Showing papers in "Cement and Concrete Research in 2010"

TL;DR: In this paper, the use of a biological repair technique is investigated in concrete repair by means of water permeability tests, ultrasound transmission measurements and visual examination, and it was shown that pure bacteria cultures were not able to bridge the cracks.

TL;DR: In this article, the authors compare the properties of slag and metakaolin cements, including the general properties of metakaol and slag, hydration products reaction mechanisms, and the role of Ca and Al.

TL;DR: In this article, the effect of elevated temperature on geopolymer paste, mortar and concrete made using fly ash as a precursor was investigated and it was shown that aggregate sizes larger than 10 mm resulted in good strength performances in both ambient and elevated temperatures.

TL;DR: In this article, the hydration of two CSA cements has been investigated experimentally and by thermodynamic modelling between 1h and 28 days at w/c ratios of 0.72 and 0.80, respectively.

TL;DR: In this paper, the increase in strength and evolution of crystalline phases in inorganic polymer cement, made by the alkali activation of slag, Class C and Class F fly ashes, was followed using compressive strength test and synchrotron X-ray diffraction in order to increase the crystallinity of the product.

TL;DR: In this paper, a conceptual diagram of predominant interactions in flowing cementitious suspensions under simple shear, as a function of shear rate and solid fraction, is presented, with the objective to understand and classify the situations where, depending on composition and processing, one or other of the physical phenomena will control the macroscopic behavior.

TL;DR: The early hydration of alite has been a subject of controversy for many decades and several theories have been proposed, principally the formation of a protective phase inhibiting dissolution or delayed nucleation and growth, but none have successfully taken into account all the experimental data available as discussed by the authors.

TL;DR: In this paper, TGA/DTG was used to quantify the amounts of carbonates formed from calcium hydroxide (CH) and calcium silicate hydrate (C-S-H), based on the CH and carbonate contents before and after carbonation.

TL;DR: In this article, the role of chloride in Portland cement formation and its relevance to corrosion of embedded steel are discussed in terms of calculated aqueous [Cl]/[OH-] molar ratios.

TL;DR: In this paper, high-energy synchrotron X-ray diffractometry of uncarbonated paste samples was used to identify the main reaction products in alkali-activated GBFS/MK blends, and aluminosilicates with a zeolitic (gismondine) structure.

TL;DR: In this article, pore solutions from hardened inorganic polymer cement (geopolymer) paste samples are extracted, and it is shown that the pore network of these materials is rich in alkali cations and has pH ≥ 13, with a relatively low dissolved Si concentration.

TL;DR: The morphology of outer product C-S-H in 20-year-old slag-cement pastes appeared in most blends to be finer than at younger ages as discussed by the authors.

TL;DR: In this paper, the authors present a comprehensive nanoindentation investigation of cement pastes prepared at substoichiometric water-to-cement (w/c) mass ratios between 0.15 and 0.4 with and without heat treatment.

TL;DR: In this article, the effects of calcination condition on the microstructure, hydration activity, and expansion property of MgO-type expansive agent have been investigated, and their correlations are also studied.

TL;DR: In this paper, the effects of potential technological improvements in the cement industry are compared to global goals of sustainability such as those from the Intergovernmental Panel Group for Climate Change, which aims to reduce CO2 emissions in developed countries in 2050 by a factor of four from their 1990 levels.

TL;DR: In this paper, it has been shown that the contraction of a mortar caused by air entrainment offsets the thermal expansion mismatch stress sufficiently to prevent cracking, and the magnitude of the contraction in air-entrained mortar is shown to account for a reduction of salt scaling damage.

TL;DR: In this paper, the fly ash reaction in two different blended OPC-FA systems was studied using a selective dissolution technique based on EDTA/NaOH, diluted NaOH solution, the portlandite content and by backscattered electron image analysis.

TL;DR: In this article, electrical resistance tomography (ERT) was applied for 3D imaging of concrete, where alternating currents were injected into the target using an array of electrodes attached to the target surface, and the resulting voltages were measured using the same electrodes.

TL;DR: In this article, short-term effects of soluble alkali and aluminium, likely to be available in an alkali-activated system, on the structure of synthetic C-S-H gels are assessed.

TL;DR: In this paper, a broad experimental study has been performed to characterize the early hydration and setting of cement pastes prepared with Class H oil well cement at water-to-cement ratios (w/c) from 0.25 to 0.40, cured at temperatures from 10 to 60°C, and mixed with chemical additives.

TL;DR: In this article, the influence of matrix compactness on the transfer properties of concrete and the importance of pore vapour pressure on spalling risk is discussed, based on which a numerical analysis of water content on the thermomechanical behavior of concrete during heating is done.

TL;DR: In this article, the effect of rigid straight fibers on the yield stress of cementitious materials is studied and a simple model describing the contact network between rigid fibers inside the material is first derived from the physical phenomena involved in the case of spherical inclusions.

TL;DR: In this article, a survey of 11 concrete bridges located in a marine environment at 0.65-48.65 years was examined in terms of chloride transport, and the apparent diffusion coefficient (D ) and surface chloride concentration (C S ) were derived to predict the chloride transport in a long term.

TL;DR: In this paper, an innovative MIP method is developed in order to provide a more accurate estimation of pore size distribution, in which the applied pressure is increased from the minimum to the maximum by repeating pressurization-depressurization cycles instead of a continuous pressing followed by a continuous depressurization.

TL;DR: A comprehensive approach to qualitative and quantitative characterization of crystalline and amorphous constituent phases of a largely heterogeneous Class F fly ash is presented in this article, where the Rietveld quantitative phase analysis method is applied to determine the relative proportion of each of these phases.

TL;DR: In this paper, a 1H nuclear magnetic resonance (NMR) relaxation analysis of water in progressively dried white cement paste is used to estimate the width and relative specific area of intra-C-S-H sheet pores and inter-C−S−H particle gel pores.

TL;DR: In this article, the authors investigated how clay admixtures affect the microstructure of cement pastes from a rheological stand point, and measured how the solids volume fraction of suspensions with different admixtures evolves with stress.

TL;DR: In this paper, the authors developed a numerical model that simulates the hydration of concrete containing fly ash or slag and determined the heat evolution rates of slag-blended concrete with different water-to-cement ratios and mineral admixture substitution ratios.

TL;DR: The pore structure of mortar was examined using thermoporometry (TPM), nitrogen adsorption/desorption (NAD), and mercury intrusion porosimetry (MIP).