Papers by Javier Rodrigo González López
Study on thermally stabilized vanadium dioxide nanoparticles solid-solid phase change thermal energy storage material, 2022
Heat storage is a feature that can be used in many components or applications. In the case of pha... more Heat storage is a feature that can be used in many components or applications. In the case of phase change materials (PCMs), the performance in heat storage will depend on the latent heat when the phase change occurs. Solid-solid PCMs are an improvement over traditional solid-liquid PCMs because problems related to their leak-off and limited applications are eliminated. Vanadium dioxide (VO 2) is a material that has been shown to be a PCM in the monoclinic phase (M). In this work, VO 2 nanoparticles were synthesized by the hydrothermal and post-vacuum annealing method at a relatively low temperature. The relationship between the effect of annealing temperature and morphology on the heat storage capacity of VO 2 nanoparticles is evaluated. The results show that the VO 2 nanoparticles resulting from the 300 to 500°C vacuum annealing presented the endothermic and exothermic peaks for the reversible transition of monoclinic VO 2 to the rutile (R) phase. The highest latent heat of 22.87 Jg-1 for the VO 2 annealed at 500°C. The VO 2 (M) nanoparticles presented good thermal stability and oxidation resistance below 265°C with excellent cycling stability for at least 20 thermal cycles, which could be promising for technical application in thermal energy management.
Effect of Adding Silica Fume, Calcium Carbonate or Silicon Carbide on the Properties of an Alternative Binder Based on Anhydrite and Blast Furnace Slag, 2022
The effect of the addition of silica fume, calcium carbonate or silicon carbide in an alternative... more The effect of the addition of silica fume, calcium carbonate or silicon carbide in an alternative cementitious matrix based on anhydrite and blast furnace slag is reported in this paper. The addition of any of these materials improved the compressive strength of the systems, with the one containing 5% silica fume exceeding 22 MPa at 28 days and 26 MPa at 360 days of curing, showing the best compressive strength over the test period. Increasing the addition of silica fume resulted in a decrease in compressive strength because silica fume interferes with the hydration reaction of anhydrite. The systems with silica fume showed lower expansions, of 0.06%, compared to 0.11% for the other systems, because the pozzolanic reaction of the silica fume to form calcium silicate hydrate densifies the matrix preventing the ettringite from finding a place to nucleate. The hydration products were identified as gypsum and ettringite, in addition to calcium silicate hydrate, which covered the gypsum crystals forming an intermixed structure between the two phases. Despite the appearance of ettringite, no cracking or spalling was observed, even after 360 days of curing.
Mixtures of a composite binder based on anhydrite synthesised from waste plaster from the ceramic... more Mixtures of a composite binder based on anhydrite synthesised from waste plaster from the ceramics industry complemented with granulated blast-furnace slag (BFS) and silica fume (SF) were studied. Small additions of potassium sulfate, calcium hydroxide and Portland cement clinker were used as chemical activators. The addition of BFS and SF to the systems was found to improve the properties and hinder the dissolution of gypsum in wet environments. The presence of ettringite was visually verified by scanning electron microscopy. The samples did not show considerable expansion or loss of mechanical properties for up to 56 d. The strength obtained by the compounds after 56 d was $20 MPa, far exceeding the typical compressive strength of gypsum plaster (about 4 MPa). The main hydrated products were gypsum, ettringite and calcium silicate hydrate type products.
There is a strong dependence between the CEB strength and the granulometry. 10% of the stabilized... more There is a strong dependence between the CEB strength and the granulometry. 10% of the stabilized lime or OPC is sufficient to develop non-structural CEB. The compaction forces increase the compressive stress when OPC is used as stabilizer. The 5% and 10% stabilizers reduced the anisotropy of the compressive strength. The microstructure is related to the durability coefficients. For the same amount of binder, the compressive stress increased more than 200% by changing the mesh distribution. a b s t r a c t This work aims to investigate the design of clay matrices with optimum granulometry for their use in compressed earth blocks with and without stabilizers. The results and discussion focus on the mechanical properties, compressive strength anisotropy according to the compaction direction, and durability tests such as abrasion and absorption coefficients. The results show that the granulometry is an important aspect for matrices without stabilizers, as well as the applied compaction forces, obtaining values greater than 2 MPa with compaction forces of 1.96 kN. The clay-sand microstructure matrices are densified when the stabilizers are added, which causes a change in the failure mechanism due to the stiffening of the matrix.
This article investigates the mechanical behavior of fiber-reinforced cementitious composites usi... more This article investigates the mechanical behavior of fiber-reinforced cementitious composites using moderate to high contents of fly ash (FA) as a replacement for cement; the goal is to create primary building elements with low environmental impact. The experimental results showed that the compressive strength, modulus of elasticity, and post-cracking flexural strength for specimens with w/cm = 0.60 and 20% FA substitution increased with respect to the control. Moreover, the specimens with high FA substitutions had significantly lower mechanical strength values and elastic modulus values. The results indicate that it is feasible to use fiber-reinforced concrete composites as an alternative for low-environmental impact primary construction. 136 Compuestos cementantes fibroreforzados de bajo impacto ambiental comportamiento mecánico RESUMEN El presente texto expone los resultados del estudio del comportamiento mecánico de compuestos cementantes fibroreforzados utilizando consumos moderados y altos de ceniza volante (CV) en sustitución de volúmenes determinados de cemento (20%, 40% y 60%), con el objetivo de producir elementos constructivos primarios de bajo impacto ambiental. La experimentación realizada indicó que el esfuerzo a compresión, el módulo de elasticidad y la resistencia a flexión post agrietamiento, para los especímenes con relación a/mc = 0.60 y con 20% de sustitución con CV registraron incrementos en sus valores con respecto al control para ambas edades. No se evidenció deterioro en las mallas de fibras naturales por la exposición al medio alcalino. Los resultados hasta ahora obtenidos indican que es viable el uso de estos compuestos cementantes fibroreforzados como alternativa de construcción primaria de bajo impacto ambiental. Palabras clave: fibra; cementicios; compuestos; ceniza volante; material de impacto. Compostos cimentantes reforçados com fibra e de baixo impacto ambiental RESUMO Este artigo apresenta algumas importantes propriedades mecânicas obtidas numa pesquisa de materiais cimentantes reforçados com fibras, nos quais foram utilizados consumos moderados e altos de cinza volante (fly ash, FA), em substituição ao cimento Portland (20%, 40% e 60%), com o objetivo de produzir elementos primários de baixo impacto ambiental. Os resultados experimentais mostraram que a resistência à compressão, o módulo de elasticidade e a resistência à flexão, aumentaram em relação ao de referência, para as misturas de a/cm = 0,60 e 20% de substituição. Para os demais casos de substituição foram encontradas resistências e módulo mais baixos que o de referência. Os resultados mostraram que pode ser viável o uso desses materiais cimentantes reforçados com fibras, como alternativa de construção primária de baixo impacto ambiental.
An electroless deposition process was used to synthesize with a controlled morphology, polycrysta... more An electroless deposition process was used to synthesize with a controlled morphology, polycrystalline ZnO on glass substrates as antimicrobial coatings. The influence of deposition temperature (Tdep) on the physicochemical and antimicrobial properties of the ZnO films was analyzed. The results indicated that a change in deposition temperature greatly affected the morphology and the degree of crystallinity of the films. Scanning electron microscope images show that the film surface is porous at a deposition temperature of 40 and 50 °C, whereas hexagonal-plate shaped morphology predominated at 60 °C and finally at 70 and 80 °C the films consisted of rod-like particles. The films showed good transparency in the visible region. All ZnO films presented notable antimicrobial activity against the gram-negative bacteria Escherichia coli (E. coli) and the gram-positive Staphylococcus aureus (S. aureus). It was found that the antimicrobial efficiency is strongly dependent on morphology and structural properties. The best antimicrobial performance was recorded for the films consisting of rod-like morphology with a high degree of crystallinity. The procedure used in this investigation is strongly recommended for the development of functional surfaces.
The building industry is facing the challenge of satisfying a growing demand for housing spaces t... more The building industry is facing the challenge of satisfying a growing demand for housing spaces that can be mitigated by
the use of construction materials manufactured with industrial by-products that allow the production of low-cost housing with
a low environmental impact. In this research, an alternative building system to manufacture lightweight masonry blocks with
polyethylene terephthalate (PET) bottles and fiber-reinforced panels using binary mixture (Portland cement and fly ash), was
studied. This building system was tested under compressive and flexural loads until failure. The average design compressive
strengths of concrete blocks for w/c ratios of 0.78 and 1.1 were fp* = 1.9 and 1.2 MPa respectively, these results were similar to
those typical masonry in accordance with the design and construction standards. On the other hand, the flexural strength, the
modulus of elasticity and the stiffness on mid span of the fiber-reinforced concrete panels were improved with adding 20% of
fly ash to both w/c ratios, mainly at 120 days. The experimental results obtained show that those building elements are viable
alternatives with mechanical properties comparable to traditional building systems, besides the reduction of the environmental
impact due to the incorporation of industrial waste materials.
The aim of this work was to study the effect of the interaction of colloidal nano SiO2 (NS) with ... more The aim of this work was to study the effect of the interaction of colloidal nano SiO2 (NS) with a hardened Portland cement paste (PCP). An electric circuit arrangement with two electrodes was used to create an electric field around a PCP sample. NS was used as catholyte and water as anolyte to assure electric conductivity. Results obtained using an optical Microscopy and Scanning Electron Microscopy showed that NS particles reached a distance up to 1.5 mm from the surface in contact with the PCP sample to the interior of the sample. Energy dispersive X-ray Spectroscopy showed an enrichment of Si in the zone where NS migrated. An alteration of the Ca/Si ratios was also observed, with values below of both conventional anhydrous and hydrated phases. Thermo-gravimetric analysis (TG) showed that NS affected the content balance between CSH gel and Ca(OH)2 in a migrated NS sample compared with a reference sample; this could represent an evidence that NS affected the cement matrix with a possible pozzolanic reaction even after the hardened stage of the PCP.
Calcium hydroxide (Ca(OH) 2) is recognized as an efficient bactericide and is widely applied as a... more Calcium hydroxide (Ca(OH) 2) is recognized as an efficient bactericide and is widely applied as a root canal filler in endodontic treatment. Ca(OH) 2 is mainly produced by hydration of calcium oxide (CaO), a product of the thermal decomposition of calcium carbonate (CaCO 3) from sources such as limestone. In this work, calcium hydroxide particles were synthetized by the thermochemical transformation of waste biomass from the tequila industry. Agave biomass processed at 600 °C was composed mostly of calcium carbonate (CaCO 3), while calcination at 900 °C followed by hydration produced Ca(OH) 2. The morphology and crystalline nature of the Ca(OH) 2 particles were characterized by micro-Raman spectroscopy, scanning electron microscopy and X-ray diffraction analysis. Bactericidal activity of synthesized calcium hydroxide was evaluated with the agar diffusion assay. Our results provide evidence that Ca(OH) 2 obtained from agave biomass is an effective bactericidal against Escherichia coli and Enterococcus faecalis. Biomass from agave is available in Mexico and the rest of the American continent, the use of processed bagasse for medical applications could provide a venue for the useful disposition of industrial waste. Palabras clave: recursos renovables, ceniza, bactericida, Ca(OH) 2 RESUMEN El hidróxido de calcio (Ca(OH) 2) es reconocido como un eficiente bactericida y es ampliamente utilizado como relleno de la raíz dental en tratamientos de endodoncia. El Ca(OH) 2 es producido por la hidratación del óxido de calcio (CaO), un producto de la descomposición térmica del carbonato de calcio (CaCO 3), obtenido principalmente de piedra caliza. En el presente trabajo, se sintetizaron partículas de hidróxido de calcio
Nowadays, ageing of existing concrete structures exposed to highly aggressive environments is
one... more Nowadays, ageing of existing concrete structures exposed to highly aggressive environments is
one the highest concerns for the construction industry. In this context, developing sustainable, efficient and
secure technologies for the repair and maintenance of such structures rises as a challenge to assure their service
life. In present paper, a non-invasive repair method, based on the application of colloidal nanosilica on
the concrete surface, is proposed. Two mechanisms to force the nanosilica penetration have been considered:
capillary suction and migration. The ability of colloidal nanosilica to consolidate the cementitious matrix has
been confirmed; nanosilica promotes the decrease of capillary pores not only filling the pores but also interacting
chemically with the substrate to form new gels, which seem to evolve with time in presence of the appropriate
humidity conditions.
Concrete performance can be improved by using colloidal nano-SiO 2 (NS) by two different methods:... more Concrete performance can be improved by using colloidal nano-SiO 2 (NS) by two different methods: direct addition at the fresh stage to improve mechanical and durability properties; and superfi cial application, such as sealing treatment to hinder further penetration of aggressive ions. Chemical interaction of NS with the hardened cement mortar (HCM) was analyzed in both situations. NS chemical reactivity was confi rmed by SEM and TGA tests. Mortar specimens with nanosilica additions (up to 2.5 % cement weight) were prepared and cured for 7 days before characterization. A superfi cial treatment by migration of colloidal NS dispersion (30 % weight concentration) under a 12 V was applied on mortar samples after 7 days of curing. Reactivity of NS with the HCM was confi rmed by energy dispersion spectroscopy analysis (EDS) coupled to scanning electron microscopy in backscat-tering (SEM-BS). The new silicon enriched C-S-H gels with C/S ratio around 1.0 were determined by TGA.
Colloidal nano-silica was used as a superficial treatment in cement mortar sample by electrochemi... more Colloidal nano-silica was used as a superficial treatment in cement mortar sample by electrochemical migration under an electric field. An electric circuit was configured in order to perform direct current through a hardened mortar sample and to force charged particles of nano-silica move into the pore system of the microstructure and to affect the durability properties of the samples. The behavior of the electric current through the time in the presence of a mortar surface was analyzed. Also, durability tests were carried out by accelerated chloride and CO2 test. The microstructure was analyzed by Scanning Electron Microscopy and Energy dispersive Spectroscopy coupled. Results show that nano- silica is able to move into the microstructure by migration treatment and affects the chemical composition (Ca/Si, C-S-H ratio) of the mortar sample; thus, affecting the properties of gas and liquid penetration resistance of the cement material.
A failure analysis was performed on bolts (Monel K-500) that serve to support and join critical c... more A failure analysis was performed on bolts (Monel K-500) that serve to support and join critical components of an electrical submergible pump (ESP) located in a saline solution environment. Based on the experimental results, it can be concluded that pitting corrosion was the primary cause of failure. All fracture surfaces displayed an initial zone of intergranular fracture promoted by pitting corrosion and a propagation zone with transgranular fracture due to mechanical load. High concentrations of sulfur (S) and chlorine (Cl) were found on two corrosion product layers covering the bolt surface, revealing that an aggressive electrochemical reaction occurred in the stagnant environment. Under these
layers, small pits of 10–30 lmin depth were observed that initiated the cracking paths that eventually became complete fractures.
The use of industrialwaste for the production of biomass is a topic that has gained increasing in... more The use of industrialwaste for the production of biomass is a topic that has gained increasing interest. This is due
to the need to use plants that do not affect the food supply when used for power generation frombiomass. Agave
salmiana residues meet these characteristics. It has nowbeen proposed as a possible source of bioenergy production
because of its growth characteristics. Therefore, in this research, the effect of combustion temperature of the
A. salmiana as it could happen in the energy production was studied. In addition, the characteristics of these residueswere
analyzed to serve as a basis for possible future applications in construction materials. Results indicate
that the ashes are mainly CaCO3 when calcined at below 700 °C, and CaO above this temperature. The apparent
particle size was between 25 and 32 μm. However, it is observed that it consists of much smaller particles of approximately
300 nm. This reduction in size is related to decomposition at higher temperatures and is reflected in
the increase of the specific area up to 70%. The compression strength at early ages was up to 90% higher than a
reference, when 5% cement replacement mixes were performed.
This paper presents the failure analysis of alumina–zirconia–silica (AZS) refractory bricks locat... more This paper presents the failure analysis of alumina–zirconia–silica (AZS) refractory bricks located in the glass level in the tank of a furnace for melting glass, since is the region where there is greater wear respect to the base. The wear of the refractory was evaluated after 4 years of campaigning, under thermal and mechanical loading during the glass manufacture. The analysis by scanning electron microscopy shows high porosity and the presence of alkalis is also detected from the glass composition, being the phase alumina–zirconia–silica (AZS),the one that shows better resistance to erosion wear by displacement of the molten glass. The analysis yielded the following mechanisms of chemical wear, removal of the vitreous phase toward the surface of the sample due to the increase in temperature of the furnace, and therefore attack by vapors through the porosity caused by the exudation of the vitreous phase, as well as deterioration of the microstructure of the refractory due to the formation of cracks. Because it is considered as the main problem in these types of furnaces, the erosion wear is related to the flows of convection currents within the tank, this occurs at the level of the glass, as it is at this point, where it has concentration of thermal and mechanical loads due to movement of the molten glass.
An innovative electrochemical treatment for the sealing of hardened mortar by nanosilica migratio... more An innovative electrochemical treatment for the sealing of hardened mortar by nanosilica migration is proposed. The composition of the colloidal suspension and the electric field power were assessed as significant parameters of the transport efficiency. The interaction between the nano-SiO2 and the cement matrix was characterized by different techniques: electrical resistivity measurements, DTA–TGA, BS-SEM with EDX microanalysis coupled and MIP. Results showed that the transport of colloidal nano-SiO2 under the action of the electric field can be achieved. An active interaction with the solid phases of the mortar samples was confirmed from the decrease in the portlandite content of treated mortar and from the smaller C/S ratio found in the solid hydrated phases of the treated mortars. A significant decrease of capillary
pores was also identified at the age of 28 days after finishing the treatment. The sealing ability of migrated silica nanoparticles was enhanced with the ageing of the treated sample; smaller amount of micropores was measured with the treated mortar ageing.
Currently, thermal energy generation through coal combustion produces ash particles which cause s... more Currently, thermal energy generation through coal combustion produces ash particles which cause serious environmental problems and which are known as Fly Ash (FA). FA main components are oxides of silicon, aluminum, iron, calcium and magnesium in addition, toxic metals such as arsenic and cobalt. The use of fly ash as a cement replacement material increases long term strength and durability of concrete. In this work, samples were prepared by replacing cement by ground fly ash in 10, 20 and 30% by weight. The characterization of raw materials and microstructure was obtained by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The final results showed that the grinding process significantly improves the mechanical properties of all samples when compared replacing a mortar made with cement by ground fly ash and the reference samples without added fly ash. The beneficial effect of the ground fly ash can increase the use of this product in precast concrete industry.
Application of nanotechnology in construction industry is a quite new field with many interesting... more Application of nanotechnology in construction industry is a quite new field with many interesting and promising possibilities. Nanosilica self healing properties, based on
the high reactivity of these particles with the calcium components of cement, are of great interest in rehabilitation treatments of hardened concrete. In present work, the
application of nanosilica to hardened concrete is proposed as innovative technology to improve the effectiveness of electrochemical repair methods and to increase the
durability of rehabilitated structures by sealing the concrete pores.
An accelerated methodology, compatible with the electrochemical repair treatments of concrete, is proposed to introduce nanosilica in hardened concrete by connecting
an external electric field. Two different commercial products with SiO2 of 7 nm and 12 nm in diameter have been analysed. Silica nanoparticles have been transported through a mortar sample under a 12 V electric field. The interaction between the SiO2 nanoparticles and the concrete have been characterised by different techniques: resistivity measurements, mercury intrusion porosity, scanning electron microscopy.
The results show that the interaction concrete/nanosilica takes place in the first centimetre of concrete cover from the surface of the nanosilica application. A denser
microstructure with higher content of capillary pores is obtained after the nanosilica penetration. Also the resistivity of the mortar increases due to the treatment with nanosilica.
The fatigue resistance of an aluminium alloy used for casting engine blocks was studied. The test... more The fatigue resistance of an aluminium alloy used for casting engine blocks was studied. The tests were carried out with specimens machined from the bulkheads of V8 engine blocks cast by the low pressure process. The samples were obtained from two different locations in the bulkheads to evaluate the effect of microstructural refining as the material was cut from regions in which the secondary dendrite arm spacing was within two different sizes, namely 30 and 45 lm. The samples were tested either in their as-cast and heat treating conditions in a computer controlled servohydraulic machine. The tests were fully reversible following staircase schedules. The specimens were fatigued to fracture or up to 107 cycles.
The results show that fatigue cracks nucleate in pores located close to the surface of the specimen. It is concluded that the fatigue resistance is affected by heat treating and microstructural refining. The enhancement in fatigue resistance due to microstructural refining is documented. An analysis was carried out to predict the cycles to failure that the material is able to sustain.
Uploads
Papers by Javier Rodrigo González López
the use of construction materials manufactured with industrial by-products that allow the production of low-cost housing with
a low environmental impact. In this research, an alternative building system to manufacture lightweight masonry blocks with
polyethylene terephthalate (PET) bottles and fiber-reinforced panels using binary mixture (Portland cement and fly ash), was
studied. This building system was tested under compressive and flexural loads until failure. The average design compressive
strengths of concrete blocks for w/c ratios of 0.78 and 1.1 were fp* = 1.9 and 1.2 MPa respectively, these results were similar to
those typical masonry in accordance with the design and construction standards. On the other hand, the flexural strength, the
modulus of elasticity and the stiffness on mid span of the fiber-reinforced concrete panels were improved with adding 20% of
fly ash to both w/c ratios, mainly at 120 days. The experimental results obtained show that those building elements are viable
alternatives with mechanical properties comparable to traditional building systems, besides the reduction of the environmental
impact due to the incorporation of industrial waste materials.
one the highest concerns for the construction industry. In this context, developing sustainable, efficient and
secure technologies for the repair and maintenance of such structures rises as a challenge to assure their service
life. In present paper, a non-invasive repair method, based on the application of colloidal nanosilica on
the concrete surface, is proposed. Two mechanisms to force the nanosilica penetration have been considered:
capillary suction and migration. The ability of colloidal nanosilica to consolidate the cementitious matrix has
been confirmed; nanosilica promotes the decrease of capillary pores not only filling the pores but also interacting
chemically with the substrate to form new gels, which seem to evolve with time in presence of the appropriate
humidity conditions.
layers, small pits of 10–30 lmin depth were observed that initiated the cracking paths that eventually became complete fractures.
to the need to use plants that do not affect the food supply when used for power generation frombiomass. Agave
salmiana residues meet these characteristics. It has nowbeen proposed as a possible source of bioenergy production
because of its growth characteristics. Therefore, in this research, the effect of combustion temperature of the
A. salmiana as it could happen in the energy production was studied. In addition, the characteristics of these residueswere
analyzed to serve as a basis for possible future applications in construction materials. Results indicate
that the ashes are mainly CaCO3 when calcined at below 700 °C, and CaO above this temperature. The apparent
particle size was between 25 and 32 μm. However, it is observed that it consists of much smaller particles of approximately
300 nm. This reduction in size is related to decomposition at higher temperatures and is reflected in
the increase of the specific area up to 70%. The compression strength at early ages was up to 90% higher than a
reference, when 5% cement replacement mixes were performed.
pores was also identified at the age of 28 days after finishing the treatment. The sealing ability of migrated silica nanoparticles was enhanced with the ageing of the treated sample; smaller amount of micropores was measured with the treated mortar ageing.
the high reactivity of these particles with the calcium components of cement, are of great interest in rehabilitation treatments of hardened concrete. In present work, the
application of nanosilica to hardened concrete is proposed as innovative technology to improve the effectiveness of electrochemical repair methods and to increase the
durability of rehabilitated structures by sealing the concrete pores.
An accelerated methodology, compatible with the electrochemical repair treatments of concrete, is proposed to introduce nanosilica in hardened concrete by connecting
an external electric field. Two different commercial products with SiO2 of 7 nm and 12 nm in diameter have been analysed. Silica nanoparticles have been transported through a mortar sample under a 12 V electric field. The interaction between the SiO2 nanoparticles and the concrete have been characterised by different techniques: resistivity measurements, mercury intrusion porosity, scanning electron microscopy.
The results show that the interaction concrete/nanosilica takes place in the first centimetre of concrete cover from the surface of the nanosilica application. A denser
microstructure with higher content of capillary pores is obtained after the nanosilica penetration. Also the resistivity of the mortar increases due to the treatment with nanosilica.
The results show that fatigue cracks nucleate in pores located close to the surface of the specimen. It is concluded that the fatigue resistance is affected by heat treating and microstructural refining. The enhancement in fatigue resistance due to microstructural refining is documented. An analysis was carried out to predict the cycles to failure that the material is able to sustain.
the use of construction materials manufactured with industrial by-products that allow the production of low-cost housing with
a low environmental impact. In this research, an alternative building system to manufacture lightweight masonry blocks with
polyethylene terephthalate (PET) bottles and fiber-reinforced panels using binary mixture (Portland cement and fly ash), was
studied. This building system was tested under compressive and flexural loads until failure. The average design compressive
strengths of concrete blocks for w/c ratios of 0.78 and 1.1 were fp* = 1.9 and 1.2 MPa respectively, these results were similar to
those typical masonry in accordance with the design and construction standards. On the other hand, the flexural strength, the
modulus of elasticity and the stiffness on mid span of the fiber-reinforced concrete panels were improved with adding 20% of
fly ash to both w/c ratios, mainly at 120 days. The experimental results obtained show that those building elements are viable
alternatives with mechanical properties comparable to traditional building systems, besides the reduction of the environmental
impact due to the incorporation of industrial waste materials.
one the highest concerns for the construction industry. In this context, developing sustainable, efficient and
secure technologies for the repair and maintenance of such structures rises as a challenge to assure their service
life. In present paper, a non-invasive repair method, based on the application of colloidal nanosilica on
the concrete surface, is proposed. Two mechanisms to force the nanosilica penetration have been considered:
capillary suction and migration. The ability of colloidal nanosilica to consolidate the cementitious matrix has
been confirmed; nanosilica promotes the decrease of capillary pores not only filling the pores but also interacting
chemically with the substrate to form new gels, which seem to evolve with time in presence of the appropriate
humidity conditions.
layers, small pits of 10–30 lmin depth were observed that initiated the cracking paths that eventually became complete fractures.
to the need to use plants that do not affect the food supply when used for power generation frombiomass. Agave
salmiana residues meet these characteristics. It has nowbeen proposed as a possible source of bioenergy production
because of its growth characteristics. Therefore, in this research, the effect of combustion temperature of the
A. salmiana as it could happen in the energy production was studied. In addition, the characteristics of these residueswere
analyzed to serve as a basis for possible future applications in construction materials. Results indicate
that the ashes are mainly CaCO3 when calcined at below 700 °C, and CaO above this temperature. The apparent
particle size was between 25 and 32 μm. However, it is observed that it consists of much smaller particles of approximately
300 nm. This reduction in size is related to decomposition at higher temperatures and is reflected in
the increase of the specific area up to 70%. The compression strength at early ages was up to 90% higher than a
reference, when 5% cement replacement mixes were performed.
pores was also identified at the age of 28 days after finishing the treatment. The sealing ability of migrated silica nanoparticles was enhanced with the ageing of the treated sample; smaller amount of micropores was measured with the treated mortar ageing.
the high reactivity of these particles with the calcium components of cement, are of great interest in rehabilitation treatments of hardened concrete. In present work, the
application of nanosilica to hardened concrete is proposed as innovative technology to improve the effectiveness of electrochemical repair methods and to increase the
durability of rehabilitated structures by sealing the concrete pores.
An accelerated methodology, compatible with the electrochemical repair treatments of concrete, is proposed to introduce nanosilica in hardened concrete by connecting
an external electric field. Two different commercial products with SiO2 of 7 nm and 12 nm in diameter have been analysed. Silica nanoparticles have been transported through a mortar sample under a 12 V electric field. The interaction between the SiO2 nanoparticles and the concrete have been characterised by different techniques: resistivity measurements, mercury intrusion porosity, scanning electron microscopy.
The results show that the interaction concrete/nanosilica takes place in the first centimetre of concrete cover from the surface of the nanosilica application. A denser
microstructure with higher content of capillary pores is obtained after the nanosilica penetration. Also the resistivity of the mortar increases due to the treatment with nanosilica.
The results show that fatigue cracks nucleate in pores located close to the surface of the specimen. It is concluded that the fatigue resistance is affected by heat treating and microstructural refining. The enhancement in fatigue resistance due to microstructural refining is documented. An analysis was carried out to predict the cycles to failure that the material is able to sustain.