Cylindrical Concrete Samples Research Articles

Implementation of Bamboo Chips from Pantai Labu Region in Enhancing Compressive Strength of Fiber Concrete

Concrete is widely used in construction due to its high compressive strength and durability. This study investigates the use of bamboo chips from the Pantai Labu region as a fiber material mixed with concrete to enhance its compressive strength. The research evaluates the effectiveness of different percentages of bamboo fiber chips, ranging from 0% to 2.5% by cement weight. Cylindrical concrete samples with diameters of 15 cm and heights of 30 cm were tested at 7, 14, and 28 days. The results demonstrate that adding 1% bamboo chips increased the compressive strength to 31.51 MPa, compared to the normal concrete strength of 30.04 MPa. This shows the potential of bamboo chips to improve the quality and sustainability of concrete production.

Evaluation of Concrete Fatigue Damage with Elastic Wave-based Measurement Techniques

Fatigue damage is a progressive and permanent change in the internal material structure due to cyclic loading. The cyclic loads can be due to wind, waves, temperature variation, and traffic loads. Each cyclic load application introduces micro-damages that accumulate to induce failure. Detecting these micro-damages requires sensitive measuring techniques. Hence this research compares the sensitivity of different measuring techniques applied to fatigue experiments of concrete. The applied NDT are the passive acoustic emission technique (AET) and active ultrasonic measurements. In addition, linear variable differential transformers (LVDTs) are applied as a reference measurement. Accordingly in this research, cylindrical concrete samples are subjected to monotonic and cyclic Brazilian splitting tests. The cylinders are 100 mm in diameter and 150 mm in length. The cyclic load is applied to these samples with a loading frequency of 5 Hz. During the tests, the damage evolution is monitored with AET, ultrasonic measurements and LVDTs. There are eight AE sensors attached to the sample. The two LVDTs are positioned at the center of the sample's front and back side. Besides passively monitoring the acoustic emissions, the AET sensors are also used to do active ultrasonic measurements. The research reports the comparison conducted on the deformations and cracks measured with the LVDTs, the damage growth identified with the AET, and the change in the ultrasonic pulse velocity measurements. In addition, the study also presents the damage analysis capacity of the methods across different types of loading: monotonic, constant amplitude, and stepped fatigue loading. The comparison shows that combination of AET and ultrasonic velocity measurement is a sensitive indicator for damage growth.

Fatigue behavior investigation of artificial rock under cyclic loading by using discrete element method

In numerous engineering projects, such as tunnel construction, underground gas storage in caverns, and the impact of earthquakes, rock materials experience cyclic loading. However, the response of rock materials to cyclic loading, which may vary in terms of waveform, frequency, and amplitude, is not uniform. Consequently, comprehending the mechanical attributes and fatigue behavior of rocks holds significant importance in engineering designs. This study focuses on subjecting a collection of cylindrical concrete specimens, categorized into three groups with distinct mechanical properties, to both monotonic and cyclic loading within a laboratory environment. Three groups of cylindrical concrete samples with different mixing designs are prepared to evaluate the effect of the mechanical strength of the samples on the fatigue response of the rock. In such a way that: The first group (G1) with Uniaxial Compressive Strength (UCS): 19 MPa, the second group (G2) with (UCS): 49 MPa, and the third group (G3) with (UCS): 71 MPa. In addition, the discrete element method is utilized to simulate uniaxial cyclic compression tests under various loading conditions, such as monotonic and cyclic loading. The resulting fracture propagation patterns and geometries are then analyzed. Numerical and experimental results show that the cyclic uniaxial compressive strength, due to the presence of damage and fatigue phenomena, has decreased relative to the monotonic tests. Also the cyclic elastic modulus values (Ec) have decreased by 53 %, 25 %, and 11 % relative to the monotonic elastic modulus (Em) for the three groups of G1, G2, and G3, respectively. The Stress-life (S-N) model is used to express the fatigue behavior of rock, and the final equation for the S-N model is expressed.

Microstructural investigation of concretes with recycled aggregates using X-ray microtomography

Recycled aggregates (RA) derive from reprocessed materials from construction and demolition activities. Although the use of RA has been growing worldwide, material standardization and new mix design protocols still need to be developed to enable its use on larger scales. For this, an investigation of the properties of this material is necessary. The present study used microcomputed tomography (microCT) to observe the material's porous structure in cylindrical concrete samples of reference concrete (RC) with natural aggregates and sustainable concrete (SC) with the addition of RA. Through a computational routine, the images obtained were evaluated qualitatively and quantitatively. The pore volume and shape in concretes with and without recycled aggregates were analyzed and correlated with their respective compressive strengths. Even though the SC samples' resistance was lower than the RC samples, the values found followed the required standards. Porosity, pore volume, and shape were similar for the two kinds of concrete. The Pore Network Modeling (PNM) approach was applied to characterize further the pores' spatial distribution and connectivity. The analysis showed that 98.20 % and 97.26 % of the pores were disconnected for the RC and SC samples, respectively. The results indicate that the addition of RA is not detrimental to the properties of concrete. Further PNM-based analysis can help evaluate both samples' absolute and relative permeability to various fluids.

Analisis Penambahan Serbuk Kayu Sebagai Kayu Sebagai Pengganti Terhadap Agregat Halus

This study aims to analyze the impact of adding sawdust as a substitute for fine aggregate in concrete mixes, with percentage variations of 1%, 1.5%, and 2%. The experiments involved the preparation of concrete mixtures with specific proportions according to each sawdust variation, and the formation of cylindrical concrete samples with a size of 15 cm x 30 cm. A total of 12 cylindrical specimens were prepared for each variation, ensuring representativeness and reliability of the results. Subsequently, mechanical properties of the concrete were tested, including compressive strength, resistance to compressive load, and resistance to deformation. The expected compressive strength plan was 16.9 MPa, but the test results showed a decrease in concrete at 1% by 11.99 MPa, at 1.5% by 7.14 MPa, and at 2% by 5.65 MPa. Analysis of these results provides a focal point for planning strategies to improve the performance of concrete with sawdust and ensure that its use does not compromise critical compressive strength. The findings of this study are expected to provide guidance for the construction industry in integrating alternative, more environmentally friendly materials into daily construction practices.

A Deep Learning Based Non-Destructive Method for Estimating Concrete Strength using Continuous Wavelet Transform of Vibration Signals Acquired using A Smartphone’s Accelerometer

Most non-destructive tests of concrete require sophis-ticated equipment and training; in this work we aim to develop a simple method to estimate the strength class of cylindrical con-crete samples based on vibrations signals that are collected after striking a concrete cylinder with a hammer. The vibration signals were collected by attaching a smartphone to the concrete cylinder and logging the vibrations registered via the smartphone’s built-in accelerometer. The acquired 1-D vibration signals are trans-formed to 2-D scalograms using continuous wavelet transform. Scalograms are then used to train a deep learning model to predict the strength class. Preliminary findings show that the model is capable of classifying the strength of concrete to low, high, or me-dium. The developed model achieved a high accuracy of 91.67%. The promising results of this work shed light into the future of smartphone-based measurements of construction materials’ properties.

A Study on the Abrasion Resistance of Hydraulic Structures with Different Repair Mortars

One of the main problems with hydraulic structures is that floating silt, gravel, ice sand, boulders, and other materials circulating over a concrete surface have an abrasive effect that causes hydraulic structures to abrade. Abrasion causes concrete to degrade, which could eventually expose the reinforcing to corrosion. In addition to section loss, reinforced concrete hydraulic structures’ endurance may also be a problem. Repair mortars are used to restore surfaces that have been abraded. The suitability of various repair materials for use as a repair layer on concrete surfaces is examined in this study. In order to apply different repair mortars to concrete specimens and subject them to abrasive forces, this work employs an experimental methodology. The ASTM C 1138 standard was followed for testing the abrasion resistance of the samples repaired using repair mortars underwater. Both silica fume mortar and polymer-modified mortar were employed in the study as forms of repair mortar. For each type of repair mortar, three cylindrical concrete specimens were cast, along with control specimens. Hence, nine cylindrical concrete samples in total were employed in this study. In order to quantify the effect of abrasion and, consequently, to assess the efficacy of various repair materials, abrasion volume loss was measured. Important findings about each type of repair material’s resistance to underwater abrasion are included in the study. The findings show that in terms of abrasion resistance underwater, the polymer-modified mortar performs better than the silica fume mortar.

Cement Kiln Dust (CKD) as a Partial Substitute for Cement in Pozzolanic Concrete Blocks

This study investigates the effect of the partial replacement of ordinary Portland cement (OPC) with cement kiln dust (CKD) on the engineering properties of pozzolanic concrete for use in block manufacturing. Ultimately, this could potentially reduce cement consumption and CO2 emissions. The study was carried out on cylindrical concrete samples prepared from five mixtures comprising 71.13% pozzolan and 14.16% water, with 0, 5, 10, 15, or 20% of the OPC fraction (14.71 wt.%) replaced by CKD. The samples were tested for density and compressive strength (UCS) at curing ages of 7, 14, 28, 56, and 91 days; and for voids and water absorption after 28 curing days. Results show that increasing CKD content lowered the voids and increased the water absorption. The 15% CKD sample had the highest UCS, regardless of the curing age. X-ray diffraction analysis confirmed that the phase responsible for hydration, calcium silicate hydrate, was higher in the 15% CKD sample than the control.

Comparative Effects of Chemical Pretreatments on Mechanical Properties of Sustainable Rubberized Concrete

Chemical pretreatments are known to have significant influence over mechanical properties of concrete and being able to quantify the effect of chemical pretreatments will be of great help in trying to anticipate the rubberized concrete’s possible mechanical properties. This paper presents an experimental study that was conducted on cylindrical concrete samples prepared by using different proportions of natural coarse aggregates (NCAs) replaced by pretreated; with different concentrations of chemicals, rubber coarse aggregates (RCAs). The aim was to ameliorate the mechanical properties of concrete using sustainable alternative; rubber coarse aggregate. After chemical treatment, washing and air drying, RCAs were first coated with cement paste and then dried and cured for 28 days to enhance their bonding behavior in concrete. The results confirmed the efficiency of pretreated RCAs, in improving the mechanical properties of rubberizes concrete especially the compressive strength. Key words: Compressive strength, Rubber coarse aggregates, Rubberized concrete, Pretreatment, Sustainability corresponding author: pc.ahmadali@gmail.com

The effect of steel and hybrid fibers on the impact resistance of concrete enclosed with FRP sheets

Due to the widespread use of concrete in all kinds of structures, the probability of its exposure to dynamic loads has increased. Since concrete is one of the most widely used materials in civil engineering, its main weakness can be pointed out, which is its brittleness and brittle performance. The use of fibers to improve the properties of concrete has been the focus of engineers for a long time. The most common fibers used to increase the impact resistance of concrete, steel and polypropylene were investigated in this research as single and hybrid fibers. In this study, by using the ACI 544-based weight projection method, the resistance of concrete against impact loading on standard cylindrical concrete samples (30 x 15) containing steel fibers and polypropylene in two cases with and without lap sheet FRPs were investigated. The results showed that the use of these fibers increases the impact resistance of concrete. Also, both CFRP and GFRP sheets that were tested improve the impact resistance of concrete and increase the number of cycles of this test. Some GFRP sheets have performed better than CFRP. Also, the presence of FRP sheets has caused a change in the type of failure compared to the absence of FRP. Also, concrete samples whith fiber delay concrete breaking, significantly.

Development of corrosion resistance of reinforcement steel bars with nano-silver coatings

The aims of this study are to examine the effect of metallic coatings on reinforcement from the perspective of the durability properties of concrete structures. Also, consider the importance of laboratory production of cover while investigating how it can be applied to steel. In this research, to increase the corrosion resistance of the structural steel, the reinforcements were coated with thin films with a system called thermionic vacuum arc (TVA). As a result of recent studies, it has been observed that such thin films protect the reinforcement from corrosion. In this study, the effect of coated reinforcement on corrosion, which is one of the most important structural defects, was investigated. The applied coatings are nano-sized and protect the structural steel against corrosion reactions occurring on the surface. Moreover, these coatings increase the adherence between concrete and reinforcement. Specifically, for this study, silver (Ag) was used as a coating component. After the coating process was completed, the reinforcements were placed in cylindrical concrete samples and their resistance to corrosion was measured with the help of the accelerated corrosion technique. The results show that the rebars coated with the TVA system was prolonged the damage occurrence time (first crack) and diminished the corrosion reactions that occurred on the reinforcement surface.

Effect of Temperature Gradient on Chloride Ion Diffusion in Nuclear Reactor Containment Building Concrete

Chloride diffusion through concrete is influenced by harsh environmental conditions such as high ambient temperature and relative humidity. This paper examined the influence of temperature gradient on chloride diffusion in concrete under high ambient temperature conditions. Chloride diffusion tests using cylindrical concrete samples were performed in constant temperature and temperature gradient conditions. In a temperature gradient condition, a much higher chloride concentration was measured than at constant temperatures, which could not be explained only by the mass diffusion driven by the concentration gradient. A new analytical model of chloride diffusion with the mass diffusion term including the temperature effect and the thermo-diffusion term including the temperature gradient effect was applied to the results, which showed that the thermo-diffusion contribution was significant. Using the analytical model with the mass diffusion (DCl) and thermo-diffusion (DT) coefficients, the service life of reactor containment buildings (RCBs) in nuclear power plants (NPPs) in the Middle Eastern and North African (MENA) region was estimated. The results showed that the service life of the RCBs could be reduced by the temperature gradient, indicating the possible application of the proposed analytical model.

Adopting an image analysis method to study the influence of segregation on the compressive strength of lightweight aggregate concretes

Aggregate segregation in concretes, especially in lightweight aggregate concretes (LWAC), is a pathology that can seriously impact on different material properties, both in terms of mechanical strength and durability. Some studies have already analysed the impact of this phenomenon in the compressive strength of LWAC , almost always adopting segregation quantification methods based on the comparison of variables such as weight or density measured in sections extracted from cylindrical samples. Although the methods used so far are simple and easy to apply, in certain circumstances they may not offer sufficient accuracy to measure the phenomenon. Moreover, the analysis of segregation in LWAC, which due to the lower density of aggregates in relation to the mortar matrix occurs in the opposite direction to the segregation of conventional concretes (from bottom to top), has not been widely studied so far. The analysis of the cross sections of cylindrical concrete samples through image analysis techniques has been increasingly used to estimate parameters related to the distribution of materials inside them. This study aims to measure the impact of segregation on the compressive strength of LWAC cylindrical specimens, employing an image analysis technique capable of quantifying the phenomenon with a more accurate segregation index. During the experimental campaign 22 scenarios were defined, combining different types of aggregate, vibration methods and vibration times, to achieve different levels of segregation. Among the main results it can be noted that the impact of the type of moulding (one layer vs. two layers) considerably affected the mechanical properties of concrete, with concretes vibrated in two layers showing a maximum reduction in compressive strength due to segregation of 9%, while concretes vibrated in only one layer showed reductions ranging from 63% to 118%. Analyzing the type of rupture of the samples, the study identifies the appearance of well-defined compression cones in samples where segregation is excessive, with 90% of the cases presenting this type of rupture and that the size of the compression cone increases as the effect of segregation is accentuated.

Effects of Low-Cost Repair Techniques on Restoration of Mechanical Properties of Fire-Damaged Concrete

Researchers have conducted numerous investigations on various repair techniques to restore the mechanical properties of fire-damaged concrete. However, most of the techniques are either expensive or require high technical skills. As a continuous work, this study involved an experimental investigation of the effects of various low-cost repair techniques to restore the mechanical properties of fire-damaged concrete. Sixty cylindrical concrete samples were subjected to heat ranging from 400°C to 800°C in a propane gas furnace. The samples were categorized into six groups, including the following: undamaged, fire-damaged, and fire-damaged and repaired using water curing; fire-damaged and repaired using cement-based slurry injection; re-curing fire-damaged and repaired with steel wire mesh along with epoxy resin wrapping; and fire-damaged and repaired using epoxy injection. The samples were tested for non-destructive and destructive tests, including ultrasonic pulse velocity, rebound hammer, and compressive strength. The results showed that the use of cement-based slurry injection along with the water-curing repair technique could regain almost 90% of its ultimate strength and secant stiffness, making it the most effective low-cost repair technique for fire-damaged concrete exposed up to 700°C.

Investigation of the Effect of using Salak Seeds as Coarse Aggregate in Concrete

This study described the effect of using salak seed waste as a substitute for coarse aggregate. The percentage of salak seed in concrete mixture became experimental variable to discover the best compressive strength of concrete.
 Quantitative study with experimental study was carried out at the Laboratory of Materials and Concrete, Faculty of Engineering, University. The design of experiment used a designed compressive strength of concrete of 20 Mpa. The experiment consisted of five variations in the percentage of salak seeds, namely 0%, 5%, 10%, 15%, and 20%. The slump test is carried out immediately after mixing the concrete in each proportion. Furthermore, 20 pieces of cylindrical concrete samples in each treatment were tested for 7,14,21 and 28 days. This method aims to compare the strength of each of the resulting concrete compositions. The results obtained showed that the use of salak seeds with a percentage of 5% and 10% gave a compressive strength value of 28 days which met the standard compressive strength of the design female. Meanwhile, the percentage of salak seeds 15% and 20% did not produce the planned compressive strength value. Therefore, salak seeds are suitable to be used as a substitute for coarse aggregate with a percentage of less than 10%. The higher the substitution of the mixture in the salak seed concrete, the lower the compressive strength of the concrete. The results of this study can be developed in green concrete studies that use waste.

The Role of Rice Husk Ash in Enhancing the Fresh Properties, Density, and Compressive Strength of Fly Ash Based Self Compacting Geopolymer Concrete

This paper describes the effect of rice husk ash on the fresh properties, density, and compressive strength of fly ash-based self compacting geopolymer concrete (SCGC). Fresh properties were tested by the slump flow test. Density and compressive strength were tested with cylindrical concrete samples. Diameters of samples were about 150 mm and 300 mm high. The variations of Rice Husk Ash (RHA) as Fly Ash (FA) substitution were 0%, 5%, 10%, and 15%. The alkaline activators used Na2SiO3 and NaOH with ratio at 1.0 and a molarity value of NaOH was fixed at 14 M. The water-binder ratio was fixed at 0.3. The dosage of superplasticizer used 1%. The treatment of concrete used ambient temperature. The test results showed that rice husk ash decreased the slump flow; was not affected on the concrete density; and increased the compressive strength of SCGC. The maximum percentage of rice husk ash substitution to achieve the EFNARC slump flow standard was 7.16%. The density of the SCGC was 2076.4 kg / m3 – 2104.3 kg / m3, and classified to the normal concrete. The maximum compressive strength of SCGC was 11.476 MPa at the percentage of rice husk ash substitution about 8.65%.

Comparison of Static and Dynamic Elastic Moduli in Concrete: Effects of Compressive Strength, Curing Conditions and Reinforcement

The elastic moduli are important parameters in engineering applications. In particular, the elasticity modulus and Poisson ratio are the main parameters for evaluating the bending and shear rigidity of concrete. Elastic modulus’s calculations are made by taking a fixed value of concrete’s Poisson ratio in the worldwide standards. The aim of this study is to show whether the Poisson ratio of concrete with different compressive strengths and different pores, saturation is a fixed value, and harmony with each other of the relationship between static and dynamic elastic moduli. Therefore, totally 540 samples were prepared. These samples consist of reinforced cubic, unreinforced cubic and unreinforced cylindrical concrete samples of the 9 concrete designs with different compressive strengths. In certain days, the ultrasonic P- and S-wave measurements and the uniaxial compressive strength test were performed on these samples exposed to water and air curing. In addition, the static and dynamic elastic moduli, the velocity ratio and the Poisson ratio of these samples were calculated using the obtained data. At the same time, the static and dynamic elastic parameters of the concrete were compared with each other depending on curing conditions because the elastic parameters could be effected from the water or air saturation of the concrete depending on location of existing structures. Consequently, new multi-parameters relationships with low RMSE were generated to determine the relationships among static and dynamic elastic parameters, and to demonstrate the effect of different curing and compressive strength conditions on static and dynamic elastic parameters. In addition, the Poisson ratio values were obtained between 0.22 and 0.34 for different curing conditions and compressive strength (2–70 MPa). This indicates that the Poisson ratio value is not a constant value.

Behavior analysis of concrete with recycled tire rubber as aggregate using 3D-digital image correlation

Owing to the rapid growth of world population and the usage of cars, scrap tires are causing serious environmental problems and ecological threats, which can be solved by recycling them, e.g., by using them as aggregates in concrete. In this study, an experimental investigation is established to understand the compression behavior of concrete by replacing natural aggregates with recycled tire rubber at different percentages, ranging from 10% to 50% by volume. In experimental testing, several compression tests were performed on cylindrical concrete samples, and a three-dimensional digital image correlation (3D-DIC) system was used to analyze the compression behavior of concrete structures during deformation. The experimental results indicated that the behavior of concrete changed from brittle to ductile and their ability to absorb compression energy (compression toughness) improved by increasing the crumb rubber percentage. Using 3D-DIC system which has a potential to replace the conventional tools, cracks onset locations were detected, failure mechanism and crack progress were tracked, and critical strain values which are usually at the interface of rubber particles and concrete were located. Although the cost of rubber crumbs is high compared with that of natural aggregates, incorporating recycled tire rubber in concrete structures can solve ecological problems.

Electrochemical behavior of mild and corrosion resistant concrete reinforcing steels

An experimental study is carried out in this paper to evaluate the corrosion performance of mild steel reinforcing bars (MS), high strength steel reinforcing bars (HS), epoxy-coated steel reinforcing bars (EC), and high-chromium steel reinforcing bars (HC) under harsh environmental conditions. Reinforcing bars (rebar) of 16 mm diameter and 310 mm length were embedded in cylindrical concrete samples of 60 mm diameter and 350 mm length, and subjected to a Southern Exposure test for sixteen months. The open circuit potential (OCP) was monitored during the exposure period until corrosion initiation. The linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and Tafel plot techniques were employed to assess the corrosion rates on the rebar surfaces. The macrocell corrosion current was monitored by connecting the corroding rebar with an external stainless steel bar of the same size. The polarization resistance of the HC was found to be 1.5 times higher than that of the MS. The EIS technique showed that EC, even with damaged epoxy coating, has the highest resistance to chloride attack. The macrocell current of HC rebar was 48% less than that of MS during the active corrosion state. The LPR, EIS and Tafel plots analysis provided the current densities, which were close to each other; indicating the validity of these techniques to study the problem at hand. The corrosion rates from electrochemical methods were compared against the ones calculated by gravimetric methods. The quantitative results from this research may be used in service life prediction of concrete structures with different types of rebar. Extensive analysis of the results indicates that the corrosion resistance of the evaluated steels was in the following decreasing order: EC, HC, MS, and HS.

Environmentally friendly interlocking concrete paver blocks produced with treated wastewater

Abstract This study aimed at supporting processes and techniques for minimization of water consumption in the production of concrete. For this purpose, the use of treated wastewater from a wastewater treatment plant (WWTP) in interlocking concrete paver block (ICPB) production was evaluated. The treated wastewater was added in various dosages (0%, 50%, 75% and 100%) to the water used to produce cylindrical concrete samples. These samples were evaluated for compressive strength and water absorption tests. After these evaluations, the dosage of 100% treated wastewater for concrete production was established and ICPB were produced with this water composition. Subsequently, an area in a parking lot was replaced by ICPB produced with treated wastewater, and an equal area was replaced by ICPB produced with potable water. A comparison between parameters obtained for cylindrical samples and ICPB samples prepared with treated wastewater and those prepared with potable water indicated that wastewater reuse would be a good alternative for potable water consumption reduction in the concrete industry.