Interaction Between Naphthalene Sulfonate and Silica Fume in Portland Cement Pastes

1987 ◽  
Vol 114 ◽  
Author(s):  
Sidney Diamond ◽  
Leslie J. Struble
Keyword(s):  
Portland Cement ◽  
Silica Fume ◽  
Cement Paste ◽  
Uv Spectrophotometry ◽  
Residual Concentration ◽  
Cement Pastes ◽  
High Ph ◽  
Substantial Concentration ◽  
Low Dosage

ABSTRACTPortland cement pastes were mixed with predissolved naphthalene sulfonate superplasticizer at normal water:cement ratios. Solutions were separated from the fresh pastes at intervals and the residual concentration of the superplasticizer determined by UV spectrophotometry. At low dosage levels essentially all of the superplasticizer was found to be removed from solution within a few minutes; at high dosage levels a substantial concentration was maintained in solution at least to approximately the time of set. In pastes in which silica fume replaced 10% by weight of the cement, it was found that the incorporation of silica fume significantly increased the uptake of superplasticizer. In separate trials it was found that the silica fume by itself adsorbed little superplasticizer, even from high pH solution simulating that of cement paste.

Mathematical modeling of cement paste microstructure by mosaic pattern. Part II. Application

1997 ◽  
Vol 12 (7) ◽  
pp. 1741-1746 ◽  
Author(s):  
Paul D. Tennis ◽  
Yunping Xi ◽  
Hamlin M. Jennings
Keyword(s):  
Mathematical Modeling ◽  
Spatial Distribution ◽  
Portland Cement ◽  
Cement Paste ◽  
Pattern Analysis ◽  
Mosaic Pattern ◽  
Cement Pastes ◽  
Multiphase Materials ◽  
Spatial Features ◽  
Complex Shapes

A model based on mosaic pattern analysis is shown to have the potential to describe the complex shapes and spatial distribution of phases in the microstructures of multiphase materials. Several characteristics of both micrographs of portland cement pastes and images generated using the few parameters of the model are determined and, for the most part, agreement is good. The advantage is that spatial features of the microstructures can be captured by a few parameters.

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.

Effect of Heat Treatment on Properties of Portland Cement Pastes: Determination through Ultra-Microhardness Test

2015 ◽  
Vol 820 ◽  
pp. 492-496
Author(s):  
D.C.S. Garcia ◽  
Roberto Braga Figueiredo ◽  
Maria Teresa Paulino Aguilar
Keyword(s):  
Heat Treatment ◽  
Portland Cement ◽  
Optical Microscopy ◽  
Silica Fume ◽  
Ordinary Portland Cement ◽  
Cement Pastes ◽  
Microhardness Test ◽  
Material Hardness ◽  
Binder Ratio ◽  
Water Binder Ratio

The aim of this paper was to investigate the influence of heat treatment on hardness evolution of cement pastes containing silica fume. The specimens were prepared with Ordinary Portland Cement, water/binder ratio of 0,40 and 25% wt. silica fume. The specimens were cast at room temperatures and after 24 hours, they were placed in a furnace for 24 hours, with heat regimes of 100°C, 200°C and 300°C and then submitted to the ultra-microhardness test. The microstructure was analyzed using optical microscopy. The results showed that the silica fume prevents the production of calcium hydroxide and the heat treatment increases the material hardness.

Shrinkage of Blended Cement Pastes with Mineral Additions

2013 ◽  
Vol 539 ◽  
pp. 55-59
Author(s):  
Yi Chen ◽  
Wu Yao ◽  
Dan Jin
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Cement Paste ◽  
Mercury Intrusion Porosimetry ◽  
Construction Materials ◽  
Blended Cement ◽  
Cement Pastes ◽  
Mercury Intrusion ◽  
Mineral Additions ◽  
By Products

Mineral additions such as fly ash and silica fume are industrial by products, and play an important role in properties improvement for construction materials. In this work, the shrinkage of cement paste blended with fly ash and silica fume by different substitute ratio was studied. Pore structures of specimens at different ages were determined by mercury intrusion porosimetry (MIP) and shrinkage deformation was measured by standard shrinkage tests. The effects of mineral addtions on shrinkage were discussed. The results show that the fly ash was significantly effective on shrinkage at early ages. Based on the research, several suitable advices were offered to optimize the performances of materials and reduce the shrinkage.

A Method for Estimating the Dynamic Moduli of Cement Paste-Aggregate Interfacial Zones in Mortar

1994 ◽  
Vol 370 ◽  
Author(s):  
Menashi D. Cohen ◽  
Turng-Fang F. Lee ◽  
Ariel Goldman
Keyword(s):  
Portland Cement ◽  
Silica Fume ◽  
Cement Paste ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Dynamic Shear Modulus ◽  
Interfacial Zone ◽  
Dynamic Moduli ◽  
Dynamic Modulus Of Elasticity ◽  
Cement Mortars

AbstractThe objective of this paper is to propose a method to estimate the average values of the dynamic modulus of elasticity and the dynamic shear modulus of cement paste-aggregate interfacial zones in mortar by applying the Logarithmic Mixture Rule (LMR). Both portland cement mortars (PC mortars) and portland cement mortars with silica fume (SF mortars) are investigated and compared, The influence of silica fume on the dynamic moduli of interfacial zone is also examined. Results indicate that for the specific ingredients and mix design used, the dynamic modulus of elasticity of interfacial zone falls between 0.4 and 2.0 (×10 6 psi) for PC mortar and 1.2 to 2.2 (× 106 psi) for SF mortar. These values are lower than the values obtained for PC mortar (4.2 ×106 psi), PC paste (2.7 ×106 psi), SF mortar (4.4 ×106 psi), and SF paste (2.5 × 106 psi).

Rectifying and thermocouple junctions based on Portland cement

2001 ◽  
Vol 16 (7) ◽  
pp. 1989-1993 ◽  
Author(s):  
Sihai Wen ◽  
D. D. L. Chung
Keyword(s):  
Carbon Fiber ◽  
Portland Cement ◽  
Cement Paste ◽  
Steel Fiber ◽  
Cement Pastes

Rectifying and thermocouple junctions have been achieved using electrically dissimilar Portland cement pastes. The preferred junction is a pn-junction involving steel fiber cement paste (n-type) and carbon fiber cement paste (p-type). For this junction, the thermocouple sensitivity is 70 εV/°C.

Impedance Spectroscopy and the Role of Admixtures in the Hydration of Portland Cement Pastes

1991 ◽  
Vol 245 ◽  
Author(s):  
Bruce J. Christensen ◽  
Thomas O. Mason ◽  
Hamlin M. Jennings
Keyword(s):  
Electrical Properties ◽  
Impedance Spectroscopy ◽  
Portland Cement ◽  
Silica Fume ◽  
Pore Fluid ◽  
Microstructural Development ◽  
Portland Cements ◽  
Cement Pastes ◽  
Degree Of Hydration

ABSTRACTMeasurements of the bulk electrical properties of cement pastes were made using impedance spectroscopy (IS) and are useful for studying hydration. Normalization of these quantities by dividing out changes in the pore fluid reveals information pertinent to the microstructural development of these materials. In this study, observations are made on the influence of accelerators, retarders and silica fume (SF) on pastes of white and ordinary portland cements (OPC). All systems show variations in the normalized electrical properties at the same degree of hydration, as compared to a control. Changes in the microstructure that are implied by these measurements are consistent with the observations of others.

Dry Shrinkage and Compressive Strength of Blended Cement Pastes with Fly Ash and Silica Fume

2012 ◽  
Vol 535-537 ◽  
pp. 1735-1738 ◽  
Author(s):  
Yan Li ◽  
Dao Sheng Sun ◽  
Xiu Sheng Wu ◽  
Ai Guo Wang ◽  
Wei Xu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Cement Paste ◽  
Blended Cement ◽  
Drying Shrinkage ◽  
Cementitious Material ◽  
Strength Increase ◽  
Cement Pastes ◽  
Dry Shrinkage

This paper reports the drying shrinkage and compressive strength results of cement pastes with fly ash and silica fume. In this study, Portland cement (PC) was used as the basic cementitious material. Fly ash (FA) and silica fume (SF) were used as cement replacement materials at levels of 0%, 5%, 10%, and 15% , 40%, 35%, 25%, and 15% by weight of the total cementitious material, respectively. The water/cement (PC + FA + SF) ratios (w/c) was 0.28 by weight. The samples produced from fresh pastes were demoulded after a day; then they were cured at 20 ±1°C with 50 ± 3% relative humidity (RH) until the samples were used for drying shrinkage and compressive strength measurement at various ages. The results show that drying shrinkage and compressive strength increase with increasing SF content, and the optimum composition of blended cement pastes is the cement paste with 30% fly ash and 10% silica fume, which possesses lower drying shrinkage values than that of plain cement paste and higher early age strength than that of blended cement pastes with fly ash. Furthermore, a linear relationship is established between compressive strength and drying shrinkage. By comparing the development of compressive strength and the drying shrinkage deformations, it appears possible to predict the drying shrinkage according to the acquired compressive strength.

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