Determination of water–cement ratio of hardened concrete by scanning electron microscopy

Sahu, Sadananda; Badger, S.; Thaulow, N.; Lee, R.J.

doi:10.1016/j.cemconcomp.2004.02.032

Cited by 68 publications

(27 citation statements)

References 5 publications

(4 reference statements)

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“…In general, higher w/c ratio results in an increase of capillary porosity (Sahu et al 2004;Powers et al 1958), subsequently reduced strength. Figures 11 and 13 show the MIP results for 28 days-cured mortar at the hydration age of 112 days for the specimens discussed in this section i.e.…”

Section: 3mentioning

confidence: 99%

The Effect of Water-to-Cement Ratio and Curing on Material Properties of Mortar Specimens in Stray Current Conditions

Susanto

Koleva

Breugel

2017

ACT

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This work reports on the synergetic effect of water-to-cement ratio, curing conditions, varying external environment and stray current on the microstructural (porosity and pore size), electrical (resistivity) and mechanical (compressive strength) properties of 28 days-cured cement-based materials. The influence of curing on porosity and pore size, in stray current conditions, was assessed by correlating the performance of 28 days cured mortar with that of fresh (24h-cured only) mortar specimens in identical environmental medium. Three different levels of electrical current density (i.e. 10mA/m 2 , 100 mA/m 2 and 1 A/m 2 ) were applied to simulate stray current flow through hardened mortar specimens with water-to-cement ratio of 0.5 and 0.35. Different environmental conditions were employed i.e. sealed conditions, partly immersed, and fully submerged in water and calcium hydroxide medium. Microstructural, mechanical and electrical properties were monitored in the course of 140 days. The outcomes suggest a potentially positive effect of the stray current, where water and/or humidity exchange with the external environment is restricted. The potential for this positive effect was experimentally supported through the recorded matrix densification and increased compressive strength of mortar specimens, subjected to stray current and treated in calcium hydroxide and/or sealed conditions, compared to equally handled and treated control cases. In contrast, for water submerged mortar specimens, subjected to stray current, coarsening of the bulk matrix and reduced compressive strength were observed. The outcomes were irrespective of w/c ratio and curing conditions. The effect of stray current was found to be predominantly determined by the current density level and increased at values > 100mA/m 2 . This would result in compromised mechanical properties and potentially reduced performance of cementbased materials within service life. Therefore, concrete curing and conditioning on site need to include considerations for the potential effect of stray currents.

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Section: 3mentioning

confidence: 99%

The Effect of Water-to-Cement Ratio and Curing on Material Properties of Mortar Specimens in Stray Current Conditions

Susanto

Koleva

Breugel

2017

ACT

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“…The evaporation of the excess of kneading water from residual spaces previously occupied leads the pores into the structure [1]. Increased kneading water in the original paste must allow to an increased porosity.…”

Section: Open Porositymentioning

confidence: 99%

“…Actually, the original water content in the mixture regulates the rate of strength development and the ultimate strength of the paste [1].…”

Section: Introductionmentioning

confidence: 99%

Lime-pastes with different kneading water: Pore structure and capillary porosity

Arandigoyen

Bernal

Bello‐López

et al. 2005

Applied Surface Science

119

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ABSTRACT:Lime mortars to be used in restoration works of Cultural Heritage are being more and more studied. The knowledge on the lime pastes allows to understand the behaviour of the binder fraction. The aim of this work is to study the influence of the kneading water on two critical aspects of the lime-pastes: pore structure and capillary porosity, because both of them are related to the service life of the material, particularly with the moisture transport. Mercury intrusion porosimetry has been performed to establish the pore size distribution: one pore range has been checked in the different pastes tested, setting linear relationships between the pore diameter and the water/lime ratio.Fractal geometry has been used from the MIP results in order to evaluate the pore surface complexity, as a function of the kneading water. From the results, it can be concluded that kneading water is only responsible for a swelling of the structure, but it does not change the pore surface (keeping constant the surface fractal dimension). DIA analysis has been carried out, confirming the previous results. Finally, the correlation obtained between the capillary coefficient and the water/lime ratio confirms the postulated pore structure for the different amount of kneading water in lime-pastes.

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“…However, a promising method developed to identify the concrete mix design encompassing binder type, w/c, cement content and aggregate content does not exist. A number of studies have been devoted to determine either cement content [1][2][3][4][5] or w/c [4][5][6][7][8] of the concrete. Even though standards such as BS 1881: Part 124 [9] describe the methods for determining the cement content and other concrete compositions in the hardened concrete, each procedure requires a substantial degree of chemical skill and relatively complicated chemical instrumentation.…”

Section: Introductionmentioning

confidence: 99%

Degree of Hydration and Mass Balance Equations for Determination of Mix Proportion of Hardened OPC Concrete

Chuosavasdi

Stitmannaithum

Sumranwanich

et al. 2016

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Abstract.A method for estimating mix proportion of hardened OPC concrete is proposed in this study. A set of mass balance equations was formed to calculate content of concrete compositions including cement, water, sand, and coarse aggregate. The degree of hydration of cement was taken into account in the analysis in order to cover the effect of age of concrete. In order to verify the accuracy of the proposed method, the determination of mix proportion of concrete was conducted on concrete specimens prepared in the laboratory with known mix proportions. Moreover, the mix proportion of concrete at different ages were calculated both with and without consideration of time-dependent degree of hydration in the analysis to clarify the enhanced capability of the proposed method when the effect of age of concrete is considered. It was found from the analytical results that the proposed method could be used to estimate mix proportion of concrete, with a satisfactory precision, at any age. The calculation of mix proportion of hardened concrete with consideration of time-dependent degree of hydration provided less error than that without consideration of the degree of hydration. The percentage of error of the mix proportion prediction of the concrete samples was less than 5%.

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Determination of water–cement ratio of hardened concrete by scanning electron microscopy

Cited by 68 publications

References 5 publications

The Effect of Water-to-Cement Ratio and Curing on Material Properties of Mortar Specimens in Stray Current Conditions

The Effect of Water-to-Cement Ratio and Curing on Material Properties of Mortar Specimens in Stray Current Conditions

Lime-pastes with different kneading water: Pore structure and capillary porosity

Degree of Hydration and Mass Balance Equations for Determination of Mix Proportion of Hardened OPC Concrete

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