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radiation shielding concrete optimization

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Ali Yadollahi
added 4 research items
The use of heavy concrete as a protective shield against high-energy gamma rays is very common. It is also an effective, versatile and economical material. The heavy concrete production can use lead slag as raw materials. The use of lead slag in the production of concrete blocks saves natural resources and reduces the environmental problems caused by the accumulation of industrial waste. However, concrete production, due to the presence of heavy metals with high atomic number can be used as an effective shield against gamma radiation. This study examines the use of lead slag produced in the battery recycling process as concrete aggregates. For this purpose, strength and gamma-ray attenuation coefficient for concrete samples prepared by replacing 40 to 60 percent lead slag instead of natural aggregate. The effect of 1 to 5 percent lead powder in setting time of concrete was measured. The results showed that by increasing the amount of lead slag, density, mechanical strength and gamma-ray attenuation coefficient for concrete samples increased significantly, but lead powder delays setting time of cement paste. In general, appropriate lead slag concrete construction with minimal thickness, reduce the cost of protection and provides the highest level of attenuation.
Utilization of wastes and by-products as concrete aggregate has received increasing attention in the last few years. Lead slag extracted from recycling of the spent batteries, is one of these waste materials which have high potential and can be utilized as substitute of raw materials in construction of radiation shielding concrete. For utilization of lead slag as Radiation-shielding concrete aggregate, we should consider different criteria. Therefore, It is necessary to find an optimal mixture to produce Lead Slag radiation shielding concrete (LSRSC) with desired quality characteristics. In the present work, Taguchi method in combination with grey relational analysis is applied to find the optimal mixture of LSRSC with multiple responses. In the application of this method, water/cement ratio, cement quantity, volume ratio of lead slag aggregate and Silica fume were selected as control factors with responses of slump, Unit weight, compressive strength and gamma attenuation coefficient to assess the optimal mixture of LSRSC. Results demonstrated that the optimal mixture of LSRSC has a water/cement ratio of 0.42, cement quantity of 390 kg, a volume fraction of lead slag aggregate of 60% and silica fume-cement ratio of 0.15.
In the production of radiation shielding concrete (RSC), it is necessary to find an optimal mixture to fulfill all the desired quality characteristics simultaneously. In this study, Taguchi method and artificial neural network (ANN) were implemented to find the optimal mixture of RSC containing lead-slag aggregate. Using Taguchi method for experimental design, 27 concrete samples with different mixtures were fabricated and tested. Water–cement ratio, cement quantity, volume ratio of lead-slag aggregate and silica fume quantity were selected as control factors and slump, compressive strength and gamma linear attenuation coefficient were considered as the quality responses. Obtained data from 27 experiments were used to train 3 ANNs. Four control factors were utilized as the inputs of all the 3 ANNs and 3 quality responses were used as the outputs, separately (each ANN for one quality response). After training the ANNs, 1024 different mixtures with different quality responses were predicted. At the final, optimum mixture was obtained among the predicted different mixtures. Results demonstrated that the optimal mixture of RSC has a water–cement ratio of 0.45, cement quantity of 390 kg, a volume fraction of lead slag aggregate of 60% and silica fume–cement ratio of 0.15.