The Experts below are selected from a list of 6336 Experts worldwide ranked by ideXlab platform
João A. Labrincha - One of the best experts on this subject based on the ideXlab platform.
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effect of the particle size range of construction and demolition waste on the fresh and hardened state properties of fly ash based geopolymer mortars with total replacement of sand
Process Safety and Environmental Protection, 2019Co-Authors: A De Rossi, Rui M Novais, João A. Labrincha, M.j. Ribeiro, Dachamir Hotza, Regina De Fatima Peralta Muniz MoreiraAbstract:Abstract This study seeks the valorization of industrial residues (fly ash and construction and demolition waste (CDW)) through the production of geopolymer mortars. The effect of the sand substitution by CDW and the influence of the particle size range of CDW fine aggregates on the fresh and hardened properties of the mortars were evaluated. Geopolymer mortars were produced using biomass fly ash waste and metakaolin as a binder, CDW as fine aggregates, and an alkali solution of sodium silicate and sodium hydroxide as activator. The geopolymer mortars were characterized in fresh state by the Flow Table Test and in the hardened state through chemical, physical/microstructural analyzes. The mortars produced with CDW showed lower Flowability when compared to the ones prepared with sand. The compressive and flexural strength of hardened mortars, respectively, obtained with residues were higher when compared to sand: 40 MPa and 8.5 MPa with CDW, against 23 MPa and 3.1 MPa for sand-based samples. It was observed that mortars developed with recycled aggregate and natural aggregate present similar chemical and mineralogical compositions. The superior results obtained in the mechanical properties of mortars produced with CDW are related to the recycled aggregate-geopolymer paste interface.
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mortar composition defined according to rheometer and Flow Table Tests using factorial designed experiments
Construction and Building Materials, 2009Co-Authors: L Senff, Dachamir Hotza, Pedro Alberto Barbetta, Wellington Longuini Repette, H Paiva, V M Ferreira, João A. LabrinchaAbstract:Abstract This paper reports the effects of distinct contents of silica fume (SF), superplasticizer (SP) and water/binder ratio (W/B) in mortars. Samples with SF (0–10 wt%), SP (1.0–1.2 wt%) and W/B ratio (0.30–0.35) were produced. Flow Table Test and rheometry were used as parameters to formulate mortars by means of a factorial design experiment. Setting time, water absorption, apparent porosity and compressive strength of mortars at 28 days were also determined. Mortar formulations with lower fluidity are restricting when a rheometer was used. For higher torques, adjustments with the regressive equation of the Bingham model are less accurate, since the Flow behavior is less constant. On the other hand, mortars with higher fluidity it is limited by spread Test. The spread value on Flow Table Test is more related to yield stress than to plastic viscosity. The design experiments identified the main factors (SF, SP and W/B) and their interactions for all properties on the fresh and hardened state, showing that experimental design with multiple regression equations is an appropriate tool to be applied in this case. Water content was the controlling parameter for practically all properties studied.
V M Ferreira - One of the best experts on this subject based on the ideXlab platform.
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effect of fine aggregate on the rheology properties of high performance cement silica systems
Construction and Building Materials, 2010Co-Authors: Luis Pedro Esteves, Paulo Cachim, V M FerreiraAbstract:Abstract This paper deals with the effect of fine aggregate particles on the rheological properties of high performance cement-based materials. The effect of narrow fractions of fine aggregate particles on the rheology of silica fume-modified low water cement systems was analysed by means of a mortar rheometer. Yield stress and plastic viscosity were derived for time intervals between 10 and up to 150 min after water addition, and comparison with the slump value taken by the Flow Table Test was done. It is concluded that the fine aggregate particles act as water fixation points in the diameter range of 75–1000 μm, via surface area, whereas for higher particle diameters the governing factor in terms of the resistance to Flow may be related to other physical phenomena, such as the particle dimension and the resultant friction forces. Moreover, the water requirement in order to give each system the same workability is performed by adjusting the water content on each system. Furthermore, a quantitative model is proposed to describe the characteristic initial torque peak and resistance to Flow behaviour of high performance concrete, as function of the particle size of aggregate. The combined effect of silica fume and fine aggregate particles on the rheology parameters is discussed.
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mortar composition defined according to rheometer and Flow Table Tests using factorial designed experiments
Construction and Building Materials, 2009Co-Authors: L Senff, Dachamir Hotza, Pedro Alberto Barbetta, Wellington Longuini Repette, H Paiva, V M Ferreira, João A. LabrinchaAbstract:Abstract This paper reports the effects of distinct contents of silica fume (SF), superplasticizer (SP) and water/binder ratio (W/B) in mortars. Samples with SF (0–10 wt%), SP (1.0–1.2 wt%) and W/B ratio (0.30–0.35) were produced. Flow Table Test and rheometry were used as parameters to formulate mortars by means of a factorial design experiment. Setting time, water absorption, apparent porosity and compressive strength of mortars at 28 days were also determined. Mortar formulations with lower fluidity are restricting when a rheometer was used. For higher torques, adjustments with the regressive equation of the Bingham model are less accurate, since the Flow behavior is less constant. On the other hand, mortars with higher fluidity it is limited by spread Test. The spread value on Flow Table Test is more related to yield stress than to plastic viscosity. The design experiments identified the main factors (SF, SP and W/B) and their interactions for all properties on the fresh and hardened state, showing that experimental design with multiple regression equations is an appropriate tool to be applied in this case. Water content was the controlling parameter for practically all properties studied.
L Senff - One of the best experts on this subject based on the ideXlab platform.
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mortar composition defined according to rheometer and Flow Table Tests using factorial designed experiments
Construction and Building Materials, 2009Co-Authors: L Senff, Dachamir Hotza, Pedro Alberto Barbetta, Wellington Longuini Repette, H Paiva, V M Ferreira, João A. LabrinchaAbstract:Abstract This paper reports the effects of distinct contents of silica fume (SF), superplasticizer (SP) and water/binder ratio (W/B) in mortars. Samples with SF (0–10 wt%), SP (1.0–1.2 wt%) and W/B ratio (0.30–0.35) were produced. Flow Table Test and rheometry were used as parameters to formulate mortars by means of a factorial design experiment. Setting time, water absorption, apparent porosity and compressive strength of mortars at 28 days were also determined. Mortar formulations with lower fluidity are restricting when a rheometer was used. For higher torques, adjustments with the regressive equation of the Bingham model are less accurate, since the Flow behavior is less constant. On the other hand, mortars with higher fluidity it is limited by spread Test. The spread value on Flow Table Test is more related to yield stress than to plastic viscosity. The design experiments identified the main factors (SF, SP and W/B) and their interactions for all properties on the fresh and hardened state, showing that experimental design with multiple regression equations is an appropriate tool to be applied in this case. Water content was the controlling parameter for practically all properties studied.
Dachamir Hotza - One of the best experts on this subject based on the ideXlab platform.
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effect of the particle size range of construction and demolition waste on the fresh and hardened state properties of fly ash based geopolymer mortars with total replacement of sand
Process Safety and Environmental Protection, 2019Co-Authors: A De Rossi, Rui M Novais, João A. Labrincha, M.j. Ribeiro, Dachamir Hotza, Regina De Fatima Peralta Muniz MoreiraAbstract:Abstract This study seeks the valorization of industrial residues (fly ash and construction and demolition waste (CDW)) through the production of geopolymer mortars. The effect of the sand substitution by CDW and the influence of the particle size range of CDW fine aggregates on the fresh and hardened properties of the mortars were evaluated. Geopolymer mortars were produced using biomass fly ash waste and metakaolin as a binder, CDW as fine aggregates, and an alkali solution of sodium silicate and sodium hydroxide as activator. The geopolymer mortars were characterized in fresh state by the Flow Table Test and in the hardened state through chemical, physical/microstructural analyzes. The mortars produced with CDW showed lower Flowability when compared to the ones prepared with sand. The compressive and flexural strength of hardened mortars, respectively, obtained with residues were higher when compared to sand: 40 MPa and 8.5 MPa with CDW, against 23 MPa and 3.1 MPa for sand-based samples. It was observed that mortars developed with recycled aggregate and natural aggregate present similar chemical and mineralogical compositions. The superior results obtained in the mechanical properties of mortars produced with CDW are related to the recycled aggregate-geopolymer paste interface.
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mortar composition defined according to rheometer and Flow Table Tests using factorial designed experiments
Construction and Building Materials, 2009Co-Authors: L Senff, Dachamir Hotza, Pedro Alberto Barbetta, Wellington Longuini Repette, H Paiva, V M Ferreira, João A. LabrinchaAbstract:Abstract This paper reports the effects of distinct contents of silica fume (SF), superplasticizer (SP) and water/binder ratio (W/B) in mortars. Samples with SF (0–10 wt%), SP (1.0–1.2 wt%) and W/B ratio (0.30–0.35) were produced. Flow Table Test and rheometry were used as parameters to formulate mortars by means of a factorial design experiment. Setting time, water absorption, apparent porosity and compressive strength of mortars at 28 days were also determined. Mortar formulations with lower fluidity are restricting when a rheometer was used. For higher torques, adjustments with the regressive equation of the Bingham model are less accurate, since the Flow behavior is less constant. On the other hand, mortars with higher fluidity it is limited by spread Test. The spread value on Flow Table Test is more related to yield stress than to plastic viscosity. The design experiments identified the main factors (SF, SP and W/B) and their interactions for all properties on the fresh and hardened state, showing that experimental design with multiple regression equations is an appropriate tool to be applied in this case. Water content was the controlling parameter for practically all properties studied.
Pedro Alberto Barbetta - One of the best experts on this subject based on the ideXlab platform.
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mortar composition defined according to rheometer and Flow Table Tests using factorial designed experiments
Construction and Building Materials, 2009Co-Authors: L Senff, Dachamir Hotza, Pedro Alberto Barbetta, Wellington Longuini Repette, H Paiva, V M Ferreira, João A. LabrinchaAbstract:Abstract This paper reports the effects of distinct contents of silica fume (SF), superplasticizer (SP) and water/binder ratio (W/B) in mortars. Samples with SF (0–10 wt%), SP (1.0–1.2 wt%) and W/B ratio (0.30–0.35) were produced. Flow Table Test and rheometry were used as parameters to formulate mortars by means of a factorial design experiment. Setting time, water absorption, apparent porosity and compressive strength of mortars at 28 days were also determined. Mortar formulations with lower fluidity are restricting when a rheometer was used. For higher torques, adjustments with the regressive equation of the Bingham model are less accurate, since the Flow behavior is less constant. On the other hand, mortars with higher fluidity it is limited by spread Test. The spread value on Flow Table Test is more related to yield stress than to plastic viscosity. The design experiments identified the main factors (SF, SP and W/B) and their interactions for all properties on the fresh and hardened state, showing that experimental design with multiple regression equations is an appropriate tool to be applied in this case. Water content was the controlling parameter for practically all properties studied.