Effect of admixture on hydration of cement, adsorptive behavior of admixture and fluidity and setting of fresh cement paste

Uchikawa, Hiroshi; Hanehara, Shunsuke; Shirasaka, Tokuhiko; Sawaki, Daisuke

doi:10.1016/0008-8846(92)90041-s

Cited by 128 publications

(47 citation statements)

References 2 publications

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“…Unfortunately, with these additives there is observed a loss of fluidity in time ('slump loss') that is an undesired effect. The 'last generation' of SPs (namely polyacrylic and polycarboxylic polymers) overcomes the previous limit with a much lower dosage and moreover increases the setting time [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Hydration water and microstructure in calcium silicate and aluminate hydrates

Fratini

Chen

Baglioni

2006

J. Phys.: Condens. Matter

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Understanding the state of the hydration water and the microstructure development in a cement paste is likely to be the key for the improvement of its ultimate strength and durability. In order to distinguish and characterize the reacted and unreacted water, the single-particle dynamics of water molecules in hydrated calcium silicates (C 3 S, C 2 S) and aluminates (C 3 A, C 4 AF) were studied by quasi-elastic neutron scattering, QENS. The time evolution of the immobile fraction represents the hydration kinetics and the mobile fraction follows a non-Debye relaxation. Less sophisticated, but more accessible and cheaper techniques, like differential scanning calorimetry, DSC, and nearinfrared spectroscopy, NIR, were validated through QENS results and they allow one to easily and quantitatively follow the cement hydration kinetics and can be widely applied on a laboratory scale to understand the effect of additives (i.e., superplasticizers, cellulosic derivatives, etc) on the thermodynamics of the hydration process. DSC provides information on the free water index and on the activation energy involved in the hydration process while the NIR band at 7000 cm −1 monitors, at a molecular level, the increase of the surface-interacting water. We report as an example the effect of two classes of additives widely used in the cement industry: superplasticizers, SPs, and cellulose derivatives. SPs interact at the solid surface, leading to a consistent increment of the activation energy for the processes of nucleation and growth of the hydrated phases. In contrast, the cellulosic additives do not affect the nucleation and growth activation energy, but cause a significant increment in the water availability: in other words the hydration process is more efficient without any modification of the solid/liquid interaction, as also evidenced by the 1 H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small 3 Author to whom any correspondence should be addressed. www.csgi.unifi.it. angle neutron scattering (USANS) and wide angle x-ray scattering (WAXD) that characterize how additives affect both the hydrated microstructure development and the original grain size. In particular, SPs alter the morphology of the hydrated phases, which no longer grow with the classic fibrillar structure on the grain surface, but nucleate in solution as globular structures. All this information converges in a quantitative, and at molecular level, description of the mechanisms involved in the setting process of one of the materials most widely used by human beings.

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Section: Introductionmentioning

confidence: 99%

Hydration water and microstructure in calcium silicate and aluminate hydrates

Fratini

Chen

Baglioni

2006

J. Phys.: Condens. Matter

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“…ITZ is a discontinuous site and a defect with many capillary pores and microcracks and has a lower strength than aggregate and other cement paste. It has been known that ITZ reduces the strength of hardened concrete [10]. As shown in Fig.4, the hardness at distances of 10-300 µm from the surface of G and PCCA was only half of that at distances of more than 300 µm at the age of 1 day in both types of concrete.…”

Section: Microhardnessmentioning

confidence: 90%

Microscopic investigation on concrete cured internally by using porous ceramic roof-tile waste aggregate

2018

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Abstract. Porous ceramic roof-tile waste aggregate (PCA), which is a recycled material, is an effective internal curing material for concrete. Part of the aggregate is replaced with saturated internal curing material to supply internal water into the cement paste continuously. Internal water is effective to promote the hydration of cement paste, especially in concrete with a low water-to-cement ratio because external curing water cannot easily reach inside the concrete. It has been reported that PCA leads to an increase in compressive strength and the reduction of autogenous shrinkage of concrete. However, the effects of PCA in previous researches are different with regards to the experimental conditions and have not been evaluated sufficiently. Therefore, the present study aims to investigate the effect of internal water supplied from PCA microscopically. In the experimental program, a compressive strength test was conducted for 6 types of concrete with a W/C of 0.35. The microhardness around the aggregate in the concrete was also measured to investigate the extent of the influence of the internal water supply. The results showed the possibility that microhardness of ITZ around PCA is improved by internal curing water supply and the compressive strength of concrete is also improved by using PCA.

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“…Admixtures can be classified by functions as air-entraining, water-reducing, plasticizers, accelerating, retarding, hydration-control, corrosion inhibitors, shrinkage reducers, alkali-silica reactivity inhibitors, and miscellaneous [10][11][12][13][14][15][16][17][18][19][20]. Admixtures modified mortars and concrete such as polymer lattices, watersoluble resins, surfactants, epoxy and polyurethane have been widely used in the world [21][22][23][24][25][26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Utilization of styrene copolymer lattices (DBSS/POE) as chemical admixture for mortar

et al. 2017

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Copolymer emulsion lattices based on styrene (St) and butyl acrylate (BuA) was synthesized with composition ratio (5/ 5) using potassium persulfate/ sodium metabisulfite (KPS/ NaMBS) as redox initiation in the presence of a coemulsifier dodecyl benzene sodium sulfonate/ polyoxyethylene glycol monomethyl ether (DBSS/ POE). The effect of concentration of copolymer lattices on the physico-mechanical properties of mortar was investigated. The results showed that, as concentration of copolymer lattices increased, W/C ratio, setting time as well as water absorption decrease, while compressive strength increases.

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Effect of admixture on hydration of cement, adsorptive behavior of admixture and fluidity and setting of fresh cement paste

Cited by 128 publications

References 2 publications

Hydration water and microstructure in calcium silicate and aluminate hydrates

Hydration water and microstructure in calcium silicate and aluminate hydrates

Microscopic investigation on concrete cured internally by using porous ceramic roof-tile waste aggregate

Utilization of styrene copolymer lattices (DBSS/POE) as chemical admixture for mortar

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