scholarly journals The Effect of an Accelerator on Cement Paste Capillary Pores: NMR Relaxometry Investigations

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5328
Author(s):  
Ioan Ardelean
Keyword(s):  
Cement Paste ◽  
Water Consumption ◽  
Calcium Nitrate ◽  
Hydration Process ◽  
Surface Evolution ◽  
New Approach ◽  
Dormant Stage ◽  
Nmr Relaxometry ◽  
Pore Evolution ◽  
General Basis

Nuclear Magnetic Resonance (NMR) relaxometry is a valuable tool for investigating cement-based materials. It allows monitoring of pore evolution and water consumption even during the hydration process. The approach relies on the proportionality between the relaxation time and the pore size. Note, however, that this approach inherently assumes that the pores are saturated with water during the hydration process. In the present work, this assumption is eliminated, and the pore evolution is discussed on a more general basis. The new approach is implemented here to extract information on surface evolution of capillary pores in a simple cement paste and a cement paste containing calcium nitrate as accelerator. The experiments revealed an increase of the pore surface even during the dormant stage for both samples with a faster evolution in the presence of the accelerator. Moreover, water consumption arises from the beginning of the hydration process for the sample containing the accelerator while no water is consumed during dormant stage in the case of simple cement paste. It was also observed that the pore volume fractal dimension is higher in the case of cement paste containing the accelerator.

scholarly journals Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1611
Author(s):  
Gintautas Skripkiūnas ◽  
Asta Kičaitė ◽  
Harald Justnes ◽  
Ina Pundienė
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Calcium Nitrate ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Cement Pastes ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Early Strength

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

scholarly journals Effect of nano-SnO2 on early-age hydration of Portland cement paste

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985194 ◽  
Author(s):  
Jianping Zhu ◽  
Genshen Li ◽  
Ruijie Xia ◽  
Huanhuan Hou ◽  
Haibin Yin ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Strength Development ◽  
Early Age ◽  
Test Machine ◽  
Portland Cement Paste ◽  
Scanning Electron

Nanomaterial, as a new emerging material in the field of civil engineering, has been widely utilized to enhance the mechanical properties of cementitious material. Nano-SnO2 has presented high hardness characteristics, but there is little study of the application of nano-SnO2 in the cementitious materials. This study mainly investigated the hydration characteristics and strength development of Portland cement paste incorporating nano-SnO2 powders with 0%, 0.08%, and 0.20% dosage. It was found that the early-age compressive strength of cement paste could be greatly improved when nano-SnO2 was incorporated with 0.08% dosage. The hydration process and microstructure were then measured by hydraulic test machine, calorimeter, nanoindentation, X-ray diffraction, scanning electron microscope, and mercury intrusion porosimetry. It was found that the cement hydration process was promoted by the addition of nano-SnO2, and the total amount of heat released from cement hydration is also increased. In addition, the addition of nano-SnO2 can promote the generations of high density C-S-H and reduce the generations of low density C-S-H indicating the nucleation effect of nano-SnO2 in the crystal growth process. The porosity and probable pore diameter of cement paste with 0.08% nano-SnO2 were decreased, and the scanning electron microscopic results also show that the cement paste with 0.08% nano-SnO2 promotes the densification of cement microstructure, which are consistent with the strength performance.

Hydration process of rice husk ash cement paste and its corrosion resistance of embedded steel bar

2020 ◽  
Vol 27 (11) ◽  
pp. 3464-3476
Author(s):  
Hui Wang ◽  
Ai-lian Zhang ◽  
Lin-chun Zhang ◽  
Qian Wang ◽  
Yan Han ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Cement Paste ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Hydration Process ◽  
Steel Bar

NMR relaxometry a new approach to detect geochemical properties of organic matter in tight shales

Fuel ◽  
2019 ◽  
Vol 235 ◽  
pp. 167-177 ◽  
Author(s):  
Seyedalireza Khatibi ◽  
Mehdi Ostadhassan ◽  
Z. Harry Xie ◽  
Thomas Gentzis ◽  
Bailey Bubach ◽  
...  
Keyword(s):  
Organic Matter ◽  
New Approach ◽  
Nmr Relaxometry ◽  
Geochemical Properties

scholarly journals The effect of micelles with random pH-sensitive/hydrophobic structure on the workability, hydration process and microstructure of cement paste

RSC Advances ◽  
2017 ◽  
Vol 7 (28) ◽  
pp. 17085-17094 ◽  
Author(s):  
Y. Y. Zhu ◽  
J. Hu ◽  
Y. W. Ma ◽  
H. B. Xie ◽  
W. H. Guo ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Cement Paste ◽  
Ph Sensitive ◽  
Hydration Process ◽  
Nucleation Effect

In this study, micelles with pH sensitive/hydrophobic structure efficiently affected the workability, hydration and microstructure of cement paste. The mechanisms are related to the nucleation effect, molecular structure and adsorption of micelles.

scholarly journals The mechanism of water–isopropanol exchange in cement pastes evidenced by NMR relaxometry

RSC Advances ◽  
2014 ◽  
Vol 4 (40) ◽  
pp. 20709-20715 ◽  
Author(s):  
Radoslaw M. Kowalczyk ◽  
Agata M. Gajewicz ◽  
Peter J. McDonald
Keyword(s):  
Cement Paste ◽  
Cement Pastes ◽  
H Nmr ◽  
Nmr Relaxometry ◽  
P Distribution

Distribution (by 1H NMR intensity) of water and isopropanol in as prepared (left bars) and exchanged (right bars) cement paste.

scholarly journals Study on adsorption, rheology and hydration behaviours of Polycarboxylate(PCE) superplasticizer synthesized by different acid to ether ratio

2021 ◽  
Vol 2133 (1) ◽  
pp. 012007
Author(s):  
Zhijun Lin ◽  
Xiaofang Zhang ◽  
Zhanhua Chen ◽  
Yue Xiao ◽  
Yunhui Fang
Keyword(s):  
Molecular Weight ◽  
Adsorption Capacity ◽  
Cement Paste ◽  
Cement Hydration ◽  
Main Chain ◽  
Chain Structure ◽  
Hydration Process ◽  
Side Chain ◽  
Structure Parameters ◽  
Polycarboxylate Superplasticizer

Abstract Polycarboxylate superplasticizer is synthesised by different acid to ether ratio, which is changing the main chain structure parameters, obtained different microstructures. The effect of different microstructure PCE superplasticizer on the fluidity of cement paste, rheological thixotropy, adsorption capacity and hydration heat are studied. The results show that dispersing performance in cement with acid to ether ratio of 3.5 is the best, the molecular weight and side chain density have rather little effect on the cement hydration process.

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