Long-term strength of high fly ash concretes

Hansen, Torben C.

doi:10.1016/0008-8846(90)90071-5

Cited by 32 publications

(11 citation statements)

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“…However, after 14 days there was an increase in the strength development. These tests should have been carried out for longer periods of time to confirm other published data (Berry, 1980;Mehta, 1981;Hansen, 1990;Wild et al, 1996) which showed that the compressive strength increases considerably after 28 days.…”

Section: Strength Activity Indexsupporting

confidence: 70%

Effect of Pakistani bentonite on properties of mortar and concrete

Ahmad¹,

Barbhuiya²,

Elahi³

et al. 2011

Clay miner.

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Bentonite is composed primarily of montmorillonite and is useful in a wide range of applications. This paper presents the results of an experimental investigation carried out to evaluate the possibility of using a Pakistani bentonite (from Jehangira, Swabi District) as a cement replacement material in mortar and concrete. The cement in mortar and concrete was replaced with the bentonite at 0%, 20%, 30%, 40% and 50% by cement mass. The strength activity index of bentonite was determined ‘as received’ (20ºC) and ‘heated’ (treatment at 500ºC and 900ºC). The test results indicated that the strength activity index of bentonite conformed to the ASTM Standard C618 specifications, except for the ‘900ºC heated’ bentonite. The water absorption decreased for mortar containing up to 30% bentonite and then steadily increased at higher bentonite loadings. When immersed in 5% Na2SO4 and 2% MgSO4 solution, the greatest compressive strength was observed for mortar containing 30% bentonite. The water demand of concrete increased with increasing bentonite content. Although the compressive strength of concrete decreased progressively as the substitution level of bentonite was increased, the compressive strength of concrete containing 30% ‘as received’ bentonite was found to be 70% of the control concrete, whereas for concrete containing 30% ‘500ºC heated’ bentonite, the strength was found to be 79% of the control concrete. It can be concluded that this Pakistani bentonite can be used to replace up to 30% of cement to produce concrete with sufficient compressive strength for low-cost construction resistant to sulphate attack.

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Section: Strength Activity Indexsupporting

confidence: 70%

Effect of Pakistani bentonite on properties of mortar and concrete

Ahmad¹,

Barbhuiya²,

Elahi³

et al. 2011

Clay miner.

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“…Ce rdsultat a ddj5 ~t~ observd par diffdrents auteurs [4,18]. Certains concernent la formulation m~me du b&on, d'autre l'environnement et les conditions de maturation.…”

Section: Ri~su Ltatsunclassified

Variation des facteurs d'efficacité caractérisant les additions minérales

et al. 2000

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Papier refu le 4 uovembre 1999; Papier accept4 le 14 mars 2000 R I~S U M I~ A B S T R A C TLa d&ision des pouvoirs publics de recycler les ddchets industriels conduit h l'utilisation quasi-syst4matique d'additions min&ales dans les b&ons. La pr4diction des r&istances m&aniques de ces b&ons conduit l'ing& nieur 5 caract&iser les additions incorpor&s : pour cela, on utilise souvent un coefficient unique, coupl4 avec une loi empirique du type Bolomey ou Abrams. Les r&ultats d'essais relev& dans une abondante bibliographie, compldtds par des mesures effectu&s par les auteurs montrent que cette d~marche est illusoire. De nombreux facteurs comme la nature 'du ciment, le taux de substitution, la finesse de l'addition, l'&h&nce d'essai font qu'il n'y a pas unicitd du facteur d'efficacit~ des additions. Aucune loi gdn&ale expliquant cette variabi-lit~ n'a encore ~t~ &ablie ~ ce jour. Les auteurs mettent en garde contre l'utilisation abusive d'un coefficient d'dquivalence unique et recommandent de prendre en compte non seulement les param&res physico-chimiques mais aussi la destination des ouvrages eux-m~mes. The decision of public authorities to recycle industrial wastes leads to the quasi-systematic use of mineral admixtures in concrete. Predicting the strength of these concretes induces the engineer to characterise the mineral admixtures: ordinarily, a single coefficient is used, calculated with an empirical law like Bolomey's or Abrams'formulas.Many results, reported in bibliography and completed by the authors, show that the determination of this single coefficient is not sufficient to characterise the activity of the admixture. Many factors like the nature of cement, the substitution rate, the fineness of the admixture and the age of concrete induce a great variability of the efficiency coefficient of the admixtures. Up to now, there is no general law explaining this variability. The authors warn against the excessive use of a single equivalence coefficient and recommend to take into account not only the physicochemical parameters but also the nature of the works themselves.

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“…Apart from this, many research works have been directed towards the utilisation of pozzolana in concrete and cement-based materials (Halse and Pratt, 1984;Hansen, 1990;Lee et al, 2003). The use of blended cements in the construction industry is common.…”

Section: Introductionmentioning

confidence: 98%

Pore size distribution modification of OPC paste through inclusion of fly ash and sand

Kondraivendhan¹,

Bhattacharjee

2013

Magazine of Concrete Research

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This paper presents a study into the modification of pore size distribution of ordinary Portland cement (OPC) paste due to inclusion of fly ash (FA) and sand as determined through mercury intrusion porosimetry. Cement-sand mortar specimens were prepared from two different grades of OPC with water to cement (w/c) ratios of 0 . 2, 0 . 3, 0 . 4, 0 . 5 and 0 . 6 and tested at different curing ages from 1 day to 90 days. Cement-FA paste and mortar specimens were also prepared by incorporating FA at four levels of FA to cement (f/c) ratio (0 . 1, 0 . 2, 0 . 3, 0 . 4) and a control mix along with four w/(c + f) ratios (0 . 25, 0 . 35, 0 . 45 and 0 . 55). These specimens were tested at 7, 28 and 90 days. The relationships involving w/c ratio and age with mean distribution radius (r 0 : 5 ) and coefficient (d ) representing dispersion of pore sizes are presented for both types of OPC-sand mortar. The relationships involving w/(c + f) ratio, f/c ratio and age with r 0 : 5 and d are also presented separately for cement-FA paste and mortar.

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Long-term strength of high fly ash concretes

Cited by 32 publications

References 0 publications

Effect of Pakistani bentonite on properties of mortar and concrete

Effect of Pakistani bentonite on properties of mortar and concrete

Variation des facteurs d'efficacité caractérisant les additions minérales

Pore size distribution modification of OPC paste through inclusion of fly ash and sand

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