scholarly journals Influence of Hydrated Lime on the Chloride-Induced Reinforcement Corrosion in Eco-Efficient Concretes Made with High-Volume Fly Ash

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5135
Author(s):  
Manuel Valcuende ◽  
Rafael Calabuig ◽  
Ana Martínez-Ibernón ◽  
Juan Soto
Keyword(s):  
Electrical Resistivity ◽  
Fly Ash ◽  
Corrosion Rate ◽  
High Volume ◽  
Hydrated Lime ◽  
Pozzolanic Reaction ◽  
Chloride Penetration ◽  
Reinforcement Corrosion ◽  
Fly Ash Concrete ◽  
Lower Corrosion Rate

The main objective of this study was to analyze the influence that the addition of finely ground hydrated lime has on chloride-induced reinforcement corrosion in eco-efficient concrete made with 50% cement replacement by fly ash. Six tests were carried out: mercury intrusion porosimetry, chloride migration, accelerated chloride penetration, electrical resistivity, and corrosion rate. The results show that the addition of 10–20% of lime to fly ash concrete did not affect its resistance to chloride penetration. However, the cementitious matrix density is increased by the pozzolanic reaction between the fly ash and added lime. As a result, the porosity and the electrical resistivity improved (of the order of 10% and 40%, respectively), giving rise to a lower corrosion rate (iCORR) of the rebars and, therefore, an increase in durability. In fact, after subjecting specimens to wetting–drying cycles in a 0.5 M sodium chloride solution for 630 days, corrosion is considered negligible in fly ash concrete with 10% or 20% lime (iCORR less than 0.2 µA/cm2), while in fly ash concrete without lime, corrosion was low (iCORR of the order of 0.3 µA/cm2) and in the reference concrete made with Portland cement, only the corrosion was high (iCORR between 2 and 3 µA/cm2).

Fly-Ash Concretes of 50% of the Replacement Ratio to Reduce the Cracking in Concrete Structures

2013 ◽  
Vol 405-408 ◽  
pp. 2665-2670 ◽  
Author(s):  
Ming Jie Mao ◽  
Qiu Ning Yang ◽  
Wen Bo Zhang ◽  
Isamu Yoshitake
Keyword(s):  
Fly Ash ◽  
Concrete Structures ◽  
High Volume ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Early Age ◽  
Replacement Ratio ◽  
Fly Ash Concrete ◽  
Massive Concrete ◽  
Normal Strength

Fly-ash concrete used in massive concrete structure has superior advantages to reduce hydration heat. On the other hand, the fly-ash concrete has negative property of low strength development at early age because pozzolanic reaction of fly-ash activates at mature age, such as after 28 days. To investigate these characteristics of fly-ash used in concrete, the present study discusses thermal cracking possibility of fly-ash concrete by using FE analysis software. The present study employs prediction formulae proposed by Zhang and Japanese design code in the simulations. The objects in this study are normal strength concrete mixed of fly-ash up to 50% of replacement ratio to cement. The comparative investigations show that temperature effect is more significant than strength development at early age. Based on the analytical study, high volume fly-ash concretes of 30-50% of the replacement ratio can be concluded as effective and useful materials to reduce the cracking possibility in massive concrete structures. Keywords-Fly-ash concrete; Early Age, Prediction Formulae for Strength; Thermal Stress Analysis

Development of the HVFAC Modulus of Elasticity

2019 ◽  
Vol 296 ◽  
pp. 155-160
Author(s):  
Martin Ťažký ◽  
Lucia Osuská ◽  
Rudolf Hela
Keyword(s):  
Fly Ash ◽  
High Volume ◽  
Pozzolanic Reaction ◽  
Strength Parameters ◽  
Fly Ash Concrete ◽  
Static Modulus ◽  
High Volume Fly Ash ◽  
Active Admixture ◽  
Term Monitoring

Concretes with high fly ash content are within a unified world nomenclature often referred to as HVFAC, resp. high volume fly ash concrete. These concretes are characterized by the percentage of fly ash as an active admixture relative to a cement dose of at least in a ratio of 1:1. The use of these concretes falls into the field of construction with the necessary reduction in the development of hydration heat. In the experiment, long-term monitoring of the development of important mechanical parameters, namely the static modulus of compressive elasticity and compressive strength, was performed. Both monitored parameters play a very important role in the design of buildings, for which construction is HVFAC often used. These parameters were monitored within the carried out research until the time of 360 days. The results of the experiment give an overview of the pozzolanic reaction progress over the in the long-term time horizon and its impact on the concrete parameters monitored. The results clearly show that even after 360 days the development of the strength parameters of these concretes is not stopped.

scholarly journals High Volume Fly Ash Self Compacting Concrete with Lime and Silica Fume as Additives

2020 ◽  
Vol 184 ◽  
pp. 01109
Author(s):  
C Chandana Priya ◽  
M V Seshagiri Rao ◽  
V Srinivasa Reddy ◽  
S Shrihari
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Silica Fume ◽  
High Volume ◽  
Hydrated Lime ◽  
Pozzolanic Reaction ◽  
Self Compacting Concrete ◽  
Conventional Concrete ◽  
High Volume Fly Ash ◽  
Reactive Silica

SCC is expensive when compared with normal conventional concrete. Hence, it is desired to produce low cost SCC by replacing cement with higher percentages of fly ash, which is a no cost material and available in abundance. At the same time to achieve higher grade HVFASCC, micro silica which is otherwise condensed silica fume can also be used along with fly ash to enhance the strength properties of HVFASCC. By replacing fly ash in high volumes in the mix, high amount of pozzolanic material becomes available, majorly reactive silica, for which more calcium hydroxide is necessary for further pozzolanic reaction. As we are reducing cement quantity, the amount of calcium hydroxide available is reduced thus demanding external addition of hydrated lime which can be supplied as additive to cater to the need of calcium hydroxide required for reactive silica in fly ash.The present investigation aims to achieve strength for high volume fly ash self-compacting concrete. The replacement of cement with fly ash is made in 45%, 50%, 55%, 60%, 65% and 70% with 20% hydrated lime and 10% silica fume in one trial. In another trial, 30% hydrated lime and 10% silica fume is added with replacement of fly ash to cement varying in same percentages. The design mix is tested for workability and flowability and cubes are casted for compression strength test and tested at 28 day,, 56 day, and 90 day,.

Mechanical and Transport Properties of High Volume UFA Cement Composites

2019 ◽  
Vol 810 ◽  
pp. 143-148
Author(s):  
Xing Yang He ◽  
Jian Xiang Huang ◽  
Ying Su ◽  
Jin Yang ◽  
Zheng Qi Zheng ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Fly Ash ◽  
High Volume ◽  
Pozzolanic Reaction ◽  
Cement Composites ◽  
Reaction Products ◽  
Chloride Permeability ◽  
High Volume Fly Ash ◽  
Medium Particle ◽  
Different Content

In this study, mechanical activation is used to generate ultra-fine fly ash (UFA) for high volume fly ash（FA）cement composites. The effects of different content and medium particle size of FA on mortar`s electrical resistivity, chloride penetration and mechanical properties are investigated. The results show that the compressive strength and resistance to chloride permeability of specimens with UFA have been enhanced, owing to higher pozzolanic reaction and higher dissolution rate of Si and Al units of UFA to accelerate the generate of reaction products. However, At the early ages, electrical resistivity of specimens increases with the increase of UFA; at later ages, specimens have a higher electrical resistivity with the increase of UFA.

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