scholarly journals Self-Desiccation of a Vernacular CSA Binder

2022 ◽  
Author(s):  
Natalia Pires Martins ◽  
Burhan Cicek ◽  
Coralie Brumaud ◽  
Guillaume Habert
Keyword(s):  
Citric Acid ◽  
Thermogravimetric Analysis ◽  
Setting Time ◽  
Bound Water ◽  
The Self ◽  
Early Age ◽  
Hydrated Cement ◽  
Hydration Products ◽  
Early Hydration ◽  
Setting Times

The fast precipitation of ettringite in conventional Calcium Sulfo Aluminate (CSA) cement causes rapid stiffening of the cement paste and is directly associated with short setting times and self-desiccation. To extend the time during which those types of cement remain workable, retarding admixtures can be used. However, retarders may affect the amounts and types of hydration products formed and as a consequence the ability of hydrated cement to chemically bind water. This work investigates the influence of two natural-based admixtures on the self-desiccation ability of a vernacular CSA ternary binder used as earth stabilization. Vicat measurements were used to study the efficiency of citric acid and sucrose as retarding admixtures on the setting time of stabilized earth. A quantitative study of the self-desiccation ability of the binder was performed on dried binder pastes using thermogravimetric analysis (TGA). Results show that both admixtures have a significant impact on the setting time of the binder. Furthermore, TGA showed that the self-desiccation ability of this vernacular CSA binder is significantly reduced when citric acid at high dosages is used, both at early hydration and after 14 days. On the contrary, the use of sucrose does not affect the water chemically bound at an early age but can maximize bound water after 14 days of hydration.

scholarly journals Analysis of the Influence of Crystalline Admixtures at Early Age Performance of Cement-Based Mortar by Electrical Resistance Monitoring

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5705
Author(s):  
Rubén Beltrán Cobos ◽  
Fabiano Tavares Pinto ◽  
Mercedes Sánchez Moreno
Keyword(s):  
Compressive Strength ◽  
Thermogravimetric Analysis ◽  
Remote Monitoring ◽  
Electrical Resistance ◽  
Setting Time ◽  
Early Age ◽  
Resistance Monitoring ◽  
Initial Setting Time ◽  
Characterization Techniques ◽  
Initial Setting

Crystalline admixtures are employed for waterproofing concrete. This type of admixtures can affect the early age performance of cement-based mixes. The electrical resistance properties of cement have been related to the initial setting time and to the hydration development. This paper proposes a system for remote monitoring of the initial setting time and the first days of the hardening of cement-based mortars to evaluate the effect of the incorporation of crystalline admixtures. The electrical resistance results have been confirmed by other characterization techniques such as thermogravimetric analysis and compressive strength measurements. From the electrical resistance monitoring it has been observed that the incorporation of crystalline admixtures causes a delay in the initial setting time and hydration processes. The measurements also allow to evaluate the influence of the amount of admixture used; thus, being very useful as a tool to define the optimum admixture dosage to be used.

scholarly journals Some microstructure properties at early age of ettringite binder based on rich C12A7 calcium aluminate cement

2018 ◽  
Vol 12 (3) ◽  
pp. 44-50
Author(s):  
Nguyen Ngoc Lam
Keyword(s):  
Calcium Aluminate ◽  
Setting Time ◽  
Rapid Evolution ◽  
Bound Water ◽  
Hydration Product ◽  
Rapid Expansion ◽  
Early Age ◽  
Initial Setting Time ◽  
Main Compound ◽  
Initial Setting

The mineral composition of calcium aluminate cements is traditionally based on CA (monocalcium aluminate-CaO·Al2O3). Recently, a new cement with the main compound of C12A7 (Mayenite) has been developed for rapid hardening binder. This cement is used in conjunction with a sulfate binder to form a new type binder called ettringite binder due to the high quantity of ettringite in the hydration product, opened new possibilities for mortar and concrete formulations. This paper focuses on some microstructure characteristics of the ettringite binder based on a C12A7 rich cement and a hemihydrate at early age. Some important characteristics of this binder were found, such as: short setting time (about 40–50 minutes), rapid expansion just after initial setting time, rapid evolution of porosity and bound water during the first 5 hours of hydration. The correlation between bound water and porosity of hardened binders was also found in this paper. Article history: Received 24 January 2018, Revised 04 April 2018, Accepted 27 April 2018  

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 Anhydrite on the Early Hydration Performance of Rapid Setting and Hardening Belite Sulfoaluminate Cement

2017 ◽  
Vol 898 ◽  
pp. 1990-1995 ◽  
Author(s):  
Ming Zhang Lan ◽  
Bin Feng Xiang ◽  
Jian Feng Wang ◽  
Xu Dong Zhao ◽  
Xiao Ying Wang
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
High Strength ◽  
Cement Clinker ◽  
Hydration Kinetics ◽  
Early Hydration ◽  
Free Lime ◽  
Calcium Sulfoaluminate ◽  
Setting Times ◽  
Rapid Setting

In order to investigate the early hydration behavior of rapid setting and hardening belite sulfoaluminate cements, the methods of X-ray Diffraction, Scanning Electron Microscope, Compressive Strength test and Setting Times test were used to identify and quantify the hydration kinetics and microstructure of this new-found cements in China. The results showed that the main mineral compositions of high belite sulfoaluminate cement clinker included calcium sulfoaluminate (4CaO·3Al2O3·CaSO4), belite (2CaO·SiO2), ferrite phase, free gypsum and free lime. It was found that not only the setting time and compressive strength but also the composition of hydration products were influenced by anhydrite to some extent. Meanwhile, a mass of AFt and AFm generated along with the hydration process at different ages, overlapped, crossed and penetrated through calcium silicate hydrate gel and aluminum oxide to form a relatively dense structure which could contribute to the high strength of cement.

Resistivity Study on Early Hydration Process of Phosphoaluminate Cementitious Material

2009 ◽  
Vol 79-82 ◽  
pp. 95-98 ◽  
Author(s):  
Ming Zhang ◽  
Zhu Ding ◽  
Feng Xing ◽  
Peng Liu
Keyword(s):  
Resistivity Measurement ◽  
Heat Evolution ◽  
Hydration Process ◽  
Early Age ◽  
Hydration Products ◽  
Microstructure Formation ◽  
Time Curve ◽  
Early Hydration ◽  
Hydration Mechanism ◽  
Acceleration And Deceleration

An electrodeless resistivity measurement system developed recently can provide a reliable method for monitoring the hydration process of cement-based materials continuously and accurately. Phosphoaluminate cement (PAC) sets quickly and develops high early strength. In order to understand the mechanism, the hydration products and microstructure formation of PAC in early age need to be studied. In the study, early hydration process of PAC with different dosage of retarder was investigated by the electrodeless resistivity equipment. According to resistivity-time curve, resistivity of freshly mixed PAC paste decreases sharply and then rises slowly, some characteristic peaks appear at different hydration stages of PAC. Heat evolution of PAC was also measured. The hydration mechanism and structure formation were studied according to these results. Depending on the dosage of retarder, the hydration process of PAC includes four stages which are dissolution, induction, acceleration and deceleration.

Study on the Desulfurization Gypsum and Steel Slag Blended Clinker-Free Cementing Material

2012 ◽  
Vol 193-194 ◽  
pp. 384-388
Author(s):  
Hai Liang Luo ◽  
Chun Sheng Li ◽  
Yi Ting Ye ◽  
Fu Dan Chen
Keyword(s):  
Setting Time ◽  
Steel Slag ◽  
Orthogonal Test ◽  
Raw Material ◽  
Water Quantity ◽  
Hydration Products ◽  
Early Hydration ◽  
Mix Proportion ◽  
Cementing Material ◽  
Micro Analysis

Based on orthogonal test with steel slag and desulfurization gypsum as main raw material, mixed appropriate amount slag and compound addition a little of activator, we explored the slag dosage, the proportion of the combined admixture activator and the desulfurization gypsum dosage impact on the performance of clinker-free cementing material, such as strength, stability, standard consistency water quantity and setting time. The results showed that the best mix proportion of cementing material with slag content 40% and activator A:activator B is equal to 2.78:2.22. We explored the structure and composition of hydration products further more by micro-analysis, such as SEM, EDS and so on. We can found that the cementing material hydration products similar with hydration products of silicate cement. The cementitious material hydration with Afm crystal content increased significantly. The Aft crystal generated in early hydration(3d) gradually transformed into Afm crystal in late hydration(28d) ,and the structure becomes more dense.

scholarly journals Evaluation of the Effect of Fly Ash on Hydration Characterization in Self-Compacting Concrete (SCC) at Very Early Ages Using Piezoceramic Transducers

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2489 ◽  
Author(s):  
Yu Zheng ◽  
Dongdong Chen ◽  
Lingzhu Zhou ◽  
Linsheng Huo ◽  
Hongwei Ma ◽  
...  
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Penetration Resistance ◽  
Electrical Signal ◽  
Experimental Results ◽  
Early Age ◽  
Hydration Reaction ◽  
Test Results ◽  
Self Compacting Concrete ◽  
Early Hydration

Nowadays, the industrial waste, Fly Ash (FA), as a mineral admixture or a replacement of cement for the production of self-compacting concrete (SCC) has been increasingly used, because of its benefits in enhancing both fresh and long-term concrete properties and in promoting environmental-friendly construction. In this study, the conventional cement was replaced by FA at different rates (0%, 20%, 40%, 60% of the cement mass) for the SCC mixtures. The early-age (0–24 h) SCC hydration, which is a complicated chemical reaction in pozzolanic behavior, was characterized by using a pair of piezoceramic Smart Aggregates (SAs). One SA works as an actuator and the other works as a sensor. A sweep sine signal from 100 Hz to100 kHz was used as the excitation signal, which is helpful to understand the quantitative influence of fly ash on the kinetics of SCC hydration. During the hydration reaction, the received electrical signal was continuously detected by the sensor. The experimental results showed that increasing the volume of fly ash resulted in longer pozzolanic reaction time in SCCs, which successfully reveals the effect of fly ash volume on the hydration behavior in early age (0–24 h) hydration. In order to quantitatively evaluate the hydration in the 0–24 h, based on the wavelet packet energy analysis, the hydration completion index (HCI) and normalized hydration completion index (NHCI) were defined. The experimental results showed that the NHCI can clearly reveal the hydration completion progress during the early hydration age (0–24 h). To validate the accuracy of the test results based on SAs, a series of mechanical tests for penetration resistance of SCCs with different volumes of fly ash were carried out. The results predicted by the signal based on SAs gave reasonable agreement with the test results of penetration resistance. It can be concluded that a successful investigation of the influence of fly ash on early-age SCC hydration response can be achieved based on the analysis of the received electrical signal using the proposed method and the important hydration characteristics, such as initial and final setting time, and can be approximately predicted by NHCI values.

The Preparation and Performance Research of the Desulphurization Gypsum Plaster Material

2013 ◽  
Vol 327 ◽  
pp. 32-35
Author(s):  
Huan Qi Zhao ◽  
Guo Zhong Li
Keyword(s):  
Citric Acid ◽  
Negative Impact ◽  
Setting Time ◽  
Sodium Hexametaphosphate ◽  
Moderate Amount ◽  
Setting Times ◽  
Gypsum Plaster ◽  
And Performance ◽  
Cementing Material ◽  
Performance Research

The cementing material is the desulfurization gypsum. The fly ash is a admixture. A moderate amount of additive is mixed. A gypsum plaster material of micro swelling and good workability, plasticity was produced. The representative two retarders, the sodium hexametaphosphate and the citric acid, were researched. The effects of the retarders on the setting times and the mechanical properties of the desulfurization gypsum were studied. The retarding effect of the citric acid is the most prominent, but its negative impact on the flexural and compressive strength of the plaster gypsum is very large. Considering the setting time and the strength, the sodium hexametaphosphate is the best retarder of the desulfurization gypsum plaster material.

scholarly journals The Relation between Concrete, Mortar and Paste Scale Early Age Properties

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1569
Author(s):  
Martin Klun ◽  
Vlatko Bosiljkov ◽  
Violeta Bokan-Bosiljkov
Keyword(s):  
Setting Time ◽  
Autogenous Shrinkage ◽  
Solidification Process ◽  
Early Age ◽  
S Wave ◽  
Conductivity Method ◽  
Early Hydration ◽  
High Maturity ◽  
Highly Correlated ◽  
The Cost

Microstructure development of concrete, mortar, and paste scale of cement-based material (CBM) during the early hydration stage has a significant impact on CBM’s physical, mechanical, and durability characteristics at the high maturity state. The research was carried out using compositions with increased autogenous shrinkage and extended early age period, proposed within the RRT+ programme of the COST Action TU1404. The electrical conductivity method, used to follow the solidification process of CBM, is capable of determining the initial and final setting time, and the end of the solidification process acceleration stage for the paste and mortar scale. Simultaneous ultrasonic P- and S-wave transmission measurements revealed that the ratio of velocities VP/VS is highly dependent on the presence of aggregates—it is considerably higher for the paste scale compared to the mortar and concrete scale. The deviation from the otherwise roughly constant ratio VP/VS for each scale may indicate cracks in the material. The non-linear correlation between the dynamic and static elastic moduli valid over the three scales was confirmed. Additionally, it was found that the static E-modulus correlates very well with the square of the VS and that the VS is highly correlated to the cube compressive strength—but a separate trendline exists for each CBM scale.

scholarly journals Early-age Properties of High-volume Fly Ash Concrete Mixes for Pavement: Volume 2

2021 ◽  
Author(s):  
Aniruddha Baral ◽  
◽  
Jeffery Roesler ◽  
Junryu Fu ◽  
◽  
...  
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
High Volume ◽  
Early Age ◽  
X Ray ◽  
Fly Ash Concrete ◽  
Setting Times ◽  
Chemical Admixtures ◽  
High Volume Fly Ash ◽  
Foam Index

High-volume fly ash concrete (HVFAC) is more cost-efficient, sustainable, and durable than conventional concrete. This report presents a state-of-the-art review of HVFAC properties and different fly ash characterization methods. The main challenges identified for HVFAC for pavements are its early-age properties such as air entrainment, setting time, and strength gain, which are the focus of this research. Five fly ash sources in Illinois have been repeatedly characterized through x-ray diffraction, x-ray fluorescence, and laser diffraction over time. The fly ash oxide compositions from the same source but different quarterly samples were overall consistent with most variations observed in SO3 and MgO content. The minerals present in various fly ash sources were similar over multiple quarters, with the mineral content varying. The types of carbon present in the fly ash were also characterized through x-ray photoelectron spectroscopy, loss on ignition, and foam index tests. A new computer vision–based digital foam index test was developed to automatically capture and quantify a video of the foam layer for better operator and laboratory reliability. The heat of hydration and setting times of HVFAC mixes for different cement and fly ash sources as well as chemical admixtures were investigated using an isothermal calorimeter. Class C HVFAC mixes had a higher sulfate imbalance than Class F mixes. The addition of chemical admixtures (both PCE- and lignosulfonate-based) delayed the hydration, with the delay higher for the PCE-based admixture. Both micro- and nano-limestone replacement were successful in accelerating the setting times, with nano-limestone being more effective than micro-limestone. A field test section constructed of HVFAC showed the feasibility and importance of using the noncontact ultrasound device to measure the final setting time as well as determine the saw-cutting time. Moreover, field implementation of the maturity method based on wireless thermal sensors demonstrated its viability for early opening strength, and only a few sensors with pavement depth are needed to estimate the field maturity.

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