scholarly journals Development of statistical models to simulate and optimize self-consolidating concrete mixes incorporating high volumes of fly ash

2021 ◽  
Author(s):  
Rajeshkumar Patel
Keyword(s):  
Fly Ash ◽  
Yield Stress ◽  
Statistical Models ◽  
Fresh Concrete ◽  
Plastic Viscosity ◽  
Chloride Permeability ◽  
Research Project ◽  
Self Consolidating Concrete ◽  
Slump Flow ◽  
Filling Capacity

Self-consolidating concrete (See), a latest version of high performance concrete, has created tremendous interest today as it can be easily placed in congested reinforced concrete structures with difficult casting conditions. It also reduces the construction time and cost of the labor. Normally see is being developed using a superplasticizer to generate desired flow and a viscosity modifying admixture (VMA) to prevent segregation in the concrete. In this research project, instead of VMA, high volumes of fly ash were used along with superplasticizer to develop see. The minimum use of superplasticizer and optimum use of fly ash were desired to achieve required properties of see. The fly ash is expected to be useful not only in generating the flow but as segregation resistance as well. The aim of the present research project was to develop see for sustainable construction by optimizing the use of high volumes of fly ash with some proposed statistical models. The rheological study for paste and mortar was carried out first, and Bingham model parameters such as plastic viscosity and yield stress were correlated with the marsh cone flow of paste and fresh concrete properties such as slump flow and filling capacity. The limits for plastic viscosity, yield stress, and specific marsh cone flow of paste and mortar were identified for concrete mixes to be qualified for see. Four independent variables such as total binder content (limit 350 to 450 kg/m3), percentage of fly ash replacing cement (limit 30 to 60 %), % of superplasticizer (limit 0.1 to 0.6 %), and W/B (limit 0.33 to 0.45) were considered for design of experiment and for development of statistical models for see. Statistically balanced twenry-one concrete mixes were chosen and fresh concrete tests such as slump and slump flow, V -funnel flow, filling capacity, L-box, bleeding, air content, segregation, and initial and final setting time tests were performed. Seven harden concrete tests (for mechanical characteristics and durability) such as compressive strength (1, 7, 28-day), freezing and thawing cycles resistance, surface scaling resistance, rapid chloride permeability, modulus of elasticity, flexural strength, and drying shrinkage were performed to evaluate the performance of see. Five statistical models for important properties of see such as slump flow, I-day strength, 28-day strength, rapid chloride permeability, and material cost were developed. The limits of rheological parameters of pastes and mortars can be useful to predict the flow behavior of see and the proposed models can be useful to design and optimize see mixes incorporating high volumes of fly ash.

scholarly journals Development of statistical models to simulate and optimize self-consolidating concrete mixes incorporating high volumes of fly ash

2021 ◽  
Author(s):  
Rajeshkumar Patel
Keyword(s):  
Fly Ash ◽  
Yield Stress ◽  
Statistical Models ◽  
Fresh Concrete ◽  
Plastic Viscosity ◽  
Chloride Permeability ◽  
Research Project ◽  
Self Consolidating Concrete ◽  
Slump Flow ◽  
Filling Capacity

Self-consolidating concrete (See), a latest version of high performance concrete, has created tremendous interest today as it can be easily placed in congested reinforced concrete structures with difficult casting conditions. It also reduces the construction time and cost of the labor. Normally see is being developed using a superplasticizer to generate desired flow and a viscosity modifying admixture (VMA) to prevent segregation in the concrete. In this research project, instead of VMA, high volumes of fly ash were used along with superplasticizer to develop see. The minimum use of superplasticizer and optimum use of fly ash were desired to achieve required properties of see. The fly ash is expected to be useful not only in generating the flow but as segregation resistance as well. The aim of the present research project was to develop see for sustainable construction by optimizing the use of high volumes of fly ash with some proposed statistical models. The rheological study for paste and mortar was carried out first, and Bingham model parameters such as plastic viscosity and yield stress were correlated with the marsh cone flow of paste and fresh concrete properties such as slump flow and filling capacity. The limits for plastic viscosity, yield stress, and specific marsh cone flow of paste and mortar were identified for concrete mixes to be qualified for see. Four independent variables such as total binder content (limit 350 to 450 kg/m3), percentage of fly ash replacing cement (limit 30 to 60 %), % of superplasticizer (limit 0.1 to 0.6 %), and W/B (limit 0.33 to 0.45) were considered for design of experiment and for development of statistical models for see. Statistically balanced twenry-one concrete mixes were chosen and fresh concrete tests such as slump and slump flow, V -funnel flow, filling capacity, L-box, bleeding, air content, segregation, and initial and final setting time tests were performed. Seven harden concrete tests (for mechanical characteristics and durability) such as compressive strength (1, 7, 28-day), freezing and thawing cycles resistance, surface scaling resistance, rapid chloride permeability, modulus of elasticity, flexural strength, and drying shrinkage were performed to evaluate the performance of see. Five statistical models for important properties of see such as slump flow, I-day strength, 28-day strength, rapid chloride permeability, and material cost were developed. The limits of rheological parameters of pastes and mortars can be useful to predict the flow behavior of see and the proposed models can be useful to design and optimize see mixes incorporating high volumes of fly ash.

Fresh, Durability and Mechanical Behavior of Self Consolidating Concrete Incorporating Fly Ash and Admixture under Hot Weather

2021 ◽  
Vol 904 ◽  
pp. 453-457
Author(s):  
Samer Al Martini ◽  
Reem Sabouni ◽  
Abdel Rahman Magdy El-Sheikh
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Absorption ◽  
Weather Conditions ◽  
Chloride Penetration ◽  
The Self ◽  
Fresh Properties ◽  
Self Consolidating Concrete ◽  
Slump Flow ◽  
Hot Weather

The self-consolidating concrete (SCC) become the material of choice by concrete industry due to its superior properties. However, these properties need to be verified under hot weather conditions. The paper investigates the behavior of SCC under hot weather. Six SCC mixtures were prepared under high temperatures. The SCC mixtures incorporated polycarboxylate admixture at different dosages and prolonged mixed for up to 2 hours at 30 °C and 40 °C. The cement paste was replaced with 20% of fly ash (FA). The fresh properties were investigated using slump flow, T50, and VSI tests. The compressive strength was measured at 3, 7, and 28 days. The durability of SCC mixtures was evaluated by conducting rapid chloride penetration and water absorption tests.

Factorial Design Approach of Ultra-High Performance Concrete

2013 ◽  
Vol 405-408 ◽  
pp. 2847-2850
Author(s):  
Wu Jian Long ◽  
Wei Lun Wang ◽  
Qi Ling Luo ◽  
Bi Qin Dong
Keyword(s):  
Mechanical Properties ◽  
Factorial Design ◽  
Statistical Models ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Design Approach ◽  
Ultra High Performance Concrete ◽  
Self Consolidating Concrete ◽  
Slump Flow

In order to understand the influence of mixture parameters on ultra-high strength self-consolidating concrete (UHS-SCC) behaviour, an experimental design was carried out in this investigation. In total, 19 SCC mixtures were prepared to determine several key responses that affect the slump flow and compressive strength of UHS-SCC. The statistical models derived from the factorial design approach can be used to quantify the effect of mixture parameters and their coupled effects on fresh and mechanical properties of SCC.

scholarly journals Evolution of flow properties, plastic viscosity, and yield stress of alkali-activated fly ash/slag pastes

2020 ◽  
Vol 5 ◽  
pp. 141-149
Author(s):  
Mohammed Fouad Alnahhal ◽  
Taehwan Kim ◽  
Ailar Hajimohammadi
Keyword(s):  
Fly Ash ◽  
Yield Stress ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Time Intervals ◽  
Increasing Trend ◽  
Binder Ratio ◽  
Drastic Effect ◽  
Effect On Yield ◽  
Alkali Activated

The development of cementless concrete is attracting increasing attention in practice and research to reduce both greenhouse gas emissions and energy consumption of concrete. Alkali-activated materials (AAMs) are one of the viable alternatives to replace Portland cement due to their lower CO2 emissions. This study investigated the evolution of rheological parameters of alkali-activated fly ash/slag pastes as a function of time. Flowability and rheological measurements were carried out to determine the fluidity, plastic viscosity, and yield stress at different time intervals. The effects of the slag content, the concentration of SiO2 in the activator, and the solution/binder ratio were considered. Based on the results, the yield stress and plastic viscosity followed an increasing trend over time coinciding with a reduction in the paste fluidity. The plastic viscosity of AAM pastes was in the range of 1.3–9.5 Pa.s and 2.6–28.9 Pa.s after 5 min and 45 min of mixing, respectively. Given the same alkali activator, the higher content of slag the paste had, the higher yield stress the paste showed. In addition, this paper confirmed that the SiO2/Na2O ratio in the activator had no significant effect on yield stress, but a drastic effect of this ratio was found on the plastic viscosity of the paste.

A Study on the Application of Artificial Neural Networks on Green Self Consolidating Concrete (SCC) under Hot Weather

2016 ◽  
Vol 677 ◽  
pp. 254-259 ◽  
Author(s):  
Mohamed Al Khatib ◽  
Samer Al Martini
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Fly Ash ◽  
Ambient Temperature ◽  
Back Propagation ◽  
Self Consolidating Concrete ◽  
Feed Forward Back Propagation ◽  
Slump Flow ◽  
Ann Models ◽  
Hot Weather

Self-consolidating concrete (SCC) has recently drawn attention to the construction industry in hot weather countries, due to its high fresh and mechanical properties. The slump flow is routinely used for quality control of SCC. Experiments were conducted by the current authors to investigate the effects of hot weather conditions on the slump flow of SCC. Self-consolidating concrete mixtures were prepared with different dosages of fly ash and superplasticizer and under different ambient temperatures. The results showed that the slump flow of SCC is sensitive to changes in ambient temperature, fly ash dosage, and superplasticizer dosage. In this paper, several artificial neural networks (ANNs) were employed to predict the slump flow of self-consolidating concrete under hot weather. Some of the data used to construct the ANNs models in this paper were collected from the experimental study conducted by the current authors, and other data were gathered from literature. Various parameters including ambient temperature and mixing time were used as inputs during the construction of ANN models. The developed ANN models employed two neural networks: the Feed-Forward Back Propagation (FFBP) and the Cascade Forward Back Propagation (CFBP). Both FFBP and CFBP showed good predictability to the slump flow of SCC mixtures. However, the FFBP network showed a slight better performance than CFBP, where it better predicted the slump flow of SCC than the CFBP network under hot weather. The results in this paper indicate that the ANNs can be employed to help the concrete industry in hot weather to predict the quality of fresh self-consolidating concrete mixes without the need to go through long trial and error testing program.Keywords: Self-consolidating concrete; Neural networks; Hot weather, Feed-forward back-propagation, Cascade-forward back propagation.

Flow Behavior of Self Consolidating Concrete Mixes with Various Maximum Size Aggregates

2019 ◽  
Vol 803 ◽  
pp. 233-238 ◽  
Author(s):  
Samer Al Martini ◽  
Ziad Hassan ◽  
Ahmad Khartabil
Keyword(s):  
Fly Ash ◽  
Flow Behavior ◽  
Aggregate Size ◽  
Maximum Size ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Binary Blends ◽  
Self Consolidating Concrete ◽  
Slump Flow

The paper investigates the effects of aggregate size and supplementary cementitious materials (SCMs) on flow behavior of self-consolidating concrete (SCC). The fresh performance of concrete mixes was evaluated through slump flow and V funnel tests. Some concrete mixes were prepared with 5 mm maximum size aggregates and other mixes with 20 mm maximum size aggregates. The effects of varying contents of SCMs (Fly ash F and GGBS) on flow behavior of SCC under binary blends were also studied. The results show that the maximum size of aggregates has effect on the flow behavior of SCC.

scholarly journals CONCRETOS AUTOADENSÁVEIS E CONVENCIONAIS: ANÁLISE DAS PROPRIEDADES EM ESTADO FRESCO E ENDURECIDO

2020 ◽  
Vol 15 (2) ◽  
pp. 167-178
Author(s):  
Ana Claudia Bergmann ◽  
Gustavo Savaris ◽  
Carlos Eduardo Tino Balestra ◽  
Lucia Bressiani
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Fresh Concrete ◽  
The Self ◽  
Structural Elements ◽  
Negative Effects ◽  
Conventional Concrete ◽  
Self Consolidating Concrete ◽  
Passing Ability ◽  
Main Factor

RESUMO: Os concretos autoadensáveis destacam-se por suas características essenciais: capacidade de preenchimento de fôrmas, habilidade passante e resistência à segregação, permitindo assim o aumento da qualidade de peças estruturais de concreto, assim como a otimização de sua execução. Contudo, para obtenção de suas características essenciais, um fator é imprescindível trata da utilização de materiais finos, com o objetivo de controlar os efeitos negativos de segregação e exsudação à que o concreto fresco é suscetível a apresentar. Neste contexto, o presente trabalho tem por objetivo comparar as propriedades no estado fresco e endurecido de um concreto autoadensável, utilizando cinza volante como material fino, com um concreto convencional, produzidos com materiais disponíveis na região de Toledo-PR. Os resultados demonstraram que o concreto autoadensável apresentou melhor desempenho quanto às propriedades mecânicas em relação ao concreto convencional. As imagens obtidas por meio da microscopia eletrônica de varredura corroboraram para sustentar as afirmativas acerca da melhora nas propriedades mecânicas do concreto autoadensável, uma vez que foi evidenciada uma menor quantidade de vazios graças à atividade pozolânica da cinza volante. Neste sentido, este trabalho contribui para a difusão do concreto autoadensável e seu uso em construções usuais, resultando em estruturas de concreto duráveis e confiáveis, reduzindo a necessidade de manutenções. ABSTRACT: The self-consolidating concretes stand out for their essential characteristics: flowability, passing ability and segregation resistance, allowing the increase of the structural elements quality, as well as the optimization of their production. However, in order to obtain its essential characteristics, the main factor is the use of fines, in order to control the negative effects of segregation and bleeding to which fresh concrete is susceptible. In this context, the aim of this paper is to compare the properties, in the fresh and hardened states, of self-consolidating concretes, using fly ash as fine material with the properties of a conventional concrete, produced with materials available in the Toledo-PR, Brazil. The results showed that the self-consolidating concrete presented better performance in relation to the mechanical properties compared to conventional concrete. Using scanning electronic microscopy the affirmations about the improvement in the mechanical properties of self-consolidating concrete were proven, since a smaller amount of voids was evidenced due to the pozzolanic activity of fly ash. In this sense, this work contributes to the diffusion of self-consolidating concrete in the literature and its use in usual constructions, resulting in durable and reliable concrete structures, reducing the maintenance works.

scholarly journals Lightweight self-compacting concrete with sintered fly-ash aggregate

2018 ◽  
Vol 27 (3) ◽  
pp. 328-337
Author(s):  
Dorota Małaszkiewicz ◽  
Daniel Jastrzębski
Keyword(s):  
Fly Ash ◽  
Fresh Concrete ◽  
Strength Loss ◽  
Partial Replacement ◽  
Hardened Concrete ◽  
Self Compacting Concrete ◽  
Natural Sand ◽  
Concrete Properties ◽  
Slump Flow ◽  
Passing Ability

The article presents the results of research assessing the possibility of making LWSCC from the locally produced sintered fly ash aggregate CERTYD. Two methods of preliminary LWA preparation were applied: pre-soaking with water and coating with a film of cement paste. The following properties of fresh LWSCC were evaluated: slump-flow, time T500 and passing ability using L-Box. Partial replacement of natural sand by fine LW sand (0/0.5 mm) improved filling and passing abilities of fresh concrete, reduced slightly the bulk density, but it resulted in compressive strength loss by 12-18%. In terms of both fresh and hardened concrete properties it is more favorable to use only fine LW sand as natural sand replacement. Considering fresh concrete properties paste impregnation of LW aggregate is more efficient than saturation with water.

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