Revista de la Construcción. Journal of Construction

Influences of nano-clay amount on flexure behavior of concrete identified by acoustic emission

Sena Tayfur — 2024-04-29

Nano-modification is an effective method currently used to improve mechanical properties of concrete by adding various nanomaterials. The results obtained from previous studies demonstrate that presence of these particles has positive effects on both mechanical and durability performances of concrete. However, while the existing studies investigate the state of resistance, revealing progressive failure mechanism of nano-particle added concrete under loading is a significant subject. In this regard, Acoustic Emission (AE) method is useful for identification of invisible damage progress by means of basic phenomenon defined as release of energy due to a fracture and propagation of it as elastic waves in a stressed medium. Apart from the existing studies in the literature, this paper is focused on investigation of the influences of nano-clay on mechanical and failure behaviors of concrete by AE. For this purpose, a plain and three different concrete mixtures including 1%, 3% and 5% nano-clay (NC) of cement weight were prepared. 100x100x600 mm beam specimens were produced from these mixtures and were tested under three-point-bending. Furthermore, to reveal invisible failure mechanisms of the specimens, all tests were simultaneously monitored with AE method. The results reveal that presence of nano-clay increases the load capacity and ductility of the concrete specimens which is also confirmed by AE results, as more amount of micro-scale events are obtained.Nano-modification is an effective method currently used to improve mechanical properties of concrete by adding various nanomaterials. The results obtained from previous studies demonstrate that presence of these particles has positive effects on both mechanical and durability performances of concrete. However, while the existing studies investigate the state of resistance, revealing progressive failure mechanism of nano-particle added concrete under loading is a significant subject. In this regard, Acoustic Emission (AE) method is useful for identification of invisible damage progress by means of basic phenomenon defined as release of energy due to a fracture and propagation of it as elastic waves in a stressed medium. Apart from the existing studies in the literature, this paper is focused on investigation of the influences of nano-clay on mechanical and failure behaviors of concrete by AE. For this purpose, a plain and three different concrete mixtures including 1%, 3% and 5% nano-clay (NC) of cement weight were prepared. 100x100x600 mm beam specimens were produced from these mixtures and were tested under three-point-bending. Furthermore, to reveal invisible failure mechanisms of the specimens, all tests were simultaneously monitored with AE method. The results reveal that presence of nano-clay increases the load capacity and ductility of the concrete specimens which is also confirmed by AE results, as more amount of micro-scale events are obtained.

Self-healing evaluation of bacteria grouted light weight aggregate concrete containing rice husk ash and steel fibers

Rajesh Anbazhagan — 2024-04-29

Utilization of microbiologically induced calcite precipitation along with fiber composite have great influence on improving strength and durable properties of concrete. The concept of mechanical properties of grouted concrete added with bacteria, steel fibers (SF), rice husk ash (RHA) and light weight aggregate (LWA) has been focused on this work. In the fabrication of concrete specimens, concentration of bacteria, combination of steel fibers and LWA was placed in the formwork, and to fill the voids flowable grout was injected. The variables studied in this work are two different sizes of LWA viz., 10 mm and 12.5 mm with constant dosage of 2% hooked end steel fibers by volume of concrete, 10% RHA was used as cement replacement for preparation of grout and bacteria was incorporated in cement grout by direct application. The properties such as compressive strength (CS), compressive strength regain (CSR), crack width healing, impact strength for first crack and final failure, rate of healing was studied for pre-cracked specimens using visual and microscopic observation. In addition, microstructure was studied for grouted concrete without bacteria and with bacteria under immersed curing conditions. From the experimental results, performance of bacteria added grouted concrete properties such as CS, CSR, cracking healing capacity, and impact strength has improved with the addition of fibers.Utilization of microbiologically induced calcite precipitation along with fiber composite have great influence on improving strength and durable properties of concrete. The concept of mechanical properties of grouted concrete added with bacteria, steel fibers (SF), rice husk ash (RHA) and light weight aggregate (LWA) has been focused on this work. In the fabrication of concrete specimens, concentration of bacteria, combination of steel fibers and LWA was placed in the formwork, and to fill the voids flowable grout was injected. The variables studied in this work are two different sizes of LWA viz., 10 mm and 12.5 mm with constant dosage of 2% hooked end steel fibers by volume of concrete, 10% RHA was used as cement replacement for preparation of grout and bacteria was incorporated in cement grout by direct application. The properties such as compressive strength (CS), compressive strength regain (CSR), crack width healing, impact strength for first crack and final failure, rate of healing was studied for pre-cracked specimens using visual and microscopic observation. In addition, microstructure was studied for grouted concrete without bacteria and with bacteria under immersed curing conditions. From the experimental results, performance of bacteria added grouted concrete properties such as CS, CSR, cracking healing capacity, and impact strength has improved with the addition of fibers.

Heavy aggregate and different admixtures effect on pavings: pyrite, corundum and water-retaining polymer

Ilker Ustabas — 2024-04-29

Concrete pavings are widely used in the construction industry as flooring for decorative and structural purposes in the gardens, parks, and roads of America, and Europe. In the present study, the effects of pyrite, corundum, and water-retaining polymer additives on the surface wear resistance of concrete pavings were investigated. Concrete pavings were poured in 2 stages and all of the bottom layers of samples were the same, but upper layers of pavings were produced by adding pyrite in the ratio of 0.10, 0.20, 0.30, 0.40 according to the mass of the aggregate, 5 kg /m² corundum-based surface hardener to the paving surface area, and a high amount of water-absorbing polymer at a ratio of 0.05 and 0.10 to the water content of the mixture. Vertical abrasion, splitting tensile strength, water absorption, freeze-thaw resistance, pendulum footed friction, and surface hardness measurements with Schmidt test hammer experiments were made to TS 2824 EN 1338 standard. Also, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were carried out to characterize the produced materials. Results of the study indicate that the use of pyrite, corundum, and water-retaining polymers provided improvements in the surface wear resistance of concrete pavings.Concrete pavings are widely used in the construction industry as flooring for decorative and structural purposes in the gardens, parks, and roads of America, and Europe. In the present study, the effects of pyrite, corundum, and water-retaining polymer additives on the surface wear resistance of concrete pavings were investigated. Concrete pavings were poured in 2 stages and all of the bottom layers of samples were the same, but upper layers of pavings were produced by adding pyrite in the ratio of 0.10, 0.20, 0.30, 0.40 according to the mass of the aggregate, 5 kg /m² corundum-based surface hardener to the paving surface area, and a high amount of water-absorbing polymer at a ratio of 0.05 and 0.10 to the water content of the mixture. Vertical abrasion, splitting tensile strength, water absorption, freeze-thaw resistance, pendulum footed friction, and surface hardness measurements with Schmidt test hammer experiments were made to TS 2824 EN 1338 standard. Also, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were carried out to characterize the produced materials. Results of the study indicate that the use of pyrite, corundum, and water-retaining polymers provided improvements in the surface wear resistance of concrete pavings.

Experimental and numerical investigation of flexural properties of larch beams reinforced with different layer numbers

Yasemin Şimşek Türker — 2024-04-29

Recent applications demonstrated how fiber-reinforced polymer (FRP) composites can improve the structural capabilities of glulam beams, particularly regarding their flexural and shear strength. With the development of precise numerical models, such systems can be optimized. There is currently a dearth of information in the literature on numerical models that can accurately anticipate the nonlinear behavior of low-grade glued laminated timber beams reinforced with FRP. In this study, larch beams were reinforced with carbon fiber reinforced polymer fabric 1, 2 and 3 layers. The effect of the number of floors on the flexural properties of the beams in reinforcement was investigated experimentally and numerically. As a result of the study, the best flexural properties were achieved with 3-layer reinforcement. It was observed that 1- and 2-layer reinforcement compared to the reference beam were also significantly effective. Numerical analyzes gave close values with experimental test results. As a result of comparing the results obtained from the numerical model with the experimental findings, it was concluded that the FRP fabric managed to significantly increase the performance of larch timber. The model is a useful tool for examining the effect of reinforcement coefficient and will be used for optimization of the larch beam.Recent applications demonstrated how fiber-reinforced polymer (FRP) composites can improve the structural capabilities of glulam beams, particularly regarding their flexural and shear strength. With the development of precise numerical models, such systems can be optimized. There is currently a dearth of information in the literature on numerical models that can accurately anticipate the nonlinear behavior of low-grade glued laminated timber beams reinforced with FRP. In this study, larch beams were reinforced with carbon fiber reinforced polymer fabric 1, 2 and 3 layers. The effect of the number of floors on the flexural properties of the beams in reinforcement was investigated experimentally and numerically. As a result of the study, the best flexural properties were achieved with 3-layer reinforcement. It was observed that 1- and 2-layer reinforcement compared to the reference beam were also significantly effective. Numerical analyzes gave close values with experimental test results. As a result of comparing the results obtained from the numerical model with the experimental findings, it was concluded that the FRP fabric managed to significantly increase the performance of larch timber. The model is a useful tool for examining the effect of reinforcement coefficient and will be used for optimization of the larch beam.

Using recycled plastic waste as fiber reinforcement on limestone residue mortar

Khadra Bendjillali — 2024-04-29

The main purpose of the paper is to study the effect of the geometry of recycled plastic fiber on the performance of mortar basing on natural limestone residue. The used fibers were collected from plastic waste of polypropylene, resulting from domestic sweeps fabrication. Two types of recycled fibers were used, straight and crimped fibers, which have the same length (20 ± 2 mm) and the same diameter (0.45 ± 0.07 mm). Four dosages of fibers were considered, 0.5, 1, 1.5 and 2 wt. %. The obtained results show that the geometry of recycled plastic fibers has an important effect on the performances of limestone residue mortar. The addition of recycled fibers to mortar decreases its workability and the decrease is higher with crimped fibers. The results revealed that the limit dosage of recycled plastic fiber necessary to obtain a workable mortar is 1 % and 0.5 % for straight and crimped fibers, respectively. The benefit of recycled plastic fibers is well observed on the flexural and compressive behavior of limestone residue mortar, but the strength’s values are higher in straight fibers mortar (SFM) than that in crimped fibers mortar (CFM). The microstructure analysis confirms the good performances of the fiber mortar.

Clay composition patterns and their influence on the adhesive strength of earthen plasters

Gonzalo García Villar — 2024-04-29

The clay fraction of earthen plasters is the part responsible for the acquisition of cohesion and adherence that they possess against deterioration factors. Adherence is the property responsible for keeping the plaster together with the wall and is influenced by the percentage content of clay as well as by its mineralogy and the heterogeneity of minerals that may be present. However, it is still unknown in depth how clay minerals perform in the adherent properties of earthen plasters when the composition is heterogeneous in the material. The objective of this study is to evaluate the incidence of the mineralogical complexity of clay mineralogy in the variability of the adherence of earth plasters. To evaluate the variability, considering that the mineralogy of the soils depends directly on the place and the formation processes, eight soils from Tucumán (Argentina) corresponding to different physiographic units were analyzed. A methodology was designed for sample preparation that allows soils to be compared through adhesion tests. They were characterized by XRD to determine their mineralogical composition and by the hydrometric method to determine their granulometry. To evaluate the adherence of mixtures made with the respective soils, it was proposed in the first instance to compensate the granulometry of the soils to equate them and, once the plasters were made, this property was evaluated through shear and pull-off tests. The results showed that they allowed us to identify that the soils presented a pattern of mineralogical composition common to all the physiographic units, made up of the Ill and K pair, the former being predominant. For this pattern, it was observed in particular that there is a positive correlation between the increase in Ill content with the increase in the adhesive strength of the plasters. Clay minerals from the Sm group also contribute to the increase in adherence when the percentage is greater than or equal to 11%. On the contrary, K and Cl do not influence the increase in adhesive strength.The clay fraction of earthen plasters is the part responsible for the acquisition of cohesion and adherence that they possess against deterioration factors. Adherence is the property responsible for keeping the plaster together with the wall and is influenced by the percentage content of clay as well as by its mineralogy and the heterogeneity of minerals that may be present. However, it is still unknown in depth how clay minerals perform in the adherent properties of earthen plasters when the composition is heterogeneous in the material. The objective of this study is to evaluate the incidence of the mineralogical complexity of clay mineralogy in the variability of the adherence of earth plasters. To evaluate the variability, considering that the mineralogy of the soils depends directly on the place and the formation processes, eight soils from Tucumán (Argentina) corresponding to different physiographic units were analyzed. A methodology was designed for sample preparation that allows soils to be compared through adhesion tests. They were characterized by XRD to determine their mineralogical composition and by the hydrometric method to determine their granulometry. To evaluate the adherence of mixtures made with the respective soils, it was proposed in the first instance to compensate the granulometry of the soils to equate them and, once the plasters were made, this property was evaluated through shear and pull-off tests. The results showed that they allowed us to identify that the soils presented a pattern of mineralogical composition common to all the physiographic units, made up of the Ill and K pair, the former being predominant. For this pattern, it was observed in particular that there is a positive correlation between the increase in Ill content with the increase in the adhesive strength of the plasters. Clay minerals from the Sm group also contribute to the increase in adherence when the percentage is greater than or equal to 11%. On the contrary, K and Cl do not influence the increase in adhesive strength.

Nonlinear finite element analysis of steel fiber reinforced concrete beams subjected to impact loads

Ahmet Hamdi Serdar — 2024-04-29

Steel fiber reinforced concrete, compared to the conventional concrete; is a composite building material that performs much better in terms of parameters such as ductility, energy absorption capacity, fracture toughness, fatigue resistance, and the use of steel fiber reinforced concrete (SFRC) in structures has become widespread. In this study, a nonlinear finite element model (FEM) has been developed that can represent the behavior of beams produced by using steel fiber concrete subjected to impact load. For this purpose, a finite element model of beam series produced with fiber-reinforced concrete obtained from the literature was created. The ABAQUS package program was used to create models simulating the behavior. Numerical results showed that the model could successfully capture the experimental results of beams selected from the literature. In addition to simulation, a parametric study was also performed to investigate the effect of stirrups, reinforcement ratio, and drop height on the behavior of SFRC beams under impact loads. The results of the parametric study showed that increasing the fiber ratio and reinforcement ratio positively affected the behavior of SFRC beams in terms of displacement recovery.Steel fiber reinforced concrete, compared to the conventional concrete; is a composite building material that performs much better in terms of parameters such as ductility, energy absorption capacity, fracture toughness, fatigue resistance, and the use of steel fiber reinforced concrete (SFRC) in structures has become widespread. In this study, a nonlinear finite element model (FEM) has been developed that can represent the behavior of beams produced by using steel fiber concrete subjected to impact load. For this purpose, a finite element model of beam series produced with fiber-reinforced concrete obtained from the literature was created. The ABAQUS package program was used to create models simulating the behavior. Numerical results showed that the model could successfully capture the experimental results of beams selected from the literature. In addition to simulation, a parametric study was also performed to investigate the effect of stirrups, reinforcement ratio, and drop height on the behavior of SFRC beams under impact loads. The results of the parametric study showed that increasing the fiber ratio and reinforcement ratio positively affected the behavior of SFRC beams in terms of displacement recovery.

Influence of basalt fiber in ultra-high-performance concrete in hybrid mode: a comprehensive study on mechanical properties and microstructure

Sujitha Magdalene.P — 2024-04-29

The end, in view of the research, is to effectively utilize natural fiber (basalt) to reinstate the mechanical strength lost by the ultra-high-performance concrete (UHPC) matrix when the metallic steel fibers are quantitatively curtailed. Also, the river sand is fractionally ousted from the mixture, and manufactured sand is substituted. In addition to the preliminary constituents of UHPC, nano silica was adopted for the adequate packing of the matrix, which aids in strength-gaining reaction as well. To induce sustainability and implement waste utilization, two different proportions using M-Sand were made with 30% and 4% replacement levels, and for each proportion of M-Sand, five different mixes were made for varying fiber incorporation. Including the control mix made without any fiber, a total of 12 mixes were made. Among the fibrous mixes, two were metallic fibrous mixtures, and the rest were hybrid fibrous mixtures, and inter-comparisons were done accordingly. The metallic fibers were added in 1% and 2%, and natural fibers were incorporated in 1%, 2%, and 3% in volumetric fractions. From the trial mixes it was identified that the inclusion of Basalt fibers of more than 3% resulted in reduced workability, and so the addition of basalt fibers was restricted to 3%. The water-to-binder ratio of the UHPC matrix ranged between 0.15 and 0.17, depending upon the dosage of fibers. High range water reducer (HRWR) was mixed with water during casting, to develop the workability. The specimens were tested for compressive strength, split tensile strength, and impact energy resistance. It was identified that the annexation of 1% steel and 3% basalt fibers with 30% M-Sand was effective as they showed better compressive strength and impact resistance than the other combinations. Further Scanning Electron Microscopic (SEM) imaging and Thermogravimetric Analysis (TGA), which were conducted, also validated the inference from the experimental investigations.The end, in view of the research, is to effectively utilize natural fiber (basalt) to reinstate the mechanical strength lost by the ultra-high-performance concrete (UHPC) matrix when the metallic steel fibers are quantitatively curtailed. Also, the river sand is fractionally ousted from the mixture, and manufactured sand is substituted. In addition to the preliminary constituents of UHPC, nano silica was adopted for the adequate packing of the matrix, which aids in strength-gaining reaction as well. To induce sustainability and implement waste utilization, two different proportions using M-Sand were made with 30% and 4% replacement levels, and for each proportion of M-Sand, five different mixes were made for varying fiber incorporation. Including the control mix made without any fiber, a total of 12 mixes were made. Among the fibrous mixes, two were metallic fibrous mixtures, and the rest were hybrid fibrous mixtures, and inter-comparisons were done accordingly. The metallic fibers were added in 1% and 2%, and natural fibers were incorporated in 1%, 2%, and 3% in volumetric fractions. From the trial mixes it was identified that the inclusion of Basalt fibers of more than 3% resulted in reduced workability, and so the addition of basalt fibers was restricted to 3%. The water-to-binder ratio of the UHPC matrix ranged between 0.15 and 0.17, depending upon the dosage of fibers. High range water reducer (HRWR) was mixed with water during casting, to develop the workability. The specimens were tested for compressive strength, split tensile strength, and impact energy resistance. It was identified that the annexation of 1% steel and 3% basalt fibers with 30% M-Sand was effective as they showed better compressive strength and impact resistance than the other combinations. Further Scanning Electron Microscopic (SEM) imaging and Thermogravimetric Analysis (TGA), which were conducted, also validated the inference from the experimental investigations.

A comparative study between linear regression analysis and various codes for predicting the mechanical characteristics of poly-mer concrete using R-sand and M-sand

Candassamy K — 2024-04-29

Numerous research studies have concentrated on advancing a sustainable construction industry through innovative concrete methods and materials. In this context, the present research specifically investigates polymer concrete, utilizing both River sand (R-sand) and Manufacturing sand (M-sand). The polymer content was incorporated into the concrete mix based on the weight of the cement, with varying percentages specifically 2%, 4%, 5%, 6%, and 8%. A slump cone test was conducted to assess the workability of the polymer concrete. Based on experimental studies, the optimal polymer percentage was determined to be 5%. This optimal dosage of polymer content significantly improved the mechanical properties of the polymer concrete. The Compressive Strength (CS), Split Tensile Strength (STS), Flexural Strength (FS), and Modulus of Elasticity (ME) were evaluated at both 7 and 28 days. When using R-sand, the mechanical properties of CS, STS, and FS increased by 13.65%, 12.20%, and 11.42%, respectively. Conversely, employing M-sand led to even greater improvements in strength properties: 19.18% for CS, 12.54% for STS, and 11.67% for FS. Based on the experimental results, the strength properties of polymer concrete M-sand mixes outperformed the R-sand mixes. Linear regression analysis and various codes were employed to predict the strength properties of CS, STS, FS and ME. The regression analysis and various codes successfully forecasted the strength properties of polymer concrete, with the predicted results closely correlated with the experimental results. Based on experimental investigations, the determined mix proportions are recommended for practical applications in various environmental conditions.Numerous research studies have concentrated on advancing a sustainable construction industry through innovative concrete methods and materials. In this context, the present research specifically investigates polymer concrete, utilizing both River sand (R-sand) and Manufacturing sand (M-sand). The polymer content was incorporated into the concrete mix based on the weight of the cement, with varying percentages specifically 2%, 4%, 5%, 6%, and 8%. A slump cone test was conducted to assess the workability of the polymer concrete. Based on experimental studies, the optimal polymer percentage was determined to be 5%. This optimal dosage of polymer content significantly improved the mechanical properties of the polymer concrete. The Compressive Strength (CS), Split Tensile Strength (STS), Flexural Strength (FS), and Modulus of Elasticity (ME) were evaluated at both 7 and 28 days. When using R-sand, the mechanical properties of CS, STS, and FS increased by 13.65%, 12.20%, and 11.42%, respectively. Conversely, employing M-sand led to even greater improvements in strength properties: 19.18% for CS, 12.54% for STS, and 11.67% for FS. Based on the experimental results, the strength properties of polymer concrete M-sand mixes outperformed the R-sand mixes. Linear regression analysis and various codes were employed to predict the strength properties of CS, STS, FS and ME. The regression analysis and various codes successfully forecasted the strength properties of polymer concrete, with the predicted results closely correlated with the experimental results. Based on experimental investigations, the determined mix proportions are recommended for practical applications in various environmental conditions.

Investigating the effect of elevated temperatures on the utiliza-tion of demolished paving block powders as supplementary cementitious materials

Jeonghyun Kim — 2024-04-29

The study investigated the effects of construction waste powders exposed to elevated temperatures on the properties of cement mortar. The waste powders were obtained from demolished granite and clay blocks after more than 15 years of their service life. The exposure temperatures were 200 °C, 400 °C, 600 °C, and 800 °C. The heat-treated and untreated waste powders replaced cement in mortars at 10% and 20% by weight. The use of untreated recycled granite and clay powders adversely affected the mechanical strength and transport properties of the cementitious mixtures. On the other hand, the effects of thermal exposure varied for the two powder materials. As the exposure temperature increased, the performance of mixtures containing granite powder gradually deteriorated, while mixtures containing clay powder improved. The efficiency was both worst and best at 800 °C. For instance, a mixture containing 10% clay powder treated at 800 °C exhibited compressive strength equivalent to the reference mortar with no waste material. In contrast, under the same conditions, the compressive strength of the mixture containing granite powder was 33% lower. These results indicate that identifying the type and characteristics of recycled materials is essential for their utilization and application of enhancement methodsThe study investigated the effects of construction waste powders exposed to elevated temperatures on the properties of cement mortar. The waste powders were obtained from demolished granite and clay blocks after more than 15 years of their service life. The exposure temperatures were 200 °C, 400 °C, 600 °C, and 800 °C. The heat-treated and untreated waste powders replaced cement in mortars at 10% and 20% by weight. The use of untreated recycled granite and clay powders adversely affected the mechanical strength and transport properties of the cementitious mixtures. On the other hand, the effects of thermal exposure varied for the two powder materials. As the exposure temperature increased, the performance of mixtures containing granite powder gradually deteriorated, while mixtures containing clay powder improved. The efficiency was both worst and best at 800 °C. For instance, a mixture containing 10% clay powder treated at 800 °C exhibited compressive strength equivalent to the reference mortar with no waste material. In contrast, under the same conditions, the compressive strength of the mixture containing granite powder was 33% lower. These results indicate that identifying the type and characteristics of recycled materials is essential for their utilization and application of enhancement methods.