Rupelian Boom clay as raw material for expanded clay manufacturing

Decleer, J.; Viaene, Willy

doi:10.1016/0169-1317(93)90032-v

Cited by 31 publications

(14 citation statements)

References 14 publications

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“…SiO 2 generally acts as a network former in glasses and thus increases the viscosity and T g [17]. It has been reported that LWA incorporating numerous small pores show enhanced mechanical strength compared to LWA with large, irregular pores [8,18]. However, these alleged, enhanced mechanical properties may be questioned, since the reported strength values are influenced by a variety of parameters (pellet size, total porosity, composition etc.)…”

Section: Addition Of Siomentioning

confidence: 94%

“…However, the pore structure changed markedly to larger pores in the centre of the pellet compared to the reference. The colour of the matrix phase also changed due to changes in the oxidation state of iron [8], whereas a red colour indicates a high amount of Fe 3+ , a greygreen colouration points to a high amount of Fe 2+ and black an intermediate oxidation state.…”

Section: Addition Of Iron (Fe 2 O 3 / Fe)mentioning

confidence: 99%

“…Iron is an important component in LWA since Fe 2 O 3 is one of the main components leading to gas formation at elevated temperatures [8,21]. Additionally, T g and the viscosity of the glass phase are significantly influenced by the oxidation state of iron as observed for iron containing silicate melts where an increased amount of Fe 3+ leads to both a higher viscosity and a higher glass transition temperature [22,23].…”

Section: Addition Of Ironmentioning

confidence: 99%

“…Riley [7] investigated different compositions of clay and defined regimes in the ternary system SiO 2 -Al 2 O 3 -flux (Riley diagram) where bloating takes place when heated to temperatures up to 1300°C and given that a gas forming reaction occurs at the same temperature. During firing gas evolution takes place [8] and the material needs to be in a plastic state in order to trap the gases and subsequently expand [7]. Plasticity is obtained by the formation of a glass phase which becomes less viscous above the softening point and allows expansion.…”

Section: Introductionmentioning

confidence: 99%

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The effect of additives on the properties of lightweight aggregates produced from clay

Bernhardt

Justnes

Tellesbø³

et al. 2014

Cement and Concrete Composites

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In an attempt to improve the properties, lightweight aggregates were produced from clay with the addition of Na 2 CO 3 , SiO 2 , Fe 2 O 3 , and Fe in quantities between 2 and 10 wt% and examined with respect to strength, density and expansion behaviour. The additives were mixed into dry clay powder, water was added and pellets were formed by hand and fired at 1120°C in a chamber furnace. Particle densities of the products ranged from 0.31-0.57 g/cm 3 , porosities from 78-89% and the solid strength from 0,54-1,58 MPa. The addition of Na 2 CO 3 proved to decrease the viscosity of the glass phase at the surface of the pellets but resulted in a 2 reduced expansion, irregular shape and pellets sticking together. SiO 2 addition did not give any major change in properties. The addition of Fe 2 O 3 increased the pore size in the centre of the pellets, however with insignificant change in strength and density. Adding 5 wt% metallic iron powder led to LWA pellets with increased porosity, reduced density, larger pores and low mechanical strength and could be an useful additive in applications where low density is more important than strength.

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Section: Addition Of Siomentioning

confidence: 94%

Section: Addition Of Iron (Fe 2 O 3 / Fe)mentioning

confidence: 99%

Section: Addition Of Ironmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effect of additives on the properties of lightweight aggregates produced from clay

Bernhardt

Justnes

Tellesbø³

et al. 2014

Cement and Concrete Composites

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“…Artificial lightweight aggregates (LWA) are produced from natural raw materials like clay or slate or industrial waste products like fly ash or sludge [1][2][3][4]. The industrial production of LWA takes place in rotary kilns where the raw material is fired at temperatures up to1300ºC.…”

Section: Introductionmentioning

confidence: 99%

The effect of heat treatment and cooling rate on the properties of lightweight aggregates

Bernhardt

Tellesbø²,

Justnes

et al. 2014

Journal of the European Ceramic Society

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Lightweight aggregates (LWA) were produced from clay in the laboratory. After firing different heat treatments and cooling rates were applied and the resulting material was investigated with respect to strength and microstructure. Fast cooling led to the formation of micro cracks and weakened the material whereas slow cooling enhanced the strength of LWA. The residence time at temperatures between 700°C and 900°C led to differences in average oxidation state of iron in the matrix phase leading to substantial changes in thermal behaviour of the matrix phase. The combination of a highly oxidized shell and a reduced core 2 proved to enhance the strength of LWA. A two hour heat treatment at 800°C in air combined with a subsequent slow cooling rate (0.7°C/min) applied to LWA produced in an industrial rotary kiln led to a strength increase of 114 % compared to material of the normal production without changing any other property.

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