Analysis of the effects of mineral admixtures on the strength of mortars: Application of the predictive model of Feret

The introduction of fine and ultra‐fine mineral admixtures in cementing materials generates a granular effect, a physico‐chemical and micro‐structural effect and, possibly, chemical effect. To analyse the specific share of each effect, we propose to use a methodology based on a volume substitution of cement by admixtures in mixes whose absolute volume of the solid phases and workability are preserved constant and then only the effects of the particles of admixtures in the cementing phase are taken into account. We expressed the compressive strength of mortars with admixtures according to a factor of compactness by applying to the mortars the principles of the predictive model of Feret. This factor makes possible to distinguish the modifications generated by the granular effect of the admixtures on the compactness of the cementing matrix independently of the physico‐chemical and chemical effects. The specific chemical action of each admixture has been evaluated by analysing the variation of the coefficient of activity K according to the rate of the cement substitution, by applying to the studied mortars the concept of the equivalent binder and by deducing the coefficient of activity from the predictive model of Feret. Mineralinių priedų įtakos skiedinių stipriui analiz­ : feret modelio taikymas Santrauka Smulkių ir labai smulkių mineralinių priedų naudojimas cementiniuose skiediniuose sukelia fizikinius, cheminius bei mikrostruktūrinius efektus. Šiems efektams įvertinti siūloma metodika, pagal kurią cemento kiekis skiedinio mišinyje pakeičiamas mineralinių priedų kiekiu taip, kad mišinio slankumas lieka nepakitęs. Skiedinių su priedais stipris gniuždant, atsižvelgiant į sutankinimo laipsnį, nustatytas, taikant Feret modelį. Tai leidžia išskirti priedų įtaką cementinio akmens sutank­jimui nepriklausomai nuo fizikinių ir cheminių procesų. Kiekvieno priedo cheminis poveikis buvo įvertintas analizuojant aktyvumo koeficiento K kitimą pagal pakeičiamo cemento kiekį. Analiz­ taip pat atlikta taikant ekvivalentinio rišiklio koncepciją bei aktyvumo koeficientą, nustatytą taikant Feret modelį. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: skiedinys, mineraliniai priedai, vandens poreikis, tankumas, stipris, fizinis ir cheminis efektas, Feret modelis

Impact de la création d'une unité d'hospitalisation de courte durée sur la prise en charge des patients de plus de 80 ans à partir des urgences du centre hospitalier de Lagny-Marne la Vallée

PARIS-BIUM (751062103) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

Valorization of Local Mineral Admixtures in Concretes

This study is an extension of previous researches on mortars with mineral admixtures and super-plasticizers. In this way, the same methodology was applied to concretes and the use of mineral admixture was limited to low cost materials available in Algeria as limestone, pozzolan and blast furnace slag, with current cement and super-plasticizer. The experimental methodology used was based on the volume substitution of the cement by admixtures in mixtures with the absolute volume of the solid phases and workability preserved constant. The main results achieved showed that the super-plasticizer demand of concretes depends on the nature and the quantity of the incorporated admixture. The combined use of admixtures and super-plasticizer has generally a favourable effect on compressive strengths at 07 and 28 days at low rates of cement substitution, which vary significantly with the nature, fineness and quantity of the used admixtures. At 07 days, limestone admixtures give better improvements and reach more than 20 % of gain to the compressive strength of the reference concrete with no admixtures or super-plasticizer, at 10 % of the cement substitution and still better until 30 %. At 28 days, blast furnace slag admixtures give better improvements at 28 days and reach more than 20 % of gain to the compressive strength of the reference concrete at 20 % of the cement substitution and still better until 30 %. This contribution to the compressive strength is explained on the one hand by the reduction of the quantity of water in the mixtures at the same consistency, by the use of the super-plasticizer and on another hand by the activity of Limestone admixtures at early ages and to the latent hydraulic properties of blast furnace slag at 28 days

Occurrence and diversity of barley yellow dwarf virus in Algeria

Cereals are prone to viral infections and the economic impact of these has increased in recent years. Among these diseases barley yellow dwarf (BYD) is one of the most destructive diseases of cereals today. For three consecutive years (2014–2015–2016) surveys were carried out in order to search for BYDV species (BYDV-PAV and -MAV) as well as other cereal viruses, wheat spindle streak mosaic virus (WSSMV), southern bean mosaic virus (SBMV) and barley stripe mosaic virus (BSMV) in seven regions of Algeria (Algiers, Boumerdes, Tipaza Médéa, Adrar, Khenchla and Batna)

Synthesis and characteristics of anorthite ceramics from steelmaking slag

© 2016 by The Minerals, Metals & Materials Society. Steelmaking slag is an alkaline solid waste consisting mainly oxides of calcium, iron, silicon, magnesium, and aluminum. Its large quantity and chemical property makes it challenging for recycling the material in various industrial applications. In this study, hot-poured steelmaking slag was used to prepare ceramics. After mixing with kaolin and quartz, ceramic products were synthesized via sintering. The appropriate sintering temperature is 1200°C. XRD analysis showed the major mineral phases were anorthite and pyroxene. SEM images showed that the new crystal particles were uniformly formed and distributed. Reaction mechanisms were discussed

Synthesis and characteristics of anorthite ceramics from Steelmaking slag

Steelmaking slag is an alkaline solid waste consisting mainly oxides of calcium, iron, silicon, magnesium, and aluminum. Its large quantity and chemical property makes it challenging for recycling the material in various industrial applications. In this study, hot-poured steelmaking slag was used to prepare ceramics. After mixing with kaolin and quartz, ceramic products were synthesized via sintering. The appropriate sintering temperature is 1200°C. XRD analysis showed the major mineral phases were anorthite and pyroxene. SEM images showed that the new crystal particles were uniformly formed and distributed. Reaction mechanisms were discussed

Identification of Algerian field-caught mosquito vectors by MALDI-TOF MS

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