The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Laila Raki - One of the best experts on this subject based on the ideXlab platform.
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dynamic mechanical thermo analysis of portland Cement Paste Hydrated for 45 years
Materials and Structures, 2016Co-Authors: Pouyan Pourbeik, Rouhollah Alizadeh, J J Beaudoin, Laila RakiAbstract:The effect of prolonged hydration of Portland Cement Paste on engineering behavior was investigated using dynamic mechanical thermo-analysis (DMTA) methods. Specimens ranged in age from 3 days to 45 years. Compacts of Hydrated Cement powders and normally Hydrated Paste specimens were tested. Age dependent nanostructural characteristics of C–S–H were shown to influence the mechanical response of Cement Paste. Evidence was provided to support the use of compacts as structural models for Hydrated Cement Paste. Details of ageing effects on the DMTA parameters (storage modulus and internal friction) as a function of temperature and porosity are reported.
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Dynamic mechanical thermoanalysis of layered calcium silicate hydrates
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Pouyan Pourbeik, James J. Beaudoin, Rouhollah Alizadeh, Laila RakiAbstract:Dynamic mechanical thermoanalysis (DMTA) was conducted on compacted specimens of calcium silicate hydrates (C-S-H), 1.4 nm tobermorite, jennite, and compacted Hydrated Portland Cement Paste powders, as well as hardened Cement Paste. The synthetic silicates are key elements for compositional models of the Hydrated calcium silicates present in Cement Paste. The study focuses on the nanostructural effects due to the removal of water from the 11 % RH condition. The DMTA results ( E ′ and tan∂ versus temperature curves) in the 25–110 °C range mimicked those of DMA ( E ′ and tan∂ versus mass loss curves) conducted at room temperature for C-S-H and Cement Paste. In addition, the DMTA curves for 1.4 nm tobermorite and jennite in the temperature range 110–300 °C were sensitive to phase changes including the transition of 1.4 nm tobermorite to 1.1 nm tobermorite and other forms, as well as the transition of jennite to metajennite. The DMTA curves of a 50/50 mixture of 1.4 nm tobermorite and jennite exhibit similarities and differences to that of Hydrated Cement Paste that are influenced by porosity and the amorphous nature of C-S-H in the Cement Paste. The study provides useful data for evaluating Taylor’s concept of a possible tobermorite-jennite model for the C-S-H present in Hydrated Cement Paste.
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c s h i a nanostructural model for the removal of water from Hydrated Cement Paste
Journal of the American Ceramic Society, 2007Co-Authors: Rouhollah Alizadeh, J J Beaudoin, Laila RakiAbstract:Helium gas is used as a nanostructural probe to investigate the structural changes in C–S–H (I) due to the removal of interlayer water. Changes in the 002 basal spacing are correlated with helium inflow characteristics. Similarities to helium inflow experiments conducted on Hydrated Portland Cement and C3S Pastes are discussed. Conclusions are drawn with respect to the viability of considering C–S–H (I) as a physical model for the drying of Portland Cement and C3S Pastes.
Zhipeng Zhang - One of the best experts on this subject based on the ideXlab platform.
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a novel carbonate binder from waste Hydrated Cement Paste for utilization of co2
Journal of CO 2 Utilization, 2019Co-Authors: Yunhua Zhang, Ruoxin Wang, Zhipeng ZhangAbstract:Abstract A novel carbonate binder for utilization of CO2 was prepared with dehydration of waste Hydrated Cement Paste. The effect of water-solid ratios (w/s) varying from 0.175 to 0.275 on carbonation properties of the carbonate binder was evaluated and its phase composition and microstructure before and after carbonation were characterized. The results showed that the compressive strength of carbonate binder exposed to a CO2-rich environment for 2 h maximized at 82.6MPa with w/s of 0.225 while the CO2 uptake was 27.2% which were on a par with that of carbonated pure dicalcium silicate (C2S) and carbonated steel slag. Analysis of phase composition and microstructure of the carbonate binder before and after carbonation revealed that the major phase beta C2S (β-C2S) in the deHydrated waste Hydrated Cement Paste transformed into granular texture carbonation products (calcite and aragonite) with a size of less than 1μm. The carbonation products closely packed to form a large number of mesoporous which result in high compressive strength. The total CO2 uptake of carbonate binder in the whole preparation process was equal to that of the waste Hydrated Cement Paste but it processed higher mechanical properties. It will provide a novel method to prepare high carbonation reactivity Cementitious materials and improve the recycling rate of waste concrete which are benefit to utilization of CO2, energy conservation and environmental protection.
Sidney Diamond - One of the best experts on this subject based on the ideXlab platform.
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on the occurrence of hollow shell hydration grains in Hydrated Cement Paste
Cement and Concrete Research, 2000Co-Authors: D W Hadley, W L Dolch, Sidney DiamondAbstract:In this paper, we provide the original illustrations of the formation and morphological characteristics of hollow-shell hydration grains taken from the 1972 thesis of the first author, along with more recent illustrations of the occurrence and importance of this feature as a normal mode of hydration of certain Cement particles.
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occurrence of large silica fume derived paticles in Hydrated Cement Paste
Cement and Concrete Research, 1992Co-Authors: David Bonen, Sidney DiamondAbstract:Abstract In an examination of a 1-year old Hydrated silica fume bearing Cement Paste a number of large (35–80 μm) rounded siliceous particles were found that had apparently been derived from the coarse fraction of the silica fume. Calcium had diffused inward from the periphery of the grains, and in most cases had reached the centet. The Ca:Si mole ratio near the outer zone was almost the same as that in the surrounding matrix CSH gel, but decreased continuously with distance toward the center. Potassium and sodium were also found within the particles, but were distributed inversely to the calcium, i.e. increasing toward the center. The reaction product generated here appears to be CSH and not potentially expansive alkali silica reaction product gel, although such gel might be produced with high alkali Cements.
A I Almana - One of the best experts on this subject based on the ideXlab platform.
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si mas nmr study of Hydrated Cement Paste and mortar made with and without silica fume
Journal of the American Ceramic Society, 1995Co-Authors: Salan U Aldulaijan, Gwilym Parryjones, A J Altayyib, M M Alzahrani, A I AlmanaAbstract:This paper presents 29 Si MAS(magic-angle spinning)-NMR measurements that trace the hydration process in both Cement Paste and mortar specimens made from ordinary Portland Cement, Type I, when the Cement content is replaced by 0, 10, 15, and 20 wt% of silica fume. The specimens were moist-cured for 3, 7, 14, 28, 90, and 180 days at a laboratory temperature of 21°C (69.8°F). Compressive strength for all tested specimens was also determined. The results show that the degree of hydration (Q 1 +Q 2 )/(Q o +Q 1 +Q 2 ) increased with increasing content of silica fume, especially at the early ages of 3 to 28 days. In the same manner, compressive strength results were markedly increased up to 14 days and were lowered at later ages, compared to the control mix (0 wt% silica fume)
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29si magic angle spinning nuclear magnetic resonance study of Hydrated Cement Paste and mortar
Journal of the American Ceramic Society, 1990Co-Authors: Salan U Aldulaijan, Gwilym Parryjones, A J Altayyib, A I AlmanaAbstract:This paper presents 29Si magic-angle-spinning nuclear magnetic resonance measurements that trace the Cement hydration process in Cement Paste and mortar specimens made from ordinary portland Cement, type I. These specimens were moist-cured for 3, 7, 14, and 28/31 d at temperatures ranging from 21° to 80°C. Compressive strength for all tested specimens was also determined. The results show that the degree of hydration (Q1+Q2) and the compressive strength increase with curing times and temperatures. However, at 80°C, the compressive strength decreases while the degree of hydration increases.
Mauricio Lopez - One of the best experts on this subject based on the ideXlab platform.
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reactivated Cementitious materials from Hydrated Cement Paste wastes
Cement & Concrete Composites, 2013Co-Authors: Ricardo Serpell, Mauricio LopezAbstract:Abstract Hydrated Cement Pastes subjected to high temperature dehydration have been shown to develop a Cementitious behavior upon rehydration that could enable recycling of Hydrated Cement wastes as alternative binders of high environmental value. In order to evaluate the potential of this recycling option it is first necessary to identify material and process factors affecting the performance of the reactivated Cementitious materials produced. This paper presents the findings of a fractional factorial experiment designed to screen factors based on their effect on the strength developed by Pastes incorporating materials reactivated from laboratory sourced Hydrated Cement Pastes. Results allowed identification of factor and factor-interaction effects involving 7 of the 9 factors under study, which would be relevant in optimizing the recycling process. Highest strengths observed in the experimental region explored were 20, 32.8 and 39 MPa at 7, 28, and 90 days, respectively, for reactivated material Pastes mixed at 0.7 W/CM ratio.
