Creep Property of Concretes with Different Types of Coarse Aggregates

2012 ◽  
Vol 174-177 ◽  
pp. 308-313 ◽  
Author(s):  
Yan Jun Liu ◽  
Mang Tia
Keyword(s):  
Prestressed Concrete ◽  
Prediction Models ◽  
Creep Property ◽  
Cementitious Materials ◽  
Prestress Loss ◽  
University Of Florida ◽  
Coarse Aggregates ◽  
Concrete Mixtures ◽  
Florida Department ◽  
Different Types

The rheological phenomenon of concrete materials, also termed as creep, is one of very important properties of concrete. Excessive deformation caused by creep does more detrimental effects on prestressed concrete structures than otherwise. Even though some investigations had been conducted on the normal concrete mixtures by the researchers and engineers all over the world, and the conclusions and the creep prediction models based on those investigations were developed, their effectiveness to be extended to all the concrete mixtures is very limited due primarily to the susceptibility of the creep property of concrete to the variation of the properties of aggregate, cement, water to cementitious materials ratio and their proportions. Especially for prestress concrete, creep induced prestress loss puts severe threat on the safety and durability of prestressed structures. Thus, in order to thoroughly understand the creep characteristics of the typical concrete mixtures used in Florida, this project was carried out by University of Florida and Florida Department of Transportation. The investigation found out that the creep strains of the concretes with different types of coarse aggregates at 91 days are very close, while the differences of creep coefficients of the concretes with different aggregates are fairly significant.

Effect of Different Types of Coarse Aggregates on Strength of Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 614-623 ◽  
Author(s):  
Yan Jun Liu ◽  
Mang Tia
Keyword(s):  
Tensile Strength ◽  
Prediction Models ◽  
Concrete Strength ◽  
Strength Development ◽  
Engineering Practice ◽  
Lower Strength ◽  
Coarse Aggregates ◽  
Local Characteristics ◽  
Concrete Mixtures ◽  
Different Types

Different types of coarse aggregates have distinguished petrological, petrographical and mineralogical and local characteristics, thus, their effects on concrete strength development are quite significant, various and unpredictable. So, the laboratory investigation on the concrete mixtures using local aggregates becomes very necessary before used in engineering practice. This paper carried out the evaluation of two types of coarse aggregates constantly used in Florida, including Miami Oolite limestone and Georgia granite, on their effects on the developments of compressive strength, splitting tensile strength and elastic modulus of concrete with time. And the prediction models based on ACI and Cario-Lew are evaluated and modified. The investigation results indicate that the concrete mixtures with Georgia granite aggregate tends to develop lower strength than those with Miami Oolite aggregate. And the modified models give better prediction on strength development of the concrete mixtures with aggregates often used in Florida.

Research on the Mechanism of Prestressed Loss for Curving Hole of Prestressed Concrete Structure Caused by Frictional Resistance

2013 ◽  
Vol 351-352 ◽  
pp. 156-163
Author(s):  
Shan Zhang ◽  
Kai Yin Zhang ◽  
Bing Yang Xie ◽  
Zhong Lin Fan
Keyword(s):  
Friction Coefficient ◽  
Theoretical Analysis ◽  
Prestressed Concrete ◽  
Concrete Structure ◽  
Influencing Factor ◽  
Frictional Resistance ◽  
Continuous Beam ◽  
Prestress Loss ◽  
Rigid Frame ◽  
Different Types

Excessive prestress loss in Prestressed Concrete (PC for short) continuous beam bridges and continuous rigid frame bridges cause structures to be different types of diseases. Based on theoretical analysis and experiment , this paper points out the imperfection of the effective prestress formula in Curving Hole at present. According to the research on the influencing factor of prestressed loss in Curving Hole of friction coefficient, it plays a remarkable role on the analysis about the prestressed loss in Curving Hole of prestressed concrete structure.

scholarly journals Effect of Aggregate Types on the Mechanical Properties of Traditional Concrete and Geopolymer Concrete

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1110
Author(s):  
Hani Alanazi
Keyword(s):  
Mechanical Properties ◽  
Laser Scanning ◽  
Large Scale ◽  
Geopolymer Concrete ◽  
Coarse Aggregates ◽  
Concrete Mixtures ◽  
Different Types ◽  
Quartz Aggregates ◽  
Large Scale Tests ◽  
Physical And Chemical

For the same concrete quality, different types of coarse aggregates may result in different mechanical properties. This paper presents a study on the effect of aggregate types on the mechanical properties of two concretes, namely, geopolymer concrete (GP) and traditional Portland cement (TC) concrete. The mechanical properties were investigated through several large-scale tests. Moreover, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and laser scanning microscope (LSM) images were obtained to study the microstructure of tested mixes. The results revealed that the aggregate type has different effects on the mechanical properties of TC and GP, as they were behaving opposite to quartz and limestone aggregates. Microstructure analysis further confirmed the growth of well-bonded regions between the paste and aggregate in the GP with limestone aggregates, and the formation of several weak interfacial zones in concrete mixtures made with quartz aggregates. It was concluded that the mechanical properties of GP are very sensitive to the stiffness of aggregate, concentrations of stress, and the physical and chemical reactions occurring in the interfacial transition zone which may lead to improved or weakened bond strength between paste and aggregates.

Effects of Aggregate Gradation on Water Permeability of Concrete

2012 ◽  
Vol 488-489 ◽  
pp. 248-252 ◽  
Author(s):  
Bint Ashraf Warda ◽  
Ahmed Noor Munaz
Keyword(s):  
Cementitious Materials ◽  
Major Constituent ◽  
Concrete Durability ◽  
Test Results ◽  
Concrete Compressive Strength ◽  
Water Penetration ◽  
Aggregate Gradation ◽  
Concrete Mixtures ◽  
Different Types ◽  
Concrete Permeability

Concrete permeability is one of the key properties of concrete which largely effects concrete durability. Conventionally concrete permeability is considered as a function of water to cementitious materials ratio. But aggregate being the major constituent of concrete, was found to have considerable effects on various properties of concrete. In this research the effects of aggregate gradation on concrete permeability have been examined for two different types of cement. Total twenty concrete mixes were prepared using two different types of aggregate gradations, CEM I and CEM II/B-M cements. Concrete permeability measured in terms of depth of water penetration under pressure as per the standard EN12390-8. It has been found that concrete mixtures having same w/c ratio and keeping all other properties same, may have different permeability only because of different aggregate gradation. This article also features the use of concrete compressive strength as an alternative parameter for controlling concrete permeability based on the test results.

The Influence of Wire Type Indentation on Longitudinal Splitting in Pre-Stressed Concrete

2021 ◽  
Vol 1165 ◽  
pp. 65-86
Author(s):  
Adrijana Savić ◽  
Aref Shafiei Dastgerdi ◽  
Robert J. Peterman ◽  
B. Terry Beck
Keyword(s):  
Prestressed Concrete ◽  
State University ◽  
Longitudinal Splitting ◽  
Prestressing Steel ◽  
Concrete Members ◽  
Concrete Mixtures ◽  
Pretensioned Concrete ◽  
Different Types ◽  
Compressive Strength Of Concrete ◽  
Kansas State University

The important characteristic in the creation of longitudinal splitting cracks in pretensioned concrete members has found to be the geometry of the pre-stressing wire indents. Longitudinal splitting along prestressing tendons can result in severe splitting of prestressed member in the field under loading over time. The research evaluated the influence of wire type indentation on the longitudinal splitting in prestressed concrete members fabricated with different concrete mixtures and different compressive strength of concrete. A key objective was to find the best type of wire to avoid failures in the field. A study was conducted at Kansas State University to understand the effect of wire type on the longitudinal splitting between prestressing steel and prestressed concrete. Three different types of wires will be presented in this paper denoted as “WB”, “WF” and “WQ”. The wires have different parameters which include indent depth, indent width, indent sidewall angle, indent pitch and indent volume.

scholarly journals Portable near Infrared Spectroscopy as a Tool for Fresh Tomato Quality Control Analysis in the Field

2021 ◽  
Vol 11 (7) ◽  
pp. 3209
Author(s):  
Karla R. Borba ◽  
Didem P. Aykas ◽  
Maria I. Milani ◽  
Luiz A. Colnago ◽  
Marcos D. Ferreira ◽  
...  
Keyword(s):  
Citric Acid ◽  
Near Infrared ◽  
Prediction Models ◽  
Quality Attributes ◽  
Internal Quality ◽  
Control Analysis ◽  
Tomato Quality ◽  
Wide Range ◽  
Different Types ◽  
Fresh Tomato

Portable spectrometers are promising tools that can be an alternative way, for various purposes, of analyzing food quality, such as monitoring in a few seconds the internal quality during fruit ripening in the field. A portable/handheld (palm-sized) near-infrared (NIR) spectrometer (Neospectra, Si-ware) with spectral range of 1295–2611 nm, equipped with a micro-electro-mechanical system (MEMs), was used to develop prediction models to evaluate tomato quality attributes non-destructively. Soluble solid content (SSC), fructose, glucose, titratable acidity (TA), ascorbic, and citric acid contents of different types of fresh tomatoes were analyzed with standard methods, and those values were correlated to spectral data by partial least squares regression (PLSR). Fresh tomato samples were obtained in 2018 and 2019 crops in commercial production, and four fruit types were evaluated: Roma, round, grape, and cherry tomatoes. The large variation in tomato types and having the fruits from distinct years resulted in a wide range in quality parameters enabling robust PLSR models. Results showed accurate prediction and good correlation (Rpred) for SSC = 0.87, glucose = 0.83, fructose = 0.87, ascorbic acid = 0.81, and citric acid = 0.86. Our results support the assertion that a handheld NIR spectrometer has a high potential to simultaneously determine several quality attributes of different types of tomatoes in a practical and fast way.

scholarly journals A Stress Measurement Method for Steel Strands Based on LC Oscillation

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Dongjun Chen ◽  
Benniu Zhang ◽  
Xingxing Li ◽  
Chong Tu ◽  
Can Yuan ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Oscillation Frequency ◽  
Stress Measurement ◽  
Resonant Circuit ◽  
Electromagnetic Signal ◽  
Prestress Loss ◽  
Factors Affecting ◽  
Existing Structures ◽  
Detection Circuit ◽  
Frequency Meter

The prestress loss is one of the main factors affecting the safety of prestressed concrete structure. While the detecting signals like sound and light are difficult to spread in steel strands, there is no effective method for prestress detection of the bonded prestressed steel strands in existing structures yet. In this paper, taking into consideration that the electromagnetic oscillation characteristic can make the signal propagate effectively on the bonded prestressed steel strands, a nondestructive prestress detection method based on the electromagnetic effect to detect oscillation frequency is proposed. In a detection circuit, the steel strands are simulated as an inductance component, in which an induced electromagnetic signal passes through the steel strands to form resonance. And then, a frequency meter is used to detect the oscillation frequency of the resonant circuit. The oscillation frequency is supposed to have relationship with the prestress loading on the steel strands. A section of steel strands with a length of 1.2 m is adopted to test the correlation of stress and oscillation frequency. Both the theoretical and experimental results show that the resonant frequency of the circuit decreases with the increase of the stress of the strand and is linear in a certain range.

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