Use of Microwave-Accelerated Curing Under Low-Pressure in the Production of Ultra-Durability Portland Type I-Portland Cement Pastes

2021 ◽  
pp. 79-91
Author(s):  
Natt Makul
Keyword(s):  
Portland Cement ◽  
Low Pressure ◽  
Type I ◽  
Cement Pastes ◽  
Accelerated Curing

Estimation and Measurement of Porosity Change in Cement Paste

2010 ◽  
Author(s):  
Eunyong Lee ◽  
Haeryong Jung ◽  
Ki-jung Kwon ◽  
Do-Gyeum Kim
Keyword(s):  
Ionic Strength ◽  
Portland Cement ◽  
Cement Paste ◽  
Thermodynamic Model ◽  
Ordinary Portland Cement ◽  
Type I ◽  
Hydration Products ◽  
Cement Pastes ◽  
Porosity Change ◽  
Dissolution Reaction

Laboratory-scale experiments were performed to understand the porosity change of cement pastes. The cement pastes were prepared using commercially available Type-I ordinary Portland cement (OPC). As the cement pastes were exposed in water, the porosity of the cement pastes sharply increased; however, the slow decrease of porosity was observed as the dissolution period was extended more than 50 days. As expected, the dissolution reaction was significantly influenced by w/c raito and the ionic strength of solution. A thermodynamic model was applied to simulate the porosity change of the cement pastes. It was highly influenced by the depth of the cement pastes. There was porosity increase on the surface of the cement pastes due to dissolution of hydration products, such as portlandite, ettringite, and CSH. However, the decrease of porosity was estimated inside the cement pastes due to the precipitation of cement minerals.

Influence of Grain Size on the Setting of Portland Cement: A Stray-Field Magnetic Resonance Imaging Study

2006 ◽  
Vol 514-516 ◽  
pp. 1633-1637 ◽  
Author(s):  
Teresa G. Nunes
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Portland Cement ◽  
Concrete Strength ◽  
Stray Field ◽  
Type I ◽  
Filling Material ◽  
Resonance Imaging ◽  
Early Hydration ◽  
Cement Pastes

A number of failures of large concrete structures during construction have been reported in the last decades [1]. The overestimation of concrete strength at early ages was one of the reasons for the failures. Consequently, reliable information about early age properties of the material is essential to guarantee life-time performance of structures. Portland cement is a complex heterogeneous particulate material and a full knowledge of kinetics of the hydration reactions, for example, is still missing. Gel constitutes the major phase in the hardening cement paste and the corresponding structure and dynamics represent an important contribution to determine the concrete performance. X-ray diffraction, which is widely used for the study of crystalline cement components, does not give information about the gel, amorphous, phase. Conversely, 1H stray-field magnetic resonance imaging (STRAFI-MRI) technique has proved to be a powerful tool to follow the early hydration and hardening periods of Portland cement (type I) [2-4]. The setting of cement pastes depends on parameters like the initial water/cement ratio, R, or particle size of the powder (G) and the compressive strength can be used to characterize the behaviour of hardening concrete. Water availability at the particle surfaces, which is controlled by R and G, limits cement hydration. At low R, G effects are less important. In general, it is accepted that for R<0.42, unreacted solid remain, as all the free volume is filled with hydration products [5]. For example, hydration of Portland cement pastes as a function of R (0.24-0.48) was studied using by STRAFI-MRI and hydrogen maps, from different types of water (capillary, gel or chemically bound water), enabled a spatially-resolved kinetics to be obtained [4]. Using STRAFI-MRI was now evaluated the influence of G (<70 μm to < 90 μm) on the early stages of hydration and hardening of Portland cement. Portland cement uses extend well beyond construction. For example, a mineral trioxide aggregate is now being applied as a root-end filling material, which was shown to have a similar chemical constitution to that of Portland cement except for the addition of bismuth compounds, seemingly to make the materials radiopaque for dental use [6].

scholarly journals Comparison of The Compressive Strength and The Microstructure of Metakaolin Metastar and Metakaolin Bangka as Additive in Ordinary Portland Cement

2018 ◽  
Vol 67 ◽  
pp. 03023 ◽  
Author(s):  
Sotya Astutiningsih ◽  
Widyaningsih Sura ◽  
Ahmad Zakiyuddin
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Room Temperature ◽  
Strength Test ◽  
Type I ◽  
Cement Type ◽  
Cement Pastes ◽  
Supplementary Cementing Materials ◽  
Local Resources ◽  
Compressive Strength Test

Various This paper presents the results of the investigation on the use of Metakaolin (Al2Si2O2) as a supplementary cementing materials to improve the strength of cement. The most effective way to increase the strength of cement is the substitution of a proportion of cement with supplementary cementing materials. One of them was Metakaolin. Metakaolin was produced by thermal treatment calcination from Kaolin at 600-800 Celcius and has highest alumina and silicate purity. By added Metakaolin to Portland Cement type I (OPC), the amount of Calcium Silicate Hydrate (CSH) will increase through binding with Calcium Hydroxide (CaOH). There were two kinds of Metakaolin used in this investigation, commercial metakaolin named Metakaolin Metastar compared with Metakaolin Bangka which derived from Indonesia local resources, Bangka Island. Four Metakaolin replacement levels were employed in this investigation: 5%, 0%, 15%, and 20% with water per cement ratio 0.35, 0.40, and 0.50 both of Metakaolin Metastar and Metakaolin Bangka. The cement pastes cured at room temperature for 7, 14, and 28 days. The mechanical strength examined by compressive strength test, the microstructure were examined by SEM-EDS. The results of the study revealed both Metakaolin Metastar and Metakaolin Bangka enhanced the compressive strength of OPC. The most appropriate strength was obtained for a substitution of 20% metakaolin metastar which had 46,15% higher than OPC and 5% metakaolin Bangka which had 39,06% higher than OPC. The hydration rate was examined by Thermal Analysis Monitor. The results indicated that metakaolin metastar released higher heat than metakaolin Bangka. It can be concluded that Metakaolin metastar was more effective than metakaolin Bangka as additive in OPC.

Hardened portland cement pastes of low porosity

1973 ◽  
Vol 3 (3) ◽  
pp. 279-293 ◽  
Author(s):  
Stephen Brunauer ◽  
Jan Skalny ◽  
Ivan Odler ◽  
Marvin Yudenfreund
Keyword(s):  
Portland Cement ◽  
Cement Pastes ◽  
Low Porosity

Effect of microcrystalline cellulose on geopolymer and Portland cement pastes mechanical performance

2021 ◽  
Vol 288 ◽  
pp. 123053
Author(s):  
Saulo Rocha Ferreira ◽  
Neven Ukrainczyk ◽  
Keoma Defáveri do Carmo e Silva ◽  
Luiz Eduardo Silva ◽  
Eduardo Koenders
Keyword(s):  
Portland Cement ◽  
Microcrystalline Cellulose ◽  
Mechanical Performance ◽  
Cement Pastes

Electrochemical behavior of Portland cement pastes containing phosphonates

1995 ◽  
Vol 2 (5) ◽  
pp. 182-188 ◽  
Author(s):  
P. Gu ◽  
V.S. Ramachandran ◽  
J.J. Beaudoin ◽  
E. Quinn
Keyword(s):  
Portland Cement ◽  
Electrochemical Behavior ◽  
Cement Pastes
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