Recycling is one of the most important issues in the construction industry in the world. Today, it is common to use different types of concrete in construction projects. One of these types of concrete is Roller Compacted Concrete (RCC), which has advantages such as fast and easy construction, lower construction costs and resistance in hot weather conditions and heavy loading. This concrete can be used in the construction of road pavements and all kinds of massive structures. In this study, the effect of replacing reclaimed asphalt pavements (RAP) as coarse aggregates and steel slag as fine aggregates with different percentages has been investigated on the mechanical properties of roller concrete. Samples were cured for 7 and 28 days after mixing design. The results of tests show that with increasing the replacement of RAP and steel slag in RCC samples, the compressive strength is significantly reduced; Compressive strength in the sample containing 100% RAP and steel slag, is approximately one third of the compressive strength of the sample; However, this declining trend has slowed down for the tensile and flexural strengths. Also, only the sample containing 25% of RAP and steel slag has the required minimum compressive strength in accordance with the relevant standards; While 28-day tensile and flexural strength in samples containing 25%, 50% and 75% of RAP and steel slag, is higher than the allowable values ​​in accordance with the relevant standards. The results of toughness test showed that with increasing RAP and steel slag, the maximum load was decreased; However, energy absorption capacity and consequently toughness increased, due to the increase in flexibility of RCC mixtures.

Many concrete structures do not meet the provisions of new regulations due to the reasons such as duplex structures and there is not direct suggestion given by provisions, so it is necessary to provide strengthening and rehabilitation methods such structures among which the use of FRP sheet. In this paper, the seismic behavior of regular and duplex reinforced concrete buildings non-strengthened and strengthened with CFRP was studied via non-linear analyses fifty buildings with 3, 5,10 and 15 stories with the span number of 1-5. Different parameters such as the maximum displacement of the structure, drift, the shear force applied on the stories, the performance points and the structure capacity curve have been studied and the structure strengthening effect and the structure making duplex effect and the height increase effect and the number of spans were investigated. The results indicated that confining the beams and columns of the reinforced concrete structure with CFRP increased the area under the pushover curve which indicates the structure depreciated energy. Even more the initial gradient and stiffness of the strengthened structure were 1.5-2.5 times more than those of original structure. Generally, 5- story building showed better behavior in terms of maximum stiffness and minimum displacement, and 15- story building showed the best performance in terms of greater energy absorption comparing the other structures. By comparing the capacity curves of the regular and duplex buildings, it can be expressed that the maximum initial stiffness and the minimum lateral displacement belong to the duplex model.

Increased population and urbanization, on the one hand, and global warming and climate change, on the other hand, have resulted in urban hydrological problems. Seasonal floods, as well as a lack of urban water supplies in specific seasons, inflict significant harm to numerous countries every year. Following the happening of frequent floods and resource scarcity, Chinese researchers introduced a new concept of sponge cities in 2014 to progress toward sustainable development. The development of the sponge cities program will be the responsibility of government agencies due to the broad-scale coverage of the areas and the necessity for substantial coordination and licensing across the country. Pervious concrete is considered as a new technology in the development of urban spaces in order to control urban runoff in recent years in many developed countries as sponge cities. In the past, this technology was associated with technical challenges such as limited mechanical resistance, durability, clogging which were solved with the development of technology. This technology, along with other components of sponge cities introduces a new concept of sustainable development. In this study, the components of Sponge City are introduced and by reviewing previous studies, the challenges of realizing this concept are studied.

In recent years, the use of nanoparticles to improve the properties of concrete has created a new perspective in concrete technology. Carbon nanotube is one of the most promising nanomaterials available to improve the performance of concrete and cement due to their excellent mechanical properties and chemical stability. Due to the tendency of nanotubes to shrink and be hydrophobic, proper distribution and dispersion of carbon nanotubes in concrete will be very effective in achieving the desired mechanical properties of concrete. Therefore, in this study, carbon nanotubes became hydrophilic using surface modification and covalent bonding. For the durability and stability of carbon nanotubes in water, C-type surfactants (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) and polycarboxylate (PCE) were used. The results of visible ultraviolet (UV-vis) spectroscopy and compressive strength tests performed on concrete showed that the combination of PEG and PCE surfactants caused the optimal dispersion of carbon nanotubes so that it is compatible with the cement matrix and leads improve the mechanical properties of concrete. Experimental results show that the compressive strength of concrete samples of 7, 14 and 28 days containing 0.015% (cement weight) of carbon nanotubes with PEG and PCE surfactant increased by 3.1, 7.4 and 14.14%, respectively, compared to the reference sample; While in concrete samples containing carbon nanotubes and CTAB surfactant, due to the incompatibility of CTAB with cement and the low stability of dispersion of carbon nanotubes with CTAB, the concrete compressive strength of 7, 14 and 28 days (compared to the reference sample) decreased by respectively 5.6%, 17% and 9%.

Today, the use of nanomaterials in various sciences has found a wide perspective. In this regard, nanoscale additives in the concrete industry with the aim of improving the mechanical properties and durability of concrete, have been considered by researchers. In the preparation of geopolymer concrete, materials containing abundant aluminosilicate materials are combined with alkaline solution. In this laboratory study, a mixing design was made of control concrete containing Portland cement. Then, slag geopolymer concrete was made in three mixing designs containing 0, 4 and 8% nanosilica (4 mixing designs in total). Then, SEM test at 90 days of curing age and tests of water permeability, compressive strength and modulus of elasticity at 7 and 28 days of curing at room temperature were performed on concrete samples. Laboratory results indicate that increasing the curing age of concrete has improved the results of compressive strength, modulus of elasticity and water permeability. In the test of water permeability, modulus of elasticity and compressive strength, the addition of 8% nanosilica to geopolymer concrete improved the results by 26, 13 and 19%, respectively, compared to the design of nanosilica-free geopolymer concrete at 28 days after curing.

Due To The Increase In Costs And Environmental Hazards In The Road Construction System By Bitumen And Asphalt, It Is Necessary To Direct Government Agencies And Active Contractors To Find Optimal Methods. Road Construction In Metropolitan Areas Should Have Minimal Pollution And Environmental Hazards, Accelerate Operation Time And Reduce Disruption Of Urban Traffic Order. In This Research, With The Feasibility Approach And Comparison Of Road Construction With Roller Concrete And Bitumen-Asphalt System In Shiraz Has Been Investigated. This Comparison Includes The Time And Cost Of Construction And Improvement Of Asphalt Roads And Roller Concrete With Msproject2016 Software For A 12-Meter-Wide And 1000-Meter-Long Passageway. The Design Basis Of This Route Is 354 Road Construction Magazine And Also The Quantity Surveying And Estimating Basis For Measuring, The Price List Of Roads, Runways, Airports In 1399 And Assuming Access To The Nearest Mines And Resources Of Shiraz City Has Been Selected. Then, 25 Mixing Plans Related To Roller Concrete Construction Were Reviewed, Citing Other Reputable Sources, To Evaluate The Strength / Cost Index For The Construction Of One Cubic Meter Of Roller Concrete. The Results Of This Study Showed That The Use Of Roller Concrete System Is Up To 24% Cheaper And Its Construction Time Is Up To 38% Faster Than Asphalt Sample.

The use of waste glass aggregates as a substitute for fine natural aggregate and glass powder as a substitute for cement can have economic and environmental benefits. In this study, the behavior of self-compacting concretes containing waste glass aggregate (up to 600 kg / m3) and glass powder (up to 180 kg / m3) has been investigated. For this purpose, flowability, stability, and viscosity of self-compacting concrete in fresh state and compressive strength, electrical resistance, resistance to chloride ion penetration and scanning electron microscopy images in hardened state were examined. The results of experiments show that the use of waste glass can have a significant effect on the properties of fresh self-compacting concrete and can increase the use of superplasticizer and potential of bleeding and segregation. Also, by replacing cement with glass powder up to 40%, the results of compressive strength, electrical resistance and chloride ion penetration resistance tests were significantly improved. In this study, it was shown that with the simultaneous use of glass powder and glass aggregates up to one third of the concrete volume, desirable results can be achieved.

Today, with the progress of the construction industry and the importance of reducing costs, the multi-purpose use of consumables has attracted the attention of builders. Exposed concrete is one of this category of materials, which, in addition to its structural use, also has an architectural function. The use of Exposed concrete requires minimizing bugholes in concrete and achieving appropriate appearance quality. In this research, the effect of the surface material of the mold, including steel and coated plywood, and the type of mold release agent on the bugholes, as well as the amount of staining on the concrete surface, was investigated. the conducted investigation shows that the performance of coated plywood mold is slightly better than steel mold and leads to less bugholes. In terms of the effect of the type of releasing agent, the results show that the mineral-based releasing agent has a better performance in terms of bugholes compared to the organic-based releasing agent in minimum consumption amounts. However if this type of substance is applied in excessive amounts, it leads to staining on the concrete surface, reducing its surface quality. The organic based material did not cause a problem in terms of staining even in high consumption rates.

The steel shear wall is an efficient lateral load-bearing system for steel and concrete structures. These members have been gaining interest because of advantages such as high stiffness, fewer architectural limitations, light weight, and lower footprint in plan. When shear walls are used in a semi-continuous state in the structure, it is possible to consider an opening in the span without creating a hole in the shear wall. In the present study, numerical research was performed on the behavior of concrete frames containing a steel shear wall with a semi-continuous connection to the frame. First, the numerical model was validated using an experimental specimen. Then, by performing 33 nonlinear static analyses, the effect of the wall width and thickness on the seismic behavior of concrete frames was investigated. Similarly, the width of the wall was considered to vary from 10 to 110 cm in 11 cases. In addition, the shear wall thickness was examined in 3 cases of 1, 2 and 3 mm, respectively. The outputs of the frame included energy loss, lateral stiffness, strength, and ductility of the frame. To calculate the shear wall stiffness, a formula was presented using the curve fitting technique based on numerical results. By using this formula, the wall stiffness can be estimated with good accuracy using its width and thickness. After comparing the results, it was observed that when the shear wall width in the frame was selected correctly, not only the stiffness and lateral strength of the frame increased, energy loss and ductility of the frame were 2.7 and 1.7 times those of the plain frame, respectively. By considering the ratio of the shear wall width to the frame span equal to 0.38, a proper width can be obtained for the shear wall.

Liquid storage tanks are one of the main components of vital arteries that should be able to continue their service during and even after the earthquake and maintain their uninterrupted usability. For this reason, seismic safety of liquid storage tanks is of considerable importance to ensure the water supply of earthquake-affected areas and fire extinguishing. Tanks of industrial liquids may also contain valuable liquids or employment that should not lose their contents during an earthquake. Elevated tanks are often used for water storage purposes and can be placed on prestressed concrete shafts, prestressed metal or concrete frames or stage of masonry. Most design standards use this conclusion and have higher seismic design performance for reservoirs compared to other buildings. In this study, the first to fourth editions of standard 2800 for elevated water tanks in four types of relative earthquake risk and four types of soil defined in the standard have been investigated and compared with the most ductile building in the relevant standard. In standard 2800 for aerial water tanks in the first to third editions, only one coefficient of behavior is presented, but in the fourth edition, two coefficients of behavior are considered. By examining the tanks and ductile buildings, their seismic design force was compared and while comparing these results, the differences between different edits of standard 2800 were investigated. The results showed that in standard 2800, in the first to third editions of standard 2800, for different soils and regions with relative earthquake risk, the seismic design force of elevated tanks is about 3 to 7 times more than the ductile buildings of the relevant edition. If in the fourth edition, this range has increased so that the seismic design force of elevated tanks is about 2.14 to 9.33 times more than the ductile buildings. Also, in the fourth edition of standard 2800, for reservoirs with behavior coefficients of 2 and 3, in soil type IV, for regions with different relative risks, there is no high bound (in long periods) and for tanks with behavior coefficient 2 and in soil type II, at low and moderate risk level of earthquake, there is no low bound (in long periods).

It is essential to properly understand the seismic behavior of reinforced concrete (RC) columns confined by stirrups that experience different corrosion rates. The current study investigated the effect of seismic performance indicators such as strength loss, energy dissipation rate, ductility and hysteresis damping on specimens and models for different stirrup corrosion rates. Analysis revealed the adverse effects of corrosion on the bond performance between the concrete and steel bars which affected the seismic performance of the columns. It was observed that severe corrosion of the stirrups undermined confinement of the concrete core and caused the seismic response to degrade. This changed the failure mode from a ductile to a brittle state. As the corrosion rate of the stirrups increased, their ductility and energy dissipation capacity decreased such that the amount of decrease depended on the corrosion rate. An attenuation relationship is proposed for the corrosion rate of the stirrups for different stirrup yield strengths, concrete compressive strengths, concrete covers and stirrup spacing. The values estimated by the proposed relationship were shown to be in acceptable agreement with the analytical results.

Constructing concrete water tanks to supply the water pressure needed in cities is inevitable. In Iran, many cities, including metropolises, are near active faults, and in some cases, the fault even passes through them; while the near-field earthquakes' effect on the seismic behavior of tanks has not been thoroughly investigated. Therefore, the effect of the vertical component of pulse-like and non-pulse-like near-fault earthquakes on the lateral hydrodynamic force acting on the tank's wall and the sloshing response of rectangular concrete tanks are numerically studied in this paper. The finite element method is used to model the tank and liquid, and the results of the numerical method employed in this study are compared and verified by the experimental results. Subsequently, eight seismic records derived from four near-field earthquakes are used for two and three-component seismic analyzes.It is found that the maximum sloshing response occurring at the corner of the tank's wall can be higher than that of the middle of the tank's wall by up to 81.6 percent. In other words, the corner of the tank's wall is the critical point for the sloshing response in all cases studied in this paper. In addition, the vertical component of near-fault earthquakes has been indicated to have a negligible effect on the sloshing response while considering this component increases the hydrodynamic force acting on the concrete tank's wall by up to 58.2 percent. On the other hand, near-field pulse-like earthquakes may alter the dynamic force response in rectangular concrete tanks. This alteration can be seen in the force distribution pattern along the tank's wall, which changes under such ground motions.