scholarly journals Proposed Model for Stress-strain Behavior of Fly Ash Concrete Under the Freezing and Thawing Cycles

2020 ◽  
Author(s):  
Ali Hemmati ◽  
Heydar Arab
Keyword(s):  
Fly Ash ◽  
Numerical Models ◽  
Test Results ◽  
Freezing And Thawing ◽  
Stress Strain ◽  
Strain Behavior ◽  
Fly Ash Concrete ◽  
Proposed Model ◽  
The Difference ◽  
Freezing And Thawing Cycles

Fly ash is a supplementary cement material using instead of Portland cement in concrete. Using this material concludes to less emission of greenhouse gas and less water demand of concrete. In this paper, an experimental investigation was carried out on compressive stress–strain behavior of three groups of concrete specimens with different water/cement ratios (0.45, 0.5 and 0.55), containing 0, 10, 20, 30 and 40 percent of fly ash (by weight), after subjecting to freezing and thawing cycles. 0, 45, 100 and 150 cycles of freezing and thawing were applied on these specimens according to ASTM C666 and the results presented. Numerical models for the stress–strain behavior of these frozen-thawed concrete were developed and compared with the available experimental data. Results show that the maximum compressive strength of these concrete specimens exposing cycles of freezing and thawing is gained by using about 10 % of fly ash. Moreover, there is a good agreement between the proposed models and test results and the difference is less than 5 %.

Uniaxial Stress-Strain Model for Concrete Confined by Rectangular Steel Tubes

2010 ◽  
Vol 163-167 ◽  
pp. 1005-1011
Author(s):  
Yue Ling Long ◽  
Jian Cai
Keyword(s):  
Triaxial Compression ◽  
Uniaxial Stress ◽  
Failure Criteria ◽  
Steel Tube ◽  
Test Results ◽  
Stress Strain ◽  
Steel Tubes ◽  
Concrete Core ◽  
Strain Behavior ◽  
The Difference

This paper presents a new model for uniaxial stress-strain relationship of concrete confined by rectangular steel tubes. The difference between concrete confinement effect provided by broad faces and that provided by narrow faces of steel tube is considered in the proposed model. The failure criteria for concrete subjected to triaxial compression is applied to estimate the ultimate strength of concrete core. The parameters of the model are determined based on the test results and the calculation of complete load-stress relationship curves is conducted for axially loaded rectangular CFT specimens using the model proposed in the paper. The concrete core strength and stress-strain behavior of rectangular CFT columns is found to exhibit good agreement with test results.

scholarly journals Experimental Study on Freezing and Thawing Cycles of Shrinkage-Compensating Concrete with Double Expansive Agents

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1850
Author(s):  
Jinjun Guo ◽  
Ting Guo ◽  
Shiwei Zhang ◽  
Yan Lu
Keyword(s):  
Frost Resistance ◽  
Large Scale ◽  
Mass Loss Rate ◽  
Test Results ◽  
Freezing And Thawing ◽  
Expansive Agent ◽  
Hydraulic Concrete ◽  
Mix Proportion ◽  
Three Stages ◽  
Freezing And Thawing Cycles

The freezing and thawing of construction concrete is becoming an increasingly important structural challenge. In this study, a shrinkage-compensating concrete based on a double expansive admixture was developed and its frost resistance was assessed through rapid freezing and thawing cycling. The frost resistance of the concrete was derived through the measurement and calculation of the relative dynamic modulus of elasticity (RDME) and the mass loss rate (MLR), and the freezing- and thawing-cycle microstructures and products of concretes with different expansive agents were analyzed using scanning electron microscopy (SEM). It was shown that changes in the properties of the concrete under freezing and thawing could be divided into three stages: slow-damage stage, fast-damage stage, and stable stage. Compared to concrete without an expansive agent, a single-expansive-agent concrete demonstrated excellent frost resistance during the slow-damage stage, but the frost resistance rapidly decreased during the fast-damage age. After 150 cycles (the stable-damage stage), the concrete with a U-type expansive agent (UEA): MgO expansive agent (MEA) mix proportion of 2:1 had the best frost resistance, with RDME and MLR values 17.35% higher and 25.1% lower respectively, than that of an expansive-agent-free concrete. These test results provide a basis for the study of frost resistance in large-scale hydraulic concrete structures.

Prediction Model for Cementing Efficiency of Fly Ash Concrete by Statistical Analyses

2011 ◽  
Vol 250-253 ◽  
pp. 1293-1296 ◽  
Author(s):  
Hong Bum Cho ◽  
Nam Yong Jee
Keyword(s):  
Fly Ash ◽  
Prediction Model ◽  
Statistical Analyses ◽  
Test Results ◽  
Construction Sites ◽  
K Value ◽  
Fly Ash Concrete ◽  
Mix Proportion ◽  
Wide Range ◽  
Binder Ratio

This paper offers the model that can estimate the cementing efficiency of fly ash (k value) based on a mix proportion of concrete containing fly ash (FA). The prediction model was derived using various statistical analyses, based on a wide range of mix proportions and a number of strength test results of ready mixed concretes used in eight construction sites. The k value increases with increasing water-binder ratio. As the FA replacement ratios increase, the k value increases at FA replacement ratios of less than 15%, but decreases at ratios of 15% or more. The k values obtained from the cementing efficiency estimate model range from 0.1 to 2.1.

Research on Durability of High Volume Fly Ash Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 380-383 ◽  
Author(s):  
Hong Zhu Quan
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Experimental Studies ◽  
High Volume ◽  
Portland Cement Concrete ◽  
Freezing And Thawing ◽  
Replacement Ratio ◽  
Rapid Reduction ◽  
Fly Ash Concrete

The paper presents the results of series of experimental studies on effects of the type and replacement ratio of fly ash to portland cement on durability of concrete. Specimens made from 28 mixes of fly ash concrete with water binder ratio of 38% to 60% and with replacement ratio of fly ash of 25% to 70% and 5 mixes of portland cement concrete with water cement ratio of 38% to 75% were tested for compressive strengths, drying shrinkage, carbonation and resistance to freezing and thawing. As a results, drying shringkage decreased with fly ash addition regardless of type and replacement ratio of fly ash. Carbonation increased with fly ash replacement ratio, and type 1 fly ash showed higher carbonation. Type 1 and tpye 2 fly ashes showed practically no change in durability factor after 300 cycles of freezing and thawing up to 55% replacement, while type 4 fly ash showed rapid reduction in durability factor up to 40% replacement ratio.

scholarly journals Stress-Strain Behavior of Cementitious Materials with Different Sizes

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Jikai Zhou ◽  
Pingping Qian ◽  
Xudong Chen
Keyword(s):  
Flexural Strength ◽  
Size Effect ◽  
Cement Mortar ◽  
Strain Curve ◽  
Cementitious Materials ◽  
Test Results ◽  
Stress Strain ◽  
Strain Behavior ◽  
Modified Equation ◽  
Good Agreement

The size dependence of flexural properties of cement mortar and concrete beams is investigated. Bazant’s size effect law and modified size effect law by Kim and Eo give a very good fit to the flexural strength of both cement mortar and concrete. As observed in the test results, a strong size effect in flexural strength is found in cement mortar than in concrete. A modification has been suggested to Li’s equation for describing the stress-strain curve of cement mortar and concrete by incorporating two different correction factors, the factors contained in the modified equation being established empirically as a function of specimen size. A comparison of the predictions of this equation with test data generated in this study shows good agreement.

Research on Some Properties of Fly Ash Concrete with Nano-CaCO3 Middle Slurry

2009 ◽  
Vol 405-406 ◽  
pp. 186-190 ◽  
Author(s):  
Kuang Liang Qian ◽  
Tao Meng ◽  
Xiao Qian Qian ◽  
Shu Lin Zhan
Keyword(s):  
Fly Ash ◽  
Chloride Ion ◽  
Test Results ◽  
Hydration Degree ◽  
Fly Ash Concrete

Some long-term properties such as anti-carbonation properties, shrinkage, penetrability of chloride ion of fly ash concrete with nano-CaCO3 middle slurry were studied. Test results showed that the properties of anti-carbonation and impenetrability for chloride of fly ash concrete increased by adding nano-CaCO3 middle slurry because the tiny hole was filled by nano-CaCO3 and the density of concrete increased. But at the same time, the shrinkage of fly ash concrete with and without nano-CaCO3 was the same. Results of SEM also implied the hydration degree of fly ash could be increased by nano-CaCO3.

A study of fly ash concrete in curb and gutter construction under various laboratory and field curing regimes

1987 ◽  
Vol 14 (5) ◽  
pp. 614-620 ◽  
Author(s):  
P. M. Gifford ◽  
B. W. Langan ◽  
R. L. Day ◽  
R. C. Joshi ◽  
M. A. Ward
Keyword(s):  
Fly Ash ◽  
Field Tests ◽  
Moisture Loss ◽  
Strength Development ◽  
Freezing And Thawing ◽  
Fly Ash Concrete ◽  
Dry Out ◽  
Air Void ◽  
Curing Regimes ◽  
Scaling Resistance

It has been assumed that cement – fly ash systems only work efficiently given full curing; low temperatures and (or) moisture loss may lead to poor (slow) strenght development and concomitant reduced freezing and thawing cycling and scaling performance.The aim of the present study, undertaken by the Calgary Fly Ash Research Group, was to examine the validity of the above assumption. Strength development and freezing and thawing durability characteristics of fly ash concretes subjected to a range of environmental variables are reported; laboratory and field tests were performed. The field study involved a coring and laboratory testing programme on three ready-mixed concretes, which were used to machine place 200 m of standard curb and gutter on a major roadway. In the laboratory programme the field concretes and an additional high fly ash mixture were cast; specimens were demoulded at the age of 4 h and were either sealed at the time of casting or allowed to dry out while curing at room temperature or at 5 °C. Strength development, freezing and thawing effects, and scaling resistance as well as air-void parameters were determined; a comparison between the field and laboratory tests is presented. Also reported are measurements of internal concrete temperature and moisture loss versus time for the different curing regimes of the laboratory specimens. Key words: concrete, fly ash, strength, durability, field trial.

scholarly journals PENGARUH PERBEDAAN BENTUK PENAMPANG SPESIMEN TERHADAP HUBUNGAN TEGANGAN DAN REGANGAN PADA BETON HIGH VOLUME FLY ASH SELF COMPACTING CONCRETE (HVFA-SCC) The Effect of Speciment Shape on Stress-Strain Behavior of High Volume Fly ash - Self Compacting Conc

2018 ◽  
Vol 6 (1) ◽  
Author(s):  
Retno Kusuma Astuti ◽  
Agus Setya Budi ◽  
Senot Sangadji
Keyword(s):  
Fly Ash ◽  
High Volume ◽  
Self Compacting Concrete ◽  
Stress Strain ◽  
Strain Behavior ◽  
High Volume Fly Ash

<p>Penggunaan <em>fly ash </em>sebagai pengganti sebagian semen dalam campuran <em>Self Compacting Concrete </em>dengan kadar lebih dari 50% disebut <em>High Volume Fly Ash Self Compacting Concrete </em>(HVFA SCC). Pengujian beton dilakukan dengan berbagai bentuk sampel sesuai dengan standar yang digunakan. Salah satu factor yang mempengaruhi hasil pengujian adalah bentuk penampang beton. Penelitian ini menggunakan total benda uji 18 buah dengan variasi bentuk penampang lingkaran, segiempat dan segienam. Rancang campur yang digunakan pada <em>High Volume Fly Ash Self Compacting Concrete</em> menggunakan teknologi SCC berdasar EFNARC S<em>pecification and Guidelines for Self-Compacting Concrete</em>, 2002. Hasil dari penelitian ini menunjukkan bahwa HVFA SCC pada umur 28 hari memiliki kuat desak yang lebih rendah dibandingkan dengan beton normal dengan rata-rata penurunan kekuatannya adalah 27%. Beton normal dengan penampang segiempat memiliki kuat desak terendah dengan kenaikan sebesar 23% untuk segienam dan 41% untuk lingkaran, begitu pula dengan HVFA-SCC, penampang segiempat memiliki kuat desak terendah dengan kenaikan sebesar 43% untuk segienam dan 52% untuk lingkaran. Nilai Modulus Elastisitas rata-rata pada HVFA-SCC lebih kecil dibandingkan beton normal, yaitu 9578,47 MPa untuk HVFA-SCC dan 13774,44 MPa untuk beton normal. . Nilai <em>toughness postcapeak </em>rata-rata dari HVFA-SCC lebih besar dibandingkan nilai <em>toughness postcapeak </em> beton normal, yaitu 0,036 untuk HVFA-SCC dan 0,033 untuk beton normal. Begitupula dengan nilai daktilitas, yaitu 6,93 untuk HVFA-SCC dan 5,44 untuk beton normal.</p>

scholarly journals Compressive stress-strain relationship for fly ash concrete under thermal steady state

2019 ◽  
Vol 104 ◽  
pp. 103371
Author(s):  
Kunjie Fan ◽  
Dawang Li ◽  
Nattapong Damrongwiriyanupap ◽  
Long-yuan Li
Keyword(s):  
Steady State ◽  
Fly Ash ◽  
Compressive Stress ◽  
Stress Strain ◽  
Fly Ash Concrete ◽  
Strain Relationship ◽  
Thermal Steady State
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