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The purpose of this paper is to propose a sorting platform to increase the quality of recycled aggregates through the supplementary use of mineral processing techniques and additional sorting. The difficulty of liberation is discussed, and the methodology currently used in mineral processing is proposed. Jigs, hydrocyclones and sensor-based sorting are considered to have good performance in the sorting of adequately recycled aggregates. The new perspectives on sorting and liberation for recycling aggregates are discussed. The new process is presented based on the current process in recycling platforms, with supplementary sorting of the recycled concrete. The gain in density and the reduction in water absorption are studied. The relation between the water content and the density of aggregates is analysed for three quality levels of recycled aggregates. The gain in density and the reduction in water absorption were linked to the aggregate replacement rates. The reduction in transport and discharge costs due to the increased aggregate quality was linked to the aggregate replacement rate and distance to quarry. In our study, replacing a lower-quality aggregate with another of medium quality leads to an expected density gain of approximately 4%. Conversely, if replaced by superior quality aggregate, the expected gain will be 8.4%. As a consequence, a 34% reduction in water absorption could also be obtained. The cost reduction is exponential with the substitution rate of recycled materials. There is a decrease in transport costs if the quality of recycled aggregates increases. Conversely, if the reduction in transport costs when the quality of recycled aggregates increases is considered, the distance between the demolition site and quarry is not important.

A multivariate data analysis was used with environmental data obtained from Hot-Mix asphalt (HMA) plants. The main objectives of the study were to describe and interpret the real “phenomena” that exist on HMA plants; also, to search for the best mixing conditions, i.e. production with less energy consumption and less emissions. Another important objective was to identify means to allow HMA plants to be designed and operated in better ways. Along the study, an approach of the manufacturing process is presented, allowing for an overall comprehension of the plant's operation. There is not only one parameter to be controlled and checked when HMA are being produced. In this context, a multivariate data analysis was carried out, and the main control parameters considered for prediction and regression analysis were Hot-Mix asphalt formula, fuel type, burner flow rate, fuel consumption, negative pressure of the drum, air temperature, moisture of aggregates, asphalt temperature and rate of production. “Global warming emissions”, “organic emissions”, and “energy consumption” were chosen as models of regression. Globally, plants powered by natural gas emit half the amount of CO 2 , nine times less NO x and eighteen times less CO than plants with fuel oil. Considering NO x and CO 2 emissions, small plants are preferable over big plants. For organic emissions, if the asphalt temperature increases, TOC emissions are increased; however, if the rate of production increases, TOC emissions are decreased. Previously supposed as an important parameter, moisture of aggregates had no great importance in the statistical analysis. Likewise, the formula of HMA produced also had no great importance, despite many types of formulas studied. The main conclusions in regards to the means with which Hot-Mix asphalt plants can be designed and operated in better ways were: the manufacturing of hyper-mobile and small HMA plants as opposed to stationary large plants, and the use of burners with natural gas instead of fuel oil in all cases. The production of HMA plants, aiming at a cleaner production, means to operate asphalt plants always considering timespan in the long term. This encompasses undertaking daily, weekly and yearly analyses. Therefore, it is necessary to produce with low rate of production and low bitumen temperature, and to maintain a regular production in order to avoid peaks of production and unnecessary starts and stops. It is also interesting to increase the culture of heated stocks. Finally, this study shows that would be an advantage to use multivariate data analysis and then to estimate with very good accuracy emissions and energy consumption in HMA plants using current parameters of control.

This work seeks to evaluate the effect of the sorting of calcium/magnesium carbonates (limestone ores) through the use of X-ray and CCD camera sensors. Collection of the 17 samples used for this study was performed after primary crushing at a size range between 76 and 152 mm (3–6″). This work seeks to evaluate the effect of the sorting of calcium/magnesium carbonates (limestone ores) through the use of X-ray and CCD camera sensors. Collection of the 17 samples used for this study was performed after primary crushing at a size range between 76 and 152 mm (3–6″). Sampling was intended to represent all of the possible variations of the ore and waste currently being extracted. For initial characterization, samples were washed and subjected to analysis by a handheld X-ray fluorescence spectrometer. Sensor based sorting tests were performed at the Federal University of Rio Grande do Sul (UFRGS) using a COMEX lab sorter. The lab sorter is comprised of a conveyor belt, mounted sensors, a data processing system, and a pneumatic flap system for the physical separation of the samples. Results of the X-ray separation showed that of the 12.2 kg of samples, 10.5 kg were sorted into product and only 1.7 kg were separated as waste. However, within the waste fraction, only 54.5% was considered waste, and likewise 7% of the product fraction was considered waste. When using the CCD camera, 100% of the ore fraction and 100% of the waste fractions were considered to be sorted correctly. While it is important to note that this is only a preliminary study analyzing the viability of implementation of the automatic sorting system, these preliminary results obtained with the use of both sensors were considered satisfactory.

This paper proposes an economic analysis of three different types of processing in CDW (construction and demolition waste) recycling platforms, according to the sophistication of the processing technologies (current advanced, advanced and advanced sorting). The methodology that is adopted is in the economic evaluation concept of projects and is classified with a scoping study phase. In these contexts, three levels of CDW processing capabilities for recycling platforms are analyzed (100, 300 and 600 thousand tons per year). This article considers databases obtained from similar projects that have been published in the specialized literature; the data sources are primarily from the European continent. The paper shows that current advanced process has better economic performance, in terms of IRR, related to the other two processes. The IRR associated with advanced and advanced sorting processes could be raised by, (i) higher price of secondary primary material, and/or (ii) higher capacity of platforms, and/or (iii) higher sharing of secondary primary material in the total production. The first two points depend on the market conditions (prices and total quantity of CDW available) and (potential) fiscal or incentive policies. The last one depends on technological progress.; Cet article propose une analyse de trois différents types de procédés de recyclage des déchets issus de la construction et la démolition de bâtiments. Trois dimensionnements (100, 300 et 600t/an) de plateformes de recyclage sont étudiés.

This work deals with the separation of concrete, brick and gypsum particles from a CDW recycled aggregate mixture. Construction and Demolition Waste materials can be handled as an ore treatment problem. Efficient sorting processes of low quality CDW recycled aggregate could allow the reuse of concrete, brick and gypsum particles. The processes also improve the remaining mixed aggregates for recycling in unbound sub-base materials, by increasing their self-cementing properties and by reducing the sulfate content through the removal of gypsum. All tests were carried out in the size range between 4 and 20 mm using a laboratory air jig. The aim of the work is to concentrate a high amount of gypsum (light material) and concrete (heavy material) particles. Three working parameters are relevant for the jigging processes control such as the sorting duration, the frequency and the expansion ratio. Each of them are studied. It was found that a quadratic model of the number of jig cycles, a product of the frequency and time, accurately predict well the sorting results, if the expansion is large enough. An optimal point seems achieved at about 320 jigging cycles. Concentrates with concrete contents higher than 90% and gypsum contents significantly lower than 1% were possible to be reached and can be an alternative in aggregates for the concrete market. Indeed, gypsum reduction in concrete concentrates was about 25 times. This level of reduction could be satisfactory in sorting real demolition products. On the other hand, contents of over 70% of gypsum concentrates were obtained, increasing the reuse and recycling abilities.

The recycling of inert construction and demolition materials (C&D) remains problematic if these materials are used to process high-quality recycled aggregates suitable for manufacturing new concrete. Even when selective demolition is employed, the crushing and classification of C&D produces recycled aggregates with an unacceptable level of impurities, with the content of gypsum being the biggest concern. Another concern is the percentage of brick content that decreases the density of the recycled aggregate as well as its homogeneity. The present work studies an air jig sorting method to separate out concrete particles from a C&D mixture that contains high amount of gypsum (22% mass) and brick (24% mass) particles. The mixture of aggregates studied had a 4–20 mm grading. After sorting, the bottom third of the mixture had less than 1% mass of gypsum and more than 90% mass of concrete particles. In contrast, the upper third of the sorted material contained gypsum in proportion of nearly 80% mass. The separation mechanism appears to be governed by both particle density and bulk density of individual components. These results are very encouraging and prove that the air jigging method is a promising technology for the use in C&D recycling plants. Further research is warranted.