Characterization and evaluation of the pozzolanic activity of Egyptian industrial by-products

Mostafa, Nasser Y.; El-Hemaly, S. A. S.; Al-Wakeel, E. I.; El-Korashy, Sabry A.; Brown, Paul

doi:10.1016/s0008-8846(00)00485-3

Cited by 99 publications

(33 citation statements)

References 21 publications

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“…This may involve measurement of properties such as compressive strength, electrical conductivity [7,10,11] or heat evolution by conduction calorimetry [12,13]. Compressive strength test methods have been used to assess the pozzolanic activity of catalytic cracking residues [14], coal bottom ash [15], glass powders [16], crushed bricks [4], silica fume [13,17] and sewage sludge ash [18,19].…”

Section: A Pozzolan Is Defined As (Astm C125) "A Siliceous and Aluminmentioning

confidence: 99%

Comparison of test methods to assess pozzolanic activity

Donatello

Tyrer

Cheeseman

2010

Cement and Concrete Composites

386

144

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Assessment of the pozzolanic activity of cement replacement materials is increasingly important because of the need for more sustainable cementitious products. The pozzolanic activity of metakaolin, silica fume, coal fly ash, incinerated sewage sludge ash and sand have been compared using the Frattini test, the saturated lime test and the strength activity index test. There was significant correlation between the strength activity index test and the Frattini test results, but the test results from these tests did not correlate with the saturated lime test results. The weight ratio of Ca(OH) 2 to test pozzolan is an important parameter. In the Frattini test and strength activity index test the ratio is approximately 1: 1, whereas in the saturated lime test the ratio is 0.15: 1. This explains why the saturated lime test shows higher removal of Ca(OH) 2 and why the results from this test do not correlate with the other test methods.Keywords: Pozzolan; Portland cement; Sustainable development; Sewage sludge ash; Metakaolin; Silica fume; Pulverised fuel ash; Frattini test INTRODUCTION A pozzolan is defined as (ASTM C125) "a siliceous and aluminous material which, in itself, possesses little or no cementitious value but which will, in finely divided form in the presence of moisture, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties".Pozzolans were the first cementitious materials used by early civilisations and some of the most important historical buildings rely on pozzolanic cement systems. Pozzolans are of increasing interest because their use reduces overall environmental impact and cost when mixed with Portland cement (CEM-I) in blended cement systems. The use of pozzolans reduces the carbon dioxide emitted per tonne of product and can also improve various physical properties of the resulting concrete [1].Pozzolans are obtained from various sources and can be naturally occurring minerals or industrial byproducts. They do not necessarily interact with Portland cement in the same way, and the mechanisms involved in hydration of coal fly ash (FA) and silica fume to form hydration products are different. A major benefit of blended cements is improved durability and this occurs because the reaction between the pozzolan and excess Ca(OH) 2 produced by CEM-I hydration forms calcium silicate hydrate (C-S-H) gel, which reduces the porosity of the binder.A wide range of test methods for assessing pozzolanic activity have been reported in the literature. These can be categorised as either direct or indirect methods. Direct methods monitor the presence of Ca(OH) 2 and its subsequent reduction in abundance with time as the pozzolanic reaction proceeds, using analytical methods such as X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) or classical chemical titration. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 ...

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Section: A Pozzolan Is Defined As (Astm C125) "A Siliceous and Aluminmentioning

confidence: 99%

Comparison of test methods to assess pozzolanic activity

Donatello

Tyrer

Cheeseman

2010

Cement and Concrete Composites

386

144

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“…In effect, it is a measure of how effective the pozzolan is. Accurately deducing a pozzolan's reactivity is complex [15] and dependant on the methodology. For this reason, the reactivity was determined using the three methods below.…”

Section: Pozzolan Reactivitymentioning

confidence: 99%

Physical properties and reactivity of pozzolans, and their influence on the properties of lime–pozzolan pastes

2010

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This paper studies how pozzolan properties including particle size, specific surface, chemical and mineral composition, amorphousness and water demand, affect their reactivity as well as the strength of lime-pozzolan pastes. Reactivity was evaluated with chemical, mechanical and mineralogical methods. A number of artificial pozzolans were investigated including Ground Granulated Blastfurnace Slag (GGBS); Leca; Pulverised Fuel Ash (PFA); Calcined Clay (Metastar); Microsilica (MS); Rice Husk Ash (RHA); Red Brick Dust (RBD); Tile and Yellow Brick Dust (YBD). The paper concludes that the pozzolan's specific surface has a much greater influence on the water demand of the paste than its particle size or the lime:pozzolan ratio. It was evidenced that each pozzolan has a particular water demand for a given workability that increased with its specific surface; and that the replacement of lime by pozzolan lowers the water demand of the paste except for Metastar, on account of its greater fineness and specific surface. There is a good correlation between the chemical and physical activity indices and the rate of portlandite consumption. These evidenced that the most amorphous pozzolans (Metastar, GGBS, RHA and MS) are the most active. Finally, it also appears from the results, that the amount of lime combined by reactive crystalline phases in the pozzolans is insignificant when compared to that bound by their amorphous fraction. The paper concludes that amorphousness determines pozzolan reactivity to a much greater extent than any other pozzolan property. It also concludes that the specific surface area of the pozzolan governs the water demand of the paste, while amorphousness largely determines the strength of the paste. In contrast, the chemical composition of the pozzolan is not instrumental as a variable affecting neither pozzolan reactivity nor the strength of the paste.

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“…It is well known that this lack of durability is mainly caused, on the one hand, by the calcium hydroxide (portlandite) of the matrix, which degrades the fibers, and, on the other, by changes in environmental moisture, which induce dimensional changes in the vegetable fibers and hence loss of physical contact with the matrix [25][26][27]. To overcome the problem of the calcium hydroxide component, several strategies have been used, such as pozzolanic additions to precipitate the portlandite as calcium silicate hydrate [28][29][30][31][32][33][34][35] or carbonation treatments with CO2 to precipitate the portlandite as calcium carbonate [36]. Concerning the pozzolanic additions, Cyr et al [37] stated that the reactivity of the pozzolan depends on the alkalinity of the matrix and on the fineness of the particles of the mixtures.…”

Section: Introductionmentioning

confidence: 99%

Natural fiber nonwoven reinforced cement composites as sustainable materials for building envelopes

Claramunt

Fernández-Carrasco

Ventura

et al. 2016

Construction and Building Materials

109

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This experimental research analyzes the mechanical performance and durability of façade pieces based on Portland cement matrix and flax nonwovens as reinforcement. Two types of pozzolanic additions (silica fume and metakaolin) combined with nonwovens subjected to different treatments to decrease their water absorption are analyzed as potential materials for fiber-cement sheets for building envelopes with high strength and durability. For this purpose, on the one hand, the mechanical performance and chemical composition of various ternary compositions were studied. On the other hand, various treatments were performed on the nonwovens and the nonwoven-matrix adherence was also analyzed. Finally, composites were prepared from some selected treated nonwovens and matrix mixtures, and their mechanical properties and durability were evaluated under four-point bending tests after 28 days of curing in a humidity chamber and after accelerated aging. The composites developed with the treated nonwovens presented very high performance combined with enough durability to be potential candidates for the development of sustainable materials for building envelopes. Highlights-Mechanical performance and durability of OPC/flax nonwovens composites for façade pieces is explored -The effect of two pozzolanic additions combined with nonwoven treatment is evaluated -Significant improvements in the durability using treated nonwovens 3

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Characterization and evaluation of the pozzolanic activity of Egyptian industrial by-products

Cited by 99 publications

References 21 publications

Comparison of test methods to assess pozzolanic activity

Comparison of test methods to assess pozzolanic activity

Physical properties and reactivity of pozzolans, and their influence on the properties of lime–pozzolan pastes

Natural fiber nonwoven reinforced cement composites as sustainable materials for building envelopes

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