References of "Cement & Concrete Composites"
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See detailInfluence of cement and aggregate type on thaumasite formation in concrete
Nielsen, peter; Sven, Nicolai; Darimont, Anne ULg et al

in Cement & Concrete Composites (2014), 53

In this study the influence of binder type on the formation of thaumasite in mortars made with expanded clay lightweight aggregates (LWA) was examined. For this purpose mortar prisms (20x20x160mm) were ... [more ▼]

In this study the influence of binder type on the formation of thaumasite in mortars made with expanded clay lightweight aggregates (LWA) was examined. For this purpose mortar prisms (20x20x160mm) were made with different binders and expanded clay lightweight aggregate or quartz sand, which after 28 days of curing in water were exposed to a 2.37 % Na2SO4 solution. The length and weight change of the prisms was recorded in triplicate as a function of time of exposure to dry-wet cycles in the sulphate solution or deionised water, at a temperature of 5 ± 1°C. The influence of the binder type on the expansion of the prisms in the 2.37 % Na2SO4 solution with dry and wet cycling can be ordered from strong to weak as follows: (1) CEM I + limestone filler, (2) CEM I, (3) CEM I + fly ash, (4) CEM III. The use of specific cements or cement blends can clearly inhibit the formation of thaumasite (and/or ettringite). The influence of the aggregate type (quartz versus LWA) on the sulphate reaction is more difficult to determine because the porosity of LWA can accommodate the growing sulphate crystals. All the mortar prisms made with quartz aggregate were bent or broken after 21 to 24 weeks exposure to the sulphate solution, while most mortar prisms made with expanded clay aggregate were still intact. The only exception being the mortar prisms containing limestone filler. The latter disintegrated between 24 and 34 weeks of exposure to the sulphate solution. The expansion of the prisms made with CEM I and CEM I + fly ash levelled off between 50 and 100 weeks of exposure to the sulphate solution. The prisms made with CEM III showed minimal expansion (≤ 0.1 %) after 3 years of exposure. The prisms exposed to demineralised water showed no or minimal expansion. The presence and mineralogy of secondary sulphate phases in the mortars was checked by XRD analysis and SEM-EDS analysis of (degraded) mortar prisms. In most cases a solid solution of ettringite-thaumasite was observed. Based on the composition, treatment and expansion of the different mortar prisms, key factors controlling the formation of thaumasite or a solid solution of thaumasite-ettringite are discussed. [less ▲]

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See detailDurability of mortar and concretes containing slag with low hydraulic activity
Hadj Sadok, Ahmed; Kenaï, Saïd; Courard, Luc ULg et al

in Cement & Concrete Composites (2012), 34(5), 671677

Granulated blast furnace slag has been widely used as a partial substitute for Portland cement in many applications because of advantages which include cost reduction, reduction in heat evolution and ... [more ▼]

Granulated blast furnace slag has been widely used as a partial substitute for Portland cement in many applications because of advantages which include cost reduction, reduction in heat evolution and improvement of durability properties. However, the effectiveness of slag depends on its hydraulic reactivity. In this paper, the results of an experimental study on the effect of slag with low hydraulicity on the mechanical and durability properties of concrete and the performance of mortar under sulfate attack are discussed. Special attention is given to gas permeability and water absorption of slag concrete. The durability of slag concrete is improved at long term at low Water/Binder ratio. Sulfate resistance of mortar is improved by slag replacement up to 30%. [less ▲]

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See detailMechanical and durability properties of concrete using contaminated recycled aggregates
Debieb, Farid; Kenaï, Saïd; Courard, Luc ULg et al

in Cement & Concrete Composites (2010), 32(6), 421-426

The degradation of concrete structures due to chlorides and sulphates penetration is of obvious importance in civil engineering as having major impact on structural durability. In this paper, the results ... [more ▼]

The degradation of concrete structures due to chlorides and sulphates penetration is of obvious importance in civil engineering as having major impact on structural durability. In this paper, the results of an investigation on the effect of contaminated crushed concrete aggregates on mechanical properties and durability of recycled concrete are presented. Natural aggregates concrete (NC) slabs were cured in water, sea water, chloride solutions or sulphate solutions and then crushed to obtain virgin and contaminated (polluted) recycled aggregates. The properties of natural (NA) and recycled aggregates (RA) and the mechanical properties and durability performances of a new concrete made from 100% of RA are analysed. The results show that contaminated RA are much sensitive to chlorides than sulphates and are rapidly leached when soaked into water. Significant differences were observed between the properties of original and new concrete and the results clearly show the necessity of taking these contaminations into account. [less ▲]

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