The impact of Fe dosage on the ettringite formation during high ferrite cement hydration

2020 ◽  
Author(s):  
Dawei Wan ◽  
Wenqin Zhang ◽  
Yong Tao ◽  
Zonghua Wan ◽  
Fazhou Wang ◽  
...  
Keyword(s):  
Cement Hydration ◽  
Ettringite Formation ◽  
The Impact

scholarly journals Influence of Steam Curing Method on the Performance of Concrete Containing a Large Portion of Mineral Admixtures

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Mengyuan Li ◽  
Qiang Wang ◽  
Jun Yang
Keyword(s):  
Chloride Ion ◽  
Mineral Admixtures ◽  
Strength Development ◽  
Steam Curing ◽  
Chloride Permeability ◽  
Curing Conditions ◽  
Volume Stability ◽  
Ettringite Formation ◽  
The Impact ◽  
Reaction Degree

A comparison was made between the impact of raising the thermostatic temperature and the impact of prolonging the thermostatic time on the performance of steam-cured concrete containing a large portion of fly ash (FA) or ground granulated blast furnace slag (GGBS) by analysing the form removal strength, chemically combined water content, reaction degree, strength development, chloride permeability, and volume stability. For the materials and test conditions reported in this study, raising the thermostatic temperature is more favourable for concrete containing FA, as indicated by the significantly higher form removal strength and the higher growth of reaction degree of FA compared with prolonging the thermostatic time. With an increase in the thermostatic temperature, the hydration degree of a binder containing FA or GGBS initially increases and subsequently decreases. Although concrete containing FA can obtain satisfactory form removal strength with steam curing at 80°C, the late strength development of concrete containing FA is slow for the same curing conditions. The effect of the late performance of resistance to chloride ion permeability improved by FA is better than the effect improved by GGBS. The risk of destroying the structure of concrete containing a large portion of FA or GGBS due to delayed ettringite formation (DEF) is minimal when specimens were steam-cured at 80°C.

scholarly journals Predicting the Impact of Multiwalled Carbon Nanotubes on the Cement Hydration Products and Durability of Cementitious Matrix Using Artificial Neural Network Modeling Technique

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Babak Fakhim ◽  
Abolfazl Hassani ◽  
Alimorad Rashidi ◽  
Parviz Ghodousi
Keyword(s):  
Cement Hydration ◽  
Model Verification ◽  
Critical Parameters ◽  
Neural Network Modeling ◽  
Efficiency Coefficient ◽  
Hydration Products ◽  
Ann Model ◽  
Multiwalled Carbon ◽  
Artificial Neural ◽  
The Impact

In this study the feasibility of using the artificial neural networks modeling in predicting the effect of MWCNT on amount of cement hydration products and improving the quality of cement hydration products microstructures of cement paste was investigated. To determine the amount of cement hydration products thermogravimetric analysis was used. Two critical parameters of TGA test are PHPlossand CHloss. In order to model the TGA test results, the ANN modeling was performed on these parameters separately. In this study, 60% of data are used for model calibration and the remaining 40% are used for model verification. Based on the highest efficiency coefficient and the lowest root mean square error, the best ANN model was chosen. The results of TGA test implied that the cement hydration is enhanced in the presence of the optimum percentage (0.3 wt%) of MWCNT. Moreover, since the efficiency coefficient of the modeling results of CH and PHP loss in both the calibration and verification stages was more than 0.96, it was concluded that the ANN could be used as an accurate tool for modeling the TGA results. Another finding of this study was that the ANN prediction in higher ages was more precise.

scholarly journals Influence of Rice Straw Fibers on Concrete Strength and Drying Shrinkage

2018 ◽  
Vol 10 (7) ◽  
pp. 2445 ◽  
Author(s):  
Feraidon Ataie
Keyword(s):  
Induction Period ◽  
Rice Straw ◽  
Cement Hydration ◽  
Inorganic Compounds ◽  
Concrete Strength ◽  
Construction Materials ◽  
Drying Shrinkage ◽  
Noticeable Improvement ◽  
Compressive And Flexural Strengths ◽  
The Impact

Fibers have been used in construction materials for centuries. This study investigated the impact of the addition of rice straw fibers (RSF) on the compressive and flexural strengths of concrete, drying shrinkage, and on the heat of cement hydration. RSF was saturated before being added to concrete. Addition of RSF in concrete reduced concrete strength, increased concrete drying shrinkage, and increased the induction period of cement hydration. It was suggested that water squeezed out of RSF during mixing and sample consolidation increased effective water-to-cement ratios (w/c) and resulted in reduction of concrete strength and increase of concrete drying shrinkage. The increase of retardation time was attributed to leaching of organic and inorganic compounds out of RSF into the pore solution. It was shown that samples containing washed RSF did not have noticeable improvement in compressive strength over samples containing unwashed (as received) RSF. However, samples containing washed RSF had lower drying shrinkage and shorter induction period compared to those containing unwashed RSF.

Effect of SRA on the Course of Hydration of Cement Composites

2019 ◽  
Vol 296 ◽  
pp. 35-40
Author(s):  
Lucia Osuská ◽  
Martin Ťažký ◽  
Milan Meruňka ◽  
Rudolf Hela
Keyword(s):  
Liquid Phase ◽  
Chemical Reaction ◽  
Cement Hydration ◽  
Cement Composites ◽  
Mechanical Parameters ◽  
Curing Time ◽  
Volume Changes ◽  
Cement Pastes ◽  
Binder Component ◽  
The Impact

Cement hydration is a chemical reaction that is associated with the development of hydration heat and changes in the volume of input components that transit from the solid and liquid phase to one homogeneous whole. In order to eliminate the volume changes already occurring during the hydration process, several principles can be applied, such as the use of active or inert admixtures as partial cement substitute or special shrinkage reducing additives. The experiment verifies the effect of anti-shrinkage additives on the course of hydration of cement pastes in terms of the development of hydration temperatures and elimination of volume changes of cement pastes. Volume changes will be monitored for the first 30 hours of cement mixing with water, i.e. in the time when the major changes occur due to this chemical reaction. Due to the expected hydration deceleration of the binder component by the effect of SRA, the impact of the use of these additives on the curing time of the composite and consequently on the mechanical parameters of the concrete will be verified.

scholarly journals Modifying Cement Hydration with NS@PCE Core-Shell Nanoparticles

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Yue Gu ◽  
Qianping Ran ◽  
Wei She ◽  
Jiaping Liu
Keyword(s):  
Cement Hydration ◽  
Fine Particles ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Pozzolanic Reactivity ◽  
Characteristic Values ◽  
Core Shell Nanoparticles ◽  
The Impact

It is generally accepted that fine particles could accelerate cement hydration process, or, more specifically, this accelerating effect can be attributed to additional surface area introduced by fine particles. In addition to this view, the surface state of fine particles is also an important factor, especially for nanoparticles. In the previous study, a series of nano-SiO2-polycarboxylate superplasticizer core-shell nanoparticles (NS@PCE) were synthesized, which have a similar particle size distribution but different surface properties. In this study, the impact of NS@PCE on cement hydration was investigated by heat flow calorimetry, mechanical property measurement, XRD, and SEM. Results show that, among a series of NS@PCE, NS@PCE-2 with a moderate shell-core ratio appeared to be more effective in accelerating cement hydration. As dosage increases, the efficiency of NS@PCE-2 would reach a plateau which is quantified by various characteristic values. Compressive strength results indicate that strength has a linear correlation with cumulative heat release. A hypothesis was proposed to explain the modification effect of NS@PCE, which highlights a balance between initial dispersion and pozzolanic reactivity. This paper provides a new understanding for the surface modification of supplementary cementitious materials and their application and also sheds a new light on nano-SiO2 for optimizing cement-based materials.

Accelerated Biodeterioration Test for the Study of Cementitious Materials in Sewer Networks: Experimental and Modeling

2016 ◽  
Vol 711 ◽  
pp. 1069-1075 ◽  
Author(s):  
Anaïs Grandclerc ◽  
Marielle Gueguen-Minerbe ◽  
Issam Nour ◽  
Patrick Dangla ◽  
Thierry Chaussadent
Keyword(s):  
Hydrogen Sulfide ◽  
Experimental Studies ◽  
Cementitious Materials ◽  
Efficient Solutions ◽  
Cement Matrix ◽  
Sulfide Concentration ◽  
Reduced Sulfur Compounds ◽  
Ettringite Formation ◽  
Set Up ◽  
The Impact

Important deteriorations have been observed in concrete sewers, due to hydrogen sulfide (H2S) production. Hydrogen sulfide environment involves the selection of sulfur-oxidizing bacteria (bacteria able to oxidize the reduced sulfur compounds) in contact with the cementitious materials. These biological reactions lead to a local production of sulfuric acid and, as a consequence, to the dissolution of cement matrix and its mineralogical transformations (gypsum and ettringite formation). This phenomenon disturbs the sewer system and leads to expansive works of rehabilitation. As a consequence, a project was initiated in order to propose more efficient solutions. The main objectives of this project are to set up an accelerated test and to develop an associated model. To date, experimental studies and some improvements of the model previously setting up were performed. The first study describes the impact of several parameters, including type of cementitious materials, on hydrogen sulfide adsorption. These abiotic tests involve monitoring hydrogen sulfide concentration as a function of time. This experiment was realized in a hermetic chamber with five types of mortars (cast with calcium aluminate cement (CAC), blended Portland cement (CEM III, CEM IV and CEM V) and super sulfated cement (SSC)) and under different relative humidity. The second study is deterioration state of mortars characterization, thanks to some analyses (SEM – EDX). After three months of exposition, different types of sulphur species are observed on mortar surfaces, which vary with the nature of mortar. All these experiments allow providing improvements to model previously setting up. Abiotic tests measurements are used to determine mathematical law, which modelises hydrogen sulphide adsorption on each type of cementitious material.

scholarly journals Effect of MXene (Nano-Ti3C2) on Early-Age Hydration of Cement Paste

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Haibin Yin ◽  
Jianping Zhu ◽  
Xuemao Guan ◽  
Zhengpeng Yang ◽  
Yu Zhu ◽  
...  
Keyword(s):  
Cement Paste ◽  
Cement Hydration ◽  
Hydration Process ◽  
Early Age ◽  
Main Role ◽  
Hydration Products ◽  
Hydration Properties ◽  
Network Connection ◽  
The Impact ◽  
Early Age Hydration

As a new two-dimensional material, MXene (nano-Ti3C2) has been widely applied in many fields, especially for reinforced composite materials. In this paper, mechanical testing, X-ray diffraction (XRD), hydration heat, scanning electron microscope (SEM), and EDS analysis were used to analyze the impact of MXene on cement hydration properties. The obtained results revealed that (a) MXene could greatly improve the early compressive strength of cement paste with 0.04 wt% concentration, (b) the phase type of early-age hydration products has not been changed after the addition of MXene, (c) hydration exothermic rate within 72 h has small difference at different amount of MXene, and (d) morphologies of hydration products were varied with the dosage of MXene, a lot of tufted ettringites appeared in 3 d hydration products when the content of MXene was 0.04 wt%, which will have a positive effect on improving the early mechanical properties of cement paste. MXene has inhibited the Portland cement hydration process; the main role of MXene in the cement hydration process is to promote the messy ettringite becoming regular distribution at a node and form network connection structure in the crystals growth process, making the mechanics performance of cement paste significantly improved.

scholarly journals Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1938
Author(s):  
Luís Urbano D. Tambara Júnior ◽  
Janaíde C. Rocha ◽  
Malik Cheriaf ◽  
Pilar Padilla-Encinas ◽  
Ana Fernández-Jiménez ◽  
...  
Keyword(s):  
Cement Hydration ◽  
Hydration Products ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Calcium Sulfoaluminate Cement ◽  
Hydration Kinetics ◽  
Sodium Salts ◽  
X Ray ◽  
Calcium Sulfoaluminate ◽  
Ettringite Formation

This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na2SO4, Na2CO3, and Na2SiO3) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH3, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. Na2SO4 induces cracking in the ≥28-d pastes due to post-hardening gypsum and ettringite formation from the excess SO42– present. Anhydrite dissolves more rapidly in the presence of Na2CO3, prompting carbonation. Na2SiO3 raises compressive strength and exhibits strätlingite as one of its reaction products.

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