چكيده فارسي :
بتن علاوه بر دارا بودن خواص سازه اي مناسب، يكي از مناسب ترين و پر كاربردترين مصالح براي ساخت حفاظ تابشهاي هسته اي نوترون و گاما ميباشد. در اين ميان استفاده از بتن سنگين به جاي بتن معمولي باعث كاهش ضخامت عضو محافظتي به ميزان قابل توجه خواهد شد. با توجه به حجم زياد بتن ريزي در نيروگاه هاي اتمي، بهينه سازي طرح اختلاط اين نوع بتن مي تواند تا حد زيادي منجر به كاهش هزينه ساخت شود، هدف اصلي از تحقيق حاضر توسعه يك روش طرح اختلاط بتن سنگين براساس اصول بهينه سازي مي باشد. بدين منظور ابتدا مدل بهينه سازي طرح اختلاط بتن سنگين تعريف مي شود، سپس با استفاده از يك الگوريتم بهينه سازي طرح اختلاط بهينه براي بتن با مقاومت مورد نظر بدست مي آيد. نتايج عددي نشان مي دهد كه با كاهش مقادير سنگدانه و سيمان و افزايش مقدار ريزدانه در طرح اختلاط به صورت همزمان، مقدار هزينه طرح اختلاط كاهش پيدا مي كند
چكيده لاتين :
The procedures for measuring, mixing, transporting, and placing heavyweight concrete are similar to those used in conventional concrete construction; however, special expertise and thorough planning are necessary for the successful completion of this type of concrete .The use of heavyweight concrete in construction is a specialized field, Heavyweight concrete is used in counterweights of bascule and lift bridges, but it is generally used in radiation shielding structures to absorb gamma rays and differs from normal weight concrete by having a higher density and special compositions to improve its attenuation properties. When heavyweight shielding concrete is used to attenuate neutrons, sufficient material of light atomic weight, which produces hydrogen, should be included in the concrete mixture. Some aggregates are used because of their ability to retain water of crystallization at elevated temperatures, which ensures a source of hydrogen not necessarily available in heavyweight aggregate Cements would be suitable for conventional concrete and produce the required physical properties, are suitable for use in heavyweight concrete. Low-alkali cement should be used when alkali-reactive constituents are present in the aggregates and a moderate or low-heat cement should be used for massive members, To avoid high and rapid heat of hydration and resultant cracking, it is advisable not to use Type III cement or accelerators unless the concrete temperature is controlled by specially designed refrigeration systems. Thorough examination and evaluation of heavyweight aggregate sources are necessary to obtain material suitable for the type of shielding required. These sources are limited, and a material survey should be conducted to determine availability, chemical and physical qualities. The supplier’s sources should be inspected to evaluate rock composition, abrasion resistance, and density since these properties may vary from one location to another within a deposit. The purchaser must realize that mineral ores are not as uniform as normal weight concrete aggregates and make appropriate allowances Limited resources and increasing use of concrete, particularly in the industrial production cause that the heavyconcrete be useful. In order to optimize production of heavyconcrete, the most basic parameters that must be changed is the mix design. Optimization of the concrete mixture design is a process of search for a mixture for which the sum of the costs of the ingredients is lowest, yet satisfying the required performance of concrete, such as workability strength and durability. For this purpose, heavy concrete mix design optimization model is firstly defined and then optimal mix design will be achieved, by using an optimization algorithm. The experimental data were utilized to carry out analysis of variance. To develop a polynomial regression model for compressive strength in terms of the five design factors ( cement, coarse aggregate, fine aggregate, water and density ) considered in this study The numerical results shows that the amounts of coarse aggregate and cement are simultaneously reduced and amount of the fine aggregate is increased in the optimum mix design. Considering mass production concrete in nuclear power plants, this optimal mix design methods and reduce the cost of concrete can greatly reduce the cost of construction
