Francisco Agrela | Universidad de Córdoba (original) (raw)

Papers by Francisco Agrela

Research paper thumbnail of Design of lightweight concrete with olive biomass bottom ash for use in buildings

Journal of Building Engineering

Research paper thumbnail of Mechanical performance of roller compacted concrete with recycled concrete aggregates

Road Materials and Pavement Design, 2016

Because the recycling of construction and demolition waste (CDW) has been deemed to be a priority... more Because the recycling of construction and demolition waste (CDW) has been deemed to be a priority, the use of a recycled aggregate has been widely demonstrated as a sustainable contribution among different materials applied in civil projects. Roller compacted concrete (RCC) applications offer technical, economic and ecological solutions in many civil construction projects. To the best of the authors' knowledge, there has been little research on the use of RCC with a coarse recycled aggregate that does not originate from pavement. This research evaluates the use of recycled concrete aggregates (RCA) from a CDW recycling plant in RCC mixtures. Four series of RCC mixtures were produced with different cement contents (110, 175, 250 and 350 kg/m 3). Each series consisted of three mixtures with different RCA incorporation ratios (0%, 50% and 100%) of natural coarse aggregates, thus producing 12 RCC mixtures to evaluate the effect on the compaction, the mechanical and physical properties while highlighting a new laboratory casting method for flexural strength and drying shrinkage tests. Based on the obtained results, the use of coarse RCA in RCC production is feasible at a replacement level of 100% when using these materials in road pavement bases.

Research paper thumbnail of Geotechnical and Engineering Properties of Expansive Clayey Soil Stabilised with Biomass Ash and Nanomaterials for its Application in Structural Road Layers

Research paper thumbnail of Design of a New Eco-Hybrid Cement for Concrete Pavement, Made with Processed Mixed Recycled Aggregates and Olive Biomass Bottom Ash as Supplementary Cement Materials

Research paper thumbnail of Specialized concrete made of processed biomass ash: lightweight, self-compacting, and geopolymeric concrete

The Structural Integrity of Recycled Aggregate Concrete Produced with Fillers and Pozzolans, 2022

Research paper thumbnail of Comparison of Leaching Methods to Assess the Release of Pollutants from Waste

Research paper thumbnail of Residual biomasses as aggregates applied in cement-based materials

Waste and Byproducts in Cement-Based Materials, 2021

Research paper thumbnail of New Teaching Method Applied to the Subject of Concrete in Civil Engineering Degrees

Research paper thumbnail of Propiedades técnicas y medioambientales de los Áridos Reciclados Mixtos según su clasificación

Se conoce como arido reciclado mixto, al subproducto obtenido del reciclaje de residuos de constr... more Se conoce como arido reciclado mixto, al subproducto obtenido del reciclaje de residuos de construccion y demolicion (RCD) mezclados, es decir, con diversos residuos en composicion procedentes de edificaciones, obras civiles, hormigones, etc. Este tipo de arido reciclado se presenta principalmente restos de mamposteria, con un alto porcentaje de particulas ceramicas y un mayor grado de impurezas que otros aridos reciclados. Sin embargo, este tipo de arido reciclado es el mas producido en la geografia espanola por lo que un estudio mas exhaustivo sobre la viabilidad de utilizacion de este material se hace necesario.El objetivo principal del presente trabajo es valorar a traves de una comparacion exhaustiva los aridos reciclados mixtos con alto grado de tratamiento (ARM-I), con los aridos reciclados que comunmente son desechados ya que son RCD cribados (ARM-III) o con poco tratamiento (ARM-II), y de esta manera, poder aumentar la tasa de reciclaje. Para lograr este objetivo, se analiz...

Research paper thumbnail of Feasible use of recycled alumina combined with recycled aggregates in road construction

Construction and Building Materials, 2019

h i g h l i g h t s A laboratory study of materials based on the addition of Aluminum Waste are p... more h i g h l i g h t s A laboratory study of materials based on the addition of Aluminum Waste are presented. RCA and MRA with AW mixtures could be used in unbound road layers. Using AW and RCA and MRA mixtures in construction is a good recycling alternative.

Research paper thumbnail of Properties of Recycled Concrete Manufacturing with All-in Recycled Aggregates and Processed Biomass Bottom Ash

Waste and Biomass Valorization, 2017

NS) and improving the mechanical properties in concretes with low quantities of cement. It is pos... more NS) and improving the mechanical properties in concretes with low quantities of cement. It is possible to improve the properties of the BBA via mechanical processes (like screening or flotation) to reduce the organic matter content and there by obtain processed BBA (Pr-BBA). This study provides interesting data on the mechanical and durability properties of the concretes manufactured with 30% aiRCA and aiRMA, and also by applying different replacement rates (0, 15, and 30%) of NA by BBA and Pr-BBA. The mechanical and durability properties were analysed over different time durations in different mixtures. It was demonstrated that it is possible to apply these recycled materials in non-structural concrete mixtures by limiting the replacement rate. The application of BBA and Pr-BBA reduced the properties of the concrete. However, this reduction was less significant with the use of Pr-BBA.

Research paper thumbnail of Effect of stainless steel slag waste as a replacement for cement in mortars. Mechanical and statistical study

Construction and Building Materials, 2017

h i g h l i g h t s Different treatments of stainless steel slag waste (SW) were performed to imp... more h i g h l i g h t s Different treatments of stainless steel slag waste (SW) were performed to improve it. Chemical properties of SW showed a positive cementitious capacity. SW processed showed an increase in mechanical strength results. SW processed through simple treatments can be used as a substitute for cement.

Research paper thumbnail of Feasible Use of Biomass Bottom Ash as Addition in the Manufacture of Lightweight Recycled Concrete

Waste and Biomass Valorization, 2016

Biomass is a renewable energy source that is increasingly being used worldwide. However, because ... more Biomass is a renewable energy source that is increasingly being used worldwide. However, because of recent increases in production, waste products from biomass combustion are becoming a relevant environmental and economic problem. Other wastes from the construction and demolition sectors have been extensively studied. For this, several research studies have been performed to study the mechanical and some durability properties in concrete manufacturing with recycled concrete and mixed aggregates from different construction origins. In previous works, the lower density of recycled mixed aggregates (RMA) and biomass bottom ash (BBA) with respect to natural aggregates was studied. This feature can be exploited for the production of construction elements that require the use of low-density materials, such as lightweight concrete. For this, the aim of this work was to study the influence of the use of recycled mixed aggregates and biomass bottom ash, as replacements for the natural aggregates, on the mechanical behaviour, durability properties and environmental risk of recycled lightweight concrete. Several replacements for natural aggregates through recycled aggregates and biomass bottom ash were applied in the manufacture of lightweight concretes. To study the concrete behaviour, properties such as density, absorption, compressive strength, flexural strength, UPV, water penetration and drying shrinkage were measured. Due to the incorporation of RMA and BBA, a decrease of the density and mechanical properties of the recycled concrete manufactured was obtained with respect to the control mix. Therefore, the results showed the possibility of applying these types of recycled materials in lightweight concretes for their application in specific constructive elements. Through this study the possibility of reuse of waste and industrial by-products (RMA and BBA) that have so far been accumulated mainly in landfill is demonstrated. The positives results show the possibility of manufacture of lightweight concrete with these by-products, achieving a material with a lower density and mechanical requirements that comply with the current standards for concrete.

Research paper thumbnail of Reduction of Leaching Impacts by Applying Biomass Bottom Ash and Recycled Mixed Aggregates in Structural Layers of Roads

Materials, 2016

This research is focused on analyzing the environmental pollution potential of biomass bottom ash... more This research is focused on analyzing the environmental pollution potential of biomass bottom ashes as individual materials, as mixtures manufactured with biomass bottom ashes and granular construction aggregates, and these mixtures treated with cement. For the environmental assessment of all of the samples and materials mentioned, the following leaching procedures have been performed: the compliance batch test of UNE-EN 12457-3:2003 for aggregates and bottom ashes; the column test according to NEN 7343:1994 for the mixtures prepared in the laboratory; and the tank test by EA NEN 7375:2004 for analyzing the behavior of mixtures after their solidification/stabilization with 5% cement. After the discussion of the data, the reduction of the pollution load of the most hazardous biomass bottom ashes after their combination with different aggregates can be confirmed, which implies their possible application in civil infrastructures, such as filler embankments and road construction layers, without negatively impacting the environment. In addition, the positive effect of the stabilization/solidification of the cement-treated mixtures with a reduction of the heavy metals that were released at the highest levels, namely As, Hg Cr, Ni, Cu, Se and Mo, was proven.

Research paper thumbnail of Mechanical performance of bedding mortars made with olive biomass bottom ash

Construction and Building Materials, 2016

h i g h l i g h t s The use of biomass bottom ash (BBA) significantly increased the porosity of m... more h i g h l i g h t s The use of biomass bottom ash (BBA) significantly increased the porosity of mortars. The incorporation of BBA led to the decline of mechanical properties. Mortars with CEM-II were more susceptible to incorporation of BBA than those with CEM-I. Bedding mortars with BBA can be made according to technical specifications, namely type M and N.

Research paper thumbnail of Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

Materials, 2016

This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in ups... more This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors' knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

Research paper thumbnail of Properties of Non-Structural Concrete Made with Mixed Recycled Aggregates and Low Cement Content

Materials, 2016

In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could b... more In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could be a suitable raw material for concrete manufacturing. The aims of this research were as follows: (i) to analyze the effect of the replacement ratio of natural coarse aggregates with MRA, the amount of ceramic particles in MRA, and the amount of cement, on the mechanical and physical properties of a non-structural concrete made with a low cement content; and (ii) to verify if it is possible to achieve a low-strength concrete that replaces a greater amount of natural aggregate with MRA and that has a low cement content. Two series of concrete mixes were manufactured using 180 and 200 kg/m 3 of CEM II/A-V 42.5 R type Portland cement. Each series included seven concrete mixes: one with natural aggregates; two MRA with different ceramic particle contents; and one for each coarse aggregate replacement ratio (20%, 40%, and 100%). To study their properties, compressive and splitting tensile strength, modulus of elasticity, density, porosity, water penetration, and sorptivity, tests were performed. The results confirmed that the main factors affecting the properties analyzed in this research are the amount of cement and the replacement ratio; the two MRAs used in this work presented a similar influence on the properties. A non-structural, low-strength concrete (15 MPa) with an MRA replacement ratio of up to 100% for 200 kg/m 3 of cement was obtained. This type of concrete could be applied in the construction of ditches, sidewalks, and other similar civil works.

Research paper thumbnail of Improvement of Bearing Capacity in Recycled Aggregates Suitable for Use as Unbound Road Sub-Base

Materials, 2015

Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates w... more Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and mixed recycled aggregates were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties. The formation of new cement hydrated particles was observed, and pozzolanic reactions were discovered by electronon microscopy in these novel materials. The properties of recycled concrete aggregates and mixed recycled aggregates suggest that these recycled materials can be used in unbound road layers to improve their mechanical behaviour in the long term.

Research paper thumbnail of Feasible use of biomass bottom ash in the manufacture of cement treated recycled materials

Materials and Structures, 2015

A focus on environmental sustainability during the last decade has led to greater use of recycled... more A focus on environmental sustainability during the last decade has led to greater use of recycled aggregates to reduce the exploitation of existing reserves. In addition, environmentally consciousness has led to an increased use of renewable energy. Biomass is an important source of energy, and it also leads to high generation of waste products from biomass combustion. Previous studies have investigated the use of recycled aggregates from construction and demolition in road bases and sub-bases with positive results. This paper aims to study the feasibility of incorporating biomass bottom ash produced in the combustion process mixed with natural aggregates and recycled aggregates for use in civil engineering. The analysis of the mechanical properties was positive, showing the ability to use biomass bottom ash mixed with natural or recycled aggregates in specified ratios. Valuing biomass bottom ash can reduce waste generation and may lead to economic and environmental benefits.

Research paper thumbnail of Comparisons of natural and recycled aggregate concretes prepared with the addition of different mineral admixtures

Cement and Concrete Composites, 2011

This paper presents the results of a laboratory study on the performance of natural and recycled ... more This paper presents the results of a laboratory study on the performance of natural and recycled aggregate concrete prepared with the incorporation of different mineral admixtures including silica fumes (SF), metakaolin (MK), fly ash (FA) and Ground granulated blast slag (GGBS). The compressive and splitting tensile strength, drying shrinkage, chloride ion penetration and ultrasonic pulse velocity (UPV) of the concrete mixtures were determined. The test results, in general, showed that the incorporation of mineral admixtures improved the properties of the recycled aggregate concretes. SF and MK contributed to both the short and long-term properties of the concrete, whereas FA and GGBS showed their beneficial effect only after a relatively long curing time. As far as the compressive strength is concerned, the replacement of cement by 10% of SF or 15% of MK improved both mechanical and durability performance, while the replacement of cement by 35% FA or 55% GGBS decreased the compressive strength, but improved the durability properties of the recycled aggregate concretes. Moreover, the results show that the contributions of the mineral admixtures to performance improvement of the recycled aggregate concrete are higher than that to the natural aggregate concrete.

Research paper thumbnail of Design of lightweight concrete with olive biomass bottom ash for use in buildings

Journal of Building Engineering

Research paper thumbnail of Mechanical performance of roller compacted concrete with recycled concrete aggregates

Road Materials and Pavement Design, 2016

Because the recycling of construction and demolition waste (CDW) has been deemed to be a priority... more Because the recycling of construction and demolition waste (CDW) has been deemed to be a priority, the use of a recycled aggregate has been widely demonstrated as a sustainable contribution among different materials applied in civil projects. Roller compacted concrete (RCC) applications offer technical, economic and ecological solutions in many civil construction projects. To the best of the authors' knowledge, there has been little research on the use of RCC with a coarse recycled aggregate that does not originate from pavement. This research evaluates the use of recycled concrete aggregates (RCA) from a CDW recycling plant in RCC mixtures. Four series of RCC mixtures were produced with different cement contents (110, 175, 250 and 350 kg/m 3). Each series consisted of three mixtures with different RCA incorporation ratios (0%, 50% and 100%) of natural coarse aggregates, thus producing 12 RCC mixtures to evaluate the effect on the compaction, the mechanical and physical properties while highlighting a new laboratory casting method for flexural strength and drying shrinkage tests. Based on the obtained results, the use of coarse RCA in RCC production is feasible at a replacement level of 100% when using these materials in road pavement bases.

Research paper thumbnail of Geotechnical and Engineering Properties of Expansive Clayey Soil Stabilised with Biomass Ash and Nanomaterials for its Application in Structural Road Layers

Research paper thumbnail of Design of a New Eco-Hybrid Cement for Concrete Pavement, Made with Processed Mixed Recycled Aggregates and Olive Biomass Bottom Ash as Supplementary Cement Materials

Research paper thumbnail of Specialized concrete made of processed biomass ash: lightweight, self-compacting, and geopolymeric concrete

The Structural Integrity of Recycled Aggregate Concrete Produced with Fillers and Pozzolans, 2022

Research paper thumbnail of Comparison of Leaching Methods to Assess the Release of Pollutants from Waste

Research paper thumbnail of Residual biomasses as aggregates applied in cement-based materials

Waste and Byproducts in Cement-Based Materials, 2021

Research paper thumbnail of New Teaching Method Applied to the Subject of Concrete in Civil Engineering Degrees

Research paper thumbnail of Propiedades técnicas y medioambientales de los Áridos Reciclados Mixtos según su clasificación

Se conoce como arido reciclado mixto, al subproducto obtenido del reciclaje de residuos de constr... more Se conoce como arido reciclado mixto, al subproducto obtenido del reciclaje de residuos de construccion y demolicion (RCD) mezclados, es decir, con diversos residuos en composicion procedentes de edificaciones, obras civiles, hormigones, etc. Este tipo de arido reciclado se presenta principalmente restos de mamposteria, con un alto porcentaje de particulas ceramicas y un mayor grado de impurezas que otros aridos reciclados. Sin embargo, este tipo de arido reciclado es el mas producido en la geografia espanola por lo que un estudio mas exhaustivo sobre la viabilidad de utilizacion de este material se hace necesario.El objetivo principal del presente trabajo es valorar a traves de una comparacion exhaustiva los aridos reciclados mixtos con alto grado de tratamiento (ARM-I), con los aridos reciclados que comunmente son desechados ya que son RCD cribados (ARM-III) o con poco tratamiento (ARM-II), y de esta manera, poder aumentar la tasa de reciclaje. Para lograr este objetivo, se analiz...

Research paper thumbnail of Feasible use of recycled alumina combined with recycled aggregates in road construction

Construction and Building Materials, 2019

h i g h l i g h t s A laboratory study of materials based on the addition of Aluminum Waste are p... more h i g h l i g h t s A laboratory study of materials based on the addition of Aluminum Waste are presented. RCA and MRA with AW mixtures could be used in unbound road layers. Using AW and RCA and MRA mixtures in construction is a good recycling alternative.

Research paper thumbnail of Properties of Recycled Concrete Manufacturing with All-in Recycled Aggregates and Processed Biomass Bottom Ash

Waste and Biomass Valorization, 2017

NS) and improving the mechanical properties in concretes with low quantities of cement. It is pos... more NS) and improving the mechanical properties in concretes with low quantities of cement. It is possible to improve the properties of the BBA via mechanical processes (like screening or flotation) to reduce the organic matter content and there by obtain processed BBA (Pr-BBA). This study provides interesting data on the mechanical and durability properties of the concretes manufactured with 30% aiRCA and aiRMA, and also by applying different replacement rates (0, 15, and 30%) of NA by BBA and Pr-BBA. The mechanical and durability properties were analysed over different time durations in different mixtures. It was demonstrated that it is possible to apply these recycled materials in non-structural concrete mixtures by limiting the replacement rate. The application of BBA and Pr-BBA reduced the properties of the concrete. However, this reduction was less significant with the use of Pr-BBA.

Research paper thumbnail of Effect of stainless steel slag waste as a replacement for cement in mortars. Mechanical and statistical study

Construction and Building Materials, 2017

h i g h l i g h t s Different treatments of stainless steel slag waste (SW) were performed to imp... more h i g h l i g h t s Different treatments of stainless steel slag waste (SW) were performed to improve it. Chemical properties of SW showed a positive cementitious capacity. SW processed showed an increase in mechanical strength results. SW processed through simple treatments can be used as a substitute for cement.

Research paper thumbnail of Feasible Use of Biomass Bottom Ash as Addition in the Manufacture of Lightweight Recycled Concrete

Waste and Biomass Valorization, 2016

Biomass is a renewable energy source that is increasingly being used worldwide. However, because ... more Biomass is a renewable energy source that is increasingly being used worldwide. However, because of recent increases in production, waste products from biomass combustion are becoming a relevant environmental and economic problem. Other wastes from the construction and demolition sectors have been extensively studied. For this, several research studies have been performed to study the mechanical and some durability properties in concrete manufacturing with recycled concrete and mixed aggregates from different construction origins. In previous works, the lower density of recycled mixed aggregates (RMA) and biomass bottom ash (BBA) with respect to natural aggregates was studied. This feature can be exploited for the production of construction elements that require the use of low-density materials, such as lightweight concrete. For this, the aim of this work was to study the influence of the use of recycled mixed aggregates and biomass bottom ash, as replacements for the natural aggregates, on the mechanical behaviour, durability properties and environmental risk of recycled lightweight concrete. Several replacements for natural aggregates through recycled aggregates and biomass bottom ash were applied in the manufacture of lightweight concretes. To study the concrete behaviour, properties such as density, absorption, compressive strength, flexural strength, UPV, water penetration and drying shrinkage were measured. Due to the incorporation of RMA and BBA, a decrease of the density and mechanical properties of the recycled concrete manufactured was obtained with respect to the control mix. Therefore, the results showed the possibility of applying these types of recycled materials in lightweight concretes for their application in specific constructive elements. Through this study the possibility of reuse of waste and industrial by-products (RMA and BBA) that have so far been accumulated mainly in landfill is demonstrated. The positives results show the possibility of manufacture of lightweight concrete with these by-products, achieving a material with a lower density and mechanical requirements that comply with the current standards for concrete.

Research paper thumbnail of Reduction of Leaching Impacts by Applying Biomass Bottom Ash and Recycled Mixed Aggregates in Structural Layers of Roads

Materials, 2016

This research is focused on analyzing the environmental pollution potential of biomass bottom ash... more This research is focused on analyzing the environmental pollution potential of biomass bottom ashes as individual materials, as mixtures manufactured with biomass bottom ashes and granular construction aggregates, and these mixtures treated with cement. For the environmental assessment of all of the samples and materials mentioned, the following leaching procedures have been performed: the compliance batch test of UNE-EN 12457-3:2003 for aggregates and bottom ashes; the column test according to NEN 7343:1994 for the mixtures prepared in the laboratory; and the tank test by EA NEN 7375:2004 for analyzing the behavior of mixtures after their solidification/stabilization with 5% cement. After the discussion of the data, the reduction of the pollution load of the most hazardous biomass bottom ashes after their combination with different aggregates can be confirmed, which implies their possible application in civil infrastructures, such as filler embankments and road construction layers, without negatively impacting the environment. In addition, the positive effect of the stabilization/solidification of the cement-treated mixtures with a reduction of the heavy metals that were released at the highest levels, namely As, Hg Cr, Ni, Cu, Se and Mo, was proven.

Research paper thumbnail of Mechanical performance of bedding mortars made with olive biomass bottom ash

Construction and Building Materials, 2016

h i g h l i g h t s The use of biomass bottom ash (BBA) significantly increased the porosity of m... more h i g h l i g h t s The use of biomass bottom ash (BBA) significantly increased the porosity of mortars. The incorporation of BBA led to the decline of mechanical properties. Mortars with CEM-II were more susceptible to incorporation of BBA than those with CEM-I. Bedding mortars with BBA can be made according to technical specifications, namely type M and N.

Research paper thumbnail of Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

Materials, 2016

This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in ups... more This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors' knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

Research paper thumbnail of Properties of Non-Structural Concrete Made with Mixed Recycled Aggregates and Low Cement Content

Materials, 2016

In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could b... more In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could be a suitable raw material for concrete manufacturing. The aims of this research were as follows: (i) to analyze the effect of the replacement ratio of natural coarse aggregates with MRA, the amount of ceramic particles in MRA, and the amount of cement, on the mechanical and physical properties of a non-structural concrete made with a low cement content; and (ii) to verify if it is possible to achieve a low-strength concrete that replaces a greater amount of natural aggregate with MRA and that has a low cement content. Two series of concrete mixes were manufactured using 180 and 200 kg/m 3 of CEM II/A-V 42.5 R type Portland cement. Each series included seven concrete mixes: one with natural aggregates; two MRA with different ceramic particle contents; and one for each coarse aggregate replacement ratio (20%, 40%, and 100%). To study their properties, compressive and splitting tensile strength, modulus of elasticity, density, porosity, water penetration, and sorptivity, tests were performed. The results confirmed that the main factors affecting the properties analyzed in this research are the amount of cement and the replacement ratio; the two MRAs used in this work presented a similar influence on the properties. A non-structural, low-strength concrete (15 MPa) with an MRA replacement ratio of up to 100% for 200 kg/m 3 of cement was obtained. This type of concrete could be applied in the construction of ditches, sidewalks, and other similar civil works.

Research paper thumbnail of Improvement of Bearing Capacity in Recycled Aggregates Suitable for Use as Unbound Road Sub-Base

Materials, 2015

Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates w... more Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and mixed recycled aggregates were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties. The formation of new cement hydrated particles was observed, and pozzolanic reactions were discovered by electronon microscopy in these novel materials. The properties of recycled concrete aggregates and mixed recycled aggregates suggest that these recycled materials can be used in unbound road layers to improve their mechanical behaviour in the long term.

Research paper thumbnail of Feasible use of biomass bottom ash in the manufacture of cement treated recycled materials

Materials and Structures, 2015

A focus on environmental sustainability during the last decade has led to greater use of recycled... more A focus on environmental sustainability during the last decade has led to greater use of recycled aggregates to reduce the exploitation of existing reserves. In addition, environmentally consciousness has led to an increased use of renewable energy. Biomass is an important source of energy, and it also leads to high generation of waste products from biomass combustion. Previous studies have investigated the use of recycled aggregates from construction and demolition in road bases and sub-bases with positive results. This paper aims to study the feasibility of incorporating biomass bottom ash produced in the combustion process mixed with natural aggregates and recycled aggregates for use in civil engineering. The analysis of the mechanical properties was positive, showing the ability to use biomass bottom ash mixed with natural or recycled aggregates in specified ratios. Valuing biomass bottom ash can reduce waste generation and may lead to economic and environmental benefits.

Research paper thumbnail of Comparisons of natural and recycled aggregate concretes prepared with the addition of different mineral admixtures

Cement and Concrete Composites, 2011

This paper presents the results of a laboratory study on the performance of natural and recycled ... more This paper presents the results of a laboratory study on the performance of natural and recycled aggregate concrete prepared with the incorporation of different mineral admixtures including silica fumes (SF), metakaolin (MK), fly ash (FA) and Ground granulated blast slag (GGBS). The compressive and splitting tensile strength, drying shrinkage, chloride ion penetration and ultrasonic pulse velocity (UPV) of the concrete mixtures were determined. The test results, in general, showed that the incorporation of mineral admixtures improved the properties of the recycled aggregate concretes. SF and MK contributed to both the short and long-term properties of the concrete, whereas FA and GGBS showed their beneficial effect only after a relatively long curing time. As far as the compressive strength is concerned, the replacement of cement by 10% of SF or 15% of MK improved both mechanical and durability performance, while the replacement of cement by 35% FA or 55% GGBS decreased the compressive strength, but improved the durability properties of the recycled aggregate concretes. Moreover, the results show that the contributions of the mineral admixtures to performance improvement of the recycled aggregate concrete are higher than that to the natural aggregate concrete.