Showing papers in "Cement and Concrete Research in 2013"

TL;DR: In this paper, two distinct gels (C-A-S-H and N-A−S−H) are formed in activated fly ash/slag blends, and under accelerated carbonation, the N−A −S −H gel behaves comparably to fly ash-based systems, while the C-A -S -H gel is decalcified similarly to alkali activated slag.

TL;DR: In this article, the microstructural development and hardening rate of fly ash-slag geopolymers were investigated using SEM-EDS, and the reaction rate was monitored using semi-adiabatic calorimetry.

TL;DR: In this paper, the modifications to C-S-H induced by isothermal curing between 5 and 60 degrees C were studied and it was shown that the microstructure of the cement paste is much coarser and porous, which explains the lower final strength obtained by curing at elevated temperatures.

TL;DR: The use of CaO demonstrates a superior potential for the activation of ground granulated blast furnace slag (GGBFS), and it produces a higher mechanical strength than calcium hydroxide [Ca(OH)2] as discussed by the authors.

TL;DR: In this article, the alite reaction is accelerated in the presence of gypsum and three exothermic peaks attributable to the aluminate reaction were observed in model cements instead of one in C(3)A-gypsum systems.

TL;DR: In this article, the main cementitious gels forming during the alkaline activation of hybrid cements (70% FA/30% OPC) were characterised by different techniques.

TL;DR: In this paper, the constitutive relationship of the Interfacial Transition Zones (ITZs) in Recycled Aggregate Concrete (RAC) is put forward based on nanoindentation tests and analysis.

TL;DR: In this paper, the creep properties of calcium silicate hydrates (C-S-H) are assessed by means of nanoindentation creep experiments on a wide range of substoichiometric cement pastes.

TL;DR: In this paper, a specially designed reactor connected to an ICP spectrometer enabled the careful determination of the dissolution rates of C 3 S, C 2 S and CaO, respectively, over a broad range of concentration of calcium and silicates under conditions devoid of C-S-H.

TL;DR: In this article, a specially constructed stress cell was used to measure the stress generated in thin-walled Portland cement mortar cylinders caused by external sulfate attack, and the effects of sulfate concentration of the storage solution and C3A content of the cement were studied.

TL;DR: In this paper, a refinement of the crystallization pressure hypothesis was proposed to explain sulfate related expansion, and it was shown that expansion is related to the transformation of monosulfate crystals embedded in the C-S-H to ettringite.

TL;DR: In this paper, the physicochemical process and the potential of self-healing due to further hydration are characterized and quantified, and the formation of healing products as a function of time was quantified as well.

TL;DR: In this paper, the impact of four different hydrated magnesium carbonates (HMCs) as cement replacements of either 20 or 50% accelerated carbonation (20 °C, 70-90% RH, 20% CO2) is compared with natural curing (20°C, 60-70% RH), ambient CO2).

TL;DR: In this article, the authors present several applications based on the precise processing of ultrasonic coda, in the case of thermal and/or stress and or damage changes, in concrete.

TL;DR: In this paper, the influence of limestone particle size and the type and extent of (partial) cement replacement on the yield stress and plastic viscosity of ternary pastes are studied.

TL;DR: In this paper, a photocatalytic additive (titanium dioxide) was added to mortars prepared with aerial lime, cement and gypsum binders, and the main goal was to study the way that microstructural changes affect the photocatalyst efficiency.

TL;DR: In this article, the effect of temperature on the hydration of Portland cement pastes blended with 50% of siliceous fly ash was investigated within a temperature range of 7 to 80°C.

TL;DR: In this article, the effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis.

TL;DR: In this paper, the influence of lateral inertia confinement, end friction confinement and aggregates in high-speed impact tests on dynamic compressive properties of concrete is investigated, and the effect of aggregate size and volume on the dynamic increase factor (DIF) is discussed.

TL;DR: In this paper, fracture experiments on cementitious specimens are conducted, where the fracture mode is controlled by modifying the experiment geometry and the process is monitored by acoustic emission, and the distinct signature of the cracking modes is reflected on acoustic waveform parameters like the amplitude, RA-value and frequency.

TL;DR: In this article, a method that allows to follow the formation of the Calcium-Silicate-Hydrates directly and quantitatively over time is presented, which can be used for direct quantification of C-S-H in cementitious pastes.

TL;DR: Suspensions of synthetic ye'elimite (C 4 A 3 S ¯ ) in a saturated gypsum (C S ¯ H 2 ) and calcium hydroxide (CH) solution were examined in-situ in a wet cell by soft X-ray transmission microscopy and exsitu by scanning electron microscopy.

TL;DR: In this article, the authors measured the thickness of the lubrication layer between the pipe and the bulk material and proposed a simple analytical relation allowing for a rough estimation of the pumping pressure.

TL;DR: In this paper, the mechanical properties, flowability, thermal behavior and durability of mortars containing 1, 2, 3% halloysite nanoclay were studied, and the results showed that with 3% and 2% nanotubes, the compressive strength and gas permeability of these mortars were improved up to 24% and 56%, respectively.

TL;DR: A detailed review of the current state of the art in the field can be found in this paper, where the authors describe the basic experiments for a cement audience new to the field and review three decades of work.

TL;DR: The main objective of as discussed by the authors is to study the hydration and properties of calcium sulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages.

TL;DR: In this paper, the influence of the fiber distribution and orientation on the post-cracking performance of steel fiber reinforced self-compacting concrete (SFRSCC) panels was studied.

TL;DR: In this paper, a series of increasing temperatures was used to explore the temperature-dependent evolution of internal pore structure and fracture networks in a cement-based material by fire, based on visual observations of the 3D internal structures revealed by X-ray CT.

TL;DR: In this paper, the authors investigated the carbonation mechanism of a heap of recycled concrete aggregates (RCA) using a dual-scale approach, associating CO 2 diffusion through a granular bed and carbonation of the cementitious matrix.

TL;DR: In this article, the authors investigated the properties of concrete concretes with reduced water and cement contents, especially their workability, strength development, design-relevant mechanical properties as well as durability aspects such as carbonation.