ABSTRACT The technology of 3D printing has been studied by different researchers, due to the possibility of producing solid objects swiftly, time reduction, labor with fewer failures the construction process. One of the challenges to be overcome is related to the development of mixtures promising. Thus, research aimed at the technology of cementitious materials is necessary to develop extrudable and sustainable mixtures. This article aimed to investigate the potential use of (FA) and (MK) in cementitious materials for application in three-dimensional printing (3D) by checking the aspects of constructibility. In the first stage, tests of normal consistency and initial and final setting time were carried out on pastes, with calcium oxide 4% and addition of (FA) and (MK) in the percentages of 8%, 10% and 15% in relation to the cement mass, in order to establish an ideal water / cement ratio. In the second stage, given a pre-determined trace of 1: 1.5, in mass, the viscosity, yield stress, extrudability and verticality tests were carried out on the cementitious materials developed in the first stage. It was observed that for the aspects related to the normal cement consistency and initial and final setting time, the paste with 15% substitution (FA) presented a longer initial setting time when compared to pastes with (MK) added. yield stress, materials with 15% substitution (FA) and without superplasticizer additive showed favorable results in the relation of the initial and final yield stress, as the mixture of 15% (MK) with 0.4% superplasticizer additive. and, therefore, they were considered promising because they were subjected to extrudability and verticality tests. Thus, it is concluded that considering the constructibility applied to prototyping, cementitious materials with 15% substitution (FA) and (MK) in relation to the cement mass present results considered relevant for the application in 3D printing.

O uso agrícola do lodo é uma alternativa viável para a reciclagem de nutrientes, embora haja certa preocupação com o aumento de espécies químicas solúveis originadas da mineralização da fração orgânica. Assim, para conhecer a disponibilidade de nutrientes e o risco de contaminação do solo e da água, o estudo da solução do solo é uma ferramenta valiosa. Nesses estudos, o número de variáveis utilizadas ultrapassa facilmente uma dezena, e ferramentas de análise exploratória, como a análise de componentes principais (ACP), revelam a existência ou não de amostras anômalas, de relações entre as variáveis medidas e sua contribuição relativa e de relações ou agrupamentos entre amostras. O objetivo deste trabalho foi identificar variáveis relacionadas com a solução do solo e alteradas, em razão do uso do lodo de esgoto e da adubação mineral, de forma a complementar os procedimentos para monitoramento/avaliação de áreas que recebem esse tipo de resíduo. A composição da solução do solo de uma área que recebeu lodo de esgoto por sete anos consecutivos foi estudada dos 22 aos 46 meses após a sua última aplicação. Com a solução do solo foi possível, por meio da ACP, distinguir as áreas em função da adubação aplicada. Após quatro anos da interrupção das aplicações sucessivas de lodo de esgoto, não verificou-se concentração apreciável de metais na solução do solo, embora ainda seja possível identificar traços da mineralização do resíduo. As variáveis pH, Mn2+, COD, SO4(2-), NO3- e NH4+ na solução do solo podem ser utilizadas no monitoramento de áreas tratadas com lodo de esgoto.

The use of sewage sludge in agriculture is a sound alternative for nutrient recycling, but the concern over increase in soluble chemical species from mineralization of organic matter remains. The study of the soil solution is a valuable tool for understanding the availability of nutrients and for assessing the risk of soil and water contamination. For such studies, where the number of parameters examined is usually more than 10, the use of multivariate analysis tools, such as principal component analysis (PCA), are quite useful in revealing outliers, the contribution of individuals and groups of parameters, and the relationship within tested samples. The objective of this study was to identify the parameters related to changes in the soil solution associated with the use of sewage sludge or mineral fertilization in order to complement procedures for monitoring/ assessing areas amended with them. The soil solution of an area which received sewage sludge for seven consecutive years was studied from 22 to 46 months after its last application. By using PCA it was possible to identify the treatments throughout the soil solution composition. Even four years after interrupting the successive applications of sewage sludge, the heavy metals in the soil solution of the area were close to the instrumental detection limits. However, changes in the soil solution composition due to mineralization of the remaining organic matter from the sewage sludge were still detectable. Based on those results, we propose a set of parameters for monitoring the soil solution of areas amended by sewage sludge: pH, Mn+2, COD, SO4(2-), NO3-, and NH4+.

O objetivo deste trabalho foi avaliar a dinâmica de mineralização do C e a capacidade do solo em fornecer N após sucessivas aplicações de lodo de esgoto, além de determinar a relação destas com a taxa de mineralização do lodo previamente aplicado. A área experimental recebeu, por sete anos, os seguintes tratamentos: 80 kg ha‑1 por ano de N mineral (L0); e 10 ou 20 Mg ha‑1 por ano de lodo (L1 e L2, respectivamente). Amostras de solo (0-20 cm) foram retiradas um ano após a última aplicação dos tratamentos. As amostras receberam doses de lodo correspondentes a 0, 120 e 240 kg ha‑1 de N e foram incubadas em laboratório por mais de 100 dias, tendo-se determinado o C‑CO2 liberado e o teor de N inorgânico no solo. A mineralização do C e do N foi mais influenciada pelo uso prévio do lodo do que pelas doses incubadas. A taxa de mineralização do nitrogênio (TMN) diminuiu de 16%, em L0, para 11%, em L1, e 8% em L2. No entanto, essa redução não resultou em menor disponibilidade de N no sistema, pois houve incremento do N potencialmente mineralizável (N0) em L1 e L2. Assim, a TMN não é um parâmetro adequado para cálculo da dose de lodo a ser aplicada em áreas previamente tratadas com o resíduo, pois subestima a capacidade do sistema em fornecer N. Neste caso, deve-se considerar o uso do N0.

The objective of this work was to evaluate the dynamics of carbon mineralization and the soil capacity in providing nitrogen after successive applications of sewage sludge, as well as to determine their relation with the mineralization rate of the sludge previously applied. The experimental area received for seven years the following treatments: 80 kg ha‑1 per year of mineral N (L0); and 10 or 20 Mg ha‑1 per year of sewage sludge (L1 and L2, respectively). Soil samples (0-20 cm) were taken one year after the last application of the treatments. Samples received sewage sludge doses corresponding to 0, 120, and 240 kg ha‑1 of N and were incubated in laboratory for more than 100 days, with determination of C‑CO2 emission and inorganic soil N content. The mineralization of C and N was more influenced by the previous use of sludge than by the incubated doses. The nitrogen mineralization rate (NMR) reduced from 16%, on L0, to 11% on L1 and 8% on L2. However, this reduction did not result in lower N availability on the system, since there was an increase of the potentially mineralizable nitrogen (N0) in L1 and L2. Therefore, the NMR is not an adequate parameter for calculating the sewage sludge dose to be applied on areas previously treated with the residue, since it underestimates the system capacity of providing N. In this case, the use of N0 should be considered.