scholarly journals The Optimization of Calcareous Fly Ash-Added Cement Containing Grinding Aids and Strength-Improving Additives

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Gökhan Kaplan ◽  
Sadık Alper Yildizel ◽  
Selçuk Memiş ◽  
Ali Uğur Öztürk
Keyword(s):  
Fly Ash ◽  
Ash Content ◽  
Early Age ◽  
Economic Factors ◽  
Hydration Products ◽  
Chemical Additive ◽  
Cement Production ◽  
Grinding Aids ◽  
Cement Mortars ◽  
Early Strength

This is an experimental study which explores the physical, mechanical, and economic factors involved in the production of type CEM II A-B/W cement. In this context, 4 cement additives were used in two different dosages (200 and 800 g/t). Class C fly ash was used for composite cement production at ratios of 5%, 20%, and 35%. It was shown that Blaine fineness increases with the increasing fly ash content. The use of fly ash at ratios of 5% and 20% was not found to have any unfavorable effects on the compressive strength at the early days. It is found that the use of additive for improving the early-age strength is preferable when fly ash is used. It is possible to produce Class 52.5 N cement using additives to improve early strength and 20% fly ash. Loss in strength was observed in cement mortars produced using glycol-based grinding aid. Increasing the dosage of chemical additive also led to loss in strength due to nonhomogeneous distribution of hydration products. As a result, grinding fly ash with clinker and the use of cement chemicals contribute to the cement sector in terms of sustainability. It is possible to produce cements with improved mechanical properties especially with the use of 20% fly ash.

Effect of Fly Ash on Mechanical Properties and Structure of CaO-Al2O3-P2O5-SiO2 System

2011 ◽  
Vol 55-57 ◽  
pp. 1233-1236
Author(s):  
Xiu Shu Tian ◽  
Shi Gang Mei ◽  
Shu Xia Ren
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Experimental Results ◽  
Early Age ◽  
Hydration Products ◽  
Different Ages ◽  
Early Strength ◽  
Gel System

In this paper, mainly CaO-Al2O3-P2O5-SiO2gel system and the effect of fly ash on the mechanical properties and the microstructure of the hydrated system without and within lay ash at different ages have been studied. The structures were characterized by XRD and SEM. The experimental results show that fly ash does not hydrate at the early age and provides the interface, so the hydration products of CaO-Al2O3-P2O5-SiO2system is deposited directly on its surface, which lead to a lower early strength; but fly ash hydrates at the later age and improves the hydration of CaO-Al2O3-P2O5-SiO2system.

The Influence of the Ash Addition from Thermal Power Plant on the Mechanical, Thermal and Dielectric Characteristics of Mortars

2018 ◽  
Vol 69 (8) ◽  
pp. 2040-2044
Author(s):  
Georgeta Velciu ◽  
Virgil Marinescu ◽  
Adriana Moanta ◽  
Ladislau Radermacher ◽  
Adriana Mariana Bors
Keyword(s):  
Thermal Conductivity ◽  
Fly Ash ◽  
Power Plant ◽  
Cement Mortar ◽  
Thermal Power ◽  
Total Content ◽  
Ash Content ◽  
Dielectric Losses ◽  
Dielectric Characteristics ◽  
Cement Mortars

The influence of fly ash adittion (90 % fraction [ 100 mm) on the cement mortar characteristics was studied. The XRD, XRF, SEM and FTIR determinations indicated that fly ash used has a hollow microstructure of microsphere and cenosphere whose total content in SiO2, Al2O3 and Fe2O3 is 88.63 % and that of CaO and MgO of 8.55 %. The mechanical, thermal and dielectric determinations made on mortar samples with content of fly ash in the 0-40 % range have highlighted fact that the mechanical strength of cement mortars is maximal at 20 %, the increase in fly ash content leads to a decrease in relative density and thermal conductivity as well as and to increased dielectric losses tgd.

scholarly journals Effect of C-S-H Nucleating Agent on Cement Hydration

2021 ◽  
Vol 11 (14) ◽  
pp. 6638
Author(s):  
Wenhao Zhao ◽  
Xuping Ji ◽  
Yaqing Jiang ◽  
Tinghong Pan
Keyword(s):  
Fractal Dimension ◽  
Cement Hydration ◽  
Nucleating Agent ◽  
Crystal Nucleation ◽  
Enhancement Effect ◽  
Hydration Products ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Cement Mortars ◽  
Early Strength

This work aims to study the effect of a nucleating agent on cement hydration. Firstly, the C-S-H crystal nucleation early strength agent (CNA) is prepared. Then, the effects of CNA on cement hydration mechanism, early strength enhancement effect, C-S-H content, 28-days hydration degree and 28-days fractal dimension of hydration products are studied by hydration kinetics calculation, resistivity test, BET specific surface area test and quantitative analysis of backscattered electron (BSE) images, respectively. The results show that CNA significantly improves the hydration degree of cement mixture, which is better than triethanolamine (TEA). CNA shortens the beginning time of the induction period by 49.3 min and the end time of the cement hydration acceleration period by 105.1 min than the blank sample. CNA increases the fractal dimension of hydration products, while TEA decreases the fractal dimension. CNA significantly improves the early strength of cement mortars; the 1-day and 3-days strength of cement mortars with CNA are more than the 3-days and 7-days strength of the blank sample. These results will provide a reference for the practical application of the C-S-H nucleating agent.

Effect of fine fly ash and calcium hydroxide on air void structure in very-early-strength latex-modified concrete

2015 ◽  
Vol 42 (10) ◽  
pp. 797-807
Author(s):  
Pangil Choi ◽  
Sung Il Jeon ◽  
Kyong-Ku Yun
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Bridge Decks ◽  
Time Frame ◽  
Early Age ◽  
Freeze Thaw ◽  
Void Structure ◽  
Early Strength ◽  
Air Void ◽  
Air Void Structure

Very-early-strength latex-modified concrete (VES-LMC) was developed for rapid repairs of distresses in concrete bridge decks and pavements, with the emphasis on early-age strength gain so that the repaired bridges and pavements can be opened to traffic within the time frame required in the specifications. However, there are two main concerns in the use of VES-LMC — early-age cracking and poor air void structure. The main objective of this study was to further improve VES-LMC to minimize early-age cracking and improve freeze–thaw durability, which included the use of fine fly ash (FFA) and calcium hydroxide (CH). Laboratory experiments were conducted on VES-LMC materials with cement replaced with FFA as well as CH, and various tests performed. Early-age drying shrinkages of VES-LMC containing both FFA and CH in the amounts evaluated in this study were smaller than that of VES-LMC with no replacements. It is expected that the use of FFA and CH in the range evaluated in this study will reduce the cracking potential of VES-LMC. Overall, the replacement of cement with FFA and CH improved the characteristics of entrained air void system, which will enhance the durability of VES-LMC against freeze–thaw damage. Scanning electron microscope and energy dispersive spectroscopy analysis indicate the primary mechanism of the generation of small sized air voids in concretes containing adequate amount of FFA and CH is the gas formation reaction between citric acid solutions and CH during concrete mixing. It is expected that the inclusion of adequate amounts of FFA and CH in VES-LMC will improve the performance of repaired bridge decks and pavements in terms of reduced cracking and improved freeze-thaw durability.

A Study on the Development Mechanism of Early Strength in Cement Mortar Using an Early-Strength Polycarboxylated Agent

2007 ◽  
Vol 348-349 ◽  
pp. 473-476
Author(s):  
Won Jun Park ◽  
Han Seung Lee ◽  
Ki Bong Park
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Cement Mortar ◽  
Early Age ◽  
Hydration Products ◽  
Degree Of Hydration ◽  
Exact Analysis ◽  
Mortar Strength ◽  
Early Strength ◽  
Micro Structures

It is well known that PC (polycarboxylate) agent is superior to other agents for the early-strength of concrete. Thus, this study investigates the development of mortar strength using various agents. To prove this, various factors were tested. Furthermore, this study measured compressive strength at the age of 18, 24, 36, 72, and 168 hours and gave a request text TG/DTA to observe minute structures. In addition, this study took pictures of minute structures using an SEM for each agent at the same age. According to the results, mortar using an early-strength PC agents is faster than a general water reducing AE agent, high performance PC agents, and other agents in the acceleration of hydration at the same early age. A TG/DTA test shows that the early-strength PC agents create more hydration products, such as Ca(OH)2, than others at the same age. The degree of pH in each agent is unrelated to the degree of hydration in mortar. An MIP analysis confirms these results. However, other methods are required the exact analysis of micro structures.

scholarly journals Early-Age Deformation of Very-Early Strength Latex- Modified Concrete with Ultra-Fine Fly Ash Contents

2010 ◽  
Vol 11 (3) ◽  
pp. 1040-1046
Author(s):  
Pan-Gil Choi ◽  
Won-Il Park ◽  
Kyong-Ku Yun ◽  
Bong-Hak Lee
Keyword(s):  
Fly Ash ◽  
Early Age ◽  
Early Strength

scholarly journals Effects of Highly Crystalized Nano C-S-H Particles on Performances of Portland Cement Paste and Its Mechanism

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 816
Author(s):  
Yuli Wang ◽  
Huijuan Lu ◽  
Junjie Wang ◽  
Hang He
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Setting Time ◽  
Tricalcium Silicate ◽  
Strength Development ◽  
Early Age ◽  
Hydration Products ◽  
X Ray ◽  
Early Strength ◽  
Portland Cement Paste

In order to improve the early age strength of ordinary Portland cement-based materials, many early strength agents were applied in different conditions. Different from previous research, the nano calcium silicate hydrate (C-S-H) particles used in this study were synthesized through the chemical reaction of CaO, SiO2, and H2O under 120 °C using the hydrothermal method, and the prepared nano C-S-H particles were highly crystalized. The influences of different amounts of nano C-S-H particles (0%, 0.5%, 1%, 2% and 3% by weight of cement) on the setting time, compressive strength, and hydration heat of cement paste were studied. The hydration products and microstructure of the cement paste with different additions of nano C-S-H particles were investigated through thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), and scanning electron microscope (SEM) tests. The results show that the nano C-S-H particles could be used as an early strength agent, and the early strength of cement paste can be increased by up to 43% through accelerating the hydration of tricalcium silicate (C3S). However, the addition of more than 2% nano C-S-H particles was unfavorable to the later strength development due to more space being left during the initial accelerated hydration process. It is suggested that the suitable content of the nano C-S-H particles is 0.5%−1% by weight of cement.

Effect of Gypsum on Strength Development of Steam-Cured Concrete

2011 ◽  
Vol 194-196 ◽  
pp. 1085-1088
Author(s):  
Zhi Min He ◽  
Xiao Ju Shen ◽  
Jun Zhe Liu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Strength Development ◽  
Early Age ◽  
Strength Gain ◽  
Fly Ashes ◽  
Steam Curing ◽  
Gain Rate ◽  
Early Strength ◽  
Chemical Activator

The use of fly ashes for cement-replacement purposes, especially in high volumes, decreases rate of early strength development of the steam curing concrete. To resolve it, this paper developed a new steam-cured concrete incorporating fly ash and a chemical activator (gypsum). Experiments were conducted to investigate the mechanical properties at early and later ages of steam and standard curing concretes. The corresponding mechanism was also discussed by testing the microstructure of concretes. Results indicate that the demoulding compressive strength of steam curing concrete with 4% gypsum dosage can meet production requirements, and compressive strength of this concrete at later ages increase well. Compared with that of ordinary pure cement steam-cured concrete, concrete with 4% gypsum has a higher compressive strength gain rate. At an early age, addition of the gypsum can distinctly accelerate the extent of hydration of the steam curing fly ash cement systems, and thus the microstructure of concrete becomes denser. However, in standard curing condtion, the effect of gypsum is not distinct.

Basic Mechanics Properties Test of Fly Ash Concrete

2012 ◽  
Vol 238 ◽  
pp. 138-141
Author(s):  
Wei Xie ◽  
Hai Juan Zhang ◽  
Shu Shan Li
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Ash Content ◽  
Early Age ◽  
Test Results ◽  
Fly Ash Concrete ◽  
Influence Mechanism ◽  
Normal Reference ◽  
Test Study

By the test study of basic mechanics properties of concrete with different fly ash content, the influence of the content of fly ash on the compressive strength, flexural strength, splitting tensile strength and static compressive elastic modulus of concrete are analyzed with the explaining of the influence mechanism of fly ash. The test results show that, comparing with the normal reference concrete, the early age strength of fly ash concrete enhances slowly, while the late strength develops rapidly, even overpasses the strength of normal reference concrete.

Effect of Thermal Environment at Early Age on Hydration Phases Composition and Strength Development of Concrete Containing Fly Ash

2010 ◽  
Vol 168-170 ◽  
pp. 582-588
Author(s):  
Feng Chen Zhang ◽  
De Jian Shen ◽  
Ji Kai Zhou ◽  
Zhong Hua Li
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Thermal Environment ◽  
Ash Content ◽  
Splitting Tensile Strength ◽  
Curing Temperature ◽  
Strength Development ◽  
Early Age ◽  
Mass Concrete ◽  
Hydration Phases

Cement hydration at early age is sometimes in a certain thermal environment probably caused by hydration heat of mass concrete as well as cement productions curing at high temperature. And phases composition and strength development in thermal environment are commonly different from those in normal curing conditions. Phases composition and strength development of concrete containing different fly ash content curing in different thermal environment are studied in this paper. Experimental results show that compressive strengths of concrete with 0.3 water to binder ratio increase with the increase of curing temperature. Splitting tensile strength of concrete not containing any fly ash curing at about 50 is the highest among those curing at temperature between 40 and 80 . For concrete with different fly ash content, splitting tensile strengths increase approximately with the increse of curing temperature. Dehydration of ettringite and formation of monosulfate solid solution and AFm at higher temperature perhaps relate to the development of concrete splitting tensile strength along with different curing temperature. Adding fly ash to binder, curing temperature at which hydration phases change occurs is raised, which helps to explain that splitting tensile strengths of concrete with different fly ash content decrease little with the increase of curing temperature between 60 and 80 .

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