SP-192: 2000 Canmet/ACI Conference on Durability of Concrete, 2000
Pozzolanic cements with 50% fly ash, and composite cements with 25% fly ash and 25% ground granul... more Pozzolanic cements with 50% fly ash, and composite cements with 25% fly ash and 25% ground granulated blast furnace slag were produced to manufacture high performance concretes. These binders are in agreement with the European standard (EN 197/1) for cements type IV/B and V/A, respectively. Unground and ground fly ash was used for pozzolanic and composite cements. Ground slag was used for composite cements. Eight different blended cements were produced and characterized by strength measurements on standard mortar bars. High performance concrete mixtures were all manufactured with a water-to cementitious material ratio as low as 0.32, a portland cement factor of 235 kg/m3, and a fly ash or slag plus fly ash content of 235 kg/m3. A naphthalene-based superplasticizer was used to produce flowing concretes with a slump in the range of 190-220 mm. A slightly higher dosage of superplasticizer was needed to compensate the slump reduction caused by the fineness increase of the blended cement...
The objective of this paper was to evaluate the behavior of reinforced concrete beam-column joint... more The objective of this paper was to evaluate the behavior of reinforced concrete beam-column joints that were subjected to cyclic loading in order to investigate and compare ductility and toughness of the joints made either of ordinary or recycled-aggregate concrete. Therefore, a recycled-aggregate concrete was prepared with water/cement of 0.35 and fluid consistency, by completely replacing natural aggregates with recycled aggregates coming from an industrial crushing plant in which rubble from building demolition was suitably treated. A reference concrete was also prepared using natural aggregates with the same fluid consistency but a water/cement of 0.60, sufficient to achieve adequate strength class. A further recycled-aggregate concrete was prepared with a water/cement of 0.40, by adding fly ash to the mixture as a partial replacement for fine aggregate. An acrylic polymer based superplasticiser was used to guarantee the same workability level. Concrete specimens were manufacture for the evaluation of compressive and tensile strength, as well as bond strength between concrete and reinforcing steel bars, to assess the suitability for structural uses. Then cyclic loading of the beam-column joints made of these concretes was carried out. The results gave further experimental evidence of the suitability of recycled-aggregate concrete for structural use, at least for ordinary reinforced concrete structures.
Abstract In this work, fiber reinforced SCLWAC (self-compacting lightweight aggregate concrete) m... more Abstract In this work, fiber reinforced SCLWAC (self-compacting lightweight aggregate concrete) mixtures were studied, in which synthetic fibers were used. Eight different SCLWACs were prepared, in which, as aggregates, different combinations of fine and coarse expanded clay were tried, also partially replaced by either quartz sand or aggregate coming from concrete recycling. SCLWACs were characterized at the fresh state by means of slump flow, V-funnel and L-box tests, and after hardening by means of compression, splitting tension and bending tests, and drying shrinkage measurements. Strength class of LC 45/50 was obtained by using synthetic macrofibres when the oven dry density of SCLWAC was about 1600 kg/m 3 , while if the oven dry density of SCLWAC was lower than 1250 kg/m 3 a strength class of LC 25/28 was reached as well. Tensile and flexural strength values were consistent with concrete strength class, while the elastic modulus was quite low with respect to normal weight self-compacting concrete (SCC). The post-cracking behavior of SCLWAC was strongly improved by the addition of synthetic macrofibers, which provided strain-hardening effect similar to that achievable by means of steel fibers, even if characterized by a sensibly lower weight. In conclusion, SCLWACs showed excellent combination of mechanical and functional properties.
The concept of sustainable development includes the judicious use of natural resources, which in ... more The concept of sustainable development includes the judicious use of natural resources, which in some areas are rapidly depleting, achieved by using industrial by-products and thereby reducing materials waste. In addition, it is necessary to reduce energy consumption that is associated with CO 2 and other greenhouse gas emissions. The production of Portland cement also releases large amounts of CO 2 into the atmosphere. For this reason supplementary cementitious materials are being used in concrete: one of these materials is fly ash, which is a by-product of thermal power generation. Fly ash exhibits pozzolanic activity, and, if not used, has to be disposed of in landfills at a considerable cost. The use of other non-renewable resources, such as virgin aggregates, also needs to be reduced by recycling rubble from demolished buildings, processed in such a way that they can be used to replace virgin fine and coarse aggregate in concrete. This replacement also allows for reduction in the volume of materials disposed of in landfills. According to the concept of sustainable development, the environmental load of a building must be evaluated throughout its life cycle, from design to construction, maintenance or repair, demolition, and rubble disposal. Therefore, from a holistic point of view, sustainable construction means designing a reinforced concrete structure with appropriate durability during a specified service life. This paper discusses the effect of partial and full replacement of natural aggregates by recycled concrete aggregates (RCA) in a fly ash concrete. Engineering properties and durability performance have been examined for mixtures designed with various proportions of the RCA by mass. Results obtained showed that while incorporating high RCA amount could lower concrete performance, the combined use of RCA and fly ash could allow us to achieve adequate engineering properties and durability.
The reuse of debris from building demolition is of increasing public interest because it decrease... more The reuse of debris from building demolition is of increasing public interest because it decreases the volume of material to be disposed to landfill. This research is focused on the evaluation of the possibility of reusing recycled aggregate from construction or demolition waste (C&D) as a substitute for natural aggregate in concrete production. In most applications, cement based materials are used for building construction due to their cost effectiveness and performance; however their impact on the surrounding environment should be monitored. The interstitial pore fluid in contact with hydrated cementitious materials is characterized by persistent alkaline pH values buffered by the presence of hydrate calcium silicate, portlandite and alkaline ions. An experimental plan was carried out to investigate concrete structural properties in relation to alkali release in aqueous solution. Results indicate that the presence of recycled aggregate increases the leachability of unreactive ions (Na, K, Cl), while for calcium the substitution resulted in a lower net leaching. In spite of the lower mechanical resistance (40% less), such a waste concrete may be suggested as more environmentally sustainable.
This work was aimed at studying the possibility of reusing waste glass from crushed containers an... more This work was aimed at studying the possibility of reusing waste glass from crushed containers and building demolition as aggregate for preparing mortars and concrete. At present, this kind of reuse is still not common due to the risk of alkali-silica reaction between the alkalis of cement and silica of the waste glass. This expansive reaction can cause great problems of cracking and, consequently, it can be extremely deleterious for the durability of mortar and concrete. However, data reported in the literature show that if the waste glass is finely ground, under 75 lm, this effect does not occur and mortar durability is guaranteed. Therefore, in this work the possible reactivity of waste glass with the cement paste in mortars was verified, by varying the particle size of the finely ground waste glass. No reaction has been detected with particle size up to 100 lm thus indicating the feasibility of the waste glass reuse as fine aggregate in mortars and concrete. In addition, waste glass seems to positively contribute to the mortar micro-structural properties resulting in an evident improvement of its mechanical performance.
... 2003, Reykjavik, Iceland THE USE OF RECYCLED AGGREGATES FROM BUILDING DEMOLITION IN SELF-COMP... more ... 2003, Reykjavik, Iceland THE USE OF RECYCLED AGGREGATES FROM BUILDING DEMOLITION IN SELF-COMPACTING CONCRETE Valeria Corinaldesi, Giacomo ... Mixture NAT+nat REC+ nat NAT+ rec REC+ rec Water/Cement Water/Powders' 0.45 0.35 0.45 0.37 0.45 ...
... selon les r~sultats de la caraet&isation et selon l'~valuation des performan... more ... selon les r~sultats de la caraet&isation et selon l'~valuation des performances, les mortiers avec granulats recyel~ semblent les meilleurs aux ... Chemical composition and Blaine fineness of all the ingredients are shown in Table 1. The proportions of the paste mixtures are shown ...
ABSTRACT The development of self-compacting concrete is considered as a milestone achievement in ... more ABSTRACT The development of self-compacting concrete is considered as a milestone achievement in concrete technology due to several advantages. In order to be self-compactable the fresh concrete must show high fluidity besides good cohesiveness. For the purpose of evaluating these properties, several concrete mixtures were prepared with a water to cement ratio of 0.45 in the presence of an acrylic-based superplasticizer at a dosage ranging from 1% to 2% by weight of very fine material fraction (maximum 150μm). Either limestone powder or fly ash or recycled aggregate powder (that is a powder obtained from the rubble recycling process) were used as mineral addition, in order to assure adequate rheological properties, in terms of cohesiveness, in the self-compacting concretes. Preliminary rheological tests were carried out on cement pastes containing these mineral additions. In some cases, recycled instead of natural aggregate was used by substituting either the coarse or the fine aggregate fraction. The fresh concrete properties were evaluated through slump flow, L-box test and segregation resistance. Compressive strength of concrete was determined at 1, 3, 7 and 28days of wet curing. Results obtained showed that an optimization of self-compacting concrete mixture seems to be achievable by the simultaneous use of rubble powder and coarse recycled aggregate with improved fresh concrete performance and unchanged concrete mechanical strength.
In order to produce thin precast elements, a self-compacting concrete was prepared. When manufact... more In order to produce thin precast elements, a self-compacting concrete was prepared. When manufacturing these elements, homogenously dispersed steel fibers instead of ordinary steel-reinforcing mesh were added to the concrete mixture at a dosage of 10% by mass of cement. An adequate concrete strength class was achieved with a water to cement ratio of 0.40. Compression and flexure tests were carried out to assess the safety of these thin concrete elements. Moreover, serviceability aspects were taken into consideration. Firstly, drying shrinkage tests were carried out in order to evaluate the contribution of steel fibers in counteracting the high concrete strains due to a low aggregatecement ratio. Secondly, the resistance to freezing and thawing cycles was investigated on concrete specimens in some cases superficially treated with a hydrophobic agent. Lastly, both carbonation and chloride penetration tests were carried out to assess durability behavior of this concrete mixture.
In this work, several self-compacting concretes were prepared by using three different types of f... more In this work, several self-compacting concretes were prepared by using three different types of fibers made of steel, poly-vinyl-alcohol (PVA) and high toughness polypropylene (PPHT) and two different types of mineral addition (limestone powder and powder from recycled concrete). The water to cement ratio was held constant at 0.40. Fresh concrete behavior was evaluated by means of slump flow, V-funnel and L-box tests while the hardened concrete behavior was evaluated by means of flexure and compression tests, as well as free drying and restrained plastic shrinkage tests. Excellent performances were generally obtained, particularly for the self-compacting concretes prepared with steel fibers and powder from recycled concrete.
Abstract: A judicious use of resources, achieved by the use of by-products and waste materials, a... more Abstract: A judicious use of resources, achieved by the use of by-products and waste materials, and a lower environmental impact, achieved through reduced carbon dioxide emission and reduced natural aggregate extraction from quarries, represent two main ...
In general, for self-compacting concrete production a high volume of very fine materials is neces... more In general, for self-compacting concrete production a high volume of very fine materials is necessary in order to make the concrete more fluid and cohesive. For this purpose, either rubble powder (which is a powder obtained from suitable treatment of rubble from building demolition) or ash from municipal solid waste incineration was used as mineral addition, in order to ensure adequate rheological properties of the self- compacting concrete in the absence of any viscosity modifying admixture. Recycled instead of natural aggregates were used by completely substituting the coarse aggregate fraction. The fresh concrete properties were evaluated through the slump flow, the V- funnel and the L-box test. Compressive strength and segregation resistance were also determined. The results obtained showed that self- compacting concrete could be successfully developed by incorporating both recycled aggregates and waste powders with an improved quality of the concrete surface finishing. This enc...
SP-192: 2000 Canmet/ACI Conference on Durability of Concrete, 2000
Pozzolanic cements with 50% fly ash, and composite cements with 25% fly ash and 25% ground granul... more Pozzolanic cements with 50% fly ash, and composite cements with 25% fly ash and 25% ground granulated blast furnace slag were produced to manufacture high performance concretes. These binders are in agreement with the European standard (EN 197/1) for cements type IV/B and V/A, respectively. Unground and ground fly ash was used for pozzolanic and composite cements. Ground slag was used for composite cements. Eight different blended cements were produced and characterized by strength measurements on standard mortar bars. High performance concrete mixtures were all manufactured with a water-to cementitious material ratio as low as 0.32, a portland cement factor of 235 kg/m3, and a fly ash or slag plus fly ash content of 235 kg/m3. A naphthalene-based superplasticizer was used to produce flowing concretes with a slump in the range of 190-220 mm. A slightly higher dosage of superplasticizer was needed to compensate the slump reduction caused by the fineness increase of the blended cement...
The objective of this paper was to evaluate the behavior of reinforced concrete beam-column joint... more The objective of this paper was to evaluate the behavior of reinforced concrete beam-column joints that were subjected to cyclic loading in order to investigate and compare ductility and toughness of the joints made either of ordinary or recycled-aggregate concrete. Therefore, a recycled-aggregate concrete was prepared with water/cement of 0.35 and fluid consistency, by completely replacing natural aggregates with recycled aggregates coming from an industrial crushing plant in which rubble from building demolition was suitably treated. A reference concrete was also prepared using natural aggregates with the same fluid consistency but a water/cement of 0.60, sufficient to achieve adequate strength class. A further recycled-aggregate concrete was prepared with a water/cement of 0.40, by adding fly ash to the mixture as a partial replacement for fine aggregate. An acrylic polymer based superplasticiser was used to guarantee the same workability level. Concrete specimens were manufacture for the evaluation of compressive and tensile strength, as well as bond strength between concrete and reinforcing steel bars, to assess the suitability for structural uses. Then cyclic loading of the beam-column joints made of these concretes was carried out. The results gave further experimental evidence of the suitability of recycled-aggregate concrete for structural use, at least for ordinary reinforced concrete structures.
Abstract In this work, fiber reinforced SCLWAC (self-compacting lightweight aggregate concrete) m... more Abstract In this work, fiber reinforced SCLWAC (self-compacting lightweight aggregate concrete) mixtures were studied, in which synthetic fibers were used. Eight different SCLWACs were prepared, in which, as aggregates, different combinations of fine and coarse expanded clay were tried, also partially replaced by either quartz sand or aggregate coming from concrete recycling. SCLWACs were characterized at the fresh state by means of slump flow, V-funnel and L-box tests, and after hardening by means of compression, splitting tension and bending tests, and drying shrinkage measurements. Strength class of LC 45/50 was obtained by using synthetic macrofibres when the oven dry density of SCLWAC was about 1600 kg/m 3 , while if the oven dry density of SCLWAC was lower than 1250 kg/m 3 a strength class of LC 25/28 was reached as well. Tensile and flexural strength values were consistent with concrete strength class, while the elastic modulus was quite low with respect to normal weight self-compacting concrete (SCC). The post-cracking behavior of SCLWAC was strongly improved by the addition of synthetic macrofibers, which provided strain-hardening effect similar to that achievable by means of steel fibers, even if characterized by a sensibly lower weight. In conclusion, SCLWACs showed excellent combination of mechanical and functional properties.
The concept of sustainable development includes the judicious use of natural resources, which in ... more The concept of sustainable development includes the judicious use of natural resources, which in some areas are rapidly depleting, achieved by using industrial by-products and thereby reducing materials waste. In addition, it is necessary to reduce energy consumption that is associated with CO 2 and other greenhouse gas emissions. The production of Portland cement also releases large amounts of CO 2 into the atmosphere. For this reason supplementary cementitious materials are being used in concrete: one of these materials is fly ash, which is a by-product of thermal power generation. Fly ash exhibits pozzolanic activity, and, if not used, has to be disposed of in landfills at a considerable cost. The use of other non-renewable resources, such as virgin aggregates, also needs to be reduced by recycling rubble from demolished buildings, processed in such a way that they can be used to replace virgin fine and coarse aggregate in concrete. This replacement also allows for reduction in the volume of materials disposed of in landfills. According to the concept of sustainable development, the environmental load of a building must be evaluated throughout its life cycle, from design to construction, maintenance or repair, demolition, and rubble disposal. Therefore, from a holistic point of view, sustainable construction means designing a reinforced concrete structure with appropriate durability during a specified service life. This paper discusses the effect of partial and full replacement of natural aggregates by recycled concrete aggregates (RCA) in a fly ash concrete. Engineering properties and durability performance have been examined for mixtures designed with various proportions of the RCA by mass. Results obtained showed that while incorporating high RCA amount could lower concrete performance, the combined use of RCA and fly ash could allow us to achieve adequate engineering properties and durability.
The reuse of debris from building demolition is of increasing public interest because it decrease... more The reuse of debris from building demolition is of increasing public interest because it decreases the volume of material to be disposed to landfill. This research is focused on the evaluation of the possibility of reusing recycled aggregate from construction or demolition waste (C&D) as a substitute for natural aggregate in concrete production. In most applications, cement based materials are used for building construction due to their cost effectiveness and performance; however their impact on the surrounding environment should be monitored. The interstitial pore fluid in contact with hydrated cementitious materials is characterized by persistent alkaline pH values buffered by the presence of hydrate calcium silicate, portlandite and alkaline ions. An experimental plan was carried out to investigate concrete structural properties in relation to alkali release in aqueous solution. Results indicate that the presence of recycled aggregate increases the leachability of unreactive ions (Na, K, Cl), while for calcium the substitution resulted in a lower net leaching. In spite of the lower mechanical resistance (40% less), such a waste concrete may be suggested as more environmentally sustainable.
This work was aimed at studying the possibility of reusing waste glass from crushed containers an... more This work was aimed at studying the possibility of reusing waste glass from crushed containers and building demolition as aggregate for preparing mortars and concrete. At present, this kind of reuse is still not common due to the risk of alkali-silica reaction between the alkalis of cement and silica of the waste glass. This expansive reaction can cause great problems of cracking and, consequently, it can be extremely deleterious for the durability of mortar and concrete. However, data reported in the literature show that if the waste glass is finely ground, under 75 lm, this effect does not occur and mortar durability is guaranteed. Therefore, in this work the possible reactivity of waste glass with the cement paste in mortars was verified, by varying the particle size of the finely ground waste glass. No reaction has been detected with particle size up to 100 lm thus indicating the feasibility of the waste glass reuse as fine aggregate in mortars and concrete. In addition, waste glass seems to positively contribute to the mortar micro-structural properties resulting in an evident improvement of its mechanical performance.
... 2003, Reykjavik, Iceland THE USE OF RECYCLED AGGREGATES FROM BUILDING DEMOLITION IN SELF-COMP... more ... 2003, Reykjavik, Iceland THE USE OF RECYCLED AGGREGATES FROM BUILDING DEMOLITION IN SELF-COMPACTING CONCRETE Valeria Corinaldesi, Giacomo ... Mixture NAT+nat REC+ nat NAT+ rec REC+ rec Water/Cement Water/Powders' 0.45 0.35 0.45 0.37 0.45 ...
... selon les r~sultats de la caraet&isation et selon l'~valuation des performan... more ... selon les r~sultats de la caraet&isation et selon l'~valuation des performances, les mortiers avec granulats recyel~ semblent les meilleurs aux ... Chemical composition and Blaine fineness of all the ingredients are shown in Table 1. The proportions of the paste mixtures are shown ...
ABSTRACT The development of self-compacting concrete is considered as a milestone achievement in ... more ABSTRACT The development of self-compacting concrete is considered as a milestone achievement in concrete technology due to several advantages. In order to be self-compactable the fresh concrete must show high fluidity besides good cohesiveness. For the purpose of evaluating these properties, several concrete mixtures were prepared with a water to cement ratio of 0.45 in the presence of an acrylic-based superplasticizer at a dosage ranging from 1% to 2% by weight of very fine material fraction (maximum 150μm). Either limestone powder or fly ash or recycled aggregate powder (that is a powder obtained from the rubble recycling process) were used as mineral addition, in order to assure adequate rheological properties, in terms of cohesiveness, in the self-compacting concretes. Preliminary rheological tests were carried out on cement pastes containing these mineral additions. In some cases, recycled instead of natural aggregate was used by substituting either the coarse or the fine aggregate fraction. The fresh concrete properties were evaluated through slump flow, L-box test and segregation resistance. Compressive strength of concrete was determined at 1, 3, 7 and 28days of wet curing. Results obtained showed that an optimization of self-compacting concrete mixture seems to be achievable by the simultaneous use of rubble powder and coarse recycled aggregate with improved fresh concrete performance and unchanged concrete mechanical strength.
In order to produce thin precast elements, a self-compacting concrete was prepared. When manufact... more In order to produce thin precast elements, a self-compacting concrete was prepared. When manufacturing these elements, homogenously dispersed steel fibers instead of ordinary steel-reinforcing mesh were added to the concrete mixture at a dosage of 10% by mass of cement. An adequate concrete strength class was achieved with a water to cement ratio of 0.40. Compression and flexure tests were carried out to assess the safety of these thin concrete elements. Moreover, serviceability aspects were taken into consideration. Firstly, drying shrinkage tests were carried out in order to evaluate the contribution of steel fibers in counteracting the high concrete strains due to a low aggregatecement ratio. Secondly, the resistance to freezing and thawing cycles was investigated on concrete specimens in some cases superficially treated with a hydrophobic agent. Lastly, both carbonation and chloride penetration tests were carried out to assess durability behavior of this concrete mixture.
In this work, several self-compacting concretes were prepared by using three different types of f... more In this work, several self-compacting concretes were prepared by using three different types of fibers made of steel, poly-vinyl-alcohol (PVA) and high toughness polypropylene (PPHT) and two different types of mineral addition (limestone powder and powder from recycled concrete). The water to cement ratio was held constant at 0.40. Fresh concrete behavior was evaluated by means of slump flow, V-funnel and L-box tests while the hardened concrete behavior was evaluated by means of flexure and compression tests, as well as free drying and restrained plastic shrinkage tests. Excellent performances were generally obtained, particularly for the self-compacting concretes prepared with steel fibers and powder from recycled concrete.
Abstract: A judicious use of resources, achieved by the use of by-products and waste materials, a... more Abstract: A judicious use of resources, achieved by the use of by-products and waste materials, and a lower environmental impact, achieved through reduced carbon dioxide emission and reduced natural aggregate extraction from quarries, represent two main ...
In general, for self-compacting concrete production a high volume of very fine materials is neces... more In general, for self-compacting concrete production a high volume of very fine materials is necessary in order to make the concrete more fluid and cohesive. For this purpose, either rubble powder (which is a powder obtained from suitable treatment of rubble from building demolition) or ash from municipal solid waste incineration was used as mineral addition, in order to ensure adequate rheological properties of the self- compacting concrete in the absence of any viscosity modifying admixture. Recycled instead of natural aggregates were used by completely substituting the coarse aggregate fraction. The fresh concrete properties were evaluated through the slump flow, the V- funnel and the L-box test. Compressive strength and segregation resistance were also determined. The results obtained showed that self- compacting concrete could be successfully developed by incorporating both recycled aggregates and waste powders with an improved quality of the concrete surface finishing. This enc...
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