Scielo RSS <![CDATA[Revista de la construcción]]> vol. 20 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Thermal resistance of raffia palm reinforced concrete]]> Abstract There are increasing interests in the usage of natural fibres as reinforcing component for concrete production due to their enormous properties such as low cost, its abundance and availability. This research examined the thermal resistance of Raffia Palm Fibre (RPF) reinforced concrete. In this study, 0% to 1% fibre content by weight of cement were incorporated in concrete and their compressive strength were tested after heating. A total number of 36 cubes were prepared, cured and tested at 28 days. Concrete cubes with 0% fibre was used as control specimen. The cubes’ compressive strengths were determined at 0 0C, 556 0C and 659 0C at 0 minutes, 5 minutes and 10 minutes respectively. The result revealed that workability of the concrete declined with a rise in the percentage of raffia palm. There is also a substantial surge in the compressive strength of raffia palm fibre reinforced concrete cubes (RPFRC) compared to the control concrete samples. The compressive strength of the concrete cubes decreased with the rise in temperature for the entire samples tested. It was concluded that increasing the percentage fibre content in concrete reduces the rate of loss in compressive strengths of concrete when subjected to heat. <![CDATA[Experimental and numerical studies on punching shear strength of concrete slabs containing sintered fly ash aggregates]]> Abstract This paper presents experimental and numerical investigations on M30 grade of concrete containing 40% of sintered fly ash aggregates (SFAs) on the punching behaviour of reinforced concrete (RC) slabs. Two 1000 x 1000 x 100 mm reinforced concrete slabs were cast and subjected to punching tests. The experimental results were compared with creating a nonlinear finite element programme using ABAQUS. These 3D Finite element analyses were performed with the appropriate modelling of element size and the constitutive modelling of concrete. The material parameters of the damaged plasticity model in ABAQUS were calibrated based on the test results of the slab - plate connection. The comparison between experimental and numerical results indicates that the calibrated model correctly predicts the punching shear response of the slabs. A modification of 0.4 is introduced in MC2010 code. <![CDATA[Assessing the performance of the BIM implementation process: a case study]]> Abstract The article proposes a system of indicators for measuring the performance of BIM projects. Proposed indicators are divided into groups as follows: quantitative (cost and time related numerical values) and qualitative (verbally expressed measures recalculated to scores according to the proposed four-point rating scale). The metrics include the time and cost variations, the assessment of the organizational scale of BIM deployment, BIM competency granularity level, BIM capability level, BIM maturity level. In the case study, the proposed indicators are applied for evaluating the results of the construction project. The limitations and difficulties faced up during the project implementation were discussed, and the benefits of the application of the BIM methodology were revealed. The application of the proposed methodology is useful in assessing at which level the BIM is applied in construction projects and measuring the progress towards achieving project goals. The proposed methodology can also be applied for constant monitoring of the BIM implementation in construction projects. <![CDATA[The effect of curing conditions on the mechanical properties of SIFCON]]> Abstract In this study, the effect of curing conditions on the mechanical properties of slurry infiltrated fiber reinforced concrete (SIFCON) was investigated. For this purpose, SIFCON samples containing 4% and 8% steel fiber with two different aspect ratios were produced. The samples were subjected to three different curing types, namely standard, dry and accelerated curing methods. Ultrasonic wave velocity, flexural strength, fracture toughness, compressive strength, impact resistance and capillary water absorption tests were performed on the samples. The highest flexural strength was found to be achieved in the samples with an aspect ratio of 55 and a content of 8% steel fiber. The most suitable curing method was determined as the standard curing method and the best flexural strength was achieved at the rate of 8%. According to the test results, the best strength properties were achieved in the samples exposed to the standard curing method. In addition, the samples exposed to the accelerated curing method showed satisfactory values. The accelerated curing method can be used as an alternative in SIFCON production especially in applications requiring mass production. <![CDATA[Investigation of mechanical properties of polymer impregnated concrete containing polypropylene fiber by taguchi and anova methods]]> Abstract The mechanical properties of polymer impregnated concrete containing polypropylene fiber were statistically and experimentally examined in this study. Taguchi L9 (33) was used in this study. The variables used for experiments were selected as the polypropylene fiber ratio (0%, 1% and 2%), cement dosage (300, 350 and 400 kg/m3) and curing time (7, 14 and 28 days). After the specimens were cured at the specified curing times, they were dried at 105 (5 °C. Then, the monomer was impregnated to the specimens for 24 hours under atmospheric conditions. The samples for the polymerization of monomer was kept within the drying oven at 60 °C for 6 hours. The compressive strength and ultrasonic pulse velocity tests of specimens, in which polymerization was applied, was conducted. Furthermore, the dynamic modulus of elasticity of samples was calculated using the ultrasonic pulse velocity. The Taguchi analysis found that the best values for the ultrasonic pulse velocity, dynamic modulus of elasticity and compressive strength were 28 days for curing, 1% for the polypropylene fiber percentage and 400 kg/m3 for the cement dosage. The Anova analysis found that the polypropylene fiber percentage had the biggest effect on the mechanical properties of polymer impregnated concrete containing polypropylene fiber. <![CDATA[Development of hybrid steel-basalt fiber reinforced concrete - in aspects of flexure, fracture and microstructure]]> Abstract The conventional concrete is considered to be critical in various constructional applications due to its setbacks such as service load failures, brittle property, low ductility and low tensile capacity. Apart from the natural bridging mechanism (aggregate bridging), an additional bridging mechanism is necessary to overcome the existing setbacks in plain cement concrete. Thus concrete with one or more types of fibers in suitable combinations can augment the mechanical performance of concrete causing a positive synergy effect. Along with the two control mixes with and without copper slag as partial replacement of fine aggregate, two different groups of hybrid combination of fibers such as steel and basalt were cast with 3 different groups of coarse aggregate proportions of sizes 20 mm and 12.5 mm. The hybridization of fibers is assessed in this study under compression, tension, flexure and fracture. Stress-strain data were recorded under compression to validate the strain capacity of the mixtures. The mechanical properties were analyzed for the positive hybrid effect and the influencing factors were copper slag, hybrid fiber combination and coarse aggregate proportions. The optimum volume fraction of fibers and mix proportions were highlighted based on various behaviors of concrete. Steel as macro fibers and basalt as microfibers were examined under microstructural studies (SEM and EDX). The results from the flexural toughness showcased the potential of hybrid fibers with greater energy absorption capacity ensuring the ductile property of the proposed hybrid fiber reinforced concrete. <![CDATA[Construction machinery hire rates deviation in Malaysia: an inflation rate effect analysis]]> Abstract Machinery has been used in the construction industry in both small- and large-scale projects for a long time. Machinery is one of the main resources of any construction projects and rates deviation within the hiring of the machinery can result in cost overrun of the project. This study has been conducted to deal with the issue of deviating the machinery hire rates in the construction industry. The study accesses the machinery hire rates and aims to investigate the percentage deviation from 2013 to 2018. In this regard, statistical analysis was conducted to identify the influence of the inflation rate in deviating the machinery hire which results in cost overrun. Also, the interconnectivity of machinery hire rates was evaluated through the correlation coefficient. The analysis shows that the inflation rate possesses a weak relationship with nine and a moderate relationship with five machinery hire rates. However, the interconnectivity of the machinery hire rates was strongly correlated with each other, which emphasize that a change due to the influential factor will affect all the rates and can cause cost overrun. It is therefore recommended to observe other factors which deviate the machinery hire rates within the construction industry. <![CDATA[Application of thermal comfort assessment models to indoor areas near glazed walls - experimental evaluation]]> Abstract In this paper, some of the results of an experimental study are presented. Its purpose was to better understand the impact of glazing on thermal comfort of users of indoor spaces (living and working), especially in the areas near glazed walls. Glazed elements, such as windows and glazed doors, allow visual access to the outdoor environment and the entrance of natural light and solar heat gains but they are often the cause of unwanted heat losses and gains and are disturbing elements in obtaining thermal comfort, both in global terms and in what concerns local discomfort due to radiant asymmetries and/or air draughts. Furthermore, solar radiation directly affecting users in the vicinity of glazing can also cause discomfort. These disturbances are recognized by users, both on cold winter days and on hot summer days. To assess thermal comfort or thermal neutrality of a person in a particular indoor space, it is important to know their location within that space. Thus, in order to adequately assess thermal comfort in the areas near the glazing, the indoor thermal environment must be characterized for this specific location. In this study, two indoor spaces (a classroom and an office-room) of a school building were monitored at different periods of the year. The measurements of the environmental parameters were performed both in the center of the rooms and in the areas near the glazing. Five models of thermal comfort assessment were then applied to the results, in order to compare the comfort conditions between the two studied locations and to evaluate the applicability of these models to the areas close to glazed walls. It was observed there was clearly a greater variability of comfort conditions in the vicinity of the glazed walls when compared to the center of the rooms. The application of thermal comfort assessment models to the two studied rooms was able to reveal the differences between the two compared locations within each space. It was also possible to show the effect of incoming solar radiation and the influence of the geometry of the spaces and of the ratio between glazed area and floor area by comparing the results for both spaces. The assessment model proposed by LNEC (Portuguese National Laboratory of Civil Engineering) proved to be the most adapted to Portuguese users’ habits. <![CDATA[Specimen size and shape effects on strength of concrete in the absence and presence of steel fibers]]> Abstract In this research, the effects of size and shape on compressive and splitting tensile strength of fibrous and non-fibrous concrete specimens with different characteristic strength were investigated. With this aim, both fibrous and non-fibrous 10 different concrete mixtures with 0.3, 0.4, 0.5, 0.6 and 0. 7 Water/Cement ratio were prepared. In the fibrous mixture specimens, the total amount of steel fibers to 1% by total volume. In the entire specimens, 42.5 R type Portland cement were used as bonding elements while crushed lime stones in 3 sizes were added to the mixtures. Furthermore, to evaluate the influence of size and shapes over specimens’ strength, for each concrete mixtures two 10 cm and 15 cm cubic specimen beside two 10×20 cm and 15×30 cm cylindrical specimens were prepared as well. The prepared specimens were subjected to compressive and splitting tensile tests. The results showed that, regardless of the fiber amount and specimens’ shapes, the decrease in specimens’ size resulted in higher strength. But in the high ratio of Water/Cement and fibrous mixtures, the mentioned behavior was not observed. <![CDATA[Performance of ambient and freezing-thawing cured metazeolite and slag based geopolymer composites against elevated temperatures]]> Abstract Today, geopolymer has an important place in producing sustainable alternative products by consuming less energy. This paper researches the elevated-temperature behavior of metazeolite (MZ) and slag (S) based geopolymer composites, reinforced by polyvinyl alcohol fiber (PVA) (at 0.3%, 0.6% and 0.9% by volume), and basalt fiber (B) (at 0.3%, 0.6% and 0.9% by volume). The curing was carried out at room temperature for up to 7 days and then the freeze-thaw test was applied as a curing method for up to 28 days. Slag was used alongside metazeolite to solve the problem of delayed setting time with its high Ca content. After 7 days, the damp environment provided by the freeze-thaw curing ensured the preservation of the compact structure and the continuation of geopolymerization. The resulting geopolymer composites were exposed to temperatures of 250, 500, and 750 oC. The flexural and compressive strengths, microstructure (FT-IR, XRD, SEM, TGA-DTA, and micro-CT analyzes), ultrasonic pulse velocity (UPV), visual inspection, and weight-losses of the geopolymers were examined to evaluate their behavior. According to the results, it was observed that geopolymer samples maintained their stability after 750oC. In this way, a sustainable geopolymer composite was produced by using less energy. <![CDATA[Dynamic properties of steel structures under different construction stages, ambient temperature and live load]]> Abstract Operational modal analysis (OMA), assessing the effect of environmental conditions on the structures has been attracting widespread interest and its results have been used for the validation of numerical models. This paper aims to validate the application of OMA on steel buildings to investigate their dynamic behavior during and after their construction. In this context, the construction stages of a steel building were monitored. With the completion of the construction, the dynamic tests were applied at different times to identify the changes in the modal characteristics of the building with respect to the temperature and service loads. Finally, the analytical model of the building was performed and the building’s dynamic properties were determined numerically. As a result, the experimentally obtained dynamic properties for the completed building were compared to those derived from numerical analysis. The results underlined the importance of slab construction for the formation of building behavior in the construction stages. Besides the effects of ambient temperature and service load on the dynamic properties of steel buildings were revealed. Finally, the lack of partition walls in the numerical model has been grasped as the main reason behind the differences between the experimentally and numerically obtained dynamic properties. <![CDATA[Serviceability analysis and increased axle load performance of heritage arch gallery railway bridge]]> Abstract This investigation deals with the serviceability analysis and increased axle load performance of Bridge No. 541 of UNESCO recognised Kalka Shimla Mountain Railways, which is a multi-storey arch gallery stone masonry bridge situated in the state of Himachal Pradesh, India. For this purpose, a finite element (FE) model was developed based on the drawings and reports available in Shimla Division, Northern Railways, India. Further, the results obtained from ambient vibration test (AVT) and operational modal analysis (OMA) is utilized to model update the initial FE model by modifying the mechanical properties of stone masonry. The serviceability against present-day axle loading (H Class Loading, Indian Railways) and present speed of the train is assessed. At last, a parametric study is conducted to understand the feasibility to attain higher speeds (up to 40 kmph) of the present axle load and higher axle load with different speeds of the train over the bridge to check the serviceability conditions advised in the Indian Railways code and also International codes. Finally, the study concluded that Bridge No. 541 of Kalka Shimla Mountain Railways can sustain speeds up to 40 kmph for current axle loading satisfying serviceability conditions. <![CDATA[The effect of calcite and blast furnace slag on the rheology properties of self-compacting concrete in meso and macro scales]]> Abstract In this study, the effects of blast furnace slag (BFS) and calcite on rheological properties of self-compacting concrete (SSC) in meso and macro scales were investigated. During the preparation of replicate samples, while BFS was replaced with the cement at the rate of 10%, 20%, 30%, and 40% by weight, calcite was added to the cement at the rate of 10%, 15%, 20%, and 25% by weight. The rheological properties (plastic viscosity and yield point) and mini-slump flow values of the cement paste prepared in meso scales were determined. The fresh flow consistency of concrete prepared in macro-scale was tested with L-box flowing test. As a result, upon evaluating the rheological parameters of the pastes according to the Bingham model, while the pastes with a plastic viscosity value close to 1 Pa·s (±100 MPa·s) and a mini-slump flow rate higher than 200 mm were observed to be more resistant to segregation and form a homogeneous flow consistency, their L-box flowing rates were determined to be homogeneous and high. Ideal SSCs were made by adding 20% and 25% calcite to 30% BFS and 40% BFS replaced mixtures respectively in this study. It was also concluded that ideal SCC could be produced with paste mixtures having 1 Pa·s (±100 MPa·s) viscosity and mini-slump flow diameter higher than 200 mm. With the increase in calcite addition rates in SSCs, the passing rate for the L box test has increased.