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In this situation, it is necessary to establish and manage a SIP (Shelter In Place) by utilizing existing facilities rather than increasing the number of evacuation facilities. These facilities can...

This study investigates the influence of steel slag (SS) and steel fibers on the electrical resistivity and electromagnetic (EM) shielding effectiveness of high-strength concrete (HSC). It was found that the electrical resistivity of mixtures were mainly influenced by free water. Thus, the EM shielding effectiveness was evaluated without the effect of free water. HSC with 20% replacement ratio of SS exhibited slightly improved EM shielding, lower electrical resistivity, and reduced strength (compressive and flexural) compared to HSC without SS. However, HSC with steel fibers exhibited significantly improved EM shielding, lower electrical resistivity, and higher strength and toughness compared to HSC without steel fibers. An increase in the steel fiber content in the HSC significantly decreased the electrical resistivity and increased the shielding effectiveness, strength, and toughness. Regardless of the fiber content in the fiber volume fraction of mixture, the shielding effectiveness is similar for cases with and without SS whose electrical resistivity values differ only slightly. This proves that the EM shielding effectiveness was mainly affected by the electrical resistivity and these properties are significantly correlated when the electrical resistivity values differ noticeably. HSC reinforced with rebar with 50 mm spacing exhibited a 23.5–75.6% increase in the shielding effectiveness in the 600–1,000 MHz frequency region compared to pristine HSC.

Following the fourth Industrial Revolution, electronic and data-based technology is becoming increasingly developed. However, current research on enhancing electromagnetic interference (EMI) shielding and the physical protection performance of structures incorporating these technologies is insufficient. Therefore, in this study aiming for the improvement of EMI shielding and structural performance of structures, twelve concrete walls were fabricated and tested to determine their shielding effectiveness and drop-weight impact resistance. Concrete walls strengthened by three thickness types of high-strength, high-ductility concrete (HSDC) have been considered. The test results showed that the shielding effectiveness with strengthening thickness increased by approximately 35.6–46.2%. Specimens strengthened by more than 40% and 10% of the strengthening area ratio of single- and double-layer, respectively, exhibited more than 20 dB of shielding effectiveness. Moreover, the relationship between the damaged area ratio and shielding effectiveness was evaluated by means of the drop-weight impact test. The structural performance and EMI shielding effectiveness improved as the HSDC thickness increased.

It is important to consider establishing a shelter in place (SIP) using existing facilities to prepare for unpredictable and no-notice disasters. In this study, we evaluate the building-information-modeling (BIM)-based approach to simulate the strategic location of SIP and its strengthening method. BIM software was used to model a light rail station and analyze the elements of the facility that can affect the evacuation time to reach the SIP. The purpose of this study was to understand the effects of structural standards on the design of SIPs using a direct simulation. The differences between domestic and overseas standards were analyzed. An analysis was carried out to evaluate whether national specifications are satisfactory. As the proposed evacuation method is based on a rational human behavior analysis through a direct simulation, it was going to be a safer and faster route of evacuation in the case of physical terror attack situations for existing infrastructure, Furthermore, the SIP design is considered where reinforcement of the SIP structure is necessary. Three types of reinforcing were considered. Here, the use of high-strength, high-ductility concrete proved to be an effective method to improve the impact resistance of reinforced concrete walls and recommended for strengthening reinforced concrete members.

Compressive strength is a major and significant mechanical property of concrete which is considered as one of the important parameters in many design codes and standards. Early and accurate estimation of it can save in time and cost. In this study, extreme learning machine (ELM) was used to predict the compressive strength of high-strength concrete (HSC). ELM is a relatively new method for training artificial neural networks (ANN), showing good generalization performance and fast learning speed in many regression applications. ELM model was developed using 324 data records obtained from laboratory experiments. The compressive strength was modeled as a function of five input variables: water, cement, fine aggregate, coarse aggregate, and superplasticizer. The performance of the developed ELM model was compared with that of ANN model trained by using back propagation (BP) algorithm. The simulation results show that the proposed ELM model has a strong potential for predicting the compressive strength of HSC.

The application of electric arc furnace oxidizing slag (EAS) in high strength concrete (HSC) as the cementitious material is investigated in this study. The microstructure and mechanical properties of HSC with four different replacement ratios of EAS were evaluated and HSC with two replacement ratios of ground granulated blast furnace slag (GBS) was used for performance comparison. The results show that the HSC with EAS replacement ratios smaller than 15% undergo similar hydration processes and result in a similar final product when compared with those of NC-NN. Increases in EAS replacement ratio cause a reduction in Ca(OH)2 content, this, in turn, leads to an increase in porosity and a reduction in compressive strength. In terms of shrinkage behavior under free conditions, mixtures with increasing replacement ratios of cementitious materials saw increasing shrinkage, with the HSC containing EAS being similar to the other specimens. The mixtures containing EAS saw a quite gradual decrease in their freezing and thawing resistance properties as the number of freeze–thaw cycles they underwent increased. However, the efficacy of HSC with less than 15% of EAS is similar to GBS, hence, EAS could replace cement in concrete for certain applications, which would lead to more environmental benefits.

This study investigates the flexural behavior of normal-strength concrete (NSC) beams that were strengthened with no-slump, high-strength, high-ductility concrete (NSHSDC). A set of slant shear tests was performed to investigate the initial performance of the NSC substrate strengthened with NSHSDC. Slant shear tests considered two types of roughness of interface and five angles of the interface between NSC and NSHSDC. The test results showed that except for specimens with a 75&deg, interface angle, the specimens with high roughness were conformed to the properties (14&ndash, 21 MPa for 28 days) of the ACI Committee 546 recommendation. For flexural strength tests, NSC beams strengthened with an NSHSDC jacket on the top and bottom sides, three sides, and four sides resulted in strength increments of about 8%, 29%, and 40%, respectively, compared to the beams without NSHSDC jacket. Therefore, the use of NSHSDC is an effective method to improve the performance of NSC beams and is recommended for strengthening reinforced concrete members.

Strain sensors can indicate the conditions of concrete structures, but these sensors are only capable of measuring local behaviors of materials. To solve this problem, researchers have introduced conductive materials that can monitor the overall behavior of concrete structures. Steelmaking slag, which contains large amounts of iron oxide (Fe2O3), is conductive, and researchers have considered the addition of this material to improve concrete monitoring. In this study, mechanical and electrical properties of concrete containing steelmaking slag as a binder were evaluated. As the incorporation of steelmaking slag increased, the setting times were delayed, but the compressive strengths were similar within the replacement ratio of 15%. It was found that the addition of steelmaking slag with Fe2O3, the main ingredient of magnetite (Fe3O4), improved the electrical resistivity, piezoresistivity, and sensitivity of the concrete. Drying of the concretes resulted in an increase in electrical resistance and fractional change in resistivity (FCR). Expansion of steelmaking slag, due to contacting of free CaO and moisture under repeated loads, resulted in cracks in the concrete and affected the gauge factor (GF). This study demonstrates the possibility that the addition of steelmaking slag as a binder may provide an economical and environmentally-friendly solution to concrete strain monitoring.

Compressive strength is considered as one of the most important parameters in concrete design. Time and cost can be reduced if the compressive strength of concrete is accurately estimated. In this paper, a new prediction model for compressive strength of high-performance concrete (HPC) was developed using a non-tuned machine learning technique, namely, a regularized extreme learning machine (RELM). The RELM prediction model was developed using a comprehensive dataset obtained from previously published studies. The input variables of the model include cement, blast furnace slag, fly ash, water, superplasticizer, coarse aggregate, fine aggregate, and age of specimens. k-fold cross-validation was used to assess the prediction reliability of the developed RELM model. The prediction results of the RELM model were evaluated using various error measures and compared with that of the standard extreme learning machine (ELM) and other methods presented in the literature. The findings of this research indicate that the compressive strength of HPC can be accurately estimated using the proposed RELM model.

Electromagnetic interference shielding has attracted attention in design processes for reducing radiation to protect humans or equipment. Traditional shielding constitutes adding strengthening, conductive paints, conductive fibers, or grids to non-damaged structures. Few studies have considered using hybrid reinforcement methods for shielding effectiveness or examined the relationship between damaged areas and shielding effectiveness. We prepared a reinforced concrete (RC) wall with different steel fiber contents, metallic grid/mesh reinforcement, and hybrid reinforcement and created damage areas via impact load. Compared with 300 mm thick RC and single-type reinforced specimens, the hybrid reinforced specimens had an approximately 25.9 times and 2.4 times higher shielding effectiveness, respectively. Specimens reinforced with metallic mesh exhibited less than 150% of free space area ratio and more than 30 dB shielding effectiveness. The hybrid metallic mesh and facultative metallic grid achieved over 40 dB. Hybrid reinforced specimens exhibited improved impact resistance and great shielding effectiveness in damaged conditions.

A new hybrid intelligent model was developed for estimating the compressive strength (CS) of ground granulated blast furnace slag (GGBFS) concrete, and the synergistic benefits of the hybrid algorithm as compared with a single algorithm were verified. While using the collected 269 data from previous experimental studies, artificial neural network (ANN) models with three different learning algorithms namely back-propagation (BP), particle swarm optimization (PSO), and new hybrid PSO-BP algorithms, were constructed and the performance of the models was evaluated with regard to the prediction accuracy, efficiency, and stability through a threefold procedure. It was found that the PSO-BP neural network model was superior to the simple ANNs that were trained by a single algorithm and it is suitable for predicting the CS of GGBFS concrete.

In this study, the performance of reinforced concrete slabs strengthened using four methods was investigated under impact loads transferred from the top side to bottom side. The top and bottom sides of test slabs were strengthened by no-slump high-strength, high-ductility concrete (NSHSDC), fiber-reinforced-polymer (FRP) sheet, and sprayed FRP, respectively. The test results indicated that the test specimens strengthened with FRP series showed a 4% increase in reaction force and a decrease in deflection by more than 20% compared to the non-strengthened specimens. However, the specimen enhanced by the NSHSDC jacket at both the top and bottom sides exhibited the highest reaction force and energy dissipation as well as the above measurements because it contains two types of fibers in the NSHSDC. In addition, the weight loss rate was improved by approximately 0.12% for the NSHSDC specimen, which was the lowest among the specimens when measuring the weight before and after the impact load. Therefore, a linear relationship between the top and bottom strengthening of the NSHSDC and the impact resistance was confirmed, concluding that the NSHSDC is effective for impact resistance when the top and bottom sides are strengthened. The results of the analysis of the existing research show that the NSHSDC is considered to have high impact resistance, even though it has lower resistance than the steel fiber reinforced concrete and ultra-high-performance-concrete, it can be expected to further studies on strengthening of NSHSDC.

The high shape-holding ability of no-slump concretes (NSC) allows is widely used in roller-compacted and prefabricated concrete. However, it is limited by its low strength properties, and low tensile properties, which lead to potential durability problem in prefabricated concrete. Therefore, this paper aims to investigate the synergy effect in tensile properties of no-slump high-strength high-ductility concrete (NSHSDC) based on polyethylene (PE) and steel fibers (SF). The compressive, flexural, and tensile strength of NSHSDC with three different water-to-binder ratios (w/b) reinforced by 0.0, 1.5 vol% of PE fiber were evaluated. The composites with 16.8% w/b were filtered out due to its poor mechanical properties. The reinforcement characteristics of compressive, flexural, and tensile strength between 16.2% and 17.2% w/b were then compared and analyzed. All composites exhibited a similar compressive strength (>120 MPa), NSHSDC hybrids with different fiber lengths exhibited a flexural strength, tensile strength, and tensile energy absorbing capacity higher than other composites at approximately 18.4%, 14.5%, and 5.4%, respectively. The composites with 17.2% w/b exhibited great mechanical properties than composites with 16.4% w/b; thus, the need for further analysis of its synergy assessment. The composites with 17.2% w/b exhibited a positive synergy and composite hybrids with different fiber lengths established a perfect synergy.

The recent increase in terrorist attacks and natural disasters has led to increased requirements for concrete structures to be impact resistant. Concrete normally has excellent impact resistance to such extreme loads in comparison with other construction materials. Nevertheless, existing concrete structures designed without consideration of the impact or blast load with high strain rate are endangered by those unexpected extreme loads. Therefore, the impact resistances of two-way concrete slabs were studied by conducting the multiple impact test. Various fiber reinforcements (Hooked-steel fiber, straight-steel fiber) were considered as variables. In the impact test, the impact load was applied to each specimen by dropping weight on the specimen from a certain height. The applied impact load level was adjusted by changing the height of the weight. Specimens were used for impact loading test, each measuring 1,600mm long, 1,600mm wide, and 105mm thick. All slabs were doubly reinforced (top and bottom layer) and each layer in a specimen had the same reinforcement layout. The performances of the specimens under the impact load were evaluated by comparing their reaction force, deflection, and surface damage. The impact test was stopped when the measured reaction force started to decrease. Based on the impact test, it was observed that the resistance against impact load can be improved by using fiber reinforced concrete.

For sustainable development in the construction industry, blast furnace slag has been used as a substitute for cement in concrete. In contrast, steel-making slag, the second largest by-product in the steel industry, is mostly used as a filler material in embankment construction. This is because steel-making slag has relatively low hydraulicity and a problem with volumetric expansion. However, as the quenching process of slag has improved recently and the steel making process is specifically separated, the properties of steel-making slag has also improved. In this context, there is a need to find a method for recycling steel-making slag as a more highly valued material, such as its potential use as an admixture in concrete. Therefore, in order to confirm the possibility of using electric arc furnace (EAF) oxidizing slag as a binder, a comparative assessment of the mechanical properties of concrete containing electric arc furnace oxidizing slag, steel-making slag, and granulated blast furnace (GBF) slag was performed. The initial and final setting, shrinkage, compressive and split-cylinder tensile strength of the slag concretes were measured. It was found that replacing cement with EAF oxidizing slag delayed the hydration reaction at early ages, with no significant problems in setting time, shrinkage or strength development found.

High-performance concrete (HPC) is widely used in construction according to great mechanical properties, but it has a high risk of shrinkage cracking due to autogenous shrinkage stress. Therefore, the aim of this research was to investigate the effect of a combination of expansive admixture (EA) and shrinkage reducing admixture (SA) on the autogenous shrinkage of high-performance concrete without heat treatment. Two different EA to cement weight ratios of 0.0, 5.0%, and two different SA to cement weight ratios of 0.0, and 1.0% were combined and considered. To investigate the differences in the time-zero conditions effect on the autogenous shrinkage behaviors, four different initial points were compared. The test results indicate that the EA and/or SA content was conductive to a little bite increase compressive strength (22.6&ndash, 37.9%) and tensile strength (&lt, 4.8%). According to the synergistic effect of the EA and SA on the HPC, the autogenous shrinkage significantly decreased (&lt, 50%), as compared to those specimens with only one type of admixture (EA or SA). Furthermore, all the specimens incurred restrained autogenous shrinkage cracks at an early age, except the specimen using the combined EA and SA. Therefore, it can be concluded that the combination of EA and SA is effective for improving the properties of HPC.