Mechanical behaviour of coarse, lightweight, recycled and natural aggregates for concrete

Pepe, Marco; Grabois, Thiago Melo; Silva, Marco Antonio; Tavares, Luís Marcelo; Filho, Romildo Dias Tolêdo

doi:10.1680/jcoma.17.00081

Cited by 20 publications

(12 citation statements)

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“…Analyzing the maximum stress theoretically for a spherical particle, the authors [20] proposed estimating the tensile strength (r t ) using Eq. 1, considering only the breakage force (F b ) and the distance between the points of application of the compressive loads (D):…”

Section: Measurement Of Strength Of Single Particlesmentioning

confidence: 99%

“…PLT has the advantage of using universal testing machines, that are commonly found in civil engineering laboratories. Tests were used to qualify particles of many rock types (gneiss, granites, quartzite, diorite, basalt, limestone, marble) for geotechnical applications [15][16][17], railway ballast [18,19], or coarse aggregates used in concrete [20]. Tensile strengths of the rock particles (from 4 to 30 mm of size) are significantly variable, varying from about 3 to 9 times even for a material with the same mineralogical origin.…”

Section: Introductionmentioning

confidence: 99%

“…Blunt cylindrical indenters or large parallel platens have been used for estimating the tensile strength of regular-shaped (spheres [16,17], cubes and prisms [15]) as well as irregularly-shaped particles [18][19][20].The types of fracture for regularlyshaped particles were similar to those expected using the point load test method. While testing irregularlyshaped particles has the benefit of convenience, it is responsible for generating large scatter in the data [7,20], since optimal loading conditions cannot be ensured. On the other hand, testing particles shaped into spheres or other regular geometries has the benefit of full control of loading conditions but at the expense of large effort in sample preparation.…”

Section: Introductionmentioning

confidence: 99%

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Improved method to measure the strength and elastic modulus of single aggregate particles

et al. 2019

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The standard methods used to determine the mechanical properties of single aggregate particles have shortcomings. Indeed, methods that are commonly used to measure the strength of irregular particles do not provide their elastic modulus and are also only semi-quantitative. The aim of this work is to determine more accurately both the tensile strength and the elastic modulus of single coarse aggregate particles using the point load test fitted with tungsten carbide semi-spheres and coupled with a linear transducer. In the experiment, the poles of the particles are made flat and parallel at the points of contact with the semi-spheres of the apparatus, allowing to estimate the elastic modulus of aggregates in accordance to Hertz contact theory. Glass particles of different shapes (spheres, cubes, and prisms) were used as reference material to validate the experimental method and establish the optimal conditions to conduct the test. These conditions consisted of a deformation rate of 0.2 mm/min, a blunt 4.0-mm diameter cylinder piston for spherical particles, while two 14.0-mm diameter semi-spheres in the case of rectangular particles (cubes/prisms). It is also hereby proposed to measure the tensile strength of irregularly-shaped particles by a modified version of Hiramatsu and Oka's formula using the equivalent core diameter. The proposed method was then applied to measure the strength and modulus of coarse granite aggregate particles (25.0 to 9.5 mm). It demonstrated that the variability of the elastic modulus and tensile strengths of the individual aggregate particles was quite significant, confirming the importance of using the proposed improved method to qualify materials for structural (high strength) concrete, or to simulate/predict the mechanical behavior of concrete. Keywords Aggregates Á Single particle Á Elastic modulus Á Hertz contact theory Á Tensile strength Á Point load test This article was published with an erroneous name of one of the authors and therefore has been corrected.

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Section: Measurement Of Strength Of Single Particlesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improved method to measure the strength and elastic modulus of single aggregate particles

et al. 2019

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“…Guidelines for RAC are needed since RAs are different from coarse natural aggregates (NAs), changing the properties of concrete. The main differences between NAs and RAs are the following: NAs are composed of particles of a single type of stone (limestone, granite and basalt are the most common), while RAs are composed of a mix of several constituents (concrete, mortar, unbound stone, ceramics, glass, and other deleterious contaminants) of different quality and properties [ 6 , 7 ]; This implies that, in general, RAs are weaker, more deformable, more porous and have larger water absorption than NAs [ 8 , 9 ]; At the same time, the mechanical and durability properties of concrete are detrimentally affected by the incorporation of RAs: for the same compressive strength, RAC is typically found to have a smaller Young’s modulus, larger creep and shrinkage and worse durability properties [ 9 , 10 , 11 ]. Fracture energy and tensile strength are also detrimentally affected, especially when the strength class of concrete is larger [ 12 , 13 ]; Regarding the structural behaviour of reinforced concrete, the use of RAs is found to result in larger short- and long-term deflections [ 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

“…This implies that, in general, RAs are weaker, more deformable, more porous and have larger water absorption than NAs [ 8 , 9 ];…”

Section: Introductionmentioning

confidence: 99%

Eurocode Shear Design of Coarse Recycled Aggregate Concrete: Reliability Analysis and Partial Factor Calibration

et al. 2021

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This paper contributes to the definition of design clauses for coarse recycled aggregate concrete. One of the main reasons for scepticism towards recycled aggregate concrete is the perceived notion that the heterogeneity of recycled aggregates may increase the uncertainty of the behaviour of concrete. Therefore, the paper uses structural reliability concepts to propose partial factors for recycled aggregate concrete’s design for shear failure. The paper builds upon a previous publication by the authors, in which the model uncertainty of recycled aggregate concrete elements designed for shear, with and without shear reinforcement, was compared with that of natural aggregate concrete elements. In that paper, the statistics of the model uncertainty for recycled aggregate concrete shear design were indeed found to be less favourable than those of natural aggregate concrete. Therefore, a partial factor for recycled aggregate concrete design is needed to ensure safety. This paper presents partial factors calibrated with explicit reliability analyses for different cases of design concerning beams (in the case of shear design of elements with shear reinforcement) and slabs (for the design of elements without shear reinforcement). For full incorporation of coarse recycled concrete aggregates and the design of elements without shear reinforcement, the calibrated partial factor reduces the design value of shear resistance by 10% (design with EN1992) or 15% (design with prEN1992) in comparison to natural aggregate concrete’s design. For the shear design of elements with shear reinforcement, the partial factor decreases resistance by 5% but a sensitivity analysis showed that the reduction might be, under pessimistic expectations, of up to 20%.

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Reliability‐based recommendations for EN1992 carbonation cover design of concrete with coarse recycled concrete aggregates

Albuquerque

Pacheco

Brito

2022

Structural Concrete

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Research argues in favor of using recycled aggregates in structural concrete.However, lack of specific clauses in standards for recycled aggregate concrete design hinders the use of recycled aggregate concrete by the industry. Recycled aggregate concrete-specific design clauses are hindered because conventional research must be complemented with experiments directed towards stochastic modeling, so that reliability concepts may evaluate whether the probabilities of failure of design comply with the expectations of Society or whether specific design rules are needed. This article compares the within-batch variability of carbonation under accelerated conditions of four natural aggregate concrete and four analogue recycled aggregate concrete mixes and analyses the reliability of Eurocode 2 cover design for carbonation exposure. In general, the incorporation of coarse recycled concrete aggregates worsened the mean durability behavior of concrete, including resistance to carbonation. However, the variability of carbonation depth was not meaningfully affected by the recycled aggregates used (coarse recycled aggregates produced from concrete waste) and the reliability of concrete cover design only decreased due to the effect of the recycled aggregates on the mean resistance to carbonation. A 5 mm increase of concrete cover was found to more than offset the detrimental influence of full incorporation of recycled aggregates on the reliability of concrete cover design.

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Mechanical behaviour of coarse, lightweight, recycled and natural aggregates for concrete

Cited by 20 publications

References 48 publications

Improved method to measure the strength and elastic modulus of single aggregate particles

Improved method to measure the strength and elastic modulus of single aggregate particles

Eurocode Shear Design of Coarse Recycled Aggregate Concrete: Reliability Analysis and Partial Factor Calibration

Reliability‐based recommendations for EN1992 carbonation cover design of concrete with coarse recycled concrete aggregates

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