optimization of mechanical properties of recycled concrete based on aggregate characteristics

2021 ◽  
Vol 28 (1) ◽  
pp. 516-527
Author(s):  
Jiangwei Bian ◽  
Wenbing Zhang ◽  
Zhenzhong Shen ◽  
Song Li ◽  
Zhanglan Chen
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Coarse Aggregate ◽  
Aggregate Size ◽  
Peak Stress ◽  
Recycled Concrete ◽  
Maximum Aggregate Size ◽  
Coarse Aggregates ◽  
Aggregate Content ◽  
Aggregate Shape

Abstract The most significant difference between recycled and natural concretes lies in aggregates. The performance of recycled coarse aggregates directly affects the characteristics of recycled concrete. Therefore, an in-depth study of aggregate characteristics is of great significance for improving the quality of recycled concrete. Based on the coarse aggregate content, maximum aggregate size, and aggregate shape, this study uses experiments, theoretical analysis, and numerical simulation to reveal the impact of aggregate characteristics on the mechanical properties of recycled concrete. In this study, we selected the coarse aggregate content, maximum aggregate size, and the aggregate shape as design variables to establish the regression equations of the peak stress and elastic modulus of recycled concrete using the response surface methodology. The results showed that the peak stress and elastic modulus of recycled concrete reach the best when the coarse aggregate content is 45%, the maximum coarse aggregate size is 16 mm, and the regular round coarse aggregates occupy 75%. Such results provide a theoretical basis for the resource utilization and engineering design of recycled aggregates.

scholarly journals A Comparison of the Compositional, Microstructural, and Mechanical Characteristics of Ni-Free and Conventional Stainless Steel Orthodontic Wires

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3424
Author(s):  
Daniela Brüngger ◽  
Theodoros Koutsoukis ◽  
Youssef S. Al Jabbari ◽  
Monika Hersberger-Zurfluh ◽  
Spiros Zinelis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Elemental Composition ◽  
Indentation Modulus ◽  
Limited Information ◽  
X Ray Diffraction ◽  
Orthodontic Wires ◽  
Promising Alternative ◽  
X Ray ◽  
Oriented Parallel

Ni-free orthodontic wires were introduced to mitigate concerns associated with the use of Ni-containing alloys in orthodontics. However, limited information is available on their properties and therefore, the aim of this study was to characterize the elemental composition, the microstructure, and the mechanical properties of Ni-free orthodontic wires and compare them with their stainless steel (SS) counterparts. Four Ni-free and four conventional SS wires were included in this study. All the wires were initially imaged with a Scanning Electron Microscopy (SEM) and their elemental compositions were determined by X-ray Energy Dispersive Spectroscopy (EDX). Then, their microstructure was assessed by X-ray Diffraction (XRD) and the indentation modulus, elastic index, Martens Hardness and Vickers Hardness by Instrumented Indentation Testing (IIT). All the wires demonstrated surface cracks and pores oriented parallel to their long axis. The elemental composition of Ni-free alloys showed an increased Mn and Cr content while both SS and Ni-free wires shared the same dominant austenite structure. In conclusion, despite the differences in elemental composition, Ni-free wires demonstrated a similar microstructure and comparable mechanical properties with their conventional SS counterparts and thus may be considered as a promising alternative for patients with Ni supersensitivity.

scholarly journals Analysis of Petro-Physico-Mechanical Properties of Coarse Aggregate and Its Implications on the Performance Characteristics of Concrete

2020 ◽  
pp. 45-60
Author(s):  
Larry Pax Chegbeleh ◽  
Lawrence Opanin Nkansah ◽  
Frank Siaw Ackah ◽  
Richard Adams Mejida
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Coarse Aggregate ◽  
Aggregate Size ◽  
Performance Characteristics ◽  
Rock Samples ◽  
Rock Types ◽  
Strength Tests ◽  
Compressive Strength Of Concrete ◽  
The Impact

The importance of concrete as one of the major materials in the building and construction industry cannot be over emphasized due to the myriad benefits and versatility to humankind. However, its performance characteristics on the stability of engineered structures have mostly been overlooked. In this paper, petrographic characteristics and physico-mechanical properties of ten (n=10) rock samples and some quantity of coarse aggregate representing one set of samples, each obtained from two quarry sites around Amasaman and Shai Hills in the Greater Accra Region of Ghana, have been investigated. This study aimed to determine the impact of aggregate size, content and type on the compressive strength of concrete. The study was conducted through petrographic and physico-mechanical properties analyses on the samples obtained. Petrographic studies were performed on the ten (n=10) rock samples from each quarry site, while the physico-mechanical property tests were conducted directly on the coarse aggregate. However, compressive strength tests were performed on cast concretes produced from aggregates with varying sizes and type obtained from the two quarry sites. Results of the petrographic analysis reveal two rock types: Quartzo-feldspathic gneiss and Granodiorites from Amasaman quarry and also two rock types: Gneiss and Meta-granite from Shai Hills quarry. Results of the physico-mechical properties tests are consistent with requirement of approved construction standards. Compressive strength tests show increasing compressive strength of concretes with increasing aggregate nominal sizes of classes A, B and C but show reduced compressive strength for aggregate nominal sizes of class D. It can therefore, be inferred that, aggregate size and content have profound impact on compressive strength of concrete. Also, aggregate type has influence on compressive strength of concrete, as observed in higher compressive strength of concretes produced from the quartzo-feldspathic gneiss and granodiorites than concretes produced from the gneiss and meta-granites.

The Influence of the Coarse Aggregate Size on Mechanical Properties of Reinforced Concrete Beams

2012 ◽  
Vol 184-185 ◽  
pp. 696-700
Author(s):  
Hong Quan Sun ◽  
Jun Ding
Keyword(s):  
Mechanical Properties ◽  
Reinforced Concrete ◽  
Coarse Aggregate ◽  
Concrete Beams ◽  
Aggregate Size ◽  
Plane Section ◽  
Reinforced Concrete Beams ◽  
Static Loads ◽  
Small Aggregate ◽  
Normal Section

This paper gives the influence of the coarse aggregate size on the mechanical properties of the beam with different coarse aggregate sizes under static loads. In the research, three reinforced concrete beams with three different coarse aggregate sizes separately are tested. The stains and the deflections of the beams under the static loads are measured. The results show that under the action of the same loads, the maximum strains of the reinforced concrete beams with the big and the small aggregate size separately are larger than that of the beam with mixed aggregate size, and the deflection of the beam with the big aggregate size is larger than that of the beam with small aggregate size. In the loading process, the changes of the normal section strain of the reinforced concrete beams are satisfied the assumption of the plane section.

scholarly journals Uniaxial Damaged Plastic Constitutive Relation of Recycled Aggregate Concrete

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Xiaobin Hu ◽  
Qinwang Lu ◽  
Shanshan Cheng
Keyword(s):  
Mechanical Properties ◽  
Cyclic Loading ◽  
Constitutive Relation ◽  
Coarse Aggregate ◽  
Experimental Studies ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Peak Strain ◽  
Test Results ◽  
Aggregate Concrete

This paper presents a proposed uniaxial damaged plastic constitutive relation of recycled aggregate concrete (RAC) based on the experimental studies. A total of five groups of RAC specimens with different recycled coarse aggregate (RCA) replacement percentages of 0, 25%, 50%, 75%, and 100%, respectively, are tested under both monotonic loading and cyclic loading. The effect of the RCA replacement percentage is thoroughly investigated on a variety of mechanical properties, including the compressive strength, the peak strain, and the elastic modulus. Based on the test results, a uniaxial damage plastic constitutive relation of the RAC is proposed within the continuous thermodynamics framework. After validated by the experimental results, the proposed damaged plastic constitutive relation of the RAC is applied to perform nonlinear analysis of the RAC columns under cyclic loading, which provides close predictions of the hysteresis behavior of the RAC columns.

scholarly journals CHARACTERISTICS OF FRAGMENTS OF SHELLS AFTER HITTING THE TRIPLEX GLASS OF THE CAR WITH SHOTS FROM A HUNTING "SAIGA" CARBINE UNDER THE CARTRIDGE 5, 45X39

2021 ◽  
Author(s):  
Sergey Leonov
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Foreign Bodies ◽  
Experimental Studies ◽  
Dispersion Analysis ◽  
Energy Dispersion ◽  
X Ray ◽  
Wooden Frame ◽  
Eds Analysis ◽  
Scanning Electron

Abstract. The article is devoted to the possibilities of innovative research methods in forensic medicine-scanning electron microscopy with energy-dispersion analysis. The described methods were used in conducting experimental studies in the case of a gunshot retrograde injury. Aim. The purpose of the work was to study the particles formed during the destruction of a semi-shell shell and an obstacle (triplex car glass) when fired from a hunting Saiga carbine with 5. 45x39 cartridges. Material and methods. Car triplex windshields from BMW and Mercedes-Benz cars were used as a barrier. The shots were fired from a hunting Saiga carbine with a 5.45x39 cartridge. The shots were fired from a distance of 10 m. As targets, white calico with dimensions of 100x150 cm was used, stretched on a wooden frame, or fixed on a chipboard. The distance between the target and the barrier was 100 cm, which roughly corresponded to the distance from the windshield of the car to the driver and the passenger in the front seat. The studies were carried out using the SEM "Hitachi FlexSem1000 II" and the energy-dispersive X-ray spectrometer "Bruker Quantax 80". Results. As a result of the conducted research with the help of microscopy, the presence of 7 types of foreign bodies on the surface of the target was established, which are the products of the destruction of the fire projectile and the barrier: glass fragments; glass fragments; crumbly deposition of glass particles; glass fragments caked with the metal of the projectile; fragments of the projectile; spherical metal particles; overlays of molten metal in the form of puddles. With the help of energy dispersion analysis, it was possible to determine the elemental composition of the particles of the barrier, the fire shell, and to identify the overlap of the target particles. Conclusion. As a result of the experimental study, it was found that the use of SEM and EDS analysis significantly increases the effectiveness and evidence-based expert research in solving the problems of causing damage through the barrier-the windscreen of modern cars. Key words: scanning electron microscopy, gunshot trauma, energy dispersion analysis, fragments of the barrier.

Properties of Environmental Friendly Concrete Containing Recycled Coarse Aggregate and Fly Ash

2013 ◽  
Vol 368-370 ◽  
pp. 957-962
Author(s):  
Xiao Shuang Shi ◽  
Qing Yuan Wand ◽  
Lang Li ◽  
Tao Long
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Reaction Products ◽  
X Ray ◽  
Transition Zones ◽  
Environmental Friendly ◽  
Scanning Electron

Six mixtures with different ratios (0%, 50% and 100%) were designed to investigate the compressive strength, elastic modulus and Poissons ratio of geopolymeric recycled concrete (GRC). The mechanical properties and failure mechanism of recycled concrete (RAC) and GRC were tested and discussed by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). The results show that, GRC concretes are stronger than RAC concretes due to different reaction products and better microstructure in interfacial transition zones (ITZs). The EDX results show that the higher compressive strength with higher Si/Al ratio.

scholarly journals Effects of Uncrushed Aggregate on the Mechanical Properties of No-Fines Concrete

2018 ◽  
Vol 8 (3) ◽  
pp. 2882-2886 ◽  
Author(s):  
M. A. Memon ◽  
M. A. Bhutto ◽  
N. A. Lakho ◽  
I. A. Halepoto ◽  
A. N. Memon
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Coarse Aggregate ◽  
Lightweight Concrete ◽  
Aggregate Size ◽  
Unit Weight ◽  
Conventional Concrete ◽  
Major Aspect ◽  
Coarse Aggregates ◽  
Cellular Concrete

Concrete’s self-weight is a major aspect of a structure’s overall weight. Recently, the use of lightweight concrete (no-fines, foamed and cellular concrete) has been increased. Normally no-fines concrete is produced with crushed coarse aggregate of uniform gradation. This study aims to investigate experimentally the effects of the use of uncrushed coarse aggregates on unit weight, compressive and tensile strength of the no-fines (NFC) as well as conventional concrete (CC). In addition, the effects of coarse aggregate size on the mechanical properties were also studied. Four gradations of uncrushed coarse aggregates ranging between (5.5-4.75) mm, (10-4.75) mm, (20-4.75) mm and (25-4.75) mm were used for preparing the concretes. The fixed cement-aggregate ratios of 1:6 (with w/c ratio=0.4) and 1:2:4 (with w/c ratio=0.5) were adopted for NFC and CC respectively. It was found that the gradation of uncrushed coarse aggregate has a significant effect on the mechanical properties of NFC. A maximum of 16% reduction in self-weight of the concrete without fines was obtained, as compared to that with fines. Moreover, the compressive strength of no-fines concrete significantly improved by replacing crushed with uncrushed coarse aggregate. The compressive strength increased by 16% for the batch of (25-4.75) mm.

Sign in / Sign up

Export Citation Format

Share Document