scholarly journals SEM Image Analysis in Permeable Recycled Concretes with Silica Fume. A Quantitative Comparison of Porosity and the ITZ

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2201 ◽  
Author(s):  
Manuel J. Chinchillas-Chinchillas ◽  
Carlos A. Rosas-Casarez ◽  
Susana P. Arredondo-Rea ◽  
José M. Gómez-Soberón ◽  
Ramón Corral-Higuera
Keyword(s):  
Image Analysis ◽  
Silica Fume ◽  
Cement Paste ◽  
Chemical Elements ◽  
Energy Dispersive Spectrometer ◽  
Recycled Aggregates ◽  
Porous Network ◽  
Transition Zones ◽  
Sem Image ◽  
Coarse Aggregates

Recycled aggregates (RA) from construction and demolition can be used in permeable concretes (PC), improving the environment. PCs have a significant porous network, their cement paste and the interaction between the paste and the RA establishing their strength. Therefore, it is important to evaluate the porosity in the interfacial transition zones. The porosity of the cement paste, the aggregate and the interfacial transitional zones (ITZ) of a PC with recycled coarse aggregates (RCA) and silica fume (SF) is measured by means of image analysis–scanning electron microscope (IA)-(SEM) and by mapping the chemical elements with an SEM-EDS (energy dispersive spectrometer) detector microanalysis linked to the SEM and, as a contrast, the mercury intrusion porosimetry technique (MIP). In the IA process, a “mask” was created for the aggregate and another for the paste, which determined the porosity percentage (for the anhydrous material and the products of hydration). The results showed that using SF caused a reduction (32%) in the cement paste porosity in comparison with the PC with RA. The use of RA in the PC led to a significant increase (190%) in the porosity at different thicknesses of ITZ compared with the reference PC. Finally, the MIP study shows that the use of SF caused a decrease in the micropores, mesopores and macropores.

scholarly journals Microstructural analysis of concretes manufactured with recycled coarse aggregates pre-soaked using different methods

2020 ◽  
Vol 70 (339) ◽  
pp. 228 ◽  
Author(s):  
Z. Sánchez-Roldán ◽  
I. Valverde-Palacios ◽  
I. Valverde-Espinosa ◽  
M. Martín-Morales
Keyword(s):  
Microstructural Analysis ◽  
Treatment Method ◽  
Absorption Capacity ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Negative Effects ◽  
Optimal Method ◽  
Transition Zones ◽  
Coarse Aggregates

Recycled concrete has a microstructure more complex than natural concrete, as it includes new interfacial transition zones, the quality of which is conditioned by the state of humidity of the aggregates used, which in turn will affect the final properties of the concrete. Bearing in mind the greater absorption capacity of recycled aggregates, it is important to improve its properties by means of a treatment method that is capable of reducing the negative effects that this may produce in the new concrete. Therefore, the influence of the pre-soaking method of recycled aggregates on the formation of the microstructure of concretes manufactured with these aggregates is analysed, to determine which treatment is the most effective for the production of concretes for non-structural use. The results show that the microstructure of the evaluated concretes differs according to the treatment method used, the most optimal method being one that uses aggregates without pre-soaking.

Pore Size Distributions in Hardened Cement Paste by Sem Image Analysis

1994 ◽  
Vol 370 ◽  
Author(s):  
Sidney Diamond ◽  
Mark E. Leeman
Keyword(s):  
Image Analysis ◽  
Pore Size ◽  
Cement Paste ◽  
Hardened Cement ◽  
Size Distributions ◽  
Hardened Cement Paste ◽  
Mercury Intrusion ◽  
Sem Image ◽  
Pore Size Distributions ◽  
Sem Image Analysis

AbstractTechnical requirements for determining the size distribution of capillary pores in hardened cement paste by SEM image analysis are discussed. Results of such measurements are reported for a set of hardened cement pastes of w:c ratio 0.40 and 0.25, and of ages ranging from 1 to 28 days. Pore size distributions based on conventional mercury intrusion porisimetry are presented for the same pastes. Estimates of pore diameters by mercury intrusion are two orders of magnitude smaller than the sizes revealed by the image analysis. Diameters of air voids are even more drastically underestimated by mercury intrusion. Typical micrographs are provided to illustrate the physical reality of the image analysis results, and the technical reasons underlying the conventional misinterpretation of MIP results for hydrated cements are reviewed.

scholarly journals Use of polypropylene fiber and silica fume modified concrete as a repair material

2018 ◽  
Vol 199 ◽  
pp. 07008
Author(s):  
Jing Liu ◽  
Wen Liu ◽  
Shugang Guan ◽  
Chao Guo ◽  
and Xinguo Zheng
Keyword(s):  
Compressive Strength ◽  
Silica Fume ◽  
Cement Paste ◽  
Polypropylene Fiber ◽  
Repair Material ◽  
Chloride Permeability ◽  
Cracking Resistance ◽  
Transition Zones ◽  
Concrete Properties ◽  
Fiber Matrix

Polypropylene fiber and silica fume were used to get high impermeability and cracking resistance concrete as a repair material. Results showed just incorporating fiber (without silica fume) had no obvious improvement on strength and impermeability of concrete. The usage of polypropylene fiber and silica fume together in concrete increased the compressive strength and caused a significant reduction in chloride permeability. The improvement of fiber and silica fume on concrete properties was attributed to both the anti-cracking effect from polypropylene fiber and densification reinforcement action to the interfacial transition zones of both fiber —matrix and aggregate—cement paste from silica fume. These properties made them suitable for certain applications such as concrete repairs.

Experiment on Improving Performance of Recycled Coarse Aggregate from Waste Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 198-201
Author(s):  
Li Sun ◽  
Ying Wei Yun
Keyword(s):  
Natural Resources ◽  
Cement Paste ◽  
Coarse Aggregate ◽  
Environmental Issues ◽  
Recycled Aggregates ◽  
Aggregate Concrete ◽  
Ordinary Concrete ◽  
Recycled Coarse Aggregate ◽  
Coarse Aggregates ◽  
Waste Concrete

Recently recycled coarse aggregate concrete tends to be developed by using waste concrete considering environmental issues and conserving natural resources. However, performances of recycled coarse aggregate concrete are relative low compared with ordinary concrete due to the differences between recycled coarse aggregates and natural ones. In this research, developed mill is used to shuck the cement paste adhering on the surface of coarse aggregates to obtain shucking recycled coarse aggregates. Experimental results demonstrate that the performances of shucking recycled aggregates and concerned concrete are both improved.

Chemical Classification and Particle Sizing of Foundry Sands

1985 ◽  
Vol 43 ◽  
pp. 388-389
Author(s):  
D.S. DeMiglio
Keyword(s):  
Image Analysis ◽  
Energy Dispersive Spectrometer ◽  
Image Analysis System ◽  
Representative Sampling ◽  
Foundry Sands ◽  
Large Atomic Number ◽  
Backscattered Electron ◽  
Sand Particles ◽  
Analysis System ◽  
Reclamation System

Much progress has been made in recent years towards the development of closed-loop foundry sand reclamation systems. However, virtually all work to date has determined the effectiveness of these systems to remove surface clay and metal oxide scales by a qualitative inspection of a representative sampling of sand particles. In this investigation, particles from a series of foundry sands were sized and chemically classified by a Lemont image analysis system (which was interfaced with an SEM and an X-ray energy dispersive spectrometer) in order to statistically document the effectiveness of a reclamation system developed by The Pangborn Company - a subsidiary of SOHIO.The following samples were submitted: unreclaimed sand; calcined sand; calcined & mechanically scrubbed sand and unused sand. Prior to analysis, each sample was sprinkled onto a carbon mount and coated with an evaporated film of carbon. A backscattered electron photomicrograph of a field of scale-covered particles is shown in Figure 1. Due to a large atomic number difference between sand particles and the carbon mount, the backscattered electron signal was used for image analysis since it had a uniform contrast over the shape of each particle.

Effect of incorporating iron‐filing waste on the properties of silica fume blended cement paste

2020 ◽  
Author(s):  
Moruf O. Yusuf ◽  
Sami I. Shamsah ◽  
Khaled A. Al‐Sodani ◽  
Salihu Lukman
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
Blended Cement ◽  
Iron Filing ◽  
Blended Cement Paste

scholarly journals Recycled Mortars with Ceramic Aggregates. Pore Network Transmutation and Its Relationship with Physical and Mechanical Properties

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1543
Author(s):  
Francisca Guadalupe Cabrera-Covarrubias ◽  
José Manuel Gómez-Soberón ◽  
Carlos Antonio Rosas-Casarez ◽  
Jorge Luis Almaral-Sánchez ◽  
Jesús Manuel Bernal-Camacho
Keyword(s):  
Mechanical Properties ◽  
Image Analysis ◽  
Open Porosity ◽  
Gas Adsorption ◽  
Physical And Mechanical Properties ◽  
Recycled Aggregate ◽  
Bet Surface Area ◽  
Sem Image ◽  
The Relationship ◽  
Sem Image Analysis

The porosity of mortars with recycled ceramic aggregates (10, 20, 30, 50, and 100% as a replacement of natural aggregate) was evaluated and analyzed using three different techniques. The results of gas adsorption (N2), Scanning Electron Microscopy (SEM) image analysis and open porosity allowed establishing the relationship between the recycled aggregate content and the porosity of these mortars, as well as the relationship between porosity and the physical and mechanical properties of the mortars: absorption, density, compressive strength, modulus of elasticity, and drying shrinkage. Using the R2 coefficient and the equation typology as criteria, additional data such as Brunauer, Emmett, and Teller (BET) surface area (N2 adsorption) established significant correlations with the mentioned properties; with SEM image analysis, no explanatory relationships could be established; and with open porosity, revealing relationships were established (R2 > 0.9). With the three techniques, it was confirmed that the increase in porosity is related to the increase in the amount of ceramic aggregate; in particular with gas adsorption (N2) and open porosity. It was concluded that the open porosity technique can explain the behavior of these recycled mortars with more reliable data, in a simple and direct way, linked to its establishment with a more representative sample of the mortar matrix.

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.

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