نشریه عمران و پروژه
سال دوم شماره 5 (پیاپی 15، امرداد 1399)

In recent years, polymer-modified bitumens have been used to produce asphalt mixtures with better corrosion resistance, fatigue cracks and heat cracks. Research in recent decades has shown that the use of polymers in asphalt mixtures improves their properties and delays breakdowns. The important role of pavement quality on the safety and comfort of road users, as well as reducing the costs of the operation period, has led researchers in the field of asphalt pavement to produce modified asphalt, to increase its strength and durability in Take action against traffic loads and various weather conditions. Deficiencies related to pure bitumen produced in refineries lead to premature failures in asphalt pavements. Various additives have been used to modify the behavior of bitumen, including a variety of polymers. In fact, polymers are among the bitumen modifying additives that are widely used in asphalt mixtures today. In this study, reviewing previous research, the need to modify the properties of bitumen will be explained. In the following, various methods of bitumen properties modification are introduced and then the types of bitumen polymer modifiers and the role of each of them in improving the properties of bitumen and asphalt mixtures will be explained.

Realistic project planning is an essence for project success. Despite its simplicity, in such method, some metrics like schedule bottleneck points, work production and, resource utilization remains vague which in turn can lead to project cost and time overruns. Besides, since project stochastic scheduling is a kind of NP-hard problems, previous project planning literature suggests metaheuristics method and optimization algorithms like genetic algorithm and ant colony optimization algorithm. This study proposed using discrete event simulation for project stochastic scheduling as an innovative method, since: firstly, construction process has kind of discreteness identically resulting from different resourced interactions. Secondly, whole of construction project concepts can be modeled by discrete event simulation modeling elements and, thirdly, the logic of simulation models for each type of project would be same, i.e., it is required just to modify activities duration and the number of available resources. This study investigates a part of the total earth-moving operation of Dalaki dam as a case study. Having modeled the operations, it is observed that they used the best resource combination regarding project cost and time. Moreover, planning performance metrics such as schedule bottleneck points, various cycle productivity and resource utilization were calculated and discussed in depth.

How to finance and prepare the necessary executive budget to carry out infrastructure projects and exploit their products and services is currently one of the most important challenges facing developing countries. In this regard, the present study has been reviewed with the aim of reviewing financing methods and ways of exploiting development projects (case study of the plans of the Ministry of Energy, Water Resources Management). The research method of the present study was applied in terms of purpose and descriptive in terms of implementation method. The statistical population of the present study included contractors, consultants and employers who are experts and experts working in the field of water resources basin, 50 of whom were selected by non-random sampling method and purposefully as a statistical sample. The data collection tool in the present study was a questionnaire and for data analysis, one-sample t-test and Friedman, and SPSS 24 software were used. Based on the research findings, the most important strategies for exploiting development projects are as follows: 1) Improving the quality of the work factor, 2) Improving the relationship between the manager and employees, and 3) Improving the use of technological efficiency. Therefore, the best way to exploit water development projects has been to improve the quality of the work factor.

The use of fiber concrete can have a significant change in the quantity and quality of running structures or future plans of the country. Fiber concrete is actually a composite that increases the tensile strength by applying the reinforcing fiber inside the concrete mixture and is not easily break down under the impact of impact loads. This composite combination has the proper integration and continuity and the possibility of using concrete as a possible material to produce wiggly-resistant surfaces. The use of macrosynthetic fibers increased the physical and chemical properties of concrete and reduced shrinkage of fresh and hardened concrete. Macrosynthetic fiber can be a suitable replacement for metal fiber and thermal rebars, so the use of this type of fiber has spread in recent years. Fiber concrete is currently widely used in various applications such as highways, foundations, military industries, protection walls, and other cases. In this research, the reason for the necessity of using kortta fiber, construction method, mechanical properties of fiber concrete samples according to the results of applications and research has been discussed.

The destruction of concrete depends on the formation of cracks and cracks in the cracks. As the load increases, the cracks are connected together, forming the cracks. In order to overcome this problem as well as the creation of homogeneous conditions, in the last few decades, a series of thin strands used in all the volume of concrete are used, which are called fibers. Fibers concrete is actually a composite that increases the tensile strength by applying the reinforcing fibers inside the concrete mixture. This composite combination has the proper integration and continuity and the possibility of using concrete as a possible material to produce wiggly - resistant surfaces. Fibers concrete is also highly capable of absorbing high energy and is not easily break down under the impact of impact loads. The historical witness of this technology is the great use of building buildings. As a matter of fact, fibers concrete is the advanced form of this technology, which is replaced by natural and synthetic fibres, replacement of straw, and cement replacement in the thatch. The fibers used in this study is of the type of polyolefin fiber and polyolefine. In this research, the reason for the necessity of using fibers, construction method, mechanical propeties and applications of fiber concrete and obtaining conversion coefficients of standard cubic samples of fiber concrete to standard cylindrical sample of fiber concrete according to the results of applications and research has been discussed.

Plastic concrete have been used for some four decades in watertight structures. In these four decades, plastic concrete has been successfully used in engineering control projects for seepage. Plastic concrete is produced by mixing of cement, bentonite, aggregates and water. Presence of bentonite and high water-cement ratio is difference between plastic concrete and conventional concrete. These two factor cause plastic concrete, besides possession of water tighting property, have a very lesser comperssive strength and modulus of elasticity in comparsion with conventional concrete and therefore be more deformable. Researches that fulfilled on this type of concrete in the word and especially in Iran, were not extensive and most of done works have been typical studies on relative projects. In order to make more economical plastic concrete, it is necessary to evaluate the effects of changes in the properties of bentonite, and in particular the effect of its plastic index change, and given that there is no extensive research in this field in our country, we try to move toward this goal in this these. Therefore after primary stduies and test, 51 mix designs were teseted and compressive strength, modulus of elasticity and workability of them were determined. Based on the results, with increasing amount of plastic index of bentonite, compressive strength, elasticity modulus and workability decrease.