This work presents a technical and economic study using sugar cane bagasse ash (SCBA) to partially replace Portland cement clinker. To evaluate the technical viability, the replacement rates of 10, 20, and 30% of Portland cement were used in the experiments. The ashes used were in the following conditions: (i) as collected (AC), (ii) ground (G), and (iii) re-burnt and ground (RG). Three composition parameters were used in the mortar mix procedures: (i) mix with water factor/fixed binder in volume, (ii) mix with water factor/fixed binder in weight, and (iii) mix with the fixed flow. After the technical feasibility analysis, the benefit of the substitutions and an analysis of the relationship between cement consumption and the acquired compressive strength, correlating with possible economic costs, were discussed. SCBA AC was not suitable for the partial replacement of Portland cement clinker. SCBA G presented a satisfactory performance and SCBA RG was the ash that presented the best performance in the partial replacement of Portland cement clinker. For the same levels of compressive strength, the consumption of Portland cement per cubic meter of concrete reduced; from this, the cost of concrete and mortar could be reduced by 8%, with the ash having the same value as cement. Furthermore, the use of SCBA RG at 30% inhibited the alkali–silica reaction (ASR) in concretes with a reactive basalt and quartzite aggregate. SCBA G (20 and 30%) and SCBA RG (10 and 20%) inhibited the ASR in concretes with a reactive basalt aggregate and reduced the expandability in concretes with a reactive quartzite aggregate. Another point to highlight was the durability shown by the cements with SCBA, which, 900 days after the accelerated test of expansion by the alkali–aggregate reaction, maintained high levels of flexural strength when compared to the results obtained before the accelerated test of expansion. The present work concluded that using sugar cane bagasse ash to replace Portland cement is feasible from a technical, environmental, and economic perspective.

The construction industry is essential to the development and economy, but is also the largest generator of construction and demolition waste (CDW). While efforts are made to minimize such generation, the construction industry has been developing applications for it in the form of aggregates to replace the commonly used natural aggregates. However, in structural applications, it is necessary to ensure that the properties of concrete produced with CDW, as recycled aggregates (CDW-concrete), guarantee adequate performance and do not put the structure at risk. For this, one of the alternatives is improving the properties of CDW aggregates through carbonation, a process called carbonate curing or accelerated carbonation. In this sense, this paper aims to investigate the carbonation of CDW aggregates, clarifying how this process occurs, the existing carbonation methods, the main properties that affect this process, and their influence on the properties of recycled aggregates and the CDW-concrete. To this end, the SREE (systematic review for engineering and experiments) method was used to search and analyze scientific manuscripts published without a time limit. The results revealed that the most widely used method for carbonate curing is recommended by Chinese standard GB50082, and highlighted the need for further research to investigate the CDW-concrete, focusing on its eco-friendly potential to capture CO2 from the atmosphere.

No abstract

Resumo A heterogeneidade dos resíduos de construção e demolição dificulta seu uso sistemático, consequentemente, têm-se problemas com a disposição final e a contínua extração e uso de recursos não renováveis para fabricação de concretos. Essa heterogeneidade decorre, majoritariamente, da não segregação dos diversos constituintes dos resíduos durante seu processamento. O presente artigo analisa a necessidade da segregação dos resíduos de construção e demolição em diferentes tipos - cerâmicas de argila e cimentícios - e as consequências da utilização desses materiais como substituintes dos agregados naturais graúdos em concretos estruturais. Para tanto, foram fabricados concretos com 0, 25, 50 e 100% de agregados reciclados, sendo três tipos de resíduos utilizados: cimentícios, cerâmicos e uma mistura dos dois, nas proporções obtidas na usina de reciclagem. As conclusões apontam não ser necessária a segregação do resíduo utilizado, uma vez que os resultados apresentam desempenho similar dos concretos com agregados cimentícios e com agregados mistos. As performances reológica e mecânica são parâmetros afetados negativamente pela adição de resíduos. Já o desempenho com relação à durabilidade pode ser melhorado com o uso de agregados reciclados.

The construction industry is responsible for the generation of large volumes of waste, known as construction and demolition waste (CDW). Around the world, millions of tons of these wastes are generated annually, which often become important environmental liabilities. The situation gets worse as the sector develops. In Europe, only 15 of the 27 countries in the European Union annually produce around 180 million tonnes of CDW, in Brazil, the data about this indicates that in 2014 the municipalities collected about 45 million tons of CDW, quantity 4.1% higher than in 2013. In this scenario, the present study aims to evaluate the partial replacement of natural aggregates by CDW (aggregates of concrete waste) in the production of concretes. In this sense, the effects of this substitution on the workability and mechanical characteristics of the concretes produced, as well as the influence of the mixing method and the percentage of superplasticizer additive on the same characteristics were evaluated. The methodology basically consists in the production of seven different traits, which are references and different combinations of mixing method, aggregate substitutions and superplasticizer percentages. Specimens of these traces were molded for mechanical characterization. Workability parameters were also evaluated. It is concluded that the workability is strongly affected by the addition of CDW, but a good workability can be obtained with the use of superplasticizer additives. The mixing method did not change the results obtained for this property. The results also indicate that the compressive and tensile strengths are not negatively affected by the substitution of aggregates, as well as being not significantly affected by the presence of the percentages of superplasticizer used, nor by the mixing methods.