Pierre Matar | Lebanese University (original) (raw)
Papers by Pierre Matar
Journal of Building Engineering
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Journal of Building Physics
The present research investigates the feasibility of manufacturing masonry mortars with recycled ... more The present research investigates the feasibility of manufacturing masonry mortars with recycled sand. The primary aim is to study the effect of fine recycled aggregates on fresh and hardened states with properties. Two series of mortars were designed by substituting natural sand with recycled sand, with variable sand replacement ratios ranging from 0% to 100%. One series, named variable workability series, has variable workability with constant water to cement ratio ( W/C), while the other series, called constant workability series, has a constant workability with variable W/C. The density, air content, and slump of mortars in fresh state were measured with a special attention devoted to the effect of pre-saturation of recycled sand on the slump. In the hardened state, the microstructure was studied by means of water accessible porosity test and mercury intrusion porosimetry test. Flexural and compressive strength as well as the dynamic modulus of elasticity were also examined and ...
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Construction and Building Materials
The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on wor... more The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on workability of self-consolidating concrete (SCC) are not quantified in literature. Different SCC series containing 25% to 100% RCA and 0.25% to 1.75% PPF are investigated in this study; the water-to-binder ratio varied from 0.38 to 0.5, while high-range water reducer adjusted to maintain slump flow at 700 ± 25 mm. Flowability, cohesiveness, passing ability, and segregation resistance were evaluated and compared with the limitations specified by the European Guidelines for SCC. Test results have shown that SCC rheological properties and passing ability dramatically curtailed with PPF inclusions, especially when mixtures are proportioned with higher RCA replacement rates. This was attributed to combined effects of fiber additions that hinder the cement matrix deformation together with increased RCA surface roughness that accentuates internal friction and resistance to flow. Mixtures containing increased RCA and PPF concentrations exhibited better stability, reflected by reduced aggregate segregation. Series of regression models were proposed to predict the coupled effects of RCA and PPF additions on SCC workability responses.
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Journal of Building Engineering
The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA)... more The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) was demonstrated in structural civil engineering applications. Yet, limited information exists regarding the effect of RCA additions, especially in presence of steel reinforcement, on lateral pressure exerted on formworks. This paper reports experimental data obtained from twenty-one SCC mixtures cast in 200 × 400 × 1600-mm formwork containing up to 4.71% vertical steel (the spacing between transverse steel was set to 450 mm). Test results have shown that mixtures incorporating RCA exhibited reduced initial pressure, which was mostly attributed to higher aggregate surface roughness that increases internal friction. The decrease in pressure was accentuated with the increase in vertical steel density, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. Special emphasis was placed to develop conservative reinforcement indices for appropriate prediction of SCC pressure, as well as propose modifications for existing models to account for the effect of RCA additions and presence of vertical steel bars.
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Materials and Structures
The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) conside... more The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) considerably increased in sustainable structural applications and civil engineering works. However, current literature and construction practices are not clear regarding the influence of RCA additions and presence of steel reinforcement on formwork pressure exerted by the plastic concrete. This paper reports experimental data obtained from 32 SCC mixtures possessing different stability levels and cast in 1.6-m high formwork containing various combinations of vertical and transverse steel bars. Test results have shown that mixtures incorporating recycled aggregates exhibited reduced initial maximum pressure, given the higher RCA surface roughness that promotes internal friction and material build-up at rest. The decrease in pressure was particularly accentuated in presence of steel bars, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. The transverse steel was around 1.5-times more influential than vertical steel in reducing the formwork pressure. The rates of pressure drop over time were not altered because of steel, implying that pressure decay is governed by the concrete intrinsic properties such as thixotropy, RCA friction, and cement hydration. Special emphasis was placed to develop regression models and examine suitability of existing ones to predict lateral pressure of RCA-modified SCC cast in formworks containing reinforcing bars.
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Bulletin of Tver State Technical University, Series: Civil Engineering, Electrical Engineering and Chemical Technology - Вестник Тверского государственного технического университета, Серия «Строительство. Электротехника и химические технологии», 2020
This paper presents an overview of research activities carried out by the authors and aiming to i... more This paper presents an overview of research activities carried out by the authors and aiming to investigate the possibility of using recycled concrete aggregates in the production of concrete mixes. It evaluates the effect of these aggregates on the physical, mechanical and durability properties of concrete, as well as the applications of the recycled aggregate concretes.
Статья представляет собой обзор исследовательской деятельности, проведенной авторами для изучения возможности использования заполнителей из рециклированного бетонного лома при производстве бетонных смесей. Исследуется влияние этих заполнителей на физические, механические свойства и долговечность бетона, а также области применения бетонов с утилизированными заполнителями.
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Journal Paper, 2019
The present research investigates the feasibility of manufacturing masonry mortars with recycled ... more The present research investigates the feasibility of manufacturing masonry mortars with recycled sand. The primary aim is to study the effect of fine recycled aggregates on fresh and hardened states with properties. Two series of mortars were designed by substituting natural sand with recycled sand, with variable sand replacement ratios ranging from 0% to I 00%. One series, named variable workability series, has variable workability with constant water to cement ratio (W/g, while the other series, called constant workability series, has a constant workability with variable W/C. The density, air content, and slump of mortars in fresh state were measured with a special attention devoted to the effect of pre-saturation of recycled sand on the slump. In the hardened state, the microstructure was studied by means of water accessible porosity test and mercury intrusion porosimetry test. Flexural and compressive strength as well as the dynamic modulus of elasticity were also examined and the correlations between these properties and the microstructure have been established. It was found that the properties of mortars with recycled sand are lower than those obtained for the natural sand mortar (- 20% for variable workability series and 45% for constant workability series at the age of 28 days). For the series with variable workability, mechanical properties decrease to a step starting from 30% replacement ratio, while linearly decrease for the mortars with constant workability. The difference between the two series lies in the difference in total porosities and the pore size distribution.
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Journal Paper, 2019
The viability of using polypropylene fibers (PPF) in concrete was largely studied. Yet, few of th... more The viability of using polypropylene fibers (PPF) in concrete was largely studied. Yet, few of the existing research studies investigated the effects of PPF on the properties of concrete containing recycled concrete aggregate (RCA). Mixes with different RCA replacement ratios and different PPF content were designed and tested. The test results showed that the addition of PPF did not change significantly the compressive strength and the density of the concrete, but slightly decreased its modulus of elasticity and Poisson's ratio. The drop in the splitting tensile strength and the flexural strength due to RCA inclusions was to a large extent compensated by the PPF addition. The water absorption decreased and the percent voids increased with increased PPF addition. Correlations between the RCA content, the PPF content and the properties of concrete were studied. Useful regression models were proposed to predict the properties of concrete in relevant ranges of RCA and PPF content.
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Journal Paper, 2019
The use of recycled concrete aggregate (RCA) in structural applications considerably increased. T... more The use of recycled concrete aggregate (RCA) in structural applications considerably increased. The main objective of this paper is to assess the effect of parent concrete (PC) quality on RCA properties including concrete durability and bond to steel reinforcement. Four RCA types are considered; three were sourced from 13, 42, and 62-MPa compressive strength (f ' c) normal-density PC, while the fourth type was derived from lightweight PC. Test results showed that the PC quality has direct influence on the transfer of stresses and ultimate bond strengths to embedded rebars. The incorporation of styrene-butadiene rubber (SBR) latexes was found efficient to mitigate the drop in concrete mechanical properties including f ' c , splitting tensile strength, electrical resistivity, and ultimate bond strength to embedded steel. The experimental data are compared to the design bond strengths specified in international codes such as ACI 318-17, European Code EC-2, and fib Model Code MC2010.
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Journal Paper, 2019
The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on wor... more The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on workability of self-consolidating concrete (SCC) are not quantified in literature. Different SCC series containing 25% to 100% RCA and 0.25% to 1.75% PPF are investigated in this study; the water-to-binder ratio varied from 0.38 to 0.5, while high-range water reducer adjusted to maintain slump flow at 700 ± 25 mm. Flowability, cohesiveness, passing ability, and segregation resistance were evaluated and compared with the limitations specified by the European Guidelines for SCC. Test results have shown that SCC rheological properties and passing ability dramatically curtailed with PPF inclusions, especially when mixtures are proportioned with higher RCA replacement rates. This was attributed to combined effects of fiber additions that hinder the cement matrix deformation together with increased RCA surface roughness that accentuates internal friction and resistance to flow. Mixtures containing increased RCA and PPF concentrations exhibited better stability, reflected by reduced aggregate segregation. Series of regression models were proposed to predict the coupled effects of RCA and PPF additions on SCC workability responses.
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Journal Paper, 2018
The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) conside... more The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) considerably increased in sustainable structural applications and civil engineering works. However, current literature and construction practices are not clear regarding the influence of RCA additions and presence of steel reinforcement on formwork pressure exerted by the plastic concrete. This paper reports experimental data obtained from 32 SCC mixtures possessing different stability levels and cast in 1.6-m high formwork containing various combinations of vertical and transverse steel bars. Test results have shown that mixtures incorporating recycled aggregates exhibited reduced initial maximum pressure, given the higher RCA surface roughness that promotes internal friction and material build-up at rest. The decrease in pressure was particularly accentuated in presence of steel bars, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. The transverse steel was around 1.5-times more influential than vertical steel in reducing the formwork pressure. The rates of pressure drop over time were not altered because of steel, implying that pressure decay is governed by the concrete intrinsic properties such as thixotropy, RCA friction, and cement hydration. Special emphasis was placed to develop regression models and examine suitability of existing ones to predict lateral pressure of RCA-modified SCC cast in formworks containing reinforcing bars.
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Paper Journal, 2017
The behaviour of concrete structures is affected by the time-dependent volume changes of concrete... more The behaviour of concrete structures is affected by the time-dependent volume changes of concrete caused by sustained loads and moisture loss. Creep deformations have an important effect on long-term integrity of reinforced concrete structures. Incorrect or inaccurate prediction of these volume changes leads to undesirable and harmful consequences for the structures. Knowing that the Eurocode 2 does not take admixtures and additives into consideration in predicting creep deformations, the aim of this study is to apply correction coefficients to the Eurocode 2 creep formulas to take into account the effect of additives and admixtures, especially silica fume and water reducer. A large database from international laboratories and research centres is used in this study. The first step consists of comparing experimental measurements of creep deformations with creep values predicted by the Eurocode 2 formulas. The second step lies in introducing correction coefficients to the creep formulas of Eurocode 2, taking into consideration the percentage of admixtures and additives. These new correction coefficients are introduced in the Eurocode 2 formulas using an approximate Bayesian computation method based on a rejection algorithm.
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Journal Paper, 2017
The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA)... more The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) was demonstrated in structural civil engineering applications. Yet, limited information exists regarding the effect of RCA additions, especially in presence of steel reinforcement, on lateral pressure exerted on formworks. This paper reports experimental data obtained from twenty-one SCC mixtures cast in 200 × 400 × 1600-mm formwork containing up to 4.71% vertical steel (the spacing between transverse steel was set to 450 mm). Test results have shown that mixtures incorporating RCA exhibited reduced initial pressure, which was mostly attributed to higher aggregate surface roughness that increases internal friction. The decrease in pressure was accentuated with the increase in vertical steel density, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. Special emphasis was placed to develop conservative reinforcement indices for appropriate prediction of SCC pressure, as well as propose modifications for existing models to account for the effect of RCA additions and presence of vertical steel bars.
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Journal Paper, 2017
The deformation due to creep has an important effect on the behavior of concrete structures espec... more The deformation due to creep has an important effect on the behavior of concrete structures especially for their long term integrity. Undesirable consequences may appear in the structures due to incorrect or inaccurate prediction of creep deformation. A large database coming from international laboratories and research centers is used in order to compare the experimental results with the Eurocode 2 creep prediction. This study shows that the Eurocode 2 underestimates the important creep compliance and overestimates the small creep compliance. In order to overcome this inaccuracy, new correction coefficients are introduced to the formulas of the Eurocode 2 using an Approximate Bayesian Computation method based on the rejection algorithm.
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Journal Paper, 2016
Concrete structures debris is the main type of construction and demolition (C&D) waste resulting ... more Concrete structures debris is the main type of construction and demolition (C&D) waste resulting from old buildings and structures. Recycled aggregate obtained from crushing concrete waste can be reused as aggregate in producing concrete mixes. Another valuable C&D waste is the glass which can be also recycled and used as aggregate in concrete.
This research aimed at studying the effect of recycled aggregates and glass on the properties of concrete wall hollow blocks. Tests have been carried out on four groups of blocks containing Portland cement, recycled aggregate, recycled glass and superplasticizer, and one group of blocks not containing recycled materials. The properties of concrete mixes and blocks have been tested.
Keywords: concrete wall blocks, recycling, aggregate, glass, properties.
Лом бетонных конструкций является основным видом отходов строительства и сноса ветхих зданий и сооружений. Рециклированный заполнитель, получаемый в результате дробления бетонного лома, может быть повторно использован в качестве заполнителя при производстве бетонной смеси. Еще одним из ценных отходов строительства и сноса является стекло, которое также может быть рециклировано и использовано в качестве заполнителя в бетоне. Целью настоящей работы явилось изучение влияния рециклированных заполнителей и стекла на характеристики пустотелых стеновых бетонных блоков. Испытания проводились на четырех группах бетонных блоков, содержащих портландцемент, рециклированный заполнитель, рециклированное стекло и суперпластификатор, а также одной группе блоков, не содержащих рециклированные материалы. Были исследованы свойства бетонных смесей и блоков, получаемых на их основе.
Ключевые слова: стеновые бетонные блоки, рециклинг, заполнитель, стекло, свойства.
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Journal Paper, Oct 2010
This paper examines the possibility of the design of reinforced concrete slabs with steel shaped ... more This paper examines the possibility of the design of reinforced concrete slabs with steel shaped flooring as reinforced concrete structures with combined reinforcement (sheet and flexible). In order to assess the degree of compatibility between the smooth shaped flooring and the reinforced concrete slab, two specimens of slabs were tested: slabs with rebars and steel shaped flooring, and slabs with only rebars. The results of experimental and theoretical studies are mentioned, a comparative analysis of the results is carried out, and recommendations for the design of reinforced concrete slabs are given.
Keywords: reinforced concrete slabs, steel shaped flooring, deformability, strength.
Рассмотрен вопрос о возможности расчета железобетонных плит co стальным профилированным настилом как железобетонных конструкций с комбинированным армированием (листовая и гибкая арматура). C целью оценки степени совместности работы гладкого профнастила с железобетонной плитой, были проведены испытания двух серий плит: плит с гибкой арматурой и стальным профилированным настилом и плит только с гибкой арматурой. Приведены результаты экспериментальных и теоретических исследований плит, выполнен cопоставительный анализ полученных результатов и даны рекомендации по расчету железобетонных плит co стальным профнастилом.
Ключевые слова: железобетонная плита, стальной профилированный настил, деформативность, прочность.
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Journal Paper, Dec 2015
The main purpose of this research is to study the prestress losses in unbonded post-tensioned con... more The main purpose of this research is to study the prestress losses in unbonded post-tensioned concrete structures and to establish the possibility of using calculation formulae given by applicable local and foreign building codes to determine the losses in such structures.
A comparative analysis of standard documents and a comparison of prestress losses calculated by using these standard documents with obtained test results is obviously the most simple way to select the reference where the algorithm is covered most fully, authentically and in easily manner for designers.
To achieve the research objective, an experimental study of unbonded post-tensioned concrete specimens was carried out.
Keywords: post-tensioned concrete structures, unbonded prestressing steel, prestress losses, building codes.
Основной целью данной работы является изучение потерь предварительного напряжения арматуры в конструкциях, не имеющих связи арматуры с бетоном, и установление возможности применения расчетных зависимостей существующих на сегодняшний день отечественных и зарубежных строительных норм для определения потерь в таких конструкциях.
Сравнительный анализ нормативных документов и сопоставление значений потерь, полученных на их основе с достоверными опытными данными – это очевидно наиболее простой путь выбора источника, в котором алгоритм освещен наиболее полно, достоверно и доступно для рядового проектировщика.
Для решения поставленных задач было проведено экспериментальное исследование преднапряженных элементов, не имеющих сцепления арматуры с бетоном.
Ключевые слова: постнапряженные железобетонные конструкции, преднапряженная арматура без сцепления с бетоном, потери предварительного напряжения, строительные нормы.
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Journal Paper, Sep 2012
L’idée de recycler les bétons est apparue dans le but principal de préserver l’environnement et d... more L’idée de recycler les bétons est apparue dans le but principal de préserver l’environnement et de s’intégrer ainsi au concept de développement durable. En effet, la réutilisation des bétons en tant que granulats dans des nouvelles compositions de béton permet de réduire les dépenses sur la gestion des déchets de démolition et, surtout, de protéger les gisements et les montagnes contre l’ouverture de nouvelles carrières. Les granulats provenant du recyclage de bétons peuvent remplacer une partie de granulats naturels lors de la fabrication de nouveaux mélanges de béton. Les taux de substitution des granulats naturels dans cette recherche sont 10, 20 et 30 %.
Le but de cette recherche est d’étudier expérimentalement l’influence des granulats recyclés sur les propriétés du béton telles que sa résistance à la compression, son ouvrabilité et sa porosité, ainsi que sa durabilité.
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Journal Paper, May 2012
Among the construction waste that could be recycled, we can mention the aggregates resulting from... more Among the construction waste that could be recycled, we can mention the aggregates resulting from crushed concrete. While the acquired knowledge about the use of recycled aggregates in new concrete mixes is fairly large, the use of such aggregates in the production of concrete blocks is very limited. This research aims to study the influence of the use of recycled aggregates in precast concrete hollow blocks on their compressive strength. Tests were carried out to determine the rate of recycled aggregates content to be used in the manufacture of concrete blocks in order to obtain blocks having suitable compressive strength. Tests were executed on several series of blocks whose composition includes recycled aggregates and on one series of reference blocks whose composition consisting exclusively of natural aggregates. Tests results have provided the maximum percentage of recycled aggregates that can be included in new concrete block mixes without affecting blocks compressive strength. Tests have shown that the use of recycled aggregates in concrete blocks could give a compressive strength similar to that of blocks manufactured without any recycled aggregates. It has been shown also that using recycled aggregates in the manufacture of concrete blocks without any natural aggregates is not economical at all because of the need to add a relatively high quantity of cement necessary to obtain the required compressive strength.
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Journal Paper, 2011
The idea of recycling concrete of demolished buildings aims at preserving the environment. Indeed... more The idea of recycling concrete of demolished buildings aims at preserving the environment. Indeed, the reuse of concrete as aggregate in new concrete mixes helped to reduce the expenses related to construction and demolition (C&D) waste management and, especially, to protect the environment by reducing the development rate of new quarries. This paper presents the results of an experimental study conducted on masonry blocks containing aggregates resulting from concrete recycling. The purpose of this study is to investigate the effect of recycled aggregates on compressive strength of concrete blocks.
Tests were performed on series of concrete blocks: five series each made of different proportions of recycled aggregates, and one series of reference blocks exclusively composed of natural aggregates.
Tests showed that using recycled aggregates with addition of cement allows the production of concrete blocks with compressive strengths comparable to those obtained on concrete blocks made exclusively of natural aggregates.
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Journal of Building Engineering
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Journal of Building Physics
The present research investigates the feasibility of manufacturing masonry mortars with recycled ... more The present research investigates the feasibility of manufacturing masonry mortars with recycled sand. The primary aim is to study the effect of fine recycled aggregates on fresh and hardened states with properties. Two series of mortars were designed by substituting natural sand with recycled sand, with variable sand replacement ratios ranging from 0% to 100%. One series, named variable workability series, has variable workability with constant water to cement ratio ( W/C), while the other series, called constant workability series, has a constant workability with variable W/C. The density, air content, and slump of mortars in fresh state were measured with a special attention devoted to the effect of pre-saturation of recycled sand on the slump. In the hardened state, the microstructure was studied by means of water accessible porosity test and mercury intrusion porosimetry test. Flexural and compressive strength as well as the dynamic modulus of elasticity were also examined and ...
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Construction and Building Materials
The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on wor... more The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on workability of self-consolidating concrete (SCC) are not quantified in literature. Different SCC series containing 25% to 100% RCA and 0.25% to 1.75% PPF are investigated in this study; the water-to-binder ratio varied from 0.38 to 0.5, while high-range water reducer adjusted to maintain slump flow at 700 ± 25 mm. Flowability, cohesiveness, passing ability, and segregation resistance were evaluated and compared with the limitations specified by the European Guidelines for SCC. Test results have shown that SCC rheological properties and passing ability dramatically curtailed with PPF inclusions, especially when mixtures are proportioned with higher RCA replacement rates. This was attributed to combined effects of fiber additions that hinder the cement matrix deformation together with increased RCA surface roughness that accentuates internal friction and resistance to flow. Mixtures containing increased RCA and PPF concentrations exhibited better stability, reflected by reduced aggregate segregation. Series of regression models were proposed to predict the coupled effects of RCA and PPF additions on SCC workability responses.
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Journal of Building Engineering
The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA)... more The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) was demonstrated in structural civil engineering applications. Yet, limited information exists regarding the effect of RCA additions, especially in presence of steel reinforcement, on lateral pressure exerted on formworks. This paper reports experimental data obtained from twenty-one SCC mixtures cast in 200 × 400 × 1600-mm formwork containing up to 4.71% vertical steel (the spacing between transverse steel was set to 450 mm). Test results have shown that mixtures incorporating RCA exhibited reduced initial pressure, which was mostly attributed to higher aggregate surface roughness that increases internal friction. The decrease in pressure was accentuated with the increase in vertical steel density, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. Special emphasis was placed to develop conservative reinforcement indices for appropriate prediction of SCC pressure, as well as propose modifications for existing models to account for the effect of RCA additions and presence of vertical steel bars.
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Materials and Structures
The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) conside... more The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) considerably increased in sustainable structural applications and civil engineering works. However, current literature and construction practices are not clear regarding the influence of RCA additions and presence of steel reinforcement on formwork pressure exerted by the plastic concrete. This paper reports experimental data obtained from 32 SCC mixtures possessing different stability levels and cast in 1.6-m high formwork containing various combinations of vertical and transverse steel bars. Test results have shown that mixtures incorporating recycled aggregates exhibited reduced initial maximum pressure, given the higher RCA surface roughness that promotes internal friction and material build-up at rest. The decrease in pressure was particularly accentuated in presence of steel bars, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. The transverse steel was around 1.5-times more influential than vertical steel in reducing the formwork pressure. The rates of pressure drop over time were not altered because of steel, implying that pressure decay is governed by the concrete intrinsic properties such as thixotropy, RCA friction, and cement hydration. Special emphasis was placed to develop regression models and examine suitability of existing ones to predict lateral pressure of RCA-modified SCC cast in formworks containing reinforcing bars.
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Bulletin of Tver State Technical University, Series: Civil Engineering, Electrical Engineering and Chemical Technology - Вестник Тверского государственного технического университета, Серия «Строительство. Электротехника и химические технологии», 2020
This paper presents an overview of research activities carried out by the authors and aiming to i... more This paper presents an overview of research activities carried out by the authors and aiming to investigate the possibility of using recycled concrete aggregates in the production of concrete mixes. It evaluates the effect of these aggregates on the physical, mechanical and durability properties of concrete, as well as the applications of the recycled aggregate concretes.
Статья представляет собой обзор исследовательской деятельности, проведенной авторами для изучения возможности использования заполнителей из рециклированного бетонного лома при производстве бетонных смесей. Исследуется влияние этих заполнителей на физические, механические свойства и долговечность бетона, а также области применения бетонов с утилизированными заполнителями.
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Journal Paper, 2019
The present research investigates the feasibility of manufacturing masonry mortars with recycled ... more The present research investigates the feasibility of manufacturing masonry mortars with recycled sand. The primary aim is to study the effect of fine recycled aggregates on fresh and hardened states with properties. Two series of mortars were designed by substituting natural sand with recycled sand, with variable sand replacement ratios ranging from 0% to I 00%. One series, named variable workability series, has variable workability with constant water to cement ratio (W/g, while the other series, called constant workability series, has a constant workability with variable W/C. The density, air content, and slump of mortars in fresh state were measured with a special attention devoted to the effect of pre-saturation of recycled sand on the slump. In the hardened state, the microstructure was studied by means of water accessible porosity test and mercury intrusion porosimetry test. Flexural and compressive strength as well as the dynamic modulus of elasticity were also examined and the correlations between these properties and the microstructure have been established. It was found that the properties of mortars with recycled sand are lower than those obtained for the natural sand mortar (- 20% for variable workability series and 45% for constant workability series at the age of 28 days). For the series with variable workability, mechanical properties decrease to a step starting from 30% replacement ratio, while linearly decrease for the mortars with constant workability. The difference between the two series lies in the difference in total porosities and the pore size distribution.
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Journal Paper, 2019
The viability of using polypropylene fibers (PPF) in concrete was largely studied. Yet, few of th... more The viability of using polypropylene fibers (PPF) in concrete was largely studied. Yet, few of the existing research studies investigated the effects of PPF on the properties of concrete containing recycled concrete aggregate (RCA). Mixes with different RCA replacement ratios and different PPF content were designed and tested. The test results showed that the addition of PPF did not change significantly the compressive strength and the density of the concrete, but slightly decreased its modulus of elasticity and Poisson's ratio. The drop in the splitting tensile strength and the flexural strength due to RCA inclusions was to a large extent compensated by the PPF addition. The water absorption decreased and the percent voids increased with increased PPF addition. Correlations between the RCA content, the PPF content and the properties of concrete were studied. Useful regression models were proposed to predict the properties of concrete in relevant ranges of RCA and PPF content.
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Journal Paper, 2019
The use of recycled concrete aggregate (RCA) in structural applications considerably increased. T... more The use of recycled concrete aggregate (RCA) in structural applications considerably increased. The main objective of this paper is to assess the effect of parent concrete (PC) quality on RCA properties including concrete durability and bond to steel reinforcement. Four RCA types are considered; three were sourced from 13, 42, and 62-MPa compressive strength (f ' c) normal-density PC, while the fourth type was derived from lightweight PC. Test results showed that the PC quality has direct influence on the transfer of stresses and ultimate bond strengths to embedded rebars. The incorporation of styrene-butadiene rubber (SBR) latexes was found efficient to mitigate the drop in concrete mechanical properties including f ' c , splitting tensile strength, electrical resistivity, and ultimate bond strength to embedded steel. The experimental data are compared to the design bond strengths specified in international codes such as ACI 318-17, European Code EC-2, and fib Model Code MC2010.
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Journal Paper, 2019
The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on wor... more The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on workability of self-consolidating concrete (SCC) are not quantified in literature. Different SCC series containing 25% to 100% RCA and 0.25% to 1.75% PPF are investigated in this study; the water-to-binder ratio varied from 0.38 to 0.5, while high-range water reducer adjusted to maintain slump flow at 700 ± 25 mm. Flowability, cohesiveness, passing ability, and segregation resistance were evaluated and compared with the limitations specified by the European Guidelines for SCC. Test results have shown that SCC rheological properties and passing ability dramatically curtailed with PPF inclusions, especially when mixtures are proportioned with higher RCA replacement rates. This was attributed to combined effects of fiber additions that hinder the cement matrix deformation together with increased RCA surface roughness that accentuates internal friction and resistance to flow. Mixtures containing increased RCA and PPF concentrations exhibited better stability, reflected by reduced aggregate segregation. Series of regression models were proposed to predict the coupled effects of RCA and PPF additions on SCC workability responses.
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Journal Paper, 2018
The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) conside... more The use of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) considerably increased in sustainable structural applications and civil engineering works. However, current literature and construction practices are not clear regarding the influence of RCA additions and presence of steel reinforcement on formwork pressure exerted by the plastic concrete. This paper reports experimental data obtained from 32 SCC mixtures possessing different stability levels and cast in 1.6-m high formwork containing various combinations of vertical and transverse steel bars. Test results have shown that mixtures incorporating recycled aggregates exhibited reduced initial maximum pressure, given the higher RCA surface roughness that promotes internal friction and material build-up at rest. The decrease in pressure was particularly accentuated in presence of steel bars, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. The transverse steel was around 1.5-times more influential than vertical steel in reducing the formwork pressure. The rates of pressure drop over time were not altered because of steel, implying that pressure decay is governed by the concrete intrinsic properties such as thixotropy, RCA friction, and cement hydration. Special emphasis was placed to develop regression models and examine suitability of existing ones to predict lateral pressure of RCA-modified SCC cast in formworks containing reinforcing bars.
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Paper Journal, 2017
The behaviour of concrete structures is affected by the time-dependent volume changes of concrete... more The behaviour of concrete structures is affected by the time-dependent volume changes of concrete caused by sustained loads and moisture loss. Creep deformations have an important effect on long-term integrity of reinforced concrete structures. Incorrect or inaccurate prediction of these volume changes leads to undesirable and harmful consequences for the structures. Knowing that the Eurocode 2 does not take admixtures and additives into consideration in predicting creep deformations, the aim of this study is to apply correction coefficients to the Eurocode 2 creep formulas to take into account the effect of additives and admixtures, especially silica fume and water reducer. A large database from international laboratories and research centres is used in this study. The first step consists of comparing experimental measurements of creep deformations with creep values predicted by the Eurocode 2 formulas. The second step lies in introducing correction coefficients to the creep formulas of Eurocode 2, taking into consideration the percentage of admixtures and additives. These new correction coefficients are introduced in the Eurocode 2 formulas using an approximate Bayesian computation method based on a rejection algorithm.
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Journal Paper, 2017
The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA)... more The feasibility of self-consolidating concrete (SCC) containing recycled concrete aggregate (RCA) was demonstrated in structural civil engineering applications. Yet, limited information exists regarding the effect of RCA additions, especially in presence of steel reinforcement, on lateral pressure exerted on formworks. This paper reports experimental data obtained from twenty-one SCC mixtures cast in 200 × 400 × 1600-mm formwork containing up to 4.71% vertical steel (the spacing between transverse steel was set to 450 mm). Test results have shown that mixtures incorporating RCA exhibited reduced initial pressure, which was mostly attributed to higher aggregate surface roughness that increases internal friction. The decrease in pressure was accentuated with the increase in vertical steel density, suggesting that the reinforcement cage confines the plastic concrete and carries part of its load. Special emphasis was placed to develop conservative reinforcement indices for appropriate prediction of SCC pressure, as well as propose modifications for existing models to account for the effect of RCA additions and presence of vertical steel bars.
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Journal Paper, 2017
The deformation due to creep has an important effect on the behavior of concrete structures espec... more The deformation due to creep has an important effect on the behavior of concrete structures especially for their long term integrity. Undesirable consequences may appear in the structures due to incorrect or inaccurate prediction of creep deformation. A large database coming from international laboratories and research centers is used in order to compare the experimental results with the Eurocode 2 creep prediction. This study shows that the Eurocode 2 underestimates the important creep compliance and overestimates the small creep compliance. In order to overcome this inaccuracy, new correction coefficients are introduced to the formulas of the Eurocode 2 using an Approximate Bayesian Computation method based on the rejection algorithm.
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Journal Paper, 2016
Concrete structures debris is the main type of construction and demolition (C&D) waste resulting ... more Concrete structures debris is the main type of construction and demolition (C&D) waste resulting from old buildings and structures. Recycled aggregate obtained from crushing concrete waste can be reused as aggregate in producing concrete mixes. Another valuable C&D waste is the glass which can be also recycled and used as aggregate in concrete.
This research aimed at studying the effect of recycled aggregates and glass on the properties of concrete wall hollow blocks. Tests have been carried out on four groups of blocks containing Portland cement, recycled aggregate, recycled glass and superplasticizer, and one group of blocks not containing recycled materials. The properties of concrete mixes and blocks have been tested.
Keywords: concrete wall blocks, recycling, aggregate, glass, properties.
Лом бетонных конструкций является основным видом отходов строительства и сноса ветхих зданий и сооружений. Рециклированный заполнитель, получаемый в результате дробления бетонного лома, может быть повторно использован в качестве заполнителя при производстве бетонной смеси. Еще одним из ценных отходов строительства и сноса является стекло, которое также может быть рециклировано и использовано в качестве заполнителя в бетоне. Целью настоящей работы явилось изучение влияния рециклированных заполнителей и стекла на характеристики пустотелых стеновых бетонных блоков. Испытания проводились на четырех группах бетонных блоков, содержащих портландцемент, рециклированный заполнитель, рециклированное стекло и суперпластификатор, а также одной группе блоков, не содержащих рециклированные материалы. Были исследованы свойства бетонных смесей и блоков, получаемых на их основе.
Ключевые слова: стеновые бетонные блоки, рециклинг, заполнитель, стекло, свойства.
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Journal Paper, Oct 2010
This paper examines the possibility of the design of reinforced concrete slabs with steel shaped ... more This paper examines the possibility of the design of reinforced concrete slabs with steel shaped flooring as reinforced concrete structures with combined reinforcement (sheet and flexible). In order to assess the degree of compatibility between the smooth shaped flooring and the reinforced concrete slab, two specimens of slabs were tested: slabs with rebars and steel shaped flooring, and slabs with only rebars. The results of experimental and theoretical studies are mentioned, a comparative analysis of the results is carried out, and recommendations for the design of reinforced concrete slabs are given.
Keywords: reinforced concrete slabs, steel shaped flooring, deformability, strength.
Рассмотрен вопрос о возможности расчета железобетонных плит co стальным профилированным настилом как железобетонных конструкций с комбинированным армированием (листовая и гибкая арматура). C целью оценки степени совместности работы гладкого профнастила с железобетонной плитой, были проведены испытания двух серий плит: плит с гибкой арматурой и стальным профилированным настилом и плит только с гибкой арматурой. Приведены результаты экспериментальных и теоретических исследований плит, выполнен cопоставительный анализ полученных результатов и даны рекомендации по расчету железобетонных плит co стальным профнастилом.
Ключевые слова: железобетонная плита, стальной профилированный настил, деформативность, прочность.
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Journal Paper, Dec 2015
The main purpose of this research is to study the prestress losses in unbonded post-tensioned con... more The main purpose of this research is to study the prestress losses in unbonded post-tensioned concrete structures and to establish the possibility of using calculation formulae given by applicable local and foreign building codes to determine the losses in such structures.
A comparative analysis of standard documents and a comparison of prestress losses calculated by using these standard documents with obtained test results is obviously the most simple way to select the reference where the algorithm is covered most fully, authentically and in easily manner for designers.
To achieve the research objective, an experimental study of unbonded post-tensioned concrete specimens was carried out.
Keywords: post-tensioned concrete structures, unbonded prestressing steel, prestress losses, building codes.
Основной целью данной работы является изучение потерь предварительного напряжения арматуры в конструкциях, не имеющих связи арматуры с бетоном, и установление возможности применения расчетных зависимостей существующих на сегодняшний день отечественных и зарубежных строительных норм для определения потерь в таких конструкциях.
Сравнительный анализ нормативных документов и сопоставление значений потерь, полученных на их основе с достоверными опытными данными – это очевидно наиболее простой путь выбора источника, в котором алгоритм освещен наиболее полно, достоверно и доступно для рядового проектировщика.
Для решения поставленных задач было проведено экспериментальное исследование преднапряженных элементов, не имеющих сцепления арматуры с бетоном.
Ключевые слова: постнапряженные железобетонные конструкции, преднапряженная арматура без сцепления с бетоном, потери предварительного напряжения, строительные нормы.
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Journal Paper, Sep 2012
L’idée de recycler les bétons est apparue dans le but principal de préserver l’environnement et d... more L’idée de recycler les bétons est apparue dans le but principal de préserver l’environnement et de s’intégrer ainsi au concept de développement durable. En effet, la réutilisation des bétons en tant que granulats dans des nouvelles compositions de béton permet de réduire les dépenses sur la gestion des déchets de démolition et, surtout, de protéger les gisements et les montagnes contre l’ouverture de nouvelles carrières. Les granulats provenant du recyclage de bétons peuvent remplacer une partie de granulats naturels lors de la fabrication de nouveaux mélanges de béton. Les taux de substitution des granulats naturels dans cette recherche sont 10, 20 et 30 %.
Le but de cette recherche est d’étudier expérimentalement l’influence des granulats recyclés sur les propriétés du béton telles que sa résistance à la compression, son ouvrabilité et sa porosité, ainsi que sa durabilité.
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Journal Paper, May 2012
Among the construction waste that could be recycled, we can mention the aggregates resulting from... more Among the construction waste that could be recycled, we can mention the aggregates resulting from crushed concrete. While the acquired knowledge about the use of recycled aggregates in new concrete mixes is fairly large, the use of such aggregates in the production of concrete blocks is very limited. This research aims to study the influence of the use of recycled aggregates in precast concrete hollow blocks on their compressive strength. Tests were carried out to determine the rate of recycled aggregates content to be used in the manufacture of concrete blocks in order to obtain blocks having suitable compressive strength. Tests were executed on several series of blocks whose composition includes recycled aggregates and on one series of reference blocks whose composition consisting exclusively of natural aggregates. Tests results have provided the maximum percentage of recycled aggregates that can be included in new concrete block mixes without affecting blocks compressive strength. Tests have shown that the use of recycled aggregates in concrete blocks could give a compressive strength similar to that of blocks manufactured without any recycled aggregates. It has been shown also that using recycled aggregates in the manufacture of concrete blocks without any natural aggregates is not economical at all because of the need to add a relatively high quantity of cement necessary to obtain the required compressive strength.
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Journal Paper, 2011
The idea of recycling concrete of demolished buildings aims at preserving the environment. Indeed... more The idea of recycling concrete of demolished buildings aims at preserving the environment. Indeed, the reuse of concrete as aggregate in new concrete mixes helped to reduce the expenses related to construction and demolition (C&D) waste management and, especially, to protect the environment by reducing the development rate of new quarries. This paper presents the results of an experimental study conducted on masonry blocks containing aggregates resulting from concrete recycling. The purpose of this study is to investigate the effect of recycled aggregates on compressive strength of concrete blocks.
Tests were performed on series of concrete blocks: five series each made of different proportions of recycled aggregates, and one series of reference blocks exclusively composed of natural aggregates.
Tests showed that using recycled aggregates with addition of cement allows the production of concrete blocks with compressive strengths comparable to those obtained on concrete blocks made exclusively of natural aggregates.
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Conference Paper, 2017
Since the predicted creep compliance according to the Eurocode 2 does not take the effect of admi... more Since the predicted creep compliance according to the Eurocode 2 does not take the effect of admixtures into consideration, a study of the influence of admixtures on creep is performed. Based on a large database established from international laboratories and research centers, a comparison between the experimental creep and the creep predicted by the Eurocode 2 is performed using statistical methods. An in-accurate estimation is detected based on the type of the admixture used. The use of a combination of water reducer and silica fume as admixtures leads to an underestimation of the creep compliance.
In order to overcome this difference, a calibration is required by adding corrective coefficients to the Eurocode 2 equations, taking into consideration the type and percentage of admixtures. The Approximate Bayesian Computation method based on the rejection algorithm is applied in order to calculate the corrective coefficients.
After implementing the corrective coefficients in the Eurocode 2 compliance formula, and in order to evaluate our updated Eurocode 2 creep model, statistical methods are used. An improvement in the results is clearly shown. Using the large experimental database, the present study demonstrates the importance of the Bayesian model assessment for the updating of the Eurocode 2 creep model, taking into account the effect of admixtures. The adoption of such a design approach would improve long-term serviceability of structures subject to creep.
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Conference Paper, Dec 2008
Concrete recycling constitutes one of the most recent research domains in material engineering an... more Concrete recycling constitutes one of the most recent research domains in material engineering and environment sciences. It consists of crushing and screening the concrete provided by demolishing the old constructions, and of using the resulted small pieces as aggregates in new concrete compositions.
Our previous researches have demonstrated that recycled aggregates diminish the strength of concrete due to the addition of water. The present communication treats of the effects of plasticizers on recycled concrete. The principal aim is to recapitulate the original strength by increasing the concrete workability without adding water.
Keywords: recycled concrete, aggregates, strength, workability
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Conference Paper, 2007
Some countries started to recycle concrete material in order to reuse it in structural or other i... more Some countries started to recycle concrete material in order to reuse it in structural or other issues. Some of them, like Germany, Australia and Canada have established their own recommendation guide for recycling concrete. This recycling consists of crushing old concrete into aggregates, and then processing it into new mixture using the recycled aggregates with specified sizes. The aim of this recycling is to save nature from deforestation and dryness, by reducing the need to gravel and so the quarries work, and also to economize the waste management.
The present research work consists of an experimental study treating the impact of using recycled aggregates on the concrete behavior and on the country’s economy. We are especially interested in determining the best composition for the new mixture of concrete resulting from reusing different types of recycled aggregates. Different types of tests have been done depending on the aggregates sizes, their origin and their state (burned or safe). The analysis is based on the comparison between compressive strength, water-cement ratio, slump, porosity and durability. Otherwise, the impact on economy is analyzed, a priori, by studying the effect of reducing the price of the resulting concrete on construction spending. The resulted recommendations indicate the sizes of aggregates which may constitute the best composition for recycling and processing concrete, and the best use for each type of concrete depending on behavior and economy effect.
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