SEM image analysis in permeable recycled concretes with silica fume. A quantitative comparison of porosity and the ITZ

Recycled aggregates (RA) from construction and demolition can be used in permeable concretes (PC), improving the environment. PCs have a significant porous network, their cement paste and the interaction between the paste and the RA establishing their strength. Therefore, it is important to evaluate the porosity in the interfacial transition zones. The porosity of the cement paste, the aggregate and the interfacial transitional zones (ITZ) of a PC with recycled coarse aggregates (RCA) and silica fume (SF) is measured by means of image analysis–scanning electron microscope (IA)-(SEM) and by mapping the chemical elements with an SEM-EDS (energy dispersive spectrometer) detector microanalysis linked to the SEM and, as a contrast, the mercury intrusion porosimetry technique (MIP). In the IA process, a “mask” was created for the aggregate and another for the paste, which determined the porosity percentage (for the anhydrous material and the products of hydration). The results showed that using SF caused a reduction (32%) in the cement paste porosity in comparison with the PC with RA. The use of RA in the PC led to a significant increase (190%) in the porosity at different thicknesses of ITZ compared with the reference PC. Finally, the MIP study shows that the use of SF caused a decrease in the micropores, mesopores and macroporesPeer ReviewedPostprint (published version

Modeling and simulation of chloride diffusion in concrete with recycled aggregates

The concrete along with steel, are the responsibility structural material required to respond to mechanical stresses; specifically, the tensile stresses are borne by the steel, and it is this material that involvement of durability can lose their resilience. Corrosion of steel is one of the main causes of this affectation in the steel, and this is caused by the entry of chloride ions in the called phenomenon diffusion. This phenomenon is governed by the diffusion equations of the Fick's first and second law [1]; for these, there are several models that describe the behavior of chloride diffusion in conventional concrete, but nevertheless, not in the recycled concrete. In this paper, are used as basis, the models of Janzhuang Xiao et al. [2] and Long-Yuang Li et al. [3] to model and simulate the phenomenon of chloride diffusion in concrete with recycled aggregates; for which it has been used a five-phase model for the aggregate: old and new Interfacial Transition Zones (ITZ), new and old mortar, and original aggregate. Furthermore, in this model were considered as variables the Thickness of the Interfacial Transition Zone (TITZ), the rate of old mortar adhered, the volume fraction of the aggregates and the continuity of the ITZ. The model considered, was composed by aPeer ReviewedPostprint (published version

Modeling and simulation of chloride diffusion in concrete with recycled aggregates

The concrete along with steel, are the responsibility structural material required to respond to mechanical stresses; specifically, the tensile stresses are borne by the steel, and it is this material that involvement of durability can lose their resilience. Corrosion of steel is one of the main causes of this affectation in the steel, and this is caused by the entry of chloride ions in the called phenomenon diffusion. This phenomenon is governed by the diffusion equations of the Fick's first and second law [1]; for these, there are several models that describe the behavior of chloride diffusion in conventional concrete, but nevertheless, not in the recycled concrete. In this paper, are used as basis, the models of Janzhuang Xiao et al. [2] and Long-Yuang Li et al. [3] to model and simulate the phenomenon of chloride diffusion in concrete with recycled aggregates; for which it has been used a five-phase model for the aggregate: old and new Interfacial Transition Zones (ITZ), new and old mortar, and original aggregate. Furthermore, in this model were considered as variables the Thickness of the Interfacial Transition Zone (TITZ), the rate of old mortar adhered, the volume fraction of the aggregates and the continuity of the ITZ. The model considered, was composed by aPeer ReviewedPostprint (published version

SEM image analysis in permeable recycled concretes with silica fume. A quantitative comparison of porosity and the ITZ

Recycled aggregates (RA) from construction and demolition can be used in permeable concretes (PC), improving the environment. PCs have a significant porous network, their cement paste and the interaction between the paste and the RA establishing their strength. Therefore, it is important to evaluate the porosity in the interfacial transition zones. The porosity of the cement paste, the aggregate and the interfacial transitional zones (ITZ) of a PC with recycled coarse aggregates (RCA) and silica fume (SF) is measured by means of image analysis–scanning electron microscope (IA)-(SEM) and by mapping the chemical elements with an SEM-EDS (energy dispersive spectrometer) detector microanalysis linked to the SEM and, as a contrast, the mercury intrusion porosimetry technique (MIP). In the IA process, a “mask” was created for the aggregate and another for the paste, which determined the porosity percentage (for the anhydrous material and the products of hydration). The results showed that using SF caused a reduction (32%) in the cement paste porosity in comparison with the PC with RA. The use of RA in the PC led to a significant increase (190%) in the porosity at different thicknesses of ITZ compared with the reference PC. Finally, the MIP study shows that the use of SF caused a decrease in the micropores, mesopores and macroporesPeer Reviewe

<i>Peumus boldus</i> Used in the Synthesis of ZnO Semiconductor Nanoparticles and Their Evaluation in Organic Contaminants

The high demand for nanomaterials in the field of industry and science has forced researchers to develop new synthesis methods that are more efficient, economical, and environmentally friendly. At present, the application of green synthesis has taken a great advantage over conventional synthesis methods because it helps with the control of the characteristics and properties of the resulting nanomaterials. In this research, ZnO nanoparticles (NPs) were synthesized by biosynthesis using dried boldo (Peumus boldus) leaves. The resulting biosynthesized NPs had a high purity, quasi-spherical shape with average sizes ranging from 15 to 30 nm and a band gap of ~2.8–3.1 eV. These NPs were used in the photocatalytic activity of three organic dyes. The results showed degradation of 100% methylene blue (MB) in 180 min, 92% methyl orange (MO) in 180 min, and 100% Rhodamine B (RhB) in 30 min of exposure. These results show that the Peumus boldus leaf extract is effective in the biosynthesis of ZnO NPs with good photocatalytic properties

Comportamieto físico y mecánico de agregados naturales y reciclados en concreto permeable

Inject more water into the subsoil is very important, because when the ground water level is below capacity, causing settlements on the ground. Coupled with this, concrete recycling is an effective way to remove debris that pollute our soil. This concrete contains interconnected pores that allow water to pass easily. We worked with natural aggregates (NA) and recycled (AR) at 25 and 50% substitution. At 28 days of curing, the permeability, flexural strength and compression was evaluated. The results are linked together as the less permeable concrete obtained mechanical strength greater and inversely, on the other hand the use of AR caused a decrease in mechanical properties and aggregate shape was influential, crushed aggregate material which is a better link between the paste and the other aggregates.Peer ReviewedPostprint (published version

Comportamieto físico y mecánico de agregados naturales y reciclados en concreto permeable

Inject more water into the subsoil is very important, because when the ground water level is below capacity, causing settlements on the ground. Coupled with this, concrete recycling is an effective way to remove debris that pollute our soil. This concrete contains interconnected pores that allow water to pass easily. We worked with natural aggregates (NA) and recycled (AR) at 25 and 50% substitution. At 28 days of curing, the permeability, flexural strength and compression was evaluated. The results are linked together as the less permeable concrete obtained mechanical strength greater and inversely, on the other hand the use of AR caused a decrease in mechanical properties and aggregate shape was influential, crushed aggregate material which is a better link between the paste and the other aggregates.Peer Reviewe

Influence of the shape of the natural aggregates, recycled and silica fume on the mechanical properties of pervious concrete

Currently the problems of water quality are increasing; much of the material is rinsed and is dragged into streams, rivers, and groundwater from the contaminated superficial draining, which contains materials that are applied to the soil surface. Therefore is that the provide the greatest amount of uncontaminated water to the subsurface is of great importance, since it can still potentially solve some important collateral problems, such as the settlement in the soil, which is related largely to levels low capacity of the aquifer. Therefore, use Pervious Concrete (PCo) can help prevent physical barrier between rainwater and underground (especially in urban areas). For the investigation of the feasibility of PCo three types of aggregate were used: Round Natural Aggregate (RNA), Natural Crushed Aggregate (NCA) and Recycled Aggregate from Concrete crushed (RAC),since the shape of the aggregates generally determines the mechanical properties; and yet very little is known about their correlation with permeability. Moreover, concrete recycling is an effective way for the elimination of debris from demolition as well as replace part of the cement by waste material as the Silica Fume (SF); in both cases, these actions production decreases and CO2 emissions associated with their production. In this work different aggregates with a substitution of SF are evaluated, for know physical and mechanical properties of pervious concrete and in part to contribute to solving the environmental problem of the construction.Peer ReviewedPostprint (published version

Influence of the shape of the natural aggregates, recycled and silica fume on the mechanical properties of pervious concrete

Currently the problems of water quality are increasing; much of the material is rinsed and is dragged into streams, rivers, and groundwater from the contaminated superficial draining, which contains materials that are applied to the soil surface. Therefore is that the provide the greatest amount of uncontaminated water to the subsurface is of great importance, since it can still potentially solve some important collateral problems, such as the settlement in the soil, which is related largely to levels low capacity of the aquifer. Therefore, use Pervious Concrete (PCo) can help prevent physical barrier between rainwater and underground (especially in urban areas). For the investigation of the feasibility of PCo three types of aggregate were used: Round Natural Aggregate (RNA), Natural Crushed Aggregate (NCA) and Recycled Aggregate from Concrete crushed (RAC),since the shape of the aggregates generally determines the mechanical properties; and yet very little is known about their correlation with permeability. Moreover, concrete recycling is an effective way for the elimination of debris from demolition as well as replace part of the cement by waste material as the Silica Fume (SF); in both cases, these actions production decreases and CO2 emissions associated with their production. In this work different aggregates with a substitution of SF are evaluated, for know physical and mechanical properties of pervious concrete and in part to contribute to solving the environmental problem of the construction.Peer Reviewe

Experimental study of XRD, FTIR and TGA techniques in geopolymeric materials

The alkali activation of fly ashes produces a solid and compact material having similar properties to those of portland cement (PC) with characteristics of sustainable high value; these materials with high silica and aluminum are referred to as geopolymers. These new materials are a new generation of environmentally friendly cement, so it is very important to study their properties to validate their implementation; for which the application of new techniques currently being used. The work presented in this study focuses on establish the usual procedures of the techniques of X-ray diffraction (XRD), Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) in its specific application to geopolymer base, or also called fly ash. Likewise, is determined the behavior of these materials for each of the above techniques.Peer Reviewe