O problema da mistura em uma indústria de concreto
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Data
2020-06-26
Autores
Scobosa, Marcelo
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Diante da importância do ramo de construção civil, existem no Brasil muitas indústrias responsáveis pelo fornecimento do concreto para grandes obras, com sua dosagem sendo realizada nos conhecidos centros de dosagens. Ainda hoje, mesmo com muita tecnologia ao alcance industrial, as empresas em boa parte usam de métodos empíricos e baseados na experiência dos funcionários para se chegar a um composto final aceitável. A proposta deste trabalho visa obter um modelo matemático de otimização linear que minimize os custos com ingredientes, sob o âmbito do clássico problema da mistura em um viés multi produto, de maneira a satisfazer toda especificação técnica e parâmetros envolvidos com a tecnologia e engenharia do concreto. Neste estudo foram realizadas duas abordagens da mistura, sendo uma sem a utilização de aditivos, com o concreto sendo formado apenas pelos seus ingredientes usuais (cimento, água, agregado fino e agregado grosso) e outra com a incorporação do aditivo plastificante polifuncional retardador de pega. Um estudo comparativo foi realizado mostrando-se a importância do uso deste componente. Na abordagem do problema da mistura com aditivo, pelo motivo de sua influência ser totalmente específica, alterando as características da reação química existente, não existe uma equação universal e genérica de maneira a relacionar quantitativamente a influência do aditivo e compostos com parâmetros a serem atendidos. Para contornar esta questão foi necessário obter várias misturas aleatórias no centro de dosagem e avaliar como a quantidade de cada componente influencia nos parâmetros mais relevantes, especialmente o abatimento. Uma análise estatística foi realizada para se obter uma equação linear completa, a qual foi introduzida ao modelo. Vários testes de validação do modelo foram realizados, como medições laboratoriais e a formação de um gráfico de dosagem, através das soluções encontradas pelo modelo, totalmente coerente com as clássicas leis da tecnologia de concreto. Ademais, testes de viabilidade econômica foram realizados comparando-se as soluções encontradas com as utilizadas pela indústria, de maneira empírica, durante um período de três meses.
Given the importance of civil construction industry, there are many industries in Brazil responsible for supplying concrete for major works, with its dosage being fulfilled in the well-known dosage centers. Even with the possibility of an easy technological access nowadays, concrete companies use empirical methods based on the experience of employees to reach an acceptable final blending. The purpose of this work is to obtain a linear optimization mathematical model that minimizes the costs with ingredients, under the multi product scope of the classic blending problem, in order to satisfy all technical specifications and parameters involved with concrete technology and engineering. In this study, two approaches to the blending problem were carried out, one without the use of additives, with the concrete being formed only by its usual ingredients (cement, water, fine aggregate and coarse aggregate) and the other with the incorporation of an additive retardant plasticizer polyfunctional. A comparative study was accomplished showing the importance of using this component. In the approach of the blending problem with additive, as its influence is totally specific, changing the characteristics of the existing chemical reaction, there is no a universal and generic equation in order to quantitatively relate the influence of the additive with parameters to be met. To get around this issue, it was necessary to obtain several random mixtures at the dosage center and assess how the quantity of each component influences the most relevant parameters, especially the slump. A statistical analysis was performed to obtain a complete linear equation, which was introduced to the model. Several tests of validation of the model were carried out, such as laboratory measurements and the formation of a dosage graph, through the solutions found by the model, totally coherent with the concrete technology classic laws. In addition, economic feasibility tests were carried out by comparing the solutions found with those used by the industry, in an empirical way, during a three month period.
Given the importance of civil construction industry, there are many industries in Brazil responsible for supplying concrete for major works, with its dosage being fulfilled in the well-known dosage centers. Even with the possibility of an easy technological access nowadays, concrete companies use empirical methods based on the experience of employees to reach an acceptable final blending. The purpose of this work is to obtain a linear optimization mathematical model that minimizes the costs with ingredients, under the multi product scope of the classic blending problem, in order to satisfy all technical specifications and parameters involved with concrete technology and engineering. In this study, two approaches to the blending problem were carried out, one without the use of additives, with the concrete being formed only by its usual ingredients (cement, water, fine aggregate and coarse aggregate) and the other with the incorporation of an additive retardant plasticizer polyfunctional. A comparative study was accomplished showing the importance of using this component. In the approach of the blending problem with additive, as its influence is totally specific, changing the characteristics of the existing chemical reaction, there is no a universal and generic equation in order to quantitatively relate the influence of the additive with parameters to be met. To get around this issue, it was necessary to obtain several random mixtures at the dosage center and assess how the quantity of each component influences the most relevant parameters, especially the slump. A statistical analysis was performed to obtain a complete linear equation, which was introduced to the model. Several tests of validation of the model were carried out, such as laboratory measurements and the formation of a dosage graph, through the solutions found by the model, totally coherent with the concrete technology classic laws. In addition, economic feasibility tests were carried out by comparing the solutions found with those used by the industry, in an empirical way, during a three month period.
Descrição
Palavras-chave
Indústria de concreto, Otimização linear, Problema da mistura, Modelagem matemática, Concrete industry, Linear optimization, Blending problem, Mathematical modelling