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

In this study, the setting property and mechanical strength of cement pastes containing accelerators (CPCA) with or without superabsorbent polymers (SAPs) were first studied. The early microstructure evolution and water distribution at 7 and 28 days were probed by 1D (T2) and 2D (T1-T2 maps) H1 nuclear magnetic resonance (NMR) relaxometry, and the microstructure was systematically investigated by using mercury intrusion porosimetry (MIP), back-scattered electron (BSE) image and energy-dispersive X-ray spectroscopy (EDX) analysis. Results showed that the SAPs in the cement paste containing accelerators had various influences on setting time and compressive strength depending on the type of accelerators. The presence of SAPs in the cement paste containing alkaline free accelerators could alleviate the decrease of internal relative humidity, promote hydration and help to modify the pore structure. Moreover, it was observed that the SAP cavities could be nicely filled with calcium hydroxide (CH) in the cement paste with alkaline free accelerators.

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

Materials ◽

10.3390/ma14071611 ◽

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.

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Quantitative Characterization of Hydration of Cement Pastes by Rietveld Phase Analysis and Thermoanalysis

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.539.19 ◽

2013 ◽

Vol 539 ◽

pp. 19-24 ◽

Cited By ~ 1

Author(s):

Yong Qi Wei ◽

Wu Yao

Keyword(s):

Phase Analysis ◽

Cement Paste ◽

Rietveld Method ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Quantitative Characterization ◽

Cement Pastes ◽

Hydration Mechanism ◽

Spot Check

The quantitative characterization of hydration of cement pastes has always been one of focuses of researchers’ attention. Rietveld phase analysis (RPA), a combination of quantitative X-ray diffraction (QXRD) and the Rietveld method, supplies a tool of an enormous potential for that. Although a few of related researches were conducted by RPA, the reported attention was not paid to the neat cement paste with a low w/c ratio. Therefore, this work aimed at the quantitative study on hydration of such a cement paste chiefly by this method, meanwhile, cooperated with the hyphenated technique of thermogravimetry with differential scanning calorimetry (TG-DSC), as a spot check. Results indicated that RPA was a reliable method in quantitatively characterizing hydration of cement pastes, and gave a clear decription of evolution of all main crystal phases in cement pastes; and that the evolution of monosulphate(Afm_12) was also able to be tracked quantitatively. This will help to understand better the hydration mechanism of cement pastes, as well as to investigate quantitatively effects of mineral and chemical admixtures on hydration of composite cementitious systems.

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Evaluation of microstructural changes in fresh cement paste using AC impedance spectroscopy vs. oscillation rheology and 1H NMR relaxometry

Cement and Concrete Research ◽

10.1016/j.cemconres.2021.106556 ◽

2021 ◽

Vol 149 ◽

pp. 106556

Author(s):

Tingjie Huang ◽

Qiang Yuan ◽

Shenghao Zuo ◽

Baiyun Li ◽

Qihong Wu ◽

...

Keyword(s):

Impedance Spectroscopy ◽

1H Nmr ◽

Cement Paste ◽

Ac Impedance ◽

Ac Impedance Spectroscopy ◽

Microstructural Changes ◽

Nmr Relaxometry ◽

1H Nmr Relaxometry ◽

Oscillation Rheology

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The Influence of Various Gypsum Dosage, Specific Area of Cement and Water Reducers on Bleeding of Fresh Cement Paste Using Low-Field NMR

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1036.255 ◽

2021 ◽

Vol 1036 ◽

pp. 255-262

Author(s):

Yan Liang Ji ◽

Zhen Ping Sun ◽

Min Pang

Keyword(s):

Cement Paste ◽

Specific Area ◽

High Water ◽

Low Permeability ◽

Cement Pastes ◽

Bleeding Rate ◽

Low Field ◽

Low Field Nmr ◽

Type Water ◽

Hot Zone

Based on the low-field NMR, this study inveitigated bleeding property of the fresh cement pastes mixed with various gypsum dosage, specific area of cement and water reducers. Results showed that the gypsum dosage between 3 % and 5 % will cause an decrease bleeding and a lower bleeding velocity, while a 1 % gypsum dosage will increase the bleeding as a function of time. The increase of the cement surface will lead to a less bleeding rate. This can be explained that the finer particle will contribute to the packing which will form a low permeability of the cement paste, as a result less bleeding water is observed. The PCEs-made sample has smaller hot zone area which indocated the PCEs has good bleeding stability when varing water cement ratio. Furthermore, bying comparing with the NPE, it was found the ACS type water reducer has higher bleeding sensitivity when high water cement ratios were used.

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Interaction Between Naphthalene Sulfonate and Silica Fume in Portland Cement Pastes

MRS Proceedings ◽

10.1557/proc-114-117 ◽

1987 ◽

Vol 114 ◽

Cited By ~ 1

Author(s):

Sidney Diamond ◽

Leslie J. Struble

Keyword(s):

Portland Cement ◽

Silica Fume ◽

Cement Paste ◽

Uv Spectrophotometry ◽

Residual Concentration ◽

Cement Pastes ◽

High Ph ◽

Substantial Concentration ◽

Low Dosage

ABSTRACTPortland cement pastes were mixed with predissolved naphthalene sulfonate superplasticizer at normal water:cement ratios. Solutions were separated from the fresh pastes at intervals and the residual concentration of the superplasticizer determined by UV spectrophotometry. At low dosage levels essentially all of the superplasticizer was found to be removed from solution within a few minutes; at high dosage levels a substantial concentration was maintained in solution at least to approximately the time of set. In pastes in which silica fume replaced 10% by weight of the cement, it was found that the incorporation of silica fume significantly increased the uptake of superplasticizer. In separate trials it was found that the silica fume by itself adsorbed little superplasticizer, even from high pH solution simulating that of cement paste.

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Study of the pozzolanic activity and hydration products of cement pastes with addition of natural zeolites

Clay Minerals ◽

10.1180/claymin.2011.046.2.241 ◽

2011 ◽

Vol 46 (2) ◽

pp. 241-250 ◽

Cited By ~ 8

Author(s):

V. Lilkov ◽

O. Petrov ◽

V. Petkova ◽

N. Petrova ◽

Y. Tzvetanova

Keyword(s):

Surface Area ◽

Cement Paste ◽

Chemical Reactions ◽

Natural Zeolite ◽

Early Stage ◽

Pozzolanic Activity ◽

Large Surface Area ◽

Natural Zeolites ◽

Hydration Products ◽

Cement Pastes

AbstractThis paper presents results from comparative thermogravimetric, calorimetric and pozzolanic activity analyses of five natural zeolite samples from Bulgaria, Slovakia, Philippines, USA and North Korea. The zeolites actively participate in the hydration processes of cement. Their activity in the early stage of hydration is based mainly on the large surface area of the particles while, in the later stages of activation, chemical reactions occur between the products of the hydration of cement and the soluble SiO2 that is present in the bulk of the zeolites. It has been shown that in all cement pastes which contain zeolite additives, the quantity of portlandite is lower than that in pure cement paste or is even totally absent. The amounts of hydration products are greater when 30% zeolite is used than when 10% zeolite is added (excluding the sample with chabazite). The lowest pozzolanic activity is shown by chabazite, which possessed the lowest SiO2/Al2O2 ratio.

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Test Methods for Rheological Properties of Self-Compacting Concrete Pastes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.338.396 ◽

2011 ◽

Vol 338 ◽

pp. 396-400

Author(s):

Bao Guo Ma ◽

Hui Xian Wang ◽

Jian Huang ◽

Liu Qing Song

Keyword(s):

Rheological Properties ◽

Cement Paste ◽

Test Methods ◽

General Study ◽

Self Compacting Concrete ◽

Cement Pastes ◽

Different Types ◽

Over Time

This paper provides a general study on cement paste flow which derived from self- compacting concretes. Rheometer, Marsh cone and mini-slump cone were used to evaluate fluidity of cement pastes containing superplasticizers of different types and dosages and loss of fluidity over time. There is a superplasticizer saturation dosage beyond which no significant fluidity increase can be found. This paper evaluated the effect of these three methods using rheometer as control and the optimum superplasticizer type for the preparation of self-compacting concrete was suggested.

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Mathematical modeling of cement paste microstructure by mosaic pattern. Part II. Application

Journal of Materials Research ◽

10.1557/jmr.1997.0240 ◽

1997 ◽

Vol 12 (7) ◽

pp. 1741-1746 ◽

Cited By ~ 1

Author(s):

Paul D. Tennis ◽

Yunping Xi ◽

Hamlin M. Jennings

Keyword(s):

Mathematical Modeling ◽

Spatial Distribution ◽

Portland Cement ◽

Cement Paste ◽

Pattern Analysis ◽

Mosaic Pattern ◽

Cement Pastes ◽

Multiphase Materials ◽

Spatial Features ◽

Complex Shapes

A model based on mosaic pattern analysis is shown to have the potential to describe the complex shapes and spatial distribution of phases in the microstructures of multiphase materials. Several characteristics of both micrographs of portland cement pastes and images generated using the few parameters of the model are determined and, for the most part, agreement is good. The advantage is that spatial features of the microstructures can be captured by a few parameters.

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