| 1. |
- Ylmén, Rikard, 1982, et al.
(författare)
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Insights into early hydration of Portland limestone cement from infrared spectroscopy and isothermal calorimetry
- 2010
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 40:10, s. 1541-1546
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Tidskriftsartikel (refereegranskat)abstract
- Isothermal calorimetry and diffuse reflectance infrared DR–FTIR spectroscopy are combined to correlate evolutions of spectroscopic signatures with rates of chemical reactions as reflected in the rate of heat emitted during the first 38 h of cement hydration. Portland limestone cement mortar is employed and the analysis is repeated for two different mixing procedures. Intensive blender mixing with quartz sand is found to cause activation of the cement resulting in a faster hydration process. At early stages of hydration, two types of C–S–H are formed. The spectral intensity of the earlier C–S–H is found to saturate, while that of the later form continues to acquire intensity throughout the 38 h of the experiment. Evidences are presented which support the interpretation that the two forms differ mainly in morphology and water content. Simultaneously with the saturation of the early C–S–H, a transient species is observed with DR–FTIR. This species correlates with the observed thermogram fine-structure.
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| 2. |
- Addassi, Mouadh, et al.
(författare)
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Inverse analyses of effective diffusion parameters relevant for a two-phase moisture model of cementitious materials
- 2018
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846 .- 1873-3948. ; 106, s. 117-129
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Tidskriftsartikel (refereegranskat)abstract
- Here we present an inverse analyses approach to determining the two-phase moisture transport properties relevant to concrete durability modeling. The purposed moisture transport model was based on a continuum approach with two truly separate equations for the liquid and gas phase being connected by the sorption kinetics. The moisture properties of ten binder-systems containing fly ash, calcined clay, burnt shale and gray micro-filler, were investigated experimentally. The experiments used were, (i) sorption test (moisture fixation), (ii) cup test in two different relative humidity intervals, (iii) drying test, and, (iv) capillary suction test. Mass change over time, as obtained from the drying test, the two different cup test intervals and the capillary suction test, was used to obtain the effective diffusion parameters using the proposed inverse analyses approach. The moisture properties obtained with the proposed inverse analyses method provide a good description of the test period for the ten different binder-systems.
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| 3. |
- Frølich, Lasse, et al.
(författare)
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Using isothermal calorimetry to predict one day mortar strengths
- 2016
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 88, s. 108-113
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated whether isothermal calorimetry measurements on cement paste are sufficiently accurate and precise to partially replace compressive strengths measurements on cement mortar as a quality control method at cement production. The study was also designed to provide information on mechanisms that will affect the relationship between heat of hydration and early strength, but not to establish a general empirical relationship. Results show a fairly strong correlation at 24 h between cement paste heat of hydration and mortar compressive strength, and the strength and calorimetry measurements had similar relative repeatability. Isothermal calorimetry may therefore be a viable alternative to early age strength measurements in cement production when allowed by relevant standards.
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| 4. |
- Huang, Liming, 1993, et al.
(författare)
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Using water vapour and N2 isotherms to unveil effects of SCMs on nanopores and evaluate hydration degree
- 2023
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 164:February 2023
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Tidskriftsartikel (refereegranskat)abstract
- Nanopores are critical for the durability of cement-based materials, but the refinement of these pores by SCMs is yet to have a clear understanding. This paper studied effects of the water–binder ratio, SCMs and the drying on the distribution of nanopores using water vapour and N2 sorption isotherms. Results show that data of water vapour sorption can be used for a practical evaluation of the hydration degree of SCMs with thermodynamic simulation. Fly ash increases the volume of large gel and capillary pores. It lowers the difference between the sorption of water vapour and N2. Slag evidently refines the nanopores by increasing the volume of ink-bottle gel pores with an interlayer-size neck. A higher w/b produces more large pores to reduce the effect of drying. Removal of water induces contraction of interlayer and reduces gel pores volume, which causes large difference between sorption of water vapour and N2.
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| 5. |
- Linderoth, Oskar, et al.
(författare)
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Long-term cement hydration studies with isothermal calorimetry
- 2021
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 141:March 2021
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate for how long the thermal power of hydration can be measured with isothermal calorimetry, which is a general measurement technique with stable properties that, in many cases, can detect low rates of processes. Measurements were conducted for 365 days on cement paste with Portland cement, fly ash blended Portland cement and different water-to-binder ratios. The results showed that all the tested systems still produced a measureable signal after one year. The samples with Portland cement were also analyzed by XRD after 365 days, and phase composition calculations were made with GEMS. Together with the calorimetric results, these results were used to determine the degree of hydration by five methods, the results of which showed good agreement.
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| 6. |
- Maier, Petra, et al.
(författare)
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Corrosion Rates by Immersion and Calorimetry on the Example of Extruded Mg10Gd(1Nd)1La
- 2024
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Ingår i: Magnesium Technology 2024. - 2367-1696 .- 2367-1181. - 9783031502392 ; , s. 35-39
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Konferensbidrag (refereegranskat)abstract
- This study is a follow-up investigation of the influence of the alloying elements Nd and La on the corrosionCorrosionby immersionImmersion of an extruded and heat-treated Mg10Gd. The previous study made clear that the age-hardened condition has the lowest corrosion rateCorrosion Rate but high pitting corrosionPitting corrosion susceptibility. The extruded Mg10Gd(1Nd)1La shows the lowest pitting factors based on severe corrosion. In this study, the corrosionCorrosion morphology and corrosion rates are discussed based on calorimetric data and 3D-analysis by µCT and compared to the results from the immersion tests. Thermal power and enthalpy readings from the isothermal calorimetryCalorimetry offer information on the reaction kinetics. The corrosion rateCorrosion Rate values are discussed based on the evaluation method—in general agreement alloying with Nd reduces the corrosion rateCorrosion Rate. The pitting factor is found to be very dependent on the reference average penetration: weight or volume loss, or evaluation by 3D volume or by 2D cross-sections.
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| 7. |
- Saeidpour, Mahsa, et al.
(författare)
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The influence of sorption hysteresis on diffusion coefficients represented with different moisture potentials
- 2016
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 90, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- This paper continues the discussion in a previous paper [Saeidpour and Wadsö doi:10.1016/j.cemconres.2016.02.003] where a clear effect of sorption hysteresis was seen in moisture diffusion coefficients for cement-based materials. Coefficients with vapor content as potential (Dv) had different values depending on whether the sample was in absorption or in desorption. In this paper we recalculate these Dv coefficients into coefficients with other potentials and draw them as a function of different potentials. The aim is to see if the effect of hysteresis disappears with an optimal choice of representation. The best choice was to draw Dv is as a function of the degree of saturation (concentration, moisture content).
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| 8. |
- Wadsö, Lars, et al.
(författare)
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An international round robin test on isothermal (conduction) calorimetry for measurement of three-day heat of hydration of cement
- 2016
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 79, s. 316-322
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Tidskriftsartikel (refereegranskat)abstract
- The results of a round robin test on isothermal (heat conduction) calorimetry are presented. A total of 18 participants using three types of instruments conducted 3-day measurements of the hydration of one rapidly hardening Portland cement and one slag-containing cement. The results confirm that isothermal calorimetry is a suitable method for the determination of heat of hydration. As a part of the study, two laboratories also conducted measurements with the standardized heat of solution method. For the Portland cement, these results were in good agreement with the isothermal measurements, but for the slag-containing cement the results differed, both between the two laboratories and between their results and the result of isothermal calorimetiy. However, this method performance study clearly shows that the heat of hydration determination of cement by heat conduction calorimetry is more precise than the traditional heat of solution method described in EN 196-8, if state-of-the-art calorimeters are used. (C) 2015 Elsevier Ltd. All rights reserved.
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| 9. |
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| 10. |
- Ahlström, Johan, et al.
(författare)
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Galvanic corrosion properties of steel in water saturated concrete
- 2015
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Ingår i: Materials and corrosion - Werkstoffe und Korrosion. - : Wiley. - 0947-5117 .- 1521-4176. ; 66:1, s. 67-75
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum-based sacrificial anodes were installed to reinforced concrete to stop ongoing corrosion in cooling water tunnels in a Swedish nuclear power plant. The steel rebars were also unintentionally connected to stainless steel water pumps. Therefore, the consumption rate of the sacrificial anodes was higher than predicted. An experimental and a field study were performed to assess if the steel rebar suffer from galvanic corrosion and if the stainless steel pumps are responsible alone for the high consumption rate. It was found from the experimental study that there is an increased risk of galvanic corrosion for steel rebar when the corrosion potential is raised to -200mV (SCE) for samples with 1% CL- by mass of cement and -500mV (SCE) for samples with 2% Cl- by mass of cement. The experimental results were compared with the corrosion potential measured in the cooling water tunnel where sacri ficial anodes were in use and not mounted at all. The cooling water tunnel without sacrificial anodes had generally more anodic corrosion potentials compared to the tunnel with anodes. The tunnel with anodes had also more anodic potentials closer to the stainless steel pumps than further away which means that the rebar is affected by the stainless steel pumps. However, the measured corrosion potentials in the tunnels were not as anodic as the potentials needed for high galvanic current measured in the experimental study.
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