Evaluation of the Fresh Properties of Cement Pastes: Part I-Response Models Applied to Changes in the One-Variable-at-a-Time Method.

The workability of cement-based materials is one of the features that makes these construction materials the most used worldwide. Measuring and understanding how cement-based constituent materials affect fresh properties depends on the experimental plans. The experimental plans deal with the constituent materials used, the tests carried out, and the run of experiments. Here, the fresh properties (workability) of cement-based pastes are evaluated based on the diameter in the mini-slump test and the time in the Marsh funnel test being measured. This overall study is composed of two parts. In Part I, tests were carried out on several cement-based paste compositions incorporating distinct constituent materials. The effects of the distinct constituent materials on the workability were analyzed. Furthermore, this work deals with an approach to the run of experiments. A typical run of experiments was applied, with basic sets of mixed compositions being studied by only changing one input parameter at a time. This approach used in Part I is faced with a more scientific approach applied in Part II of the work where, based on the design of experiments, multiple input parameters were changed at a time. This work showed that a basic run of experiments is quick and easy to apply and leads to results for simple analyses; conversely, it lacks information for advanced analyses and scientific conclusions. The tests carried out included studies on the effect on the workability caused by changes in the limestone filler content, the type of cement, the water-to-cement ratio, distinct superplasticizers, and shrinkage-reducing admixture.

Environmental benefits of using sewage sludge in the production of ceramic bricks.

The production of sludge from the sewage treatment plants is increasing as a result of population increase and public policies to improve the sanitation sector. This sludge presents a potential risk to health and the environment representing major challenge for sanitation companies regarding treatment and final disposal of this material. The solution is in the circular economy concept: This sludge presents favorable characteristics to be used as raw material in the ceramic industry. This study seeks to quantify the environmental impacts related to the atmospheric emissions caused and to the consumption of resources when 10% of clay is replaced by sewage sludge in the production of bricks. Life cycle assessment tools were used to establish a comparison between the common scenario of the brick production using ceramic mass only from clay and the scenario with the incorporation of 10% of sewage sludge. The results revealed that the incorporation of the sewage sludge has multiple benefits, regarding the decrease of the environmental impacts in all the categories studied: 15% in the energy savings, 15% in the terrestrial acidification and the formation of fine particles, 10% in scarcity of mineral resources, and 8-10% in formation of photochemical ozone.

Particleboard panels made with sugarcane bagasse waste-an exploratory study.

The reuse of natural fibers, in order to manufacture a new product, is already becoming popular due to the generation of a series of advantages in social areas. Sugarcane bagasse is a set of tangled fibers of cellulose, produced in large quantities due to increased acreage and industrialization of sugarcane resulting from public and private investments in production aimed for the alcohol industry. The aim of this study was to evaluate the feasibility of producing sheet timber manufacture from the sugarcane bagasse, analyzing mechanical strength properties. A form of metal sheet for the molding of 12 specimens based on sugarcane bagasse and industrialized resin was made. Soon after molding, specimens were submitted to a three-point bending test, with the aid of a press. The analysis of the results allowed to conclude that the tensile strength and the modulus of elasticity did not obtain the minimum values recommended by the standard. The tensile strength must be improved to allow panels to be useful for ordinary strength applications.

Briquettes from sludge in sewage treatment plant: calorific power.

Due to the large volume of sewage generated every day, there is a high demand for its treatment. The by-product (called sludge) generated after the treatment process has caused problems in terms of its final disposal. Since the typical end off for this waste is landfills, it is mandatory reducing the landfill amount and the risk of soil contamination. The present work explored an adequate final disposal of the sludge as a sustainable alternative. For this purpose, briquettes were produced using dry sludge from the Sewage Treatment Plant of the Minas Gerais (Brazil) Sanitation Company and vegetable oil used to thicken the briquettes. These briquettes were compared to eucalyptus charcoal in terms of their calorific potential, through immediate analysis, since Brazil has a high demand for primary energy, especially in the industrial sphere. The calorific potential of charcoal reached 16.66 MJ/kg, while that of briquette reached 12.94 MJ/kg. However, briquettes had a density much higher than charcoal, so it takes a smaller volume of briquettes to achieve the same burning capacity as a large volume of charcoal.

Experimental dataset from a central composite design with two qualitative independent variables to develop high strength mortars with self-compacting properties.

Fresh and hardening properties of cement-based materials are key factors for correctly choosing the constituent materials and their mix proportions. To optimize design-based mortar compositions for specific applications, response models are frequently applied to data collected from scientific approaches. Here, experimental dataset regarding to a design of experiments carried out in mortars through a central composite design with five independent variables is presented. Among the five independent variables, four were quantitative ones: Waterv/Cementv, Superplasticyzerm/Powderv, Waterv/Powderv, Sandv/Mortarv. The other independent variable was a qualitative one: Superplasticiser A or Superplasticiser B. In total 60 mortar compositions were done: for each qualitative variable a 24 factorial design comprising of 16 treatment combinations enlarged by 8 axial runs plus 6 central runs, resulting in a central composite design with 30 mortar trial mix compositions. The following dependent variables were tested: the D-flow and the t-funnel to evaluate the fresh properties and the compressive at the age of 24 h and at the age of 28 days to evaluate the hardened properties. Based on this dataset, response models can be applied to find optimized mix compositions, with the effect of the two qualitative variables being determined.

Experimental dataset from a central composite design to develop mortars with self-compacting properties and high early age strength.

The concrete workability and the compressive strength are the principal properties of the fresh and hardened concrete, respectively. When self-compacting properties are required, scientific knowledge is important and appropriate models applied to achieve optimized compositions. Here, experimental data regarding to the mortars is presented. The dataset regards to a design of experiments carried out in mortars with commercial materials through a central composite design with five independent variables: Waterv/Cementv, Superplasticyzerm/Powderv, Waterv/Powderv, Sandv/Mortarv, FineSandv/Sandv. In total 64 mortar composition were done: 25 factorial design consisting on 32 treatment combinations augmented by 10 axial runs plus 8 central runs, resulting in a central composite design with 50 mortar trial mix composition. Beside 14 extra mixes were done to allow comparing and validating results for the response models to be applied. Four dependent variables were measured: the D-flow and the t-funnel to measure the workability and the tensile strength and the compressive at the age of 24 h to assess the mechanical properties. Since the experiments were run based in a central composite design and extra mixes were prepared, response models can be applied to the dataset in order to find optimized mix compositions.