scholarly journals Altered Volcanic Tuffs from Los Frailes Caldera. A Study of Their Pozzolanic Properties

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5348
Author(s):  
Jorge Costafreda ◽  
Domingo Martín ◽  
Leticia Presa ◽  
José Parra
Keyword(s):  
Electrical Conductivity ◽  
Portland Cement ◽  
Mechanical Strength ◽  
Iberian Peninsula ◽  
Volcanic Glass ◽  
Petrographic Analysis ◽  
High Mechanical Strength ◽  
Physical Chemical ◽  
Strength Tests ◽  
Pozzolanic Properties

This work presents the results of the study of the physical, chemical, mineralogical and pozzolanic properties of the altered volcanic tuffs (AVT) that lie in the Los Frailes caldera, south of the Iberian Peninsula, and demonstrates their qualities as pozzolans for the manufacturing of mortars and pozzolanic cements of high mechanical strength. The main objective of this research is to show to what extent the AVTs can replace portland cement (PC) in mortars, with standardised proportions of 75:25% and 70:30% (PC-AVT). To achieve these objectives, three AVT samples were studied by a petrographic analysis of thin section (PATS), DRX, FRX and MEB. The pozzolanic properties were determined by three methods: electrical conductivity (ECT), chemical pozzolanicity tests (CPT) at 8 and 15 days and mechanical strength tests (MS) of the specimens at 2, 7, 28 and 90 days. Studies of a PATS, DRX, FRX and MEB showed that the AVT samples’ constitutions are complex where smectite (montmorillonite), mordenite, quartz, halloysite, illite, kaolinite, volcanic glass and lithic fragments coexist. The results of the ECT and CPT tests confirmed the pozzolanic properties of the samples analysed and proved an increase in mechanical strength from 2 to 90 days of testing.

scholarly journals Effects of a Natural Mordenite as Pozzolan Material in the Evolution of Mortar Settings

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5343
Author(s):  
Jorge L. Costafreda ◽  
Domingo A. Martín ◽  
Leticia Presa ◽  
José Luis Parra
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Mechanical Strength ◽  
Setting Time ◽  
Volcanic Glass ◽  
Positive Influence ◽  
Partial Replacement ◽  
X Ray ◽  
Initial Setting Time ◽  
Pozzolanic Cement

This paper shows the results of a study focused on the evolution and properties of mortars made with a mixture of portland cement (PC) and natural mordenite (Mor). To begin, samples of mordenite, cement and sand were studied with X-ray diffraction (XRD), X-ray fluorescence (XRF) and granulometric analysis (GA). Next, mortars with a ratio of 75% PC and 25% mordenite were prepared to determine their initial and final setting times, consistency and density. Continuing, the density, weight and compressive strength of the specimens were determined at 2, 7, 28, 90 and 365 days. Finally, the specimens were studied using SEM, XRD and XRF. The results of the study of the mordenite sample showed a complex constitution where the major mineral component is mordenite, and to a lesser degree smectite (montmorillonite), halloysite, illite, mica, quartz, plagioclase and feldspar, in addition to altered volcanic glass. Tests with fresh cement/mordenite mortar (CMM) showed an initial setting time of 320 min and a final setting time of 420 min, much longer than the 212–310 min of portland cement mortar (PCM). It was established that the consistency of the cement/mordenite mortar (CMM) was greater than that of the PCM. The results of the density study showed that the CMM has a lower density than the PCM. On the other hand, the density of cement/mordenite specimens (CMS) was lower than that of portland cement specimens (PCS). The CMS compressive strength studies showed a significant increase from 18.2 MPa, at 2 days, to 72 MPa, at 365 days, with better strength than PCS at 28 and 365 days, respectively. XRD, XRF and SEM studies conducted on CMS showed a good development of primary and secondary tobermorite, the latter formed at the expense of portlandite; also, ettringite developed normally. This work proves that the partial replacement of PC by mordenite does not have a negative effect on the increase in the mechanical strength of CMS. It indicates that the presence of mordenite inhibits the spontaneous hydration of C3A and controls the anomalous formation of ettringite (Ett). All this, together with the mechanical strength reported, indicates that mordenite has a deep and positive influence on the evolution of the mortar setting and is an efficient pozzolan, meaning it can be used in the manufacture of mortars and highly resistant pozzolanic cement, with low hydration heat, low density, stability in extremely aggressive places and a low impact on the environment.

Effects of Various Amounts of Natural Pozzolans from Volcanic Scoria on Performance of Portland Cement Mortars

2017 ◽  
Vol 32 ◽  
pp. 36-52 ◽  
Author(s):  
Willy Hermann Juimo Tchamdjou ◽  
Sophie Grigoletto ◽  
Frédéric Michel ◽  
Luc Courard ◽  
Toufik Cherradi ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Portland Cement ◽  
Mechanical Strength ◽  
Calcium Hydroxide ◽  
Supplementary Cementitious Materials ◽  
Strength Development ◽  
Natural Pozzolan ◽  
X Ray ◽  
Natural Pozzolans ◽  
Cement Mortars

The aim of this paper is to assess the possibility of using natural pozzolans (NPs) from Cameroonian volcanic scoria as supplementary cementitious materials (SCMs) in the production of Portland cement mortars. Four natural pozzolans (Black Natural Pozzolan: BNP, Dark-Red Natural Pozzolan: DRNP, Red Natural Pozzolan: RNP and Yellow Natural Pozzolan: YNP) with 3600, 4500, 4700 and 5200 cm2/g Blaine fineness respectively were produced from different colors (Black, Dark red, Red and Yellow) volcanic scoria in a laboratory mill. Natural pozzolans were characterized with regard to particle size distribution, particle shape, electrical conductivity, X-ray fluorescence (XRF) and X-ray diffraction (XRD). The calcium hydroxide consumption by NPs was assessed firstly by electrical conductivity measurements of calcium hydroxide/NPs suspensions with calcium hydroxide excess. Evidence of pozzolanic reactivity of NPs is revealed in hydrated lime pastes, and low reactivity was observed in aqueous suspensions. The effects of 15, 25, and 35 wt.% of NPs as cement substitution on the properties of Portland cement mortars were investigated. Different properties were studied such as setting time, consistency, mechanical strength, pozzolanic activity, absorption by capillarity and resistance to carbonation. The reactivity of NPs was also assessed by means of the mechanical strength development of mortars. The results obtained show that pozzolanic and hydraulic reactions take place in OPC systems. The correlation between mechanical strengths and physical properties of NPs has been established. The study concludes that using DRNP and RNP at 15 wt. % cement replacement can ameliorate globally the performance of mortar. Using all NPs at 35 wt. % has negative effect on the fundamental properties of cementitious mortars.

scholarly journals Expanded obsidian as a soil aerator, its porosity, physical and mechanical characteristics

2020 ◽  
Vol 175 ◽  
pp. 09019
Author(s):  
Artsruni Safaryan ◽  
Tamara Sarkisyan ◽  
Tatevik Paytyan ◽  
Marine Kalantaryan ◽  
Armine Baghdagyulyan
Keyword(s):  
Heat Treatment ◽  
Mechanical Strength ◽  
Mechanical Characteristics ◽  
Raw Materials ◽  
Volcanic Glass ◽  
Total Porosity ◽  
Average Density ◽  
Strength Increase ◽  
High Mechanical Strength ◽  
Physical And Mechanical Characteristics

Today, the decline in soil fertility progress, therefore, special attention paid to the search for new, including non-traditional sources of raw materials that allow cultivating agricultural crops. It is propose to use expanded obsidian as a soil aerator. Obsidian is a volcanic rock, consisting of volcanic glass in which water content does not exceed 1%. A characteristic feature of this stone is the ability to expand under heat treatment. The expansion of obsidian is possible to implement at temperatures of 1050… 1150 °C. It has been shown that due to obsidian expansion it is possible to obtain a light porous filler with an average density of 200… 350 kg/m3, where the heat treatment of 5… 10 mm grains should be performed under temperatures from 1050 to 1150°C, during 3…5 minutes. The mechanical strength of the expanded obsidian is due to the thickness of the internal partitions of the pores and depends on the total porosity. Increased porosity decreases the strength of the expanded obsidian grains as the internal partitions of the pores become thinner. Relatively high mechanical strength develop grains with less porosity, ie lower coefficient of expansion. At the same time, the nature of the external surface of the grain has a significant influence on the mechanical strength. The melted surface,under other equal conditions provides mechanical strength increase of the expanded obsidian.

scholarly journals A Study on Mechanical Characteristics of Cement Composites Fabricated with Nano-Silica and Carbon Nanotube

2020 ◽  
Vol 11 (1) ◽  
pp. 152
Author(s):  
Ali Raza ◽  
Manan Bhandari ◽  
Hyeong-Ki Kim ◽  
Hyeong-Min Son ◽  
Baofeng Huang ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Electrical Conductivity ◽  
Mechanical Strength ◽  
Cement Composites ◽  
Nano Silica ◽  
Dense Microstructure ◽  
Strength Tests ◽  
Multi Walled Carbon Nanotubes ◽  
Compressive And Flexural Strengths ◽  
Walled Carbon Nanotubes

In this study, cement composites were fabricated with various contents of added nano-silica (NS) and multi-walled carbon nanotubes (MWNTs). The compressive and flexural strengths of the resultant cement composites were examined. To explore the microstructures and MWNT distribution, electrical conductivity tests, and scanning electron microscopy were conducted. In addition, the strength results were analyzed based on thermal analysis and porosity evaluations. The electrical conductivity results indicated that MWNTs were satisfactorily distributed in the cement composites. In the mechanical strength tests, the composite with a 0.6% MWNT and 5% NS content and another with a 0.3% MWNT and 5% NS content yielded enhancements in the compressive and flexural strengths of 17.2% and 52% compared with the control samples, respectively. However, composites containing relatively large amounts of both NS and MWNTs showed degradation in the mechanical strength. The enhancement or degradation of the strength was supported by porosity evaluations and thermal analysis results. In particular, the degradation of the strength due to the incorporation of large amounts of both MWNTs and NS was explained by thermogravimetric analysis, which indicated a limited generation of calcium silicate hydrate (C-S-H) hydration products. The lower generation of C-S-H was likely due to the dense microstructure of MWNT/NS-incorporated cement hindering the reactions between calcium hydroxide and the NS.

scholarly journals Versatile fabrication of a superhydrophobic and ultralight cellulose-based aerogel for oil spillage clean-up

2016 ◽  
Vol 18 (40) ◽  
pp. 28297-28306 ◽  
Author(s):  
Hui Zhang ◽  
Yuqi Li ◽  
Yaoguang Xu ◽  
Zexiang Lu ◽  
Lihui Chen ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Plasma Treatment ◽  
Low Density ◽  
High Mechanical Strength ◽  
Marine Oil ◽  
Highly Efficient ◽  
Modification Process ◽  
Physical Chemical ◽  
Oil Spillage ◽  
Silane Modification

To deal with marine oil spillage and chemical leakage issues, a highly efficient absorbent (cellulose based aerogel) with a low density (ρ < 0.034 g cm−3, φ > 98.5%) and high mechanical strength was fabricated via a novel physical–chemical foaming method, plasma treatment and subsequent silane modification process.

scholarly journals CARACTERIZAÇÃO ANATÔMICA E DESCRIÇÃO FÍSICO-QUÍMICA E MECÂNICA DA MADEIRA DE Mimosa schomburgkii

FLORESTA ◽  
2017 ◽  
Vol 47 (4) ◽  
pp. 383 ◽  
Author(s):  
Luciano Junqueira Costa ◽  
Camila Batista da Silva Lopes ◽  
Matheus Fernandes de Carvalho Reis ◽  
Welliton Lelis Cândido ◽  
Bruno De Freitas Homem de Faria ◽  
...  
Keyword(s):  
Specific Gravity ◽  
Mechanical Strength ◽  
Basic Density ◽  
Raw Material ◽  
Mechanical Resistance ◽  
Extractive Content ◽  
Anisotropy Coefficient ◽  
High Mechanical Strength ◽  
Physical Chemical ◽  
Vessel Elements

O uso de madeira de espécies alternativas na construção civil é uma alternativa para reduzir a utilização concentrada em poucas espécies e evitar a falta de matéria prima no mercado. Diante do exposto, o objetivo deste estudo foi avaliar propriedades físicas, químicas, anatômicas e mecânicas da madeira de Mimosa schomburgkii visando identificar o seu potencial para o uso na construção civil. Foi utilizada a madeira de Mimosa schomburgkii, com idade de 33 anos. As características anatômicas avaliadas foram as dimensões dos elementos de vasos (diâmetro e frequência), dos raios (altura e largura) e das fibras (comprimento, largura total, espessura de parede e de lume). Foi determinada a constituição química com a quantificação do teor de extrativo, lignina e holocelulose.  Para a caracterização físico-mecânica, foram avaliadas a densidade básica e aparente, contrações, o coeficiente de anisotropia, a resistência à flexão estática, à compressão paralela às fibras, à tração paralela às fibras, ao cisalhamento e a dureza Janka (paralela e perpendicular às fibras). A madeira possui fibras libriformes, com comprimento médio de 1180 μm, sendo classificadas como curtas. A densidade básica da madeira é em média 0,80 g.cm-3 (alta densidade), o coeficiente de anisotropia, em média 1,74. A madeira apresenta elevada resistência mecânica, sendo classificada como pertencente à classe C 60. Pelos resultados obtidos no estudo, a madeira de jurema (Mimosa schomburgkii) apresenta aspectos estéticos atrativos e elevada resistência mecânica, sendo, portanto, indicada para uso na construção civil.Palavras–chave: Propriedades da madeira, construção civil, elevada resistência mecânica, alta densidade básica. AbstractAnatomical characterization and physical-chemical and mechanical description of Mimosa schomburgkii wood. The use of wood of alternative species in civil construction has been an option to reduce the concentrated use of few species and to avoid the lack of raw material in the market. The objective of this study was to evaluate the physical, chemical, anatomical and mechanical properties of Mimosa schomburgkii wood, in order to identify its potential use in civil construction. Mimosa schomburgkii wood, at the age of 33 years, was used. The anatomical characteristics evaluated were the dimensions of vessel elements (diameter and frequency), rays (height and width) and fibers (length, width, wall thickness and lumen thickness). The chemical constitution was determined with the quantification of extractive content, lignin and holocellulose. For the physical-mechanical characterization, it was evaluated the specific gravity and apparent density, contractions, anisotropy coefficient, static bending strength, compression strength parallel to grain, traction strength parallel to grain, shear strength and Janka hardness (parallel and perpendicular to grain). The wood has libriform fibers, average length of 1180 μm, and it is classified as short. The wood basic density is on average of 0.80 g.cm-3 (high density). The anisotropy coefficient is on average of 1.74. The wood presents high mechanical strength, being classified as C 60 class. From the results obtained in this study, the Mimosa schomburgkii wood presents attractive aesthetic aspects and high mechanical resistance. Therefore, this wood is indicated for use in civil construction.Keywords: Wood properties, civil construction, high mechanical strength, high specific gravity.

scholarly journals Properties Of Thin Metal Layers Deposited On Textile Composites By Using The Pvd Method For Textronic Applications

2017 ◽  
Vol 17 (3) ◽  
pp. 229-237 ◽  
Author(s):  
R. Pawlak ◽  
E. Korzeniewska ◽  
C. Koneczny ◽  
B. Hałgas
Keyword(s):  
Mechanical Strength ◽  
Surface Resistance ◽  
Textile Composites ◽  
High Mechanical Strength ◽  
Metal Structures ◽  
Composite Substrate ◽  
Strength Tests ◽  
Microscopic Studies ◽  
Thermal Vapor Deposition ◽  
Metal Layers

AbstractIn this paper, the results of mechanical strength tests of thin conductive Ag and Au layers created on Cordura composite substrate using the thermal vapor deposition method are presented. The resistance of the conductive layers to the bending and tensile stresses was tested and changing the surface resistance of the test structures was accepted as a criterion. The layers created on unmodified and plasma-treated surfaces have been examined. As a result of the surface modification, the electrical and mechanical properties of the thin Ag and Au metal structures have been improved. The results of measurements of surface resistance changes during strength tests and SEM microscopic studies of stressed samples indicate the high mechanical strength of the electroconductive layers deposited on Cordura, which may be the basis for the application of such technology in textronics applications.

Pozzolanicity Evaluation of Mineral Additions by Electrical Conductivity Measurements

2016 ◽  
Vol 881 ◽  
pp. 239-244
Author(s):  
Felipe Araujo Cedrim ◽  
Guilherme Augusto de Oliveira e Silva ◽  
Tiago Assunção Santos ◽  
Daniel Véras Ribeiro
Keyword(s):  
Electrical Conductivity ◽  
Portland Cement ◽  
Silica Fume ◽  
Conductivity Measurements ◽  
Alternative Materials ◽  
Mineral Additions ◽  
Pozzolanic Materials ◽  
Pozzolanic Properties

The search for alternative materials that can replace Portland cement promotes discussion about the use of pozzolanic materials in cementitious matrices. Several techniques and procedures can determine the pozzolanic properties of a particular material based on electrical conductivity. Being an innovative and a subject of demand and minimum resource method, this article seeks validation by the comparison with chemical titration tests. To this end, were tested several possible pozzolanic materials (silica fume, metakaolin and eucalyptus ash) through the mentioned techniques

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