نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهل و سوم شماره 1 (پیاپی 70، بهار 1392)

1. IntroductionRepair of concrete is an important aspect of maintenance of concrete structures. Durability of such repair and rehabilitation has become the biggest concern to the repair industry as well as to the end users. Substantial advances have been made in the field of repair materials، while the industry still has an unacceptable high level of defects and failures of concrete repairs. Recent investigations of repairs to bridge decks and other structures have indicated an overwhelming incidence of premature failures resulting from a range of factors. These factors include inappropriate selection of repair materials، poor workmanship، and inadequate characterization of substrate concrete [1]. A good repair improves the function and performance of the concrete structure، whether the structure is a pavement، or a bridge، or a building. On the other hand، poor repair fails early in a relatively short period of time. Selection of appropriate repair materials depends on the material properties and behavior of composite section under anticipated service exposure conditions [1]. Previous studies show that the differences in material properties such as compressive strength، flexural strength، stiffness، Poisson’s ratio، creep coefficient and drying shrinkage affect durability of the concrete repair [2-4]. Such differences may result in initial tensile strains that either crack the concrete repair، or cause de-bonding at the interface between repair material and substrate concrete. Both of these results (cracking and de-bonding) reduce the load-carrying capacity and durability of the concrete structure. To achieve a durable repair، it is essential that the properties of the repair materials and substrate concrete should match properly. This helps ensuring that the repair material can withstand all loads and the stresses resulting from the volume changes، such as relative shrinkage or expansion for a specified environment over a design period of time، without experiencing distress or deterioration. Durability therefore، is a function of not only the basic components (material properties) of the repair materials، but also how such components and the system as a whole responds to load and to the exposure conditions of the structure. There are different repair materials available in the concrete repair industry، with a wide range of physical and mechanical properties. Therefore، the selection of a repair material for a particular repair of concrete is challenging. Previous studies show that the failure of concrete repairs is mainly due to improper selection of the repair material based on repair material properties، without investigating the compatibility between repair material and substrate concrete [3، 4]. 2. Methodology2. 1. Experimental studyIn this paper، the compatibility between three repair materials (named PT، ZH and BR) and substrate concrete is experimentally investigated in three stages. First، individual properties of the repair materials such as flow، compressive strength، flexural strength، and split tensile bond strength are determined using different standard ASTM test procedures. Second، the compatibility is investigated using a composite beam of the repair material and substrate concrete under third point loading based on ASTM C78 test procedure (Fig. 1). Test program and the number of specimens for different types of tests are presented in Table 1. In different test specimens، compressive and flexural strength of repair materials and substrate concrete، slant shear bond strength، curing method (moist or combined) and surface texture are selected as variants. The dimensions of flexural beam specimens and slant shear bond specimens are shown in Fig. 2 and Fig. 3، respectively. Third، the correlation of the repair material properties with the compatibility is investigated to predict the durability of the concrete repair3. Results and discussionCorrelation of compatibility with individual material properties، such as compressive strength، flexural strength and bond strength is also investigated with the compatibility. Typically، the repair materials are selected based on their properties instead of studying the behavior of composite section formed by the repair material and the substrate concrete. Table 2 presents the results of different tests and specimens in moist curing condition. The results for combined curing condition are given in Table 3. 4. ConclusionsFrom this study، it is observed that no significant correlation exists between the compatibility and individual repair material properties. However، among all repair material properties as investigated، flexural strength ratio in moist curing condition has the highest correlation coefficient. Another parameter influencing the compatibility is bond strength in moist curing condition with rough surface texture. Other parameters investigated have no significant correlation with the composite beam flexural strength. Bond strength is significantly influenced by strength ratios، surface texture and curing method. Some repair materials have higher bond strength with rough surface texture. However، smooth surface texture results in higher bond strength in some other cases. 5. References [1] Vaysburd، A. M.، Emmons، P. H.، Mailvaganam، N. P.، Mcdonald، J. E.، Bissonnette، B.، “Concrete Repair Technology – A Revised Approach is Needed”، Concrete International، 2004، 26 (1)، 59-65. [2] Vaysburd، A. M.، “Holistic System Approach to Design and Implementation of Concrete Repair”، Cement and Concrete Composites، 2006، 28 (8)، 671-678. [3] Cusson، D.، Mailvaganam، N.، “Durability of Repair Materials”، Concrete International، 1996، 18 (3)، 34-38. [4] Poston، R. W.، Kesner، K.، McDonald، J. E.، Vaysburd، A. M.، Emmons، P. H.، “Concrete Repair Material Performance – Laboratory Study”، ACI Materials Journal، 2001، 98 (2)، pp. 137-147.

1. IntroductionThe study of river flow is one of the most important cases in the designing of a water storage structure and management of extreme events such as floods and droughts.The rate of river flow depends on various parameters and the nonlinear relationship between them has caused river behavior to be dynamic, nonlinear and complex.Chaos theory is the study of complex systems that, at first glance, do not appear to follow the regular laws of science. Chaos theory is one of the most fascinating and promising developments in the late 20th century mathematics and science. It provides a way of making sense out of phenomena such as river flow that seem to be totally without organization or order. A chaotic system is defined as a deterministic system in which small changes in the initial conditions may lead to completely different behavior in the future. Instability, non-periodic behavior, certain systems, being nonlinear, together is defined the chaotic systems. For the first time, chaos theory was used by Edward Lorenz in 1965 in meteorology. Later it has been implemented in all fields of science and empirical issues e.g. mathematics, behavioral, astronomy, mechanics, physics, mathematics, biology, economics etc.To date, a lot of attention has been devoted on analysing hydrological processes and elements by means of deterministic chaos approach. For example, Domenico and Ghorbani [1], Ghorbani et al. [2], Islam and Sivakumar [3], Sivakumar et al. [4] and Regonda et al. [5] have used nonlinear deterministic approaches to detect the presence of chaos and achieve more accurate river flow predictions.These investigations suggest that characterization (chaotic or stochastic) of river flow should be a necessary first step in any study, as it could provide important information on appropriate approaches for transforming data.There are other applications of chaos theory in the various topics that are not discussed in here. In this paper, the behaviour of river flow is forecasted by means of chaos theory.2. Methodology2.1. Case studyNahandchai drainage basin is located between the coordinates 38° 13' to 38° 29' east longitude and from 46° 20' north latitude to 46° 33'. The area of river basin witch is situated in the upstream of Nahand dam and hydrometric station is 219 kilometers.2.2. Phase space reconstructionOne way of characterizing dynamical systems is by the concept of phase space. The Takens theorem states that the underlying dynamics can be fully recovered by building an m-dimensional space wherein the components of each state vector Yt are correlated to observed values, which are discrete scalar time series, Xt={x1, x2,. ..xN} with N-observed values, with delay coordinates in the -dimensional phase space: (1)Where is referred to as the delay time and, for a digitized time series, it is a multiple of the sampling interval used, and m is termed the embedding dimension. The reconstruction of phase-space by plotting Xt against can show the presence of an attractor as a visual evidence for deterministic chaos in a given time series.Mathematical approaches for the reconstruction of the phase space diagram of chaotic behaviours may be carried out by one of the following

(i) Autocorrelation Function, ACF, (ii) Average Mutual Information, AMI.Correlation dimension is a nonlinear measure of the correlation between pairs lying on the attractor. The behavior of (correlation exponent or the slope of versus) provides one technique for determining the presence of chaos in a time series, such that (i) for stochastic processes, varies linearly with increasing m, without reaching a saturation value; (ii) for deterministic processes, the value of saturates after a certain value of m.3. Results and discussion3.1. Identification of low-dimensional chaos in the time seriesIn this study, the 39 years dataset of Nahandchai station is used. A visual assessment for the existence of chaotic behavior in the river flow time series may be obtained by the reconstruction of phase space diagram and a selection of results for those at Nahandchai station show chaotic behavior. This is suggestive of a possible existence of low-dimensional chaos in both of the dataset, in which the narrow dark band signifies strong determinism and the scattered band signifies the presence of noise in the data.Two methods are used to identify a possible existence of chaos in the river flow time series at Nahandchai station. Using the AFC method, the delay time τ is estimated for the time series at both of the stations at each timescale of the time series as the intercept with the x-axis of the curves by plotting the values of the ACF evaluated by the TISEAN package against delay times progressively increased from 1 to 100. The values of delay times are obtained as the zero intercepts of ACF equal to 55.The correlation function method is implemented by setting the embedding dimension values, m, from 1 to 20 and varying systematically the values of r from a low value to say 100. The result is shown in Fig. 1 for Nahandchai station. The method identifies the existence of chaos in the following ways: (i) By plotting logC(r)/log(r) versus log(r), the function values tend to fluctuate at low values of radius r, signifying their stochastic strength, but for higher values of r the function tends to find a plateaux, where the values of logC(r)/log(r) becomes saturated for each timescale value providing visual evidence for a deterministic behavior. (ii) The behavior of correlation function C(r) against radius r for values of increasing m for the time series, providing further evidence for deterministic chaos if the correlation function converges towards a single point underpinning the role of deterministic processes. (iii) The values D2(m) increase with increasing the embedding dimension values, m, up to a certain value but the existence of chaotic behavior is only underpinned if the values D2(m) saturate by reaching a plateau.3.2. Results by local prediction Local prediction algorithm is used to predict river flow time series at Nahandchai station. The procedure involves varying the value of the embedding dimension in a range, say 2–10, and estimating the value of correlation coefficient (R2) and Root Mean Square Error (RMSE). The embedding function with the highest coefficient of correlation is selected as the solution. 4. The slope of the line in figure (2-a) is the correlation dimension values and the embedding dimension values is shown in Figure (2-b). The saturation of the correlation dimension beyond a certain embedding dimension value is an indication of the existence of deterministic dynamics. The saturated correlation dimension is about 3.02 (D2=3.02). Results show that the best prediction is achieved when the embedding dimension is delay time=55 day and mopt=4.Fig. 2. Results of AFC: (a) Log C(r) Versus Log(r) for m= 1-20, (b) Relationship between embedding dimension and correlation dimension4. ConclusionsChaos theory with quantum theory and relativity is one of the most important discoveries of the last century. With review of time series caused by dynamical systems, such as behavior of rivers, behavior of system can be predicted by chaos theory. Dimensionality of a time series represents the level of complexity of the underlying system dynamics (and number of dominant governing variables), and therefore the above mentioned nonlinear dynamic and dimensionality-based classification certainly helps in identifying the appropriate structure and complexity of models. Sivakumar and Singh [6] have classified stream flow in the western United States according to correlation dimension to 4 classes.The nearest integer above the saturation value, fractals dimension, is generally considered to provide the minimum number of phase-space or variables necessary to model the dynamics of the attractor. The value of the embedding dimension at which the saturation of the correlation exponent occurs generally provides an upper bound on the number of variables sufficient to model the dynamics. Results of this study (D2=3.02) indicates low chaotic and less complex system. Number of variables necessary for model is 3 (fractals dimension=3). The optimum embedding dimension (mopt=4) from the nonlinear prediction method providing the presence of low-dimensional chaotic behavior in the river flow dynamics. The near-accurate predictions achieved for the runoff series time (correlation coefficient of about 0.87 and root mean square error of about 0.08) indicate the appropriateness of the chaotic dynamical approach for characterizing and predicting the runoff dynamics at the Nahandchai catchment.5. References[1] Domenico, M., Ghorbani, M. A., "Chaos and Scaling in Daily River flow", arxiv, 2010.[2] Ghorbani, M. A., Kisi, O., Alinezhad, M., "A Probe into the Chaotic Nature of Daily Streamflow Time series by Correlation Dimension and largest Lyapunov Methods", Applied Mathematical Modeling, 2010, 34, 4050-4057.[3] Islam, M. N., Sivakumar, B., "Characterization and Prediction of Runoff Dynamics: A Nonlinear Dynamics View", Advances in Water Resources, 2002, 25, 179-190.[4] Sivakumar, B., Berndtsson, R., Person, M., "Monthly Runoff prediction Using Phase Space Reconstruction", Hydrological Sciences-Journal-des Sciences Hydrologiques, 2001, 46 (3), 377-387.[5] Regonda, S. K., Sivakumar, B., Jain, A., "Temporal Scaling in River Flow: Can it be Chaotic?", Hydrological Sciences-Journal-des Sciences Hydrologiques, 2004, 49 (3), 373-385.[6] Sivakumar, B., Singh. V. P., "Hydrologic system complexity and nonlinear dynamic concepts for a catchments classification framework", Hydrology and Earth System Sciences, 2012, 16, 4119-4131.

1. IntroductionEach year, huge amounts of budget are spent for urban transportation projects, in order to improve traffic performance and reduce travel time. In some cases, they may produce adverse impacts on the whole network due to the lack of adequate studies. These adverse effects are in addition to financial and human resource losses and environmental impacts on urban communities. Usually in urban arterial streets, at-grade intersections are changed into grade-separated in order to reduce delays and increase the capacity of the intersection. But experiences have shown that the construction of grade-separated intersections in urban arterial streets may lead to increase travel time and delay in the adjacent network and intersections. Accordingly, deeper and more scientific studies are needed to address this phenomenon and to obtain a reliable criterion for assessing the performance of the network with at-grade or grade-separated intersection.Despite extensive studies on the performance of grade-separated intersections and establishment of necessary rules for assuring the performance and quality of traffic in recent decades, few researches has been done on measuring the traffic impacts of grade-separated intersections [1]. This could be due to the difficulty of field data collection required for this evaluation. In addition, before and after studies of grade-separated intersection are long lasting, meanwhile the traffic parameters may change. In these circumstances, the use of simulation techniques is inevitable. The main objective of this paper is to examine the effect of grade-separation on traffic indices in an urban arterial street network based on a simulation approach. To this end, using micro-simulation software, a hypothetical network is modeled, with and without a grade-separated intersection, and under different traffic and geometric conditions. The simulation results will be used to develop a two-fluid model. The two-fluid model establishes relatively simple relationship between stopping and moving vehicles in an urban street network at aggregate level. The simulation results in terms of traffic indices as traffic delay speed and volume as well as the two-fluid parameters will be compared. 2. Methodology2.1. Theoretical backgroundIn general, traffic flow modeling is possible at micro and macro levels. In disaggregate modeling, micro variables as vehicle’s speed and spacing are used. Simulation is considered amongst disaggregate models, in which based on the specific models, the behavior of vehicles on the network elements regenerates step by step. Aggregate models are developed based on the macro variables in the network, and their relationships. This study was intended to deploy both these models to assess the effects of grade-separated intersection. To this end, the strong and well-known software, CORSIM, was used for traffic flow simulation on a hypothetical network. Based on the simulation results a two-fluid model of network was developed.The two-fluid model gives a relatively simple relationship between stopped and moving vehicles variables [2]. The first assumption in this model is that the speed of moving vehicles is proportional to the ratio of vehicles in motion, and the second assumption the model is that the average ratio of stopping to moving time of vehicles in the network is equal to the average ratio of total vehicles stopped on the network, fs. The travel time, stopped vehicles, and free flow travel time data can be used for logarithmic regression to obtain parameter n, of the network [3].2.2. Simulation DetailsThe simulation model was intended to be similar to actual situation and the results could be generalized to various conditions of urban arterial street network [4]. There fore various geometric and traffic conditions were applied to the model. The model includes the following states: - network, with or without grade-separated intersection- different intersection spacing (300, 400, 500 m), - different network loading (300 500, 700, 900, 1100, 1300, 1500 vehicles per hour),3. Results and discussionThe hypothetical model was established under each of the spacing and loading for both at-grade and grade-separated intersection in order to compare the parameters and changes in these parameters, as well as the effect of each geometric and traffic variable. The hypothetical network which was a grid type street network consisting of 21 nodes. Was connected by two-way, six-lane streets at regular spacing, without right or left turn lines. The network structure and intersections are shown in Fig. 1. All intersections of the grid, with the exception of central intersection (node A), are signalized. But the central intersection was considered in both cases of at-grade and grade-separated, with the possibility of turning movements at single point level.4. ConclusionsThe analysis of simulation results showed that: - Construction of grade-separated intersection at high traffic volumes can decrease the network throughput, up to 30%. This effect increases as the distance between intersections decreases. - Grade-separation only at low volume would reduce the network delay and at short intersection spacing and high intersection volume the delay may increase up to 50%.- Construction of grade-separated intersection merely at low volumes increases the average speed of traffic. With increasing spacing, this effect is reduced.- Percentage of stopped vehicles in the network increases the grade-separation at medium and large volumes. But as spacing increases, this effect is reduced.- Based on the parameter n, the construction of the grade-separated intersection at low to medium volumes results in the improved performance of network; and in other conditions, the impact is negative.5. References[1] Garber N. J., Fontaine M. D., “Guidelines for Preliminary Selection of the Optimum Interchange Type for a Specific Location”, VTRC Report No.99-R15, Charlottesville, Virginia Transportation Research Council, 1999.[2] Amini, B. Shahi, J., Ardekani, S., “An observational Study of the Network – Level Traffic Variables”, Transportation Research, 1998, 32 (4), 271-274.[3] Williams J. C., Mahmassani H., Herman R., “Analysis of Traffic Network Flow Relation and Two-Fluid Model Parameter Sensitivity", Transportation Research Record 1985, 95-106.[4] CORSIM User’s Manual, Version 5.1, 2008.

1. IntroductionNatural processes associated with rivers lead to meandering, degradation of the channel, erosion of banks and the migration of river bends. Bendway weirs are one of the structures which may be used to control these changes. Bendway weirs are generally built from stone and are usually constructed at the outer bank to deflect the flow and to prevent erosion of outer bank of river bends. These structures are straight extending riverwards from the bank that should be protected, but unlike the more familiar spur structures, they are intended to be overtopped by the design flow. The flow over the weir crest is supposed to be directed perpendicular to the plane of the weir, and so by appropriate placement of the weirs, the flow can be directed away from the bank. 2. MethodologyIn this research study, the experiments have been carried out taking advantage of an existing model at the Institute of Water Researches of Tehran, Iran. The bend geometry of this model was built with an appropriate scale of the actual morphology of Karoon River, downstream of the Ahvaz city, Iran. The geometrical reduction scale was 1:80. Two series of tests were performed without and with weirs. In the first series, a 35 cm thick layer of sand was initially placed in the flume and scraped. Then, water was slowly added to the model from both the downstream and upstream sections. After the water level was raised, upstream water discharge was carefully regulated. Firstly, a discharge ratio Q/Qd=0.67 was set and then sediment was fed into the channel until nearly equilibrium conditions were attained (i.e., the mean water surface slope was not changed any more and the bed forms were stabilized). At the end of each test, the water flow was cut and after draining the channel slowly, the bed topography was measured with a laser meter with an accuracy of 0.1 mm. For each run, but the firs, the initial bed configuration was that obtained at the end of the previous test. In this case, the movable channel bed attained an equilibrium condition quite rapidly. In the second series of tests, 3, 4 and 5 concrete weirs were built in the correspondence of the outer bank of the middle bend at the lengths of 0.4B, 0.3B and 0.2B, respectively. After weirs were arranged within the channel, sediments were accurately leveled and tests were performed by considering the same flow discharge of the first series of tests. In these series of runs, sand was also continuously fed into the channel. The time needed for reaching equilibrium conditions ranged between 6 and 18 hours, depending on flow discharge. At the end of each run, the water level recorded by ultrasonic sensor, then the flow discharge was slowly decreased and the bed was drained completely. The channel bed was then surveyed using a laser meter. In this study, an attempt was made to investigate the effects of the length of bendway weirs on water level, erosion and sedimentation processes. The ranges of variables are illustrated in Table 1. Weir spacing ‘S’ was kept fixed in all tests, and set equal to three times the weir length (3L). The height of weirs for all tests was constant and was equal to 33% of average flow depth, D. The bed sediment for all tests consisted of a uniform sand with mean grain size ds50=1.6 mm and density 2400 kg/m3. One type of sediment with d50 equal to 1.6 mm was used for live bed (continuous injection of sediment). 3. Results and discussionThe results showed that the length ratios of 0.4 and 0.2 caused an increase and decrease of water level equal to 1 percent, respectively. But the length ratio equal to 0.3 did not have an effect on water level. The ratio of the transverse profile slope of water surface with presence of weirs in comparison with the cases without weirs (Swe / Sno-we) for the length ratio of 0.2 was less than what was measured for the length ratios of 0.3 and 0.4. Surface area of sediments in the outer bank and longitudinal and transverse dimensions of hole scour around weirs were increased with increasing of length ratio. The effect of length ratio equal to 0.4 in erosion control (control of outer bank erosion) was more than the other considered cases. It was also found that with increasing the bendway length ratio, the longitudinal dimension of scour hole would be increased and it was supposed that this phenomenon occurd due to forming the strong vortices.4. ConclusionsThe main conclusion drawn from this research study can be summarized as follows:- Bendways are not very effective on water surface rising, as with the bendway length ratio of 0.4, the water surface changed only about 1%, and for this ratio being equal to 0.2, the water surface elevation was decreased about 1%.- By increasing the bendway length ratio, the dimensions of scour hole were increased, with the length and width of the hole being measured about 95% and 80% of the channel top width, respectively. - The order of the effect of length ratio on river outer bank protection was obtained as 0.4>0.3>0.2.5. References[1] Abad, J. D., Rhoads, B. L., Guneralp, I., Garcia, M. H., “Flow Structure at Different Stages in a Meander-Bend with Bendway Weirs”, ASCE Journal of Hydraulic Engineering, 2008, 134 (8), 1052-1063.[2] Kinzli, K. D., Thornton, C., “Predicting Velocity in Bendway Weir Eddy Fields”, River Research and Applications, 2010, 26, 823-634.

1. IntroductionConcrete structures in aggressive environments greatly suffer from corrosion which causes a premature failure in their life span. Persian Gulf region is one of the most aggressive environments in which concrete structures need further attention in order to increase their durability and serviceability as well. In the present investigation, the half-cell potential and corrosion resistance of rebar embedded in concrete with different water to cement ratios (0.35, 0.40, 0.45 and 0.50) exposed to splash zones in Qeshm Island for 18 month ware studied (Fig 1). The results demonstrated that concretes with lower water to cement ratio perform better in terms of corrosion protection and process retardation.2. Experimental Study2.1. MaterialsType II Portland cement was used throughout the experiment. Total aggregate mass of about 1850 kg/m3 with a largest size of 19 mm were used. Also, to achieve desired workability of 7-10cm in different mixture designs, the use of poly carbixilate-based superplasticiser was necessary.2.2. Mixture proportionsFour mix proportions with different w/c ratios were used for casting the concrete specimens. The details of mix proportion are shown in Table1.2.3. Concrete specimensReinforced concrete specimens of size 550X300X200 mm were prepared each having three rebars (anode) at top and six rebars (cathode) at bottom embedded at 30 mm cover from both sides (Fig. 2). Concrete prisms of size 150X150X600 mm were made for determination of chloride penetration after nine months of exposure. Prism samples were also moist cured for 2 days and were sealed at all sides with polyurethane-based coating and only the top side of prisms was left uncoated to be exposed to chloride ions.2.4. Methods of measurementThe macro cell and micro cell corrosion were investigated in this study. For this reason, various methods of corrosion measurements such as macro cell, half cell and corrosion rate methods were used throughout the investigation.3. Results and discussion3.1. MacrocellThe variation of macrocell current with time was almost negligible for specimen C1. In specimen C2, there was no indication of corrosion initiation while the current in specimen C3 reached the threshold value of 10μA after 13 months. The anodic current of specimen C4 passed the threshold value after about 6 months of exposure to chloride ion. The unusual behavior of cell 1 in specimen C3 was due to the fact that the steel rebars might be slightly rusted at the time they were embedded in concrete.3.2. Halfcell Specimens C1 and C2 did not reach the threshold value, while the specimens C3 and C4 attained a more negative potential of -230 after 14 and 5 months of exposure, respectively. Results obtained from macrocell and halfcell potential measurements indicate that the rebars in specimens C1 and C2 have steel remained unaffected by corrosion whilst specimen C3 and C4 have reached the threshold value after 14 and 6 months of exposure, respectively. 3.3. Corrosion rateAt splash zone, even after 18 months of exposure, the corrosion rate of rebar in specimen C1 did not pass the threshold value required for the initiation of corrosion. In specimen C2, although the corrosion rate passed the threshold value but it followed a continues trend and there was no sudden changes in the rate of corrosion concluding that the corrosion had not started yet. But in specimen C3, sudden changes in corrosion rate confirmed the initiation of corrosion after 13 month of exposure. Specimen C4 experienced the corrosion process in month 9-11. It is interesting to note that after 12 month of exposure, specimen C4 showed a marginal increase of corrosion rate and the measurement of corrosion rate was not possible after that. 3.4. Critical chloride measurementThe chloride amount penetrated into concrete specimens was measured after 9 months of exposure and thus the bases for comparison of chloride content and variations in macrocell current, halfcell potential and corrosion rate for critical chloride determination were taken as 9 month’s measurements. The results are presented in Table 2. According to these results, the macrocell current and the halfcell potential methods are environmentally dependant, and therefore, these two methods have more accuracy in corrosion activity estimation at splash zone. The data from these studies clearly indicate that macrocell current and halfcell potential methods are practical when the corrosion activity has passed the threshold value otherwise they are not more accurate for the estimation of corrosion initiation time. However, comparing the chloride content and corrosion rate of specimens with different w/c ratio, it can be inferred that critical chloride content in concrete specimens is higher at splash zone with the estimated value of about 0.11 % of concrete weight at splash zone.4. Conclusion[1] The critical chloride content required for corrosion to initiate was found to be 0.11% of concrete weight at splash zone under environmental condition of Persian Gulf region.[2] Considering the test results, splash zone is found to be the most sever zone in terms of chloride ion penetration and corrosion activity.[3] According to the test results, the macrocell current and halfcell potential have acceptable accuracy in the determination of corrosion initiation time.[4] The use of high w/c ratio concretes in reinforced concrete structures in Persian Gulf region causes an accelerated corrosion and failure in those structures; and as mentioned earlier, the corrosion in concrete specimens with w/c ratio of above 0.4 and the cover of 30 mm is evident. Therefore, the modification of concrete structures by using pozzolans as cement replacement is necessary.

1. IntroductionAging in asphalt mixtures is a phenomenon that starts from the time of construction in the factory and by passing the time, it will progress and finally it leads to stiffening of the asphalt and deterioration of the mixture. Asphalt undergoes hardening primarily due to two factors: loss of volatiles and oxidation of asphalt. The main loss of volatiles occurs in asphalt-aggregate mixtures between the time of mixing and final placement, when the mixture is at elevated temperatures. This is referred to as short-term aging. The longer, never-ending process of oxidation occurs partially throughout the short-term aging time frame, but much more extensively over time, while the mixture is in service and exposed to the environment. This is referred to as long-term aging [1]. Aging does not progress among different types of asphalts at the same rate, and also aggregate types are effective in this phenomenon [2]. Aging is not negative completely, because a small amount of this leads to improvement of the characteristics of the mixture [3]. 2. Methodology2.1. Experimental studyIn this study three kinds, of asphalt cements namely SBS, 60/70 and 85/100 were mixed with celicious aggregates and specimens were subsequently prepared in three states: un-aged, short-term aged, short-and long-term aged specimens to compare durability of different types of asphalts in combination with special materials. Because of the effect of void ratio on the results, all of the three mixtures were prepared by one optimum asphalt content and compaction of the specimens were done by Marshall hammer by ASTM D1559. After preparing the specimens, the indirect tensile strength and Marshall compressive strength of specimens were measured.2.2. Laboratory aging of the specimensThere are two ways to simulate laboratory aging of asphalt cement: aging of asphalt cement alone and aging of asphalt mixture. The aging of asphalt-mixtures is influenced by both materials: asphalt and aggregates. Testing of aged asphalt alone does not appear to predict adequately performance of the mixture, because of the apparent effect that aggregates has on aging [4]. Therefore, laboratory aging was done on asphalt mixtures by SHRP#1025 and SHRP#1030 standards (short and long term aging respectively) in a forced draft oven. 3. Results and discussion3.1. Contrast compressive and indirect tensile strength of the samples Results show that the amount of increase in indirect tensile strength due to aging is more considerable than Mashall compressive strength. Therefore, based on the results and regarding that in the past compressive test hasn’t used for aging, we conclude that marshall compressive test is more sensitive to the increase of the void ratio relative to tensile strength and it is not an accurate measure to evaluate the effect of aging in asphalt mixtures. Hence in this research, indirect tensile strength test was used to classify the asphalts. The results of tests are presented in Table 1 and 2.3.2. Adjustment of the results Increase in void ratio due to aging leads to the error in the results, therefore to prorate this error, we have to adjust them. For each percent increase in void ratio, we should increase the strength a special amount. Firstly, we could use the suggested numbers by researchers and secondly we could calculate an approximate scale based on the indirect tensile strength and void ratio for the increase in the strength. In this research, the second method was used. Of course these procedures are not completely precise, but for grading the asphalts we have to apply one of these styles. Adjusted results are presented in Table 3.4. Conclusions and suggestionsIn this research, we can conclude that indirect tensile strength is a better measure than compressive strength to survey the aging phenomenon.SBS asphalt in combination with celicious aggregates has the highest durability against aging phenomenon and 60-70 and 85-100 asphalts are in the next steps respectively.In this experiment, one type of aggregates has been blended with three kinds of asphalts and the durability of the mixtures has been compared with each other, hence we suggest that to complete this investigation, much more combinations of asphalts and aggregates should be examined in the future.5. References[1] Bell, Wieder, Fellin, “Laboratory Aging of Asphalt-Aggregate Mixtures: Field Validation”, Strategic Highway Research Program, SHRP-A-390, National Research Council Washington DC, 1994.[2] Anderson. Christensen. Bahia. Dongre. Sharma. Antle, “Binder Characterization and Evaluation Volume 3: Physical Characterization”, Strategic Highway Research Program, SHRP-A-369, National Research Council Washington, DC 1994.[3] Bell, A., Sosnovske, C., “Selection of Laboratory Aging Procedures for Asphalt-Aggregate Mixtures”, Strategic Highway Research Program, SHRP-A-383, National Research Council Washington DC, 1994.[4] Bell, A., Sosnovske, C., “Aging: Binder Validation”, Strategic Highway Research Program, SHRP-A-384, National Research Council, Washington DC, 1994.