Mechanical strength and durability properties of concrete containing treated recycled concrete aggregates under different curing conditions

Ismail, Shariman Ismadi; Kwan, Wai Hoe; Ramli, Mahyuddin

doi:10.1016/j.conbuildmat.2017.08.076

Cited by 94 publications

(33 citation statements)

References 37 publications

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“…In general, the factors determining the mechanical performance of concrete are the strength of the cement matrix, the strength of aggregates, and the strength of interface between the aggregate and the cement matrix and the stress acting on the interface of cement matrix/aggregates. This is a particularly weak area of concrete, which consists of pores around the hydrates and aggregate, and is characterized by a discontinuous porous area between the aggregate and cement paste [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Effect of Surface Modifications of Recycled Concrete Aggregate on Concrete Properties

Junak

Sičáková

2017

Buildings

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The experiment aims to test the specific way of producing concrete with recycled concrete aggregate (RCA). To reduce its negative impact on the concrete properties, two different ways of treatment of the RCA with geopolymer slurry were applied-coating during the mixing using the specific mixing approach and coating prior to the mixing of concrete. As control samples, a mixture prepared by natural aggregate only and a mixture with RCA that was prepared by standard mixing with no coating process were tested as well. The results of density, total water absorption, and compressive strength in periods of 28, 90, 180, and 365 days of curing are presented and evaluated. Both methods of coating of the RCA with geopolymer slurry allow for the preparation of concrete with properties comparable to those of normal concrete (prepared by standard mixing with natural aggregate); thus, it seems to be a promising way to enhance the rate of RCA application. The positive effect of coating is clearly visible after a longer period of curing (180 days). When comparing the methods of RCA coating, coating directly during the mixing yields somewhat better results; it is also positive from the technological point of view, since the process is simpler in practice.

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Section: Introductionmentioning

confidence: 99%

Effect of Surface Modifications of Recycled Concrete Aggregate on Concrete Properties

Junak

Sičáková

2017

Buildings

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“…Microhardness testing around recycled aggregates at 28 days revealed that the Vickers microhardness is found to be 30% larger around natural aggregates than around the old mortar from recycled aggregates [42]. These observations were further corroborated by scanning electron microscopic studies, showing that the ITZs around old mortar appeared to be more porous than around natural aggregates [11,12,43].…”

Section: Materials Phase Propertiesmentioning

confidence: 95%

“…Notably, the ITZs might be improved if recycled aggregates are saturated [12], if a two-stage mixing approach is applied [11], or if the aggregate surface is treated chemically [43]. The observed ITZ porosity increase around old mortar or old cement paste originates most likely from water migration mechanisms or from a localized release of carbon dioxide from the carbonated old cement paste [9].…”

Section: Materials Phase Propertiesmentioning

confidence: 99%

Micromechanical Multiscale Modeling of ITZ-Driven Failure of Recycled Concrete: Effects of Composition and Maturity on the Material Strength

Königsberger

Staquet

2018

Applied Sciences

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Recycled concrete, i.e., concrete which contains aggregates that are obtained from crushing waste concrete, typically exhibits a smaller strength than conventional concretes. We herein decipher the origin and quantify the extent of the strength reduction by means of multiscale micromechanics-based modeling. Therefore, the microstructure of recycled concrete is represented across four observation scales, spanning from the micrometer-sized scale of cement hydration products to the centimeter-sized scale of concrete. Recycled aggregates are divided into three classes with distinct morphological features: plain aggregates which are clean of old cement paste, mortar aggregates, and aggregates covered by old cement paste. Macroscopic loading is concentrated via interfacial transition zones (ITZs)-which occur mutually between aggregates, old, and new cement paste-to the micrometer-sized hydrates resolved at the smallest observation scale. Hydrate failure within the most unfavorably loaded ITZ is considered to trigger concrete failure. Modeling results show that failure in either of the ITZs might be critical, and that the failure mode is governed by the mutual stiffness contrast between aggregates, old, and new paste, which depend, in turn, on the concrete composition and on the material's maturity. The model predicts that the strength difference between recycled concrete and conventional concrete is less pronounced (i) at an early age compared to mature ages, (ii) when the old cement paste content is small, and (iii) when recycling a high-quality parent concrete.

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“…Fiber distributed in the matrix creates a bridging effect, thereby delaying crack propagation, enhancing the toughness of concrete, and maintaining the ability to carry a load after the first crack appears [9]. In the case of concrete or mortar, the increasing proportion of recycled aggregate will increase the brittleness of concrete or mortar, leading to deteriorated mechanical properties [6], [10]. Previous studies demonstrated that the inclusion of monofiber, that is, steel [11], polypropylene (PP) [12], nylon (NY) [13], and natural fiber [14], can enhance the mechanical properties, restrain the progression of cracks, and convert it into a ductile material, thereby increasing energy absorption.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties and microstructure of recycled mortar reinforced with hybrid fiber

Ismail

Hamid

Yaacob³

et al. 2018

IJET

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This study investigated the hybrid effects of two types of microfiber, namely, polypropylene and nylon, on the mechanical properties of high-strength mortar, which produced fine recycled aggregate (FRA). The amount of microfibers was maintained at a volumetric fraction of 0.6%. The microstructure and mechanical strength properties (compressive strength and flexural strength) of recycled mortar reinforced with hybrid-size microfibers were evaluated at various curing ages. Experimental results show that the inclusion of hybrid fibers significantly influenced the mechanical performance of the recycled mortar. The hybridization fiber at volume fraction 0.3% polypropylene + 0.3% nylon yielded the most promising mechanical performance. Enhancements of 8% on compressive and 11% flexural strength were achieved at 28 days. Scanning electron microscopy observations revealed that reinforcement at the microscale prohibited the initiation and growth of cracks at the micro level. High loads were required to form macrocracks within composites, thereby improving the mechanical strength of the mortar matrix.

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Mechanical strength and durability properties of concrete containing treated recycled concrete aggregates under different curing conditions

Cited by 94 publications

References 37 publications

Effect of Surface Modifications of Recycled Concrete Aggregate on Concrete Properties

Effect of Surface Modifications of Recycled Concrete Aggregate on Concrete Properties

Micromechanical Multiscale Modeling of ITZ-Driven Failure of Recycled Concrete: Effects of Composition and Maturity on the Material Strength

Mechanical properties and microstructure of recycled mortar reinforced with hybrid fiber

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