Abstract null null This article reports new scientific evidence on the hydrated phases present in blended cement pastes formulated with 10%, 20% or 25% metakaolin (MK) and stored at 60 °C for 15 years. XRD-Rietveld, SEM/EDX, NMR, FT-IR and TG/DTG findings attested to substantial difference in the mineralogy and morphology of the phases present (C2ASH8, C4AH13 and hydrogarnet) between long-term and short-term curing. The predominant crystalline phases in OPC and 10% MK-blended pastes, portlandite...
Abstract null null Viscosity modifying agents (VMAs) are essential ingredients for the production of flowable cement-based materials. This paper presents an overview of commonly used VMAs and attempts to shed some light on the underlying physics at the origin of their mechanisms of action. The main molecular parameters of VMA controlling the rheological properties of the cement pore solution are highlighted. As the mechanisms of action of VMAs in cement-based materials are closely related to the...
Last. Xiangming Kong(THU: Tsinghua University)H-Index: 21
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Abstract null null The impact of polycarboxylate (PCE) superplasticizers on calcium hydroxide (CH) precipitation and morphology were studied aiming at further understanding retardation effect of PCEs on cement hydration. Three comb-like PCEs with varied architecture and two linear copolymers (PAS) charged by carboxylic and sulfonic groups were synthesized. CH precipitate was prepared by simultaneous feeding NaOH and CaCl2 solutions in bulk solution containing various polymers. Analytical techniq...
Abstract null null Understanding the formation of Alkali-silica reaction gel (ASR gel) and its behavior in cement pore network solutions is the key to mitigate one of the main causes of the strength retrogression of concrete. We herein propose a scenario to explain how ASR formation in cement pores can damage the cement paste structure that is supported by state-of-the-art atomistic simulations. We show the formation of an ASR gel at the atomic scale and how the drying or calcification affects i...
Abstract null null A scale-linking, experimental study complemented by an analytical model was carried out to investigate the influence of fiber orientation on the crack-opening behavior of strain-hardening cement-based composites (SHCC). Three SHCC compositions were investigated with polyvinyl alcohol (PVA) and ultra-high molecular weight polyethylene (UHMWPE) fibers in combination with normal- and high-strength matrices. The micromechanical experiments with fiber inclinations of 0°, 30°, 45°, ...
Abstract null null Mechanical characterization of Portland cement with hollow glass microspheres of two different crushing strengths, 500 (FM) and 10,000 psi (3 M), was carried out to determine both quasi-static and dynamic responses of the cementitious composites. In the dynamic tests, the time resolved high speed camera photos of the deforming specimens revealed the stress levels at which incipient damage occurred. The dynamic split-Hopkinson pressure bar experiments elucidated that statistica...
#1Fabien Georget(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 4
#2Calixe Bénier(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 1
Last. Karen Scrivener(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 87
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Abstract null null The validation of reactive transport models requires the understanding and quantification of the chloride sorption by C-S-H, but the experimental methods are lacking. In this paper, we use SEM-EDX hypermaps to quantify the chloride sorption in hydrated an C3S paste, after equilibrium in solutions of chloride salts (NaCl, KCl, CaCl2, MgCl2), with and without the addition of sodium hydroxide. The errors and uncertainties of the method are analysed to demonstrate the relevance of...
Abstract null null Clinkers activated by SO3 and modified by Li2O, CuO and MgO were prepared from industrial raw materials and burned at 1350 °C. The role of dopants on the burnability of the raw mix was monitored by TG-DTA and heating microscopy. The phase composition of the clinker was characterized by light microscopy, scanning electron microscopy, and X-ray powder diffraction. Predominance of M1 over M3 C3S was determined in all combinations of dopants. Hydration of cement pastes was followe...
#1Yanjie Sun(HKPU: Hong Kong Polytechnic University)H-Index: 1
#2Jian Xin Lu(HKPU: Hong Kong Polytechnic University)H-Index: 15
Last. Chi Sun Poon(HKPU: Hong Kong Polytechnic University)H-Index: 102
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Abstract null null Interest in investigating seawater concrete has been increasing in recent years, but most studies of the strength degradation of seawater mixed concrete have only been carried out on the macro-scale. In this study, alite, the main phase in ordinary Portland cement, was hydrated with various salt solutions (NaCl, MgCl2, CaCl2 and simulated seawater) with a solution-to-binder ratio of 0.5 to explore the effects of common cations in seawater on the micro-mechanical performance of...
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