Revista de la Construcción. Journal of Construction

Evaluation of the uses of treated sawdust as a partial replacement for aggregate in hot mix asphalt

Mohamed Lakhder Guesmi — 2023-12-31

Undoubtedly, the damage to the upper layer of the road pavement caused by a tremendous load of vehicles and climate factors is an alarming and challenging fact to both government and researchers in the respective field. Thus, and with the aim to come up with a remedy, the potential of sawdust, as a renewable material for replacing aggregate in hot-mix asphalt, was examined. Therefore, a full factorial design of experiment (DOE) was conducted to evaluate the effects of sawdust content (5%, 10%, and 15% of total aggregate volume) on Marshall stability flow values and density. The range of binder from (5.77% to 6.45% means from low level to high level) and the temperature of mixing (140°C to 180°C) and the time of mixing (2 minutes to 4 minutes) as well. Also, to improve its durability, the sawdust was treated with an established emulsion coating. Accordingly, it has been demonstrated in this study that sawdust can be utilized as a partial replacement for (3/8) aggregate. Indeed, the use of this renewable material resulted in an increase in Marshall stability, a decrease in density, and flow values within the accepted range, leading to a positive environmental impact. Additionally, sawdust is considered a waste material, making it cost-effective. Ultimately, the acceptance criterion allows for the replacement of up to 7% of the aggregate for both low and high-level values; however, if more than 7% is replaced, only the highest-level value is considered acceptable. Thus, an economically and technically efficient solution may have been provided by this study.

Investigation of usability of mineral fiber in stone mastic asphalt

M.A. Rasekh — 2023-12-31

Stone mastic asphalt (SMA) pavements were developed to prevent rutting, abrasion, and various pavement deteriorations and to increase the life of the superstructure. They certainly stand out with their high grain contact, stone-stone interlocking ability, and high bitumen ratio on heavy-traffic roads with heavy axle loads. This study aimed to investigate the effects of basalt fiber in different sizes, partly cellulose, and partly basalt fiber addition, on the drain down of the performance of bitumen and the changes in rutting performance as additives to stone mastic asphalt pavements. To determine the absorption performance of bitumen fiber additives, 19 mixtures were pre-pared and the Schellenberger drain down test was carried out. The results, including the witness mixture, showed that the Schellenberger test result was below the value specified in the motorway technical specification by a maximum of 0.3%. For the Hamburg wheel tracking test (HWTT) additive and witness mixtures were prepared at optimum bitumen ratios using a gyratory compactor. HWTT was applied to the mixtures numbered 1, 4, 10 and 14, which have the best the Schellenberger drain down performance, and the witness sample. As a result of the experiments, the highest rutting deformation was measured at the samples using 12mm basalt fiber at the rate of 0.2%. The lowest rut deformation was measured in samples containing 12mm basalt fiber at the rate of 0,3% and cellulose fiber at the rate of 0.2%. It was determined that the combined use of cellulose and basalt fiber mixture improved the resistance against rutting by 37%. As a result of the HWTT, it was determined that stone mastic asphalt mixtures with basalt and cellulose fiber additives were more resistant to rutting than the witness and basalt-only mixtures.

Recycling waste expanded polystyrene as aggregate in produc-tion of lightweight screed mortar

Serhat Çelikten — 2023-12-31

The potential use of waste-expanded polystyrene (EPS) beads in the production of lightweight screed mortar (LSM) was investigated. LSM specimens were produced by replacing waste EPS with normal weight aggregate at 20%, 40%, 60%, 80%, and 100% proportions by volume. Workability, unit weight, capillarity, flexural and compressive strength, abrasion resistance, drying shrinkage, and thermal conductivity of the LSMs were determined. Waste EPS replacement by the normal weight aggregate reduced the abrasion resistance and strength properties of LSMs. Waste EPS also caused the LSMs to have lower unit weight and thermal conductivity, significantly. It was concluded that substitution of waste EPS by normal weight aggregate up to 60% can be proposed for adequate strength and heat-insulating properties of LSMs. LSM produced with 60% waste EPS (M60) has 16.3 MPa 28th-day compressive strength with 0.4562 W/m.K thermal conductivity and 1.35 g/cm³ unit weight. Moreover, the recovery of waste EPS contributes to both reducing environmental pollution and storage problems.

Seismic analysis of RC building frames with vertical mass and stiffness irregularities using adaptive pushover analysis

Brahim Benaied — 2023-12-31

Irregular multistory buildings constitute a large part of modern urban infrastructure due to architectural aesthetics and functional requirements. In contrast, their behavior during recent major earthquakes indicated that severe structural damage was observed due to non-uniform distributions of mass, stiffness and strength either in plan or in elevation. Notably, abrupt changes in these quantities between adjacent stories are always associated with changes in the structural system along the height of the building. The present study investigates the inelastic response of RC buildings with mass and stiffness irregularities subjected to earthquake action. Thus, the displacement-based adaptive pushover method is used. This latter is motivated by the application of a lateral displacement pattern obtained by combining different mode shapes and updated incrementally at each analysis step. For this purpose, a ten-story regular frame structure is chosen and modified by incorporating vertical irregularities in various forms in order to estimate and quantify essential parameters' responses. The results obtained are discussed under the following headings: base shear forces, roof displacement, inter-story drift and story-shear distribution. With respect to the vertical mass and stiffness irregularities, it was noticed that the seismic response is more significantly influenced by stiffness irregularities compared to mass irregularities, which were found to have a slight impact on the seismic behavior of the building. It is also established that the simple procedure allows the evaluation of design forces and displacements in a more rational manner, in accordance with the current state of knowledge and modern trends in building codes. The results conclude, however, that the irregular structure cannot meet the seismic design requirements and must be constructed to minimize seismic effects.

Experimental investigations the effects of dusty, humidity and temperature conditions on chemical anchors

Özlem Çalışkan — 2023-12-31

Chemical anchor applications are frequently used to add new structural elements to existing structures. Chemical anchors can be applied quickly and easily, if anchors apply according to a detailed installation and cleaning procedure depending on environmental conditions and workmanship. In this work, the relationship between the axial tensile capacity of chemical anchors and the effect of dust, humidity, and temperature were examined as adverse conditions. The effect of using different conditions, anchorage diameters and embedment depth on the tensile strength of the anchors was evaluated. In the experimental study, anchors diameter 12, 16 and 20 mm were selected to be used as anchors. The depth of embedding was determined to be 5, 10, 15 and 20 times the diameter of used anchors. The initial stiffness, displacement ductility ratio, energy absorption capacity, failure modes, and safety levels according to ACI 318 were obtained by using the load-displacement curves. According to the parameters considered in the experimental program, the most unfavorable situation was obtained in anchors embedded in a wet environment. In addition, it was observed that the diameter of the drilled holes causes a decrease in the axial tensile capacity by increasing the exposure time of the anchors to water and temperature.

Effect of sodium silicate and cement on the improvement of engineering properties of organic soil

Veronica Gacambi Kiuna — 2023-12-31

The study is aimed at evaluating the effect of adding sodium silicate and cement to organic soil. Geotechnical properties of organic soil are determined before and after the addition of the stabilizing materials, which in this case are cement and sodium silicate. The results obtained after treatment were analyzed and evaluated to determine whether the strength values reached are adequate for strong subgrades for pavement, and airports construction. Organic soil samples used in this study were obtained from Kayseri Free Area in Turkey. Index properties and geotechnical properties of organic soil, which was identified as sample P, were determined and this formed the reference upon which strength improvements of each mix design sample were obtained. Optimum moisture content and maximum dry density of the soil and the various mixes were obtained using standard proctor test. Unconfined compressive tests (UCS), California bearing ratio (CBR), and Falling head permeability tests were used to determine geotechnical properties. UCS tests were conducted on air cured samples for 1, 7, and 28 days. Soaked and unsoaked CBR samples were tested after 1, 7 and 28 days. Hydraulic conductivity was determined using the falling head permeability test. From the experiments, sodium silicate and cement were seen to improve the strength of organic soil and provide acceptable subgrade strength and CBR values. CBR and UCS tests indicated that longer curing periods improved strength even more. Higher values were obtained for 7 days cured samples than for 1-day samples with the highest values being obtained for 28 days cured samples. Design mixes with higher cement and sodium silicate compositions gave the highest values of strength. In conclusion, sodium silicate and cement give positive results when it comes to stabilizing organic soil.

A new hybrid MCDM method for optimizing natural stone se-lection for building envelopes

Alptekin Ulutaş — 2024-01-31

Most kinds of natural stones are perfect coating materials. Through utilizing stones with less thermal conductivity coefficients, isolation of constructions improves with energy effective resolution. Modern building technologies prefer either decreasing stone to the weakest plausible extents or utilizing natural stones because natural stones have lower thermal conductivity with lighter weights. For this reason, first, the thermal and physical characteristics of natural stones used as coating material on the exterior walls of the buildings were investigated in this study. Then, in the light of these characteristics, natural stones with the best performance in terms of energy efficiency were determined using multi-criteria decision-making methods including FFSWARA and COBRA. The findings show that compressive strength is the most significant criteria and Isparta andesite stone is the most superior natural stone in terms of performance. This study contributes to the literature in three ways. First, the COBRA method used in this study has recently been introduced to the literature. Therefore, it has not been covered much in the literature. Second, this method has not been used in the selection of natural stone selection in the literature to our best knowledge. Third, this method has not been used together with the FFSWARA method before.

A criticism on strengthening glued laminated timber beams with fibre reinforcement polymers, numerical comparisons between different modelling techniques and strengthening configurations

Dilan Çankal — 2023-12-31

The application of CFRP for strengthening timber structures has proven its efficiency in enhancing load-bearing capacity and, in some cases, the stiffness of structural elements, thus providing cost-effective and competitive alternatives both in new design and retrofitting existing historical buildings. In this study, glued laminated timber beams strengthened with CFRP were examined. A number of test beams with different reinforcement configurations and beam sizes were selected from the literature. These beams were analysed with three different methods as numerical, theoretical and code perspective. For the numerical method, a 3D nonlinear finite element model which includes damage and fracture mechanics was constructed. All test beams were studied with different methods and results were compared with respect to initial flexural stiffness, midspan vertical displacement and failure load. The effectiveness of methods and strengthening configurations were stated and suggestions for practical application of FRP-strengthened timber beams were presented.

Feasibility study of using waste badminton string fibers in con-crete by morphological, microstructural and tensile characteristics

Kumaresan M — 2023-12-31

As the strings are cut off from the badminton racquet system, the whole string will be replaced with a new one and there is no other alternative. Hence those cut-off strings are considered as waste and cannot be recycled, tons of waste are retained as debris. Among many research on recycled synthetic fiber, this application of waste material is a new context in sustainable construction. Here five different samples are examined based on wide usage, recycled Waste Badminton String Fiber (WBSF) is characterized and physically examined using a Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy, and X-ray diffraction to use it as a recycled synthetic fiber in various fiber reinforced concrete applications. The diameter and cross-sectional area of WBSF are studied using the Scanning Electron Microscope imaging technique and Image J application, which shows that the fiber is highly engineered with 3 layers namely elasticity outer, outer layer, and core fiber with the mean diameter and net cross-sectional area is 777.6 µm and 5,05,959 µm² respectively. The surface roughness of fiber is analyzed using ImageJ application which varies between 16-32 nm. The fiber samples are subjected to tensile loading the average tensile stress lies between 544.34 - 639.94 MPa. From the above examinations, the accurate diameter, net cross-sectional area, and voided area of the WBSF are calculated. The structural property and polymer relationship of the fiber are investigated using the X-ray diffraction technique and Fourier transform infrared spectroscopy, this reveals that the WBSF is of polyamide 6,6 form. The superior tensile stress compared to other recycled nylon fibers. So, the use of waste badminton string fiber in concrete is a new merging idea for fiber-reinforced concrete applications like pavements, pipes, tunnel lining, and other structural elements.

A comparative study between buckling behaviour and statistical analysis of axially loaded fully encased composite columns made with high strength concrete

SASIKUMAR P — 2023-12-31

This research presents a buckling behaviour of axially loaded fully encased composite columns made with high strength concrete (HSC). Additionally, the research includes experimental study, numerical analysis, and statistical analysis. Three fully encased composite columns (FECC) cast with different cross sections are 200mm x 200mm, 230mm x 200mm, 250mm x 200mm, and 2800mm, respectively. The FECC specimens were made with 80MPa grade of concrete and ISMB 100 x 50 x 7 x 4.2 steel section, including the experimental, analytical, and numerical analyses. The buckling resistance of FECC specimen results were compared to Euro code – 1994 and American Institute of Steel of Construction 360 – 2010 codes. Finite element analysis (FEM) studied the FECC specimens and predicted the buckling resistance compared to the experimental test results. The FEM analysis closely correlated to the experimental results. The statistical analysis was performed on the FECC specimens with current design codes and previous experimental research work. The statistical study compared the experimental test results of buckling resistance and flexural stiffness of FECC specimens to the predicted values from codes. The numerical and statistical analysis results were compared to the experimental test results. Also, it is highly correlated and helps the performance of columns.

Optimization of fiber-reinforced deep cement-fly ash mixing column materials

Arda Burak Ekmen — 2023-12-31

The flexural and compressive strength requirements of deep cement mixing (DCM) columns subjected to lateral loading have brought forth the demand to specify how the incorporation of fiber and fly ash improves these properties and the mixture quality, including the construction design characteristics of segregation and swelling. The paper addresses this issue considering the experimental results from the extensive parametric study in which various lengths and content of carbon fiber (4-, 6-, and 12-mm lengths and 0.1, 0.4, 0.8% by volume of the mixture) are incorporated into the cement-based mixtures with and without the optimized fly ash content. Along the strength parameters, the effects of mixture quality responses on the performance of DCM columns are also investigated. The segregation results of the fresh mixtures, unconfined compression strength (UCS), flexural strength, and swelling values from the 28-day cured specimens are presented. The novel version of the Goal Attainment Method is used for the optimizations, in which the procedures of high-order regression equations and the multi-objective desirability contents are included to obtain more accurate optimization results in terms of the controlling parameters of segregation, swelling, UCS, and flexural strength. The setting time and workability results from the mixtures having the optimized parameters are also presented to demonstrate the fluidity of the optimized mixtures. The addition of carbon fiber led to significant improvements in the segregation and swelling ratios, with gains of up to 35%. Moreover, the three-point flexural strength and unconfined compressive strength were enhanced by 278% and 54%, respectively. The paper specifically reveals that the incorporation of carbon fiber significantly improves the mixture quality characteristics of segregation and swelling as well as the parameters of flexural strength and UCS.