Journal of Rehabilitation in Civil Engineering
Volume:11 Issue: 1, Winter 2023

The destructive effects of global warming have attracted attention to the optimal using of resources and recycling. Therefore, slag has been considered as a solution in various industrial sectors including the road construction. Also, among the new materials, cement carbon nanostructures which can improve the concrete mechanical properties and resistance are used. These nanostructures are produced through Chemical Vapor Deposition method during the cement production process on the type II cement. In this study, it is aimed to improve the mechanical properties and resistance of concrete pavements with slag and cement carbon nanostructures. The results showed that using 66% slag and 5% cement carbon nanostructures (SC66N5) have been shown the best performance in concrete pavements. Increasing the amount of slag and carbon nanostructures enhance the compressive strength, flexural strength, tensile strength, chlorine passing current and durability against freezing and thawing cycles, and decrease permeability and water absorption percentage. The results showed that in SC66N5 28-day sample, the compressive strength (52%), flexural strength (32%), tensile strength (53%), chlorine passing current (88%) and passing ultrasonic pulse velocity after freezing and thawing (7%) are increased with respect to the cement concrete sample. Furthermore, the permeability (46%), water absorption percentage (45%), weight loss after freezing and thawing cycles (78%) are reduced in comparison to the cement concrete sample. The results revealed that using slag and cement carbon nanostructures improve the durability of concrete pavements.

An environmentally friendly building system with suitable properties including durability can be made by using geopolymer concrete and FRP bars. The flexural behavior of geopolymer concrete beams made from Iran mines soil and reinforced with FRP and steel bars was examined in this work. In terms of reinforcement and concrete, the findings of the experimental investigation of geopolymer concrete beams were compared to those of standard cement concrete beams. To accomplish this purpose, a four-point flexural test was performed on 24 specimens of geopolymer and cement concrete beams reinforced with steel, GFRP, and CFRP bars. The initial cracking load, ultimate load, failure modes, number and width of cracks, load-deflection behavior, crack pattern, strain distribution, effective moment of inertia, and ductility were all investigated. The failure modes of tested beams were approximately similar to those predicted by codes, and a comparison of experimental findings with codes predictions reveals that these codes underestimated the beams' flexural strength, but ACI predictions are almost 20% more accurate than CSA ones. Geopolymer beams reinforced with FRP rebars and made with Iran mine soil showed similar results to reinforced cement beams, and the ductility ratio of FRP and steel reinforced geopolymer beams is 5% and 34% greater than that of reinforced OPC concrete, respectively.

In the present study, The main purpose is to focus on the applicability of using non-prestressed tendons as the main reinforcement in concrete beams. Therefore, the main reason for the analytical study is to develop a model that can predict the flexural behavior of RC beams with ordinary reinforcements and/or with non-prestressed tendons (cables). An experimental program, as well as a computational program, was designed to see the behavior of such concrete reinforced beams. To do so, 9 beam models of one concrete mix were cast. The beams were cast in accordance with ACI recommendations and all tests were conducted under the same condition. The beams tested include two types of beams with ordinary steel rebar and with cables (tendons). The beams studied in this research are classified as deep beams (L/h<4); so the effect of shear deformations was considered. In addition, test results were compared with the predicted theoretical values. The theoretical model was able to predict the experimental load-deflection curves almost accurately. Therefore, it was demonstrated that the same concepts of the normal reinforced concrete beams can be applied for reinforced concrete beams using tendons as main reinforcement for both stiffness and strength calculations. Also, the same methodology used in concrete beams with steel rebar is applicable to the ones with non-prestressed tendons. The results showed that using the nominal flexural strength equations of regular reinforced concrete beams can accurately predict the strength of the beams with cables.

Some of the desirable properties of concrete include high impact resistance and great energy-sucking capacity to name a few. These properties can be improved through the use of sustainable materials. This study investigated the effects of partly replacing fine aggregate with linear low-density polyethylene (LLDPE) and waste rubber (WR) as fine aggregates on the efficiency of concrete under impact loading. Two water to binder ratio (W/B) percentages of (0.40 and 0.55) were selected, with six (LLDPE-R) replacement grades (0%, 5%, 10%, 15%, 20%, and 30%) and two silica fume (SF) replacement grades (0% and 15%). Six cylinders with 150 and 60 mm were subjected to an impact by a 4.45 kg hammer striking. Test results indicated that impact resistance for the first visible crack and the ultimate failure increased with LLDPE-R content, where it increased by 4.76 times. This study also demonstrated that the impact resistance for the first visible crack of LLDPE-R concrete was improved by an average of 295% for specimens without SF and 292% for specimens containing SF. This enhancement for the ultimate failure is 291% and 290% for specimens without SF and containing SF, respectively.

The Project Management Institute (PMI) described project management as “Project Management is the application of knowledge, skills, tools, and techniques to project activities to meet the project requirements”. The nature of projects is always dynamic, uncertainty and different from each other. Project lifecycle is along with risk, changes and even sometimes failing happened. Therefore, to bridge these gaps and to achieve the project goal within budget, time, scope and quality. All projects-oriented organizations such as construction firms, consultancy firms, and information and communication technology (ICT) firms, need for trained, competent, leader and experienced project managers. Among the most important elements for a successful project manager, there are combination of knowledge, skill, leadership, ability and personal attitude which are necessary for successful project completion. So, to percept these combinations in detail it is the main purpose of this paper, to review project manager’s competencies and leadership constituents for construction projects throughout lifecycle.

This study evaluates the rheology and mechanical properties and durability of concrete, which at the same time has properties of three types of self-compacting concrete (SCC), fiber-reinforced and ultra-high performance. This concrete contains pozzolans, garnet and basalt aggregates, and steel fiber. The purpose of this research is feasibility construction fiber-reinforced ultra-high performance self-compacting concrete (UHPSCC) of durable. Therefore, the required tests on this concrete have been carried out in two steps. The first step is the importance of rheology properties of self-compacting concrete, containing the tests of fresh concrete including slump flow, V-funnel test, and L-box test. The second step involves tests related to the determination of hardened concrete properties divided into two parts. The first part corresponds to the mech anical properties test, including compressive strength, and the second part pertains to durability tests (surface water absorption, surface electrical resistivity and RCMT) and microstructural test, including Scanning Electron Microscopy. The above tests show that this type of concrete has rheology properties in the acceptable range EFNARC, ultra-high compressive strength, negligible surface water absorption, minimal chlorine ion migration coefficient, and very high-level electrical resistance has this type of concrete in the ultra-high concrete cluster.

Road infrastructure facilities have a crucial role in the development of countries by providing connectivity of cities for humans and goods. Moisture intrusion is one of the main pavement damages that can decline the pavement surface conditions and reduce structural strength and load-carrying capacity. The design of the pavement layers needs to collect data about soil properties, regional precipitation, pavement geometries, surface and subsurface drainage properties, and vehicular traffic. In this study, the drainage of the pavement layers of Qom-Kashan Freeway (Amirkabir Freeway) located in Iran has been investigated. In experimental studies, the classification, physical and chemical properties, Atterberg limits and Sand Equivalent (SE), density and moisture of the pavement layers, the load-bearing capacity of the pavement layers materials, and drainage system quality have been evaluated. The classification of materials is mostly of the type (GW-GM) A-1-a and (GP-GM) A-1-b, which are suitable materials for the implementation of the subgrade, sub-base, and base layers. The percentage of weight loss of materials of the sub-base and base layers, with Los Angeles and sodium sulfate abrasion tests, is within the allowable limits. Results of the test of Atterberg limits determination of the pavement layers indicate that most of the materials in the subgrade, sub-base, and base layers are non-plastic (NP). So, the problem of swelling is not observed in these layers. To prevent water permeation into the pavement body, destruction of the bottom layers, and pumping the paving materials, four strategies have been suggested and applied to improve the drainage performance.

In this paper, the transient thermal stress intensity factors for circumferential semi-elliptical crack located on the external surface of the cylinder are determined numerically. The internal surface of the cylinder is exposed to ultra-cold fluid, and the external wall is kept at a constant temperature. The three-dimensional finite element method in ABAQUS software and singular elements in the crack front has been used. In order to ensure the accuracy of the modelling process, stress intensity factors on the cylinder containing the semi-elliptical crack under mechanical loading for different geometric dimensions of the cylinder are extracted, and the results are evaluated with available data. In the research process, transient thermal stress has been modelled using an uncoupled thermoelasticity model in the quasi-static state. Also, the thermal stress results in steady-state are compared to the existing analytical data and, excellent agreement is achieved. Finally, transient thermal stress intensity factors are presented for different values of cylinder radius ratio and various relative depths and aspect ratios of the crack.

Experimental and numerical studies are carried out in this study to characterize the flexural properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams with and without an initial notch reinforced with micro steel fibers in overall ratios of 2% by volume. Dimensions of the notch were 5 mm in width, and 25 mm in height. For this purpose, three-point bending tests were carried out on UHPFRC specimens. Thereafter, numerical studies were carried out to validate experimental findings and in subsequent, sensitivity analyses were carried out to provide better insight with regard to the investigated parameters. Variables of the study were: mesh size, width, height, length, overall size of the beam, tensile strength, compressive strength, modulus of elasticity, crack mouth-opening displacement (CMOD), and crack tip-opening displacement (CTOD). Furthermore, vertical deflection-CMOD findings were compared against available equations in the literature and discussions were made where relevant. Results showed that finer mesh leads to negligible stiffer results with similar observations for the maximum sustained stress by the modulus of elasticity, compressive strength, and width variations. Moreover, 40% increase in the tensile strength led to 47% increase in the sustained stress and doubling the clear span led to 5.5% increase in the sustained stress and 20% peak deflection.; depth variations led to size effect phenomenon and  nonlinear regression analyses successfully captured the flexural load-deflection, load-CMOD, and load-CTOD trends of the flexural beams with coefficient of correlation values ( ) close to unity. Finally, a brief cost analysis was given for the fabrication of 1  of UHPFRC.