University of GuilanConcrete Research2008-424211419700101The Effect of the Change in Composition Ratios and Additives on the Workability and Rheology of Self-Consolidating ConcreteThe Effect of the Change in Composition Ratios and Additives on the Workability and Rheology of Self-Consolidating Concrete515304310.22124/jcr.2018.8242.1220FAParvizGhoddousiFaculty Member of Iran University of science and technologyAmir MasoudSalehiFaculty Member of Kharazmi UniversityJournal Article19700101Although self-consolidating concrete (SCC) has been developed for about 2 decades, but its widespread use is still limited. One of the most important factors is the lack of complete recognition of the properties (especially in fresh state) of this concrete and the effect of changing the composition ratios and additives on its performance. In the present study, 7 mixtures has been designed based on a mixture (by changing the composition ratios and the use of additives),and the three main fresh properties (filling and passing ability and segregation resistance) and rheological parameters (by rheometer) have been measured. The results of this study show that reducing the amount of paste volume causes the most improper changes to SCC fresh properties. According to the results of rheograph, the simultaneous increase in plastic viscosity and yield stress has reduced the segregation resistance and reducing yield stress and plastic viscosity could be suitable for improving the concrete stability. On the other hand, based on the results of this study, in self-consolidating concrete with the same water-to-cement ratio, the simultaneous increase in yield stress and the plastic viscosity indicates the lower compressive strength of the concrete.Although self-consolidating concrete (SCC) has been developed for about 2 decades, but its widespread use is still limited. One of the most important factors is the lack of complete recognition of the properties (especially in fresh state) of this concrete and the effect of changing the composition ratios and additives on its performance. In the present study, 7 mixtures has been designed based on a mixture (by changing the composition ratios and the use of additives),and the three main fresh properties (filling and passing ability and segregation resistance) and rheological parameters (by rheometer) have been measured. The results of this study show that reducing the amount of paste volume causes the most improper changes to SCC fresh properties. According to the results of rheograph, the simultaneous increase in plastic viscosity and yield stress has reduced the segregation resistance and reducing yield stress and plastic viscosity could be suitable for improving the concrete stability. On the other hand, based on the results of this study, in self-consolidating concrete with the same water-to-cement ratio, the simultaneous increase in yield stress and the plastic viscosity indicates the lower compressive strength of the concrete.https://jcr.guilan.ac.ir/article_3043_21db233917977e86baed36ca0b1899d5.pdfUniversity of GuilanConcrete Research2008-424211420181222Numerical Modeling of Masonry Wall Under In-Plane Cyclic Loading With Using the Concrete Damaged Plasticity Model and Assessment of Its ParametersNumerical Modeling of Masonry Wall Under In-Plane Cyclic Loading With Using the Concrete Damaged Plasticity Model and Assessment of Its Parameters1732303710.22124/jcr.2018.5612.1119FAAmir HosseinKarimiFaculty of civil engineering, Semnan university, semnan, iranMohammad SaeedKarimiAliKheyroddinAbdulazimAmir ShahkaramiJournal Article20160921In this paper, the parametric investigation was carried out on the concrete damaged plasticity criterion which was used for modeling concrete and other brittle and crispy materials in ABAQUS software. This criterion was used to simulate masonry wall under in-plane cyclic loading. The equations of the criterion were first presented, and then the criterion was used to simulate masonry wall the laboratory results of which is available. The dimensions of the wall under investigation were 195×1500×1720 mm (thickness, height, and length, respectively) which were under in-plane cyclic loading. The effect of parameters such as cracking strain, dilation angle, damage, cracking stress, stiffness recovery, and the like was investigated, and the impact of each was presented in the hysteretic curve of the masonry wall. The results indicated the concrete damaged plasticity criterion was useful in simulating the masonry wall under in-plane cyclic loading, but not useful in simulating the effect of pinching on the hysteretic curve. The parametric investigation gave us a substantial understanding of the impact of each of them in the hysteretic curve derived from numerical simulation.In this paper, the parametric investigation was carried out on the concrete damaged plasticity criterion which was used for modeling concrete and other brittle and crispy materials in ABAQUS software. This criterion was used to simulate masonry wall under in-plane cyclic loading. The equations of the criterion were first presented, and then the criterion was used to simulate masonry wall the laboratory results of which is available. The dimensions of the wall under investigation were 195×1500×1720 mm (thickness, height, and length, respectively) which were under in-plane cyclic loading. The effect of parameters such as cracking strain, dilation angle, damage, cracking stress, stiffness recovery, and the like was investigated, and the impact of each was presented in the hysteretic curve of the masonry wall. The results indicated the concrete damaged plasticity criterion was useful in simulating the masonry wall under in-plane cyclic loading, but not useful in simulating the effect of pinching on the hysteretic curve. The parametric investigation gave us a substantial understanding of the impact of each of them in the hysteretic curve derived from numerical simulation.https://jcr.guilan.ac.ir/article_3037_25b43880ad4414172146fc4f6b9577b5.pdfUniversity of GuilanConcrete Research2008-424211420181222Effect of Glass Powder, Nano Silica, and Steel, Glass and Polypropylene Fibres on Mechanical Properties of Reactive Powder ConcreteEffect of Glass Powder, Nano Silica, and Steel, Glass and Polypropylene Fibres on Mechanical Properties of Reactive Powder Concrete3348304410.22124/jcr.2018.9598.1265FAMehrdadHejaziHosseinAbdollahiCivil Engineer / Headquarters of Roads and Urban DevelopmentJournal Article20180122In this paper, the effect of glass powder, nanosilica, glass fibres and polypropylene fibres on the mechanical properties of reactive powder concrete is studied.<br />At first, in order to obtain the proper control mix design, the effect of the type, amount and the maximum dimension of the sand, the amount and dimension of the glass powder, and the microsilica to cement ratio on the 7-day compressive strength of the reactive powder concrete was studied. Then, the effect of the glass powder as a substitute for sand and cement, nanosilica as a substitute for the cement, the combination of glass powder and nanosilica as a substitute for the cement, and the use of glass fibres and polypropylene fibres on 7-day and 28-day compressive and flexural strength was studied.<br />Obtained results showed that adding the glass powder as a substitute of sand reduced the compressive strength by 8.5% and increased the flexural strength by 5%. Replacing the cement with nanosilica increased the compressive and flexural strengths by 4% and 17%, respectively. Adding the combination of nanosilica and glass powder as a substitute of cement increased the compressive strength by 12% but it had not a considerable effect on flexural strength. Adding glass fibres reduced the compressive strength by 6% and increased the flexural strength by 30%. Polypropylene fibres decreased the compressive strength by 12% and increased the flexural strength by 15%.In this paper, the effect of glass powder, nanosilica, glass fibres and polypropylene fibres on the mechanical properties of reactive powder concrete is studied.<br />At first, in order to obtain the proper control mix design, the effect of the type, amount and the maximum dimension of the sand, the amount and dimension of the glass powder, and the microsilica to cement ratio on the 7-day compressive strength of the reactive powder concrete was studied. Then, the effect of the glass powder as a substitute for sand and cement, nanosilica as a substitute for the cement, the combination of glass powder and nanosilica as a substitute for the cement, and the use of glass fibres and polypropylene fibres on 7-day and 28-day compressive and flexural strength was studied.<br />Obtained results showed that adding the glass powder as a substitute of sand reduced the compressive strength by 8.5% and increased the flexural strength by 5%. Replacing the cement with nanosilica increased the compressive and flexural strengths by 4% and 17%, respectively. Adding the combination of nanosilica and glass powder as a substitute of cement increased the compressive strength by 12% but it had not a considerable effect on flexural strength. Adding glass fibres reduced the compressive strength by 6% and increased the flexural strength by 30%. Polypropylene fibres decreased the compressive strength by 12% and increased the flexural strength by 15%.https://jcr.guilan.ac.ir/article_3044_0de4d0b7a5d041392cc5557bedd9d252.pdfUniversity of GuilanConcrete Research2008-424211419700101Investigation on the mechanical properties and durability of modified cement based materials with Ethylene vinyl acetate and Styrene acrylicInvestigation on the mechanical properties and durability of modified cement based materials with Ethylene vinyl acetate and Styrene acrylic4961304110.22124/jcr.2018.9522.1262FAHadiChehrazi SefiddashtiM.Sc. Department of Civil Engineering, Graduate University of Advanced Technology, Kerman, IranHesamMadaniAliSaeedikiaM.Sc. Department of Civil Engineering, Graduate University of Advanced Technology, Kerman, IranJournal Article19700101Abstract<br />In this experimental study the effects of two types of polymers including ethylene vinyl acetate and styrene acrylic on the properties of cement mixtures have been investigated. Polymer contents of the mixtures were 5, 10, 15 and 20% by weight of cement and the ratio of water to cement was 0.33. In order to investigate and evaluate the effect of polymer materials on the properties mixtures, the compressive, flexural and tensile strengths, impact resistance, shrinkage, rapid chloride migration coefficient and the capillary water absorption contents were investigated. The specimens were cured under wet conditions at early ages (7 days) and dry periods at later ages (After 7 days). The results indicate an improvement in several mechanical characteristics such as flexural strength, tensile strength, impact resistance and a significant influence on reducing the permeability of cement mixtures in the rapid chloride migration and water absorption tests by use of polymers.Abstract<br />In this experimental study the effects of two types of polymers including ethylene vinyl acetate and styrene acrylic on the properties of cement mixtures have been investigated. Polymer contents of the mixtures were 5, 10, 15 and 20% by weight of cement and the ratio of water to cement was 0.33. In order to investigate and evaluate the effect of polymer materials on the properties mixtures, the compressive, flexural and tensile strengths, impact resistance, shrinkage, rapid chloride migration coefficient and the capillary water absorption contents were investigated. The specimens were cured under wet conditions at early ages (7 days) and dry periods at later ages (After 7 days). The results indicate an improvement in several mechanical characteristics such as flexural strength, tensile strength, impact resistance and a significant influence on reducing the permeability of cement mixtures in the rapid chloride migration and water absorption tests by use of polymers.https://jcr.guilan.ac.ir/article_3041_29dee4d626c6bc9501505960616fd668.pdfUniversity of GuilanConcrete Research2008-424211419700101Fracture Mechanics Analysis of Pre-stressed Concrete Sleepers by Investigating Effects of Notch SizeFracture Mechanics Analysis of Pre-stressed Concrete Sleepers by Investigating Effects of Notch Size6375303810.22124/jcr.2018.6345.1156FASeyed MohammadFarnamBu Ali Sina universityFreydoonRezaieBu Ali Sina university0000-0002-8191-4781MahdiBayat AvarzamaniJournal Article19700101High-speed heavy-haul pre-stressed concrete sleepers are used in railway lines with bearing capacity up to 30 tons and with an allowable speed up to 200 km/hr due to their high performance capability. In this study, it is tried to analyze the fractural behavior of pre-stressed concrete sleepers based on fracture mechanics of concrete. To determine the parameters, a positive three-point bending load is applied to the rail seat of a sleeper with 6 different initial crack (notch) lengths, starting from 0 to 40 mm, with an increasing increment of 10 mm, and also 45 mm. The modelling of high-speed heavy-haul sleeper is done by ABAQUS finite element software. In this paper, some paramount parameters of fracture mechanics for concrete are considered for analyzing and designing e.g. the initial and final stress intensity, load-displacement diagram, final load and the sleeper energy. The results indicate that the fracture parameters of pre-stressed concrete sleeper are different from plain concrete. Unlike plain concrete which the stress intensity factor does not depend on the initial length of the notch, in pre-stressed concrete by increasing the crack length, both of the initial and final stress intensity factors are increased. Also, the results of the time-displacement diagram show that by increasing the crack length, the final load and energy of the pre-stressed concrete sleeper decreases almost linearly. Results represent that by increasing the notch length up to 25%, the area under load-displacement curve decreases up to 37%; while the final load decreases up to 22%.High-speed heavy-haul pre-stressed concrete sleepers are used in railway lines with bearing capacity up to 30 tons and with an allowable speed up to 200 km/hr due to their high performance capability. In this study, it is tried to analyze the fractural behavior of pre-stressed concrete sleepers based on fracture mechanics of concrete. To determine the parameters, a positive three-point bending load is applied to the rail seat of a sleeper with 6 different initial crack (notch) lengths, starting from 0 to 40 mm, with an increasing increment of 10 mm, and also 45 mm. The modelling of high-speed heavy-haul sleeper is done by ABAQUS finite element software. In this paper, some paramount parameters of fracture mechanics for concrete are considered for analyzing and designing e.g. the initial and final stress intensity, load-displacement diagram, final load and the sleeper energy. The results indicate that the fracture parameters of pre-stressed concrete sleeper are different from plain concrete. Unlike plain concrete which the stress intensity factor does not depend on the initial length of the notch, in pre-stressed concrete by increasing the crack length, both of the initial and final stress intensity factors are increased. Also, the results of the time-displacement diagram show that by increasing the crack length, the final load and energy of the pre-stressed concrete sleeper decreases almost linearly. Results represent that by increasing the notch length up to 25%, the area under load-displacement curve decreases up to 37%; while the final load decreases up to 22%.https://jcr.guilan.ac.ir/article_3038_49df8fc1d7602c52facb0214d501fee6.pdfUniversity of GuilanConcrete Research2008-424211419700101Flexural strengthening of old‐type RC columns with near surface mounted GFRP or steel barsFlexural strengthening of old‐type RC columns with near surface mounted GFRP or steel bars7793304210.22124/jcr.2018.9035.1241FAAliSeifiSchool of Civil Engineering, College of Engineering, University of TehranAbdollahHosseiniSchool of Civil Engineering, College of Engineering, University of TehranMohammad SadeghMarefatSchool of Civil Engineering, College of Engineering, University of TehranMohammadKhanmohammadiSchool of Civil Engineering, College of Engineering, University of TehranJournal Article19700101The old-type RC buildings constructed before 1970s are mostly designed according to gravity loads and lack seismic detailing. In these buildings, the strong column-weak beam concept is not usually observed, and due to the probability of soft-storey event, they are vulnerable to seismic loads. Therefore, the flexural strengthening of the columns is proposed as one of the top priorities in seismic retrofitting of these buildings. This paper experimentally studies the flexural strengthening of old-type RC columns with near surface mounted (NSM) technique. Six half-scale columns, including two control columns and four columns strengthened via NSM method with GFRP and steel bars, were tested under constant axial load and increasing lateral load; the effect of strengthening method and materials were also investigated. The mean flexural strength and energy dissipation capacity of the strengthened columns with GFRP bars increased respectively by 62% and 46% compared to corresponding control columns; but the equivalent hysteresis damping of these columns did not have a substantial increase. In addition, the mean flexural strength, energy dissipation capacity, and equivalent hysteresis damping of the strengthened columns with steel bars increased respectively by 86%, 197%, and 104% compared to the corresponding control columns. The results indicate that NSM technique remarkably increases the flexural strength and improves the seismic parameters of columns, especially when steel bar are used as NSM reinforcement.The old-type RC buildings constructed before 1970s are mostly designed according to gravity loads and lack seismic detailing. In these buildings, the strong column-weak beam concept is not usually observed, and due to the probability of soft-storey event, they are vulnerable to seismic loads. Therefore, the flexural strengthening of the columns is proposed as one of the top priorities in seismic retrofitting of these buildings. This paper experimentally studies the flexural strengthening of old-type RC columns with near surface mounted (NSM) technique. Six half-scale columns, including two control columns and four columns strengthened via NSM method with GFRP and steel bars, were tested under constant axial load and increasing lateral load; the effect of strengthening method and materials were also investigated. The mean flexural strength and energy dissipation capacity of the strengthened columns with GFRP bars increased respectively by 62% and 46% compared to corresponding control columns; but the equivalent hysteresis damping of these columns did not have a substantial increase. In addition, the mean flexural strength, energy dissipation capacity, and equivalent hysteresis damping of the strengthened columns with steel bars increased respectively by 86%, 197%, and 104% compared to the corresponding control columns. The results indicate that NSM technique remarkably increases the flexural strength and improves the seismic parameters of columns, especially when steel bar are used as NSM reinforcement.https://jcr.guilan.ac.ir/article_3042_deb4599fb0ab53733dfe84c7c0523383.pdfUniversity of GuilanConcrete Research2008-424211419700101Investigation the effect of steel fibers and coarse aggregate ratio on self-compacting concrete propertiesInvestigation the effect of steel fibers and coarse aggregate ratio on self-compacting concrete properties95107304510.22124/jcr.2018.10099.1283FASasanMotaghedAssistant Prof., Civil Engineering, Faculty of Engineering, Behbahan Khatam Alanbia University of Technology, Behbahan, Iran.0000-0001-7062-0457Mohammad RezaHalavatM.Sc., Civil Engineering, Faculty of Engineering, Behbahan Khatam Alanbia University of Technology, Behbahan, Iran.MohammadSalehi VaysiAssistant Prof., Department of Mathematics, Faculty of science, Behbahan Khatam Alanbia University of Technology, Behbahan, Iran.Journal Article19700101The ultimate goal of concrete as the most important and most used building material is the durable resistance properties. Self-compacting Concrete, as an option to solve the major problems of conventional concretes, has a higher cost due to the use of special additives and aggregates size. Also, the presence of fine grains increases the cracking potential of the concrete. The aim of this paper is to assess the effect of coarse aggregate ratio and steel fibers on the properties of self-compacting concrete (SCC). For this purpose, 27 SCC mixtures with C/T(coarse aggregates as a fraction of the total combined aggregate mass) for 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35% and 30% and 12 SCC mixtures containing hook end steel fibers with volume fractions of 0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5% were prepared. The effect of C/T ratio on the fresh properties and mechanical properties of SCC was studied. The test results indicated that aggregate with C/T ratio for 50% has the best fresh and hardened properties. With the change in fiber ratio from 0% to 2.5%, the slump flow, blocking and segregation ratio are increasing, while in the fiber ratio above 2%, the self-consolidation property is lost. Fibers increase the tensile strength above than 40 % and decrease shrinkage cracking more than 50%. Fiber has no positive effects on compressive strength. According to the results, the best percentage of hook end steel fibers which can be recommended for self-compacting concrete is 1.5%.The ultimate goal of concrete as the most important and most used building material is the durable resistance properties. Self-compacting Concrete, as an option to solve the major problems of conventional concretes, has a higher cost due to the use of special additives and aggregates size. Also, the presence of fine grains increases the cracking potential of the concrete. The aim of this paper is to assess the effect of coarse aggregate ratio and steel fibers on the properties of self-compacting concrete (SCC). For this purpose, 27 SCC mixtures with C/T(coarse aggregates as a fraction of the total combined aggregate mass) for 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35% and 30% and 12 SCC mixtures containing hook end steel fibers with volume fractions of 0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5% were prepared. The effect of C/T ratio on the fresh properties and mechanical properties of SCC was studied. The test results indicated that aggregate with C/T ratio for 50% has the best fresh and hardened properties. With the change in fiber ratio from 0% to 2.5%, the slump flow, blocking and segregation ratio are increasing, while in the fiber ratio above 2%, the self-consolidation property is lost. Fibers increase the tensile strength above than 40 % and decrease shrinkage cracking more than 50%. Fiber has no positive effects on compressive strength. According to the results, the best percentage of hook end steel fibers which can be recommended for self-compacting concrete is 1.5%.https://jcr.guilan.ac.ir/article_3045_3bc5710b0b2924e22ec591e73117fe6f.pdfUniversity of GuilanConcrete Research2008-424211420181222Seismic Assessment of RC Frames with HPFRCC in Plastic Hinges of Beams and ColumnsSeismic Assessment of RC Frames with HPFRCC in Plastic Hinges of Beams and Columns109122304610.22124/jcr.2018.10986.1309FAMOHAMMAD HOSSEINSAGHAFIDtAliGolafsharAssistant Professor, Department of Civil Engineering, Semnan Branch, Islamic Azad University, Semnan, IranJournal Article20180802Because of the high strain capacity of (HPFRCC), using this material in the beam-column connection is more attention paid by researchers. After verification of numerical models for 3 type of beam-column connections using OPENSEES software and comparison with experimental results, two 2D frames with 5 and 10 stories has been created to study. Each frame is considered in 4 format containing conventional concrete in all elements (RC), containing of (HPFRCC) in beam-column connections (RCH1) and at the end of beams, containing of (HPFRCC) in beam-column connections, end of beams and first story column base (RCH2) and containing of (HPFRCC) in beam-column connections, end of beams, first story column base and end of other columns. Results from nonlinear time history analysis show using of (HPFRCC) in frames has been decreased maximum story drift angle, maximum roof displacement and has been increased maximum base shear based on average results from seven earthquake records. With regard to Higher dissipated energy and stiffness in beam column connections with (HPFRCC) respect to conventional concrete, result show the average of maximum drift angle of 5-RCH1, 5-RCH2 and 5-RCH3 frames have been decreased up to 35%, 31% and 38% with respect to 5-RC frame. Also these parameters for 10-RCH1, 10-RCH2 and 10-RCH3 frames have been decreased up to 44%, 41% and 49% with respect to 10-RC frame.Because of the high strain capacity of (HPFRCC), using this material in the beam-column connection is more attention paid by researchers. After verification of numerical models for 3 type of beam-column connections using OPENSEES software and comparison with experimental results, two 2D frames with 5 and 10 stories has been created to study. Each frame is considered in 4 format containing conventional concrete in all elements (RC), containing of (HPFRCC) in beam-column connections (RCH1) and at the end of beams, containing of (HPFRCC) in beam-column connections, end of beams and first story column base (RCH2) and containing of (HPFRCC) in beam-column connections, end of beams, first story column base and end of other columns. Results from nonlinear time history analysis show using of (HPFRCC) in frames has been decreased maximum story drift angle, maximum roof displacement and has been increased maximum base shear based on average results from seven earthquake records. With regard to Higher dissipated energy and stiffness in beam column connections with (HPFRCC) respect to conventional concrete, result show the average of maximum drift angle of 5-RCH1, 5-RCH2 and 5-RCH3 frames have been decreased up to 35%, 31% and 38% with respect to 5-RC frame. Also these parameters for 10-RCH1, 10-RCH2 and 10-RCH3 frames have been decreased up to 44%, 41% and 49% with respect to 10-RC frame.https://jcr.guilan.ac.ir/article_3046_c589411cb8015087df1c5cc840b3b537.pdfUniversity of GuilanConcrete Research2008-424211419700101Investigate the relationship between of the bond work index and the physical and mechanical properties of rocks (case study: the feed of Uremia cement plant)Investigate the relationship between of the bond work index and the physical and mechanical properties of rocks (case study: the feed of Uremia cement plant)123131317010.22124/jcr.2018.10834.1304FAAtaallahBahramiAssociate professor of mining engineering, Department of mining, university of uremiaHasanMoomivandAssociate professor of mining engineering, Department of mining, university of uremiaFatemehKazemiGraduate of MSC mining engineering, university of uremiaAbusalehDehghaniStudent of mining engineering, university of uremiaMehdiMutabExpert of mine engineering department, university of uremiaJournal Article19700101The bond work index is the most important parameter that determines the amount of energy consumed and examines the efficiency of the grinding circuit. In this research, the bond work index of mineral feed of Uremia cement plant was determined using by standard bands method. The bonding index for iron ore, low grade and high grade limestone and pozzolan were calculated to be 14.75, 11.61, 11.87 and 10.80 Kwh/t, respectively. In order to investigate the relationship between the bond index and the physical and mechanical properties of rocks, experiments were conducted to determine the physical and mechanical properties of rocks. The bonding index with the porosity of the samples, there is an inverse relationship (R2=0.7253), but increased with logarithmic relationships by increasing the density. Also, the bond index increases with increasing mechanical properties of rock such as compressive strength, tensile strength and elastic coefficient as logarithmic function with good correlation (R2=0.80). According to the results, the bond work index has a very high correlation (about 0.93) with tensile strength and one-axial compressive strength compared to other rock properties. By Using the results and formulas, we can estimate the bond work index of mineral feeds of Uremia cement plant using physical and mechanical properties.The bond work index is the most important parameter that determines the amount of energy consumed and examines the efficiency of the grinding circuit. In this research, the bond work index of mineral feed of Uremia cement plant was determined using by standard bands method. The bonding index for iron ore, low grade and high grade limestone and pozzolan were calculated to be 14.75, 11.61, 11.87 and 10.80 Kwh/t, respectively. In order to investigate the relationship between the bond index and the physical and mechanical properties of rocks, experiments were conducted to determine the physical and mechanical properties of rocks. The bonding index with the porosity of the samples, there is an inverse relationship (R2=0.7253), but increased with logarithmic relationships by increasing the density. Also, the bond index increases with increasing mechanical properties of rock such as compressive strength, tensile strength and elastic coefficient as logarithmic function with good correlation (R2=0.80). According to the results, the bond work index has a very high correlation (about 0.93) with tensile strength and one-axial compressive strength compared to other rock properties. By Using the results and formulas, we can estimate the bond work index of mineral feeds of Uremia cement plant using physical and mechanical properties.https://jcr.guilan.ac.ir/article_3170_3819b2e0788295eca063ae816d556db8.pdfUniversity of GuilanConcrete Research2008-424211419700101Utilization of Recycled Concrete Powder as Cement Replacement or Filler in Masonry MortarUtilization of Recycled Concrete Powder as Cement Replacement or Filler in Masonry Mortar133143317110.22124/jcr.2018.10197.1285FAMiladAghili Lotfschool of civil engineering, university of tehranAmir MohammadRamezanianpourFaculty of Civil Engineering, College of Engineering, University of Tehran,
Tehran, IranAlirezaHabibiMSc. candidate, Faculty of environmental Engineering, University of Tehran, Tehran, IranJournal Article19700101Portland cement is the most energetically demanding component among all cement-based materials. It not only consumes high levels of energy, but also is one of the important CO2 emission sources in the world. So any efforts to reduce the consumption of cement can lead to lower environmental pollution. One way to handle this problem is using recycled powders (remained at construction and demolition waste recycling sites) as a partial replacement of cement. According to the literature, recycled concrete powders can be successfully used as cement replacement or filler in cement-based products. This strategy can lead to consumption of construction waste recycling products as well as reduction in the greenhouse emissions. However, due to lower hydration activity of recycled concrete powder compared to cement, utilization of it in masonry mortars seems more practical as opposed to concrete. In this research three different groups of mortar mixes were designed. The first group consisted of mixes in which 25%, 50% and 75% of the total ordinary Portland cement were replaced with recycled concrete powder. In the second group, 10% and 15% silica fume were replaced with ordinary Portland cement, and finally in the third one, both 10% and 15% silica fume was used in mixes containing 25% recycled concrete powder. The results of physical (both fresh and hardened states) and mechanical tests showed that utilizing 10% or 15% silica fume in mortar containing 25% recycled concrete powder can lead to a similar or even better physical and mechanical performance compared to reference mix.Portland cement is the most energetically demanding component among all cement-based materials. It not only consumes high levels of energy, but also is one of the important CO2 emission sources in the world. So any efforts to reduce the consumption of cement can lead to lower environmental pollution. One way to handle this problem is using recycled powders (remained at construction and demolition waste recycling sites) as a partial replacement of cement. According to the literature, recycled concrete powders can be successfully used as cement replacement or filler in cement-based products. This strategy can lead to consumption of construction waste recycling products as well as reduction in the greenhouse emissions. However, due to lower hydration activity of recycled concrete powder compared to cement, utilization of it in masonry mortars seems more practical as opposed to concrete. In this research three different groups of mortar mixes were designed. The first group consisted of mixes in which 25%, 50% and 75% of the total ordinary Portland cement were replaced with recycled concrete powder. In the second group, 10% and 15% silica fume were replaced with ordinary Portland cement, and finally in the third one, both 10% and 15% silica fume was used in mixes containing 25% recycled concrete powder. The results of physical (both fresh and hardened states) and mechanical tests showed that utilizing 10% or 15% silica fume in mortar containing 25% recycled concrete powder can lead to a similar or even better physical and mechanical performance compared to reference mix.https://jcr.guilan.ac.ir/article_3171_ba88e07f437f1a47f1659d6c0b63be96.pdf