The coupling effect of calcium concentration and pH on early hydration of cement

Chen, Heng; Pan, Feng; Ye, Shaoxiong; Sun, Wei

doi:10.1016/j.conbuildmat.2018.07.067

Cited by 45 publications

(7 citation statements)

References 40 publications

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“…The dilution effect can be due to this reduction. Indeed, an increase in the rate of mineral addition is followed by a decrease in the content of the clinker, which naturally implies fewer hydration products [34,35] These results are in good agreement with those of [36,37], they actually found that the total heat of the cement paste containing 30% Slag was 200 J/g after 140 h of hydration, compared to 260 J/g for the reference cement paste. It can be shown according to the results obtained in Figure 3 that the compressive strength of mortars increases proportionally with age and decreases with increasing slag content.…”

Section: Heat Of Hydration Of the Cements Studiedsupporting

confidence: 74%

The Study of Slag Cement’s Microstructural Properties

Boualleg¹

2021

ACSM

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The objective of this work is the quantification of hydration in cement. To monitor this quantity of hydrated cement "hydration degrees" we adopted the method of thermogravimetric analysis (TGA) which allowed us to determine the degree of hydration α(t), bound water (WB) and non-evaporable water. This study is completed by the analysis of diffractometers (DRX). Cements containing different percentages of slag. The evolution of the kinetics was studied during 3, 7 and 28 days. According to the results obtained, the hydration rate is inversely proportional to the addition content in the cement. The degree of hydration is directly related to the formation of hydrates and portlandite, more non-evaporable water retained in the hydrates corresponds to a high degree of hydration. This technique is coupled with the carbonation and strength of ordinary mortar. The experimental data obtained have been correlated and interpreted with regard to the evolution of strength and carbonation as a function of the degree of hydration, bound water and non-evaporable water of the cement hydrates. The Bhatty method is verified for the calculation of the degree of hydration and can be successfully applied for composite cements.

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Section: Heat Of Hydration Of the Cements Studiedsupporting

confidence: 74%

The Study of Slag Cement’s Microstructural Properties

Boualleg¹

2021

ACSM

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“…They determined that concrete wash water decreased the setting time of OPC. The additional amount of calcium ions from concrete wash water correlated with the faster precipitation of calcium hydroxide (CH) and C-S-H and the acceleration of the cement hydration [ 35 ].…”

Section: Resultsmentioning

confidence: 99%

The Using of Concrete Wash Water from Ready Mixed Concrete Plants in Cement Systems

et al. 2021

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Concrete plants accumulate large amounts of concrete wash water. This water, which pH is highly alkaline, has a negative impact on the environment. Its reuse in fresh concrete slightly reduces its mechanical properties. The combination of concrete wash water and zeolitic by-product led to an increase of 4.6% in the compressive strength at 7 days hydration and up to 30% at 28 days hydration. The same combination led to the denser microstructure compared to the samples made with concrete wash water. This could be explained by the pozzolanic reaction of the zeolitic by-product. The complex chemical reactions of cement, zeolitic by-product, and fines presented in the concrete wash water occurred. Therefore, it was suggested the reusing method of concrete wash water together with zeolitic by-product in the fresh concrete mixtures by substituting some amount of tap water with concrete wash water. In this way, the consumption of tap water is possible to reduce in cement systems.

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“…By referring to [17], the decrease is ascribed to the physi- and chemisorption of the acidic SO 2 by the alkaline silicates of the mortar, as in carbonation. Hydration products such as calcium hydroxides induce sample alkalinity [30], which generates a neutralization effect. This effect was also proved by Chen et al [15].…”

Section: Resultsmentioning

confidence: 99%

Sulfur Dioxide Degradation by Composite Photocatalysts Prepared by Recycled Fine Aggregates and Nanoscale Titanium Dioxide

Chen

Kou

2019

Nanomaterials

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To alleviate the heavy burden on landfilling, construction and demolition wastes (C&DWs) are recycled and reused as aggregates in cementitious materials. However, the inherent characteristics of recycled fine aggregates (RFA), such as the high crushing index and high-water absorption, magnify the reusing difficulty. Nevertheless, attributing to the high porosity and high level of calcium hydroxides existing in the old mortar, RFA is featured with a high specific surface area and a high alkalinity. These features are useful to augment the total photo-degradation of SO2 by nano-TiO2 (NT) intermixed mortar, leading RFA to be an excellent potential carrier to load nano-TiO2 and prepare the composite photocatalyst. Hence, this study proposed to load NT onto the surface of RFAs and river sands (RSs) (the control) by the soaking method, preparing composite photocatalysts denoted as NT@RFA and NT@RS, respectively. The prepared composite photocatalysts were then utilized as sands in photocatalytic mortar to evaluate for SO2 degradation. Experiments identified a 50% higher amount of NT was loaded onto the surface of FRA relative to the control. This higher loading amount plus higher alkalinity ultimately translated into a higher photocatalytic activity. In addition, the mortar containing NT@RFA exhibited 46.3% higher physiochemical absorption and 23.9% higher photocatalytic activity than that containing NT@RS. In addition, the durability, embodied by the reuse and anti-abrasive properties, of NT@RFA exceeded that of NT@RS. The overall findings reveal that the NT@RFA not only garners beneficial effect from the high porosity but also generates positive effect from the high alkalinity. Though a number of studies deal with building materials with NT, this study is the first to load NT onto RFA and prepare composite photocatalysts which were then used as fine aggregates in building materials. Consequently, this study proves the potential high-added-value reusability of RFA in green construction materials and provides a low-cost, high-efficiency approach to degrade atmospheric SO2.

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The coupling effect of calcium concentration and pH on early hydration of cement

Cited by 45 publications

References 40 publications

The Study of Slag Cement’s Microstructural Properties

The Study of Slag Cement’s Microstructural Properties

The Using of Concrete Wash Water from Ready Mixed Concrete Plants in Cement Systems

Sulfur Dioxide Degradation by Composite Photocatalysts Prepared by Recycled Fine Aggregates and Nanoscale Titanium Dioxide

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