scholarly journals Comparison of the Hydration Characteristics of Ultra-High-Performance and Normal Cementitious Materials

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2594
Author(s):  
Haiyun Zhou ◽  
Hongbo Zhu ◽  
Hongxiang Gou ◽  
Zhenghong Yang
Keyword(s):  
High Performance ◽  
Isothermal Calorimetry ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Chemical Shrinkage ◽  
Hydration Kinetics ◽  
Degree Of Hydration ◽  
Phase Development ◽  
Hydration Characteristics ◽  
Development Tendency

The hydration mechanism of ultra-high-performance cementitious materials (UHPC) departs considerably from that of normal cementitious materials (NC). In this study, the strength, isothermal calorimetry, chemical shrinkage, X-ray diffraction (XRD), and thermogravimetry (TG) methods are used to determine the hydration characteristics of UHPC and NC that contain silica fume (SF). A simple device was modified to test the chemical shrinkage for long-term growth, and the ultimate chemical shrinkage is obtained by semi-empirical formula fitting. It is found that the degree of hydration of UHPC is significantly lower than that of NC. The hydration kinetics analyzed using the Krstulovic-Dabic model shows that the hydration process of NC is type NG-I-D, which is characterized by gentle and prolonged hydration. However, the hydration of UHPC is type NG-D with the distinguishing features of early sufficiency and later stagnation. The growth of the strength, exothermic evolution, and phase development of UHPC is decelerated as the hydration process proceeds, which confirms the weak development tendency of hydration at the later stage. In addition, the effect of SF on the hydration of UHPC is minor, and the higher content of SF is beneficial to the hydration at the later stage.

scholarly journals The Influence of Superabsorbent Polymers and Nanosilica on the Hydration Process and Microstructure of Cementitious Mixtures

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5194
Author(s):  
Gerlinde Lefever ◽  
Dimitrios G. Aggelis ◽  
Nele De Belie ◽  
Marc Raes ◽  
Tom Hauffman ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Isothermal Calorimetry ◽  
Autogenous Shrinkage ◽  
Hydration Process ◽  
Microstructural Development ◽  
Self Healing ◽  
Hydration Kinetics ◽  
Superabsorbent Polymers ◽  
Water To Cement Ratio ◽  
Supplementary Material

Superabsorbent polymers (SAPs) are known to mitigate the development of autogenous shrinkage in cementitious mixtures with a low water-to-cement ratio. Moreover, the addition of SAPs promotes the self-healing ability of cracks. A drawback of using SAPs lies in the formation of macropores when the polymers release their absorbed water, leading to a reduction of the mechanical properties. Therefore, a supplementary material was introduced together with SAPs, being nanosilica, in order to obtain an identical compressive strength with respect to the reference material without additives. The exact cause of the similar compressive behaviour lies in the modification of the hydration process and subsequent microstructural development by both SAPs and nanosilica. Within the present study, the effect of SAPs and nanosilica on the hydration progress and the hardened properties is assessed. By means of isothermal calorimetry, the hydration kinetics were monitored. Subsequently, the quantity of hydration products formed was determined by thermogravimetric analysis and scanning electron microscopy, revealing an increased amount of hydrates for both SAP and nanosilica blends. An assessment of the pore size distribution was made using mercury intrusion porosimetry and demonstrated the increased porosity for SAP mixtures. A correlation between microstructure and the compressive strength displayed its influence on the mechanical behaviour.

scholarly journals Influence of Glass Powder on Hydration Kinetics of Composite Cementitious Materials

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Xiaolin Chang ◽  
Xinping Yang ◽  
Wei Zhou ◽  
Guoshuai Xie ◽  
Shuhua Liu
Keyword(s):  
Glass Powder ◽  
Isothermal Calorimetry ◽  
Cementitious Materials ◽  
Heat Emission ◽  
Hydration Heat ◽  
Hydration Kinetics ◽  
Period Increase ◽  
Acceleration Period ◽  
Boundary Reaction ◽  
Kinetics Of

The influence of glass powder (GP) on hydration kinetics of composite cementitious materials has been investigated by isothermal calorimetry test and hydration kinetics methods in this paper. The hydration heat emission rate and hydration heat decrease gradually while the induction and acceleration period increase with the increase of GP content. According to Krstulovic-Dabic model, the hydration process of composite cementitious materials containing GP is controlled by a variety of complicated reaction mechanisms, which can be divided into three periods: nucleation and crystal growth (NG), phase boundary reaction (I), and diffusion (D). The NG and I process are shortened after incorporating GP.

scholarly journals Nanofibrillated celluloses for the performance improvement of ultra-high ductility cementitious composites

2021 ◽  
Author(s):  
Long Liang ◽  
Xin Zhang ◽  
Qiaoling Liu ◽  
Xiurong Li
Keyword(s):  
Isothermal Calorimetry ◽  
Peak Stress ◽  
Rheological Parameters ◽  
Cementitious Composites ◽  
High Ductility ◽  
Hydration Kinetics ◽  
Early Hydration ◽  
Degree Of Hydration ◽  
Low Field ◽  
Flexural Tests

Abstract This study explored the effect of nanofibrillated celluloses (CNF), namely 0%, 0.05%, 0.1%, and 0.15% of binders weight, on the hydration, rheology, pore structure, and mechanical properties of ultra-high ductility cementitious composites (UHDCC). The hydration kinetics were conducted with different CNF contents using isothermal calorimetry (IC), showing a retardation effect of CNF on the early hydration of UHDCC matrices at 70 h due to the absorption of CNF on the surface of cement particles. Then, thermogravimetric analysis (TGA) demonstrated that CNF improved the degree of hydration at 28 days due to the formation of the CNF transport of water into unhydrated cement cores. The two rheological parameters, namely the yield stress and plastic viscosity, of the fresh UHDCC matrices increased with the increasing CNF contents. Low-field nuclear magnetic resonance (LF-NMR) analysis, as a non-destructive method, proved that the addition of CNF could reduce the porosity of UHDCC and refine its pore size distribution, and the 8.9–46.1% enhancement in the compressive strength of corresponding specimens was found. Notably, CNF could increase the tensile initial cracking stress by 91.2% and tensile stress by 30.8% of UHDCC, and maintain or increase its over 8% of tensile strain-hardening capacity. The flexural tests also were found a 54.6% increase in the initial stress and a 14.8% increase in the peak stress. As a preliminary, CNF shows crucial promising as a greener nanomaterial to improve the strength and ductility of UHDCC.

scholarly journals The influence of curing temperature, plastic additives and polypropylene fibers on the mechanical behaviour of cementitious materials

2020 ◽  
Vol 150 ◽  
pp. 02012
Author(s):  
Mohammed Aqil ◽  
Lahcen Bahi ◽  
Latifa Ouadif ◽  
Siham Belhaj ◽  
Raounak Edderkaoui
Keyword(s):  
Compressive Strength ◽  
Mechanical Behaviour ◽  
Mechanical Performance ◽  
Cementitious Materials ◽  
Curing Temperature ◽  
Polypropylene Fibers ◽  
Hydration Kinetics ◽  
Degree Of Hydration ◽  
History Of ◽  
Kinetics Of

An experimental company was carried out to better understand the influence of curing temperature on the mechanical behaviour of cementitious materials, particularly compressive strength, the study focused on two types of mortars, the first containing polypropylene fibers while the second contains a proportion of PVC-type plastic grains from industrial waste, the hydration kinetics of the different components of the formulated mortar has been characterized by the isothermal calorimetric test, thus a history of the hydration degrees has been established, Afterwards, an attempt was made to correlate the compressive strength with the evolution of the degree of hydration for the different formulations, based on the results obtained, it is clearly observable that the compressive strength evolves with the degree of hydration and that the specimen containing the polypropylene fibers has the best mechanical performance with respect to compression.

Chemical Shrinkage of Pastes Made with Shrinkage Reducing Admixtures

2011 ◽  
Vol 466 ◽  
pp. 105-113 ◽  
Author(s):  
António Bettencourt Ribeiro ◽  
Vasco Medina ◽  
Augusto Gomes ◽  
Arlindo Gonçalves
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Chemical Shrinkage ◽  
Cement Pastes ◽  
Degree Of Hydration ◽  
Shrinkage Cracks ◽  
Large Application ◽  
Shrinkage Reducing Admixtures

Shrinkage Reducing Admixtures (SRA) are being used more often in concrete structures in order to better control shrinkage cracks. High-performance concrete, nowadays with large application, has more proneness to crack at very early age due to the lower W/C. In this type of concrete, autogenous shrinkage is usually more important than drying shrinkage. Autogenous shrinkage is due to the volume decrease inherent to binder hydration reactions. The rate of these reactions is influenced not only by the type of binder but also by the presence of chemical admixtures. It is recognized that SRA delay the hydration, being a secondary effect of this type of admixtures. In this work changes on the degree of hydration of cement pastes with SRA and different binders are presented, using the chemical shrinkage test.

Influence of Re-Dispersible Powders on Very Early Shrinkage in Functional Mortars

2015 ◽  
Vol 1129 ◽  
pp. 77-85
Author(s):  
Thomas A. Bier ◽  
Adrian Bajrami ◽  
Torsten Westphal ◽  
Elsa Qoku ◽  
Anxhelina Qorllari
Keyword(s):  
High Performance ◽  
Water Resistance ◽  
Hydration Kinetics ◽  
Dimensional Changes ◽  
Plastic Shrinkage ◽  
Setting Times ◽  
Phase Development ◽  
Hydrate Phase ◽  
Aluminate Cement

Functional, high performance mortars such as Self-Leveling Underlayments (SLU), Tile Adhesives (TA) or Grouting Mortars (GM) are composed, besides complex binders, of mineral and organic fillers, and most importantly admixtures. Amongst the organic fillers, re-dispersible powders produced by spray drying from emulsions, are added to improve flexibility, adhesion and water resistance. These powders, however, also influence fresh properties such as workability and plastic shrinkage or sedimentation. Additionally they are prone to interfere with the hydration kinetics thus playing a role in the very early structuring process of a cement-based mortar.In this study, the influence of re-dispersible powders on sedimentation, plastic as well as chemical shrinkage in ternary binder composites has been investigated for the first 24 hours. The structuring process has been additionally characterized by the hydrate phase development. Ternary binders are defined in this study as compositions of Calcium Aluminate Cement (CAC), Ordinary Portland Cement (OPC) and Calcium Sulfate (CS̅).The addition of re-dispersible powders showed not only the well-known retardation in hydration kinetics, longer setting times and increased gel times but also changed dimensional stability. Dimensional changes occurring during the first 24 hours were monitored by different test devices in order to separate different shrinkage/expansion mechanisms. The measurements are compared to the in-situ measurement of phase development by XRD.

scholarly journals Influence of Ultrasonication of Functionalized Carbon Nanotubes on the Rheology, Hydration, and Compressive Strength of Portland Cement Pastes

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5248
Author(s):  
Laura Silvestro ◽  
Artur Ruviaro ◽  
Geannina Lima ◽  
Paulo de Matos ◽  
Afonso R. G. de Azevedo ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Compressive Strength ◽  
Portland Cement ◽  
Mechanical Performance ◽  
Isothermal Calorimetry ◽  
Hydration Kinetics ◽  
Cement Pastes ◽  
Degree Of Hydration ◽  
Vis Spectroscopy ◽  
Localized Defects

The functionalization process usually increases the localized defects of carbon nanotubes (CNT). Thus, the ultrasonication parameters used for dispersing non-functionalized CNT should be carefully evaluated to verify if they are adequate in dispersing functionalized CNT. Although ultrasonication is widely used for non-functionalized CNT, the effect of this dispersing process of functionalized CNT has not been thoroughly investigated. Thus, this work investigated the effect of ultrasonication on functionalized CNT + superplasticizer (SP) aqueous dispersions by ultraviolet-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR). Furthermore, Portland cement pastes with additions of 0.05% and 0.1% CNT by cement weight and ultrasonication amplitudes of 0%, 50% and 80% were evaluated through rheometry, isothermal calorimetry, compressive strength at 1, 7 and 28 days, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). FTIR results from CNT + SP dispersions indicated that ultrasonication may negatively affect SP molecules and CNT graphene structure. The increase in CNT content and amplitude of ultrasonication gradually increased the static and dynamic yield stress of paste but did not significantly affect its hydration kinetics. Compressive strength results indicated that the optimum CNT content was 0.05% by cement weight, which increased the strength of composite by up to 15.8% compared with the plain paste. CNT ultrasonication neither increases the degree of hydration of cement nor the mechanical performance of composite when compared with mixes containing unsonicated CNT. Overall, ultrasonication of functionalized CNT is not efficient in improving the fresh and hardened performance of cementitious composites.

scholarly journals Hydration Characteristics of Tricalcium Aluminate in the Presence of Nano-Silica

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 199
Author(s):  
Dapeng Zheng ◽  
Manuel Monasterio ◽  
Weipeng Feng ◽  
Waiching Tang ◽  
Hongzhi Cui ◽  
...  
Keyword(s):  
Isothermal Calorimetry ◽  
Pozzolanic Reaction ◽  
Nano Silica ◽  
Hydration Kinetics ◽  
Reactive Component ◽  
Nano Sio2 ◽  
Pozzolanic Reactivity ◽  
Tricalcium Aluminate ◽  
Hydration Characteristics ◽  
Kinetics Of

Tricalcium aluminate (C3A) is the most reactive component of the Portland cement and its hydration has an important impact on the workability and early strength of concrete. Recently, nanomaterials such as nano-silica (nano-SiO2) have attracted much attention in cement-based materials because of its pozzolanic reactivity and the pore-filling effect. However, its influence on the hydration of C3A needs to be well understood. In this study, the hydration kinetics of C3A mixed with different percentages of nano-SiO2 were studied and compared with pure C3A. The hydration products were examined by different characterization techniques including XRD, XPS, and NMR spectroscopy and isothermal calorimetry analyses. The XRD results showed that the addition of nano-SiO2 promoted the conversion of the intermediate product C4AH13. The isothermal calorimetry results showed that the addition of nano-SiO2 significantly reduced the hydration exotherm rate of C3A from 0.34 to less than 0.1 mW/g. With the presence of nano-SiO2, the peaks for Q1 were observed in 29Si MAS-NMR measurements, and the content of Q1 increased from 6.74% to 30.6% when the nano-SiO2 content increased from 2 wt.% to 8 wt.%, whereas the proportion of Q4 gradually decreased from 89.1% to 63.6%. These results indicated a pozzolanic reaction provoked by the nano-SiO2 combined with aluminate structures generating C-A-S-H gel.

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