Cure-state monitoring and water-to-cement ratio determination of fresh Portland cement-based materials using near-field microwave techniques

This paper investigates the dispersion of cement particles in water at different mix proportions using optical microscope, and the dispersion and absorption of SBR latex in the system of mono-dispersed cement particles in water using environmental scanning electron microscope (ESEM). The results show that the mono-dispersed cement can be well obtained at the water to cement ratio (mw/mc) of 10:1. The ESEM images present that SBR latex is dispersed on the surface of the cement particles as well as the solution phase. SBR latex does not prefer to be absorbed on the cement particles in spite of their opposite electric charge but chooses to be dispersed in the system proportionally. In addition, SBR particles are single-layer absorbed on the surface of cement particles in all the SBR latex to cement ratios (mp/mc). Several SBR particles absorbed on the surface of cement particle get close enough to form groups at the mp/mc of 15% and 20%. The results of this paper provide some bases for analyzing the influence of polymer on cement hydration and the microstructure formation of polymer-modified cement-based materials in a new view.

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Effective Absorption Capacity Examined by Isothermal Calorimetry: Effect of Pore Structure and Water-to-Cement Ratio

Advances in Materials Science and Engineering ◽

10.1155/2020/7692751 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Joo-Ha Lee ◽

Do Guen Yoo ◽

Bo Yeon Lee

Keyword(s):

Activated Carbon ◽

Carbon Fibre ◽

Pore Structure ◽

Isothermal Calorimetry ◽

Absorption Capacity ◽

Cement Ratio ◽

Effective Absorption ◽

Water To Cement Ratio ◽

Cement Based Materials ◽

Activated Carbon Fibre

The accurate measurement of effective absorption capacity is crucial for highly absorptive materials when they are used within cement-based materials. In this study, a method for examining effective absorption capacity using isothermal calorimetry is reviewed and investigated in detail to accommodate different circumstances. Specifically, the effect of different pore structures and water-to-cement ratios in determining effective absorption capacity is experimentally examined using activated carbon fibre and powdered activated carbon. The results suggest that the method may be suitable for porous materials with micropores but not suitable for those with mesopores. Also, the results indicate that the effective absorption capacity value can change with the water-to-cement ratio used. These findings can be used to find the effective absorption capacity of highly absorptive materials more accurately using the isothermal calorimetry method.

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The Determination Of Diffusive Tortuosity In Concrete Specimens Using X-Ray Microtomography

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0140 ◽

2015 ◽

Vol 60 (2) ◽

pp. 1115-1119 ◽

Cited By ~ 9

Author(s):

Z. Ranachowski ◽

D. Jóźwiak-Niedźwiedzka ◽

P. Ranachowski ◽

M. Dąbrowski ◽

S. Kudela ◽

...

Keyword(s):

Random Walk ◽

Three Dimensional ◽

Micro Ct ◽

Connectivity Analysis ◽

Pore Connectivity ◽

Cement Ratio ◽

X Ray ◽

Water To Cement Ratio ◽

Random Walk Simulation

Abstract The paper presents a method of pore connectivity analysis applied to specimens of cement based composites differing in water to cement ratio. The method employed X-ray microtomography (micro-CT). Microtomography supplied digitized three-dimensional radiographs of small concrete specimens. The data derived from the radiographs were applied as an input into the application based on the algorithm called ‘random walk simulation’. As the result a parameter called diffusive tortuosity was established and compared with estimated porosity of examined specimens.

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Influence of Cement Type and Water-to-Cement Ratio on the Formation of Thaumasite

Advances in Materials Science and Engineering ◽

10.1155/2017/7643960 ◽

2017 ◽

Vol 2017 ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Ailian Zhang ◽

Linchun Zhang

Keyword(s):

Portland Cement ◽

Cement Mortar ◽

Sulfate Solution ◽

Sulfate Attack ◽

Strength Development ◽

X Ray Diffraction ◽

Limestone Filler ◽

Visual Appearance ◽

Cement Ratio ◽

Water To Cement Ratio

Cement mortar prisms were prepared with three different cement types and different water-to-cement ratios plus 30% mass of limestone filler. After 28 days of curing in water at room temperature, these samples were submerged in 2% magnesium sulfate solution at 5°C and the visual appearance and strength development for every mortar were measured at intervals up to 1 year. Samples selected from the surface of prisms after 1-year immersion were examined by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The results show that mortars with sulfate resisting Portland cement (SRC) or sulphoaluminate cement (SAC) underwent weaker degradation due to the thaumasite form of sulfate attack than mortars with ordinary Portland cement (OPC). A lower water-to-cement ratio leads to better resistance to the thaumasite form of sulfate attack of the cement mortar. A great deal of thaumasite or thaumasite-containing materials formed in the OPC mortar, and a trace of thaumasite can also be detected in SRC and SAC mortars. Therefore, the thaumasite form of sulfate attack can be alleviated but cannot be avoided by the use of SAC or SRC.

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Determination of electrical properties of early-age concrete using near-field microwave techniques

2014 IEEE International Workshop on Electromagnetics (iWEM) ◽

10.1109/iwem.2014.6963657 ◽

2014 ◽

Author(s):

Kwok L. Chung ◽

Sergey Kharkovsky

Keyword(s):

Electrical Properties ◽

Near Field ◽

Early Age ◽

Microwave Techniques ◽

Early Age Concrete

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Control of Drying Shrinkage of Magnesium Silicate Hydrate Gel Cements

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.709.109 ◽

2016 ◽

Vol 709 ◽

pp. 109-113 ◽

Cited By ~ 2

Author(s):

Ting Ting Zhang ◽

Xiao Min Liang ◽

M. Lorin ◽

Zhen Lin Wu ◽

Chris Cheeseman ◽

...

Keyword(s):

Portland Cement ◽

Magnesium Oxide ◽

Silica Fume ◽

Drying Shrinkage ◽

Magnesium Silicate ◽

Hydration Products ◽

Cement Ratio ◽

Water To Cement Ratio ◽

Order Of Magnitude ◽

Forced Drying

Cracks were observed when the magnesium silicate hydrate gel cement (prepared by 40% MgO/ 60% silica fume) was dried. This drying cracking is believed to be caused when unbound water evaporates from the binder. The shrinkage upon forced drying to 200 °C of mortars made up from a reactive magnesium oxide, silica fume and sand was measured using dilatometry. The magnitude of the drying shrinkage was found to decrease when more sand or less water was added to the mortars and can be as low as 0.16% for a mortar containing 60 wt% sand and a water to cement ratio of 0.5, which is of a similar order of magnitude as observed in Portland cement based mortars and concretes. A simple geometrical interpretation based on packing of the particles in the mortar can explain the observed drying shrinkages and based on this analysis the drying shrinkage of the hydration products at zero added solid is estimated to be 7.3% after 7 days of curing.

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Does a High Amount of Unhydrated Portland Cement Ensure an Effective Autogenous Self-Healing of Mortar?

Materials ◽

10.3390/ma12203298 ◽

2019 ◽

Vol 12 (20) ◽

pp. 3298 ◽

Cited By ~ 2

Author(s):

Magdalena Rajczakowska ◽

Lennart Nilsson ◽

Karin Habermehl-Cwirzen ◽

Hans Hedlund ◽

Andrzej Cwirzen

Keyword(s):

Portland Cement ◽

High Performance ◽

Cement Content ◽

Healing Process ◽

Self Healing ◽

Aging Effects ◽

Cement Ratio ◽

Dense Microstructure ◽

Water To Cement Ratio ◽

Very High

It is commonly accepted that the autogenous self-healing of concrete is mainly controlled by the hydration of Portland cement and its extent depends on the availability of anhydrous particles. High-performance (HPCs) and ultra-high performance concretes (UHPCs) incorporating very high amounts of cement and having a low water-to-cement ratio reach the hydration degree of only 70–50%. Consequently, the presence of a large amount of unhydrated cement should result in excellent autogenous self-healing. The main aim of this study was to examine whether this commonly accepted hypothesis was correct. The study included tests performed on UHPC and mortars with a low water-to-cement ratio and high cement content. Additionally, aging effects were verified on 12-month-old UHPC samples. Analysis was conducted on the crack surfaces and inside of the cracks. The results strongly indicated that the formation of a dense microstructure and rapidly hydrating, freshly exposed anhydrous cement particles could significantly limit or even hinder the self-healing process. The availability of anhydrous cement appeared not to guarantee development of a highly effective healing process.

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