Gladis Camarini

Characteristics of Gypsum Recycling in Different Cycles

In Brazil, the gypsum plaster waste is 4% to 15% of construction and demolition waste. The environmental legislation advises that this waste should be recycled to avoid the contamination of soil and groundwater. The aim of this work is to show that the recycled gypsum plaster maintains its characteristics when submitted to different recycling cycles. The recycled gypsum plasters were produced by grinding and burning the waste along three successive recycling cycles. The recycled materials were evaluated by chemical and physical properties. The obtained results showed that both recycled and commercial gypsum plaster are similar to using in the Construction Industry.

Recycled Plaster: Physical and Mechanical Properties

Commercial plaster (CaSO4•1/2H2O) is a material used in building construction all over the world. This construction material is used renderings in internal and dry environment because it is soluble in water. According to different studies, the plaster manually applied as renderings produces high volume of material loss (values varying from 18% to 35%). In this way, the aim of this work was to study the physical and mechanical properties from pastes made with commercial plaster and pastes obtained from hydrated plaster that was lost from their applications (recycled plaster). The recycled plaster was grounded and burnt at different temperatures in order to loose its non-evaporated water and to make possible its reuse as binder. After burning, their physical and mechanical properties were studied. The results showed that recycled plaster had a good performance as binder. Their physical and mechanical properties related to commercial plaster were very similar. In this way, the results show that it is possible to reuse the recycled plaster as binder again, which permit to contribute to a sustainable construction.

Benefits in the Implementation of Safety, Health, Environmental and Quality Integrated System

This article aims to present the benefits in the implementation of the integrated management system based on the standards ISO 9001, ISO 14001 and OHSAS 18001. It is a case study in a sector of the construction industry chain, located in the southeastern Brazil. An exploratory study using a questionnaire with leaders from this particular industry was conducted, as well as a documentary analysis from the Integrated Management System (IMS) archives. The obtained results of the documentary analysis and perceptions of leaders survey were observed based on previous IMS research. The results indicated that almost all leaders identify several benefits in systems integration, with an improvement in the routine management as the main benefit, and the financial savings as the smallest benefit. It was also found that in leader perception the most of IMS documents are integrated. The same result was found in many documents in the documentary analysis.

Thermal Analysis of Recycled Gypsum from Construction and Demolition Waste

Construction and demolition waste has in its composition gypsum plaster which is a soil and groundwater contaminating material. Some works have been developed to recyle this gypsum waste. The aim of this work is to show a thermal analysis of recycled plaster. The recycled plaster was produced through a recycling process consisting of grinding and burnig the gypsum waste. Physical and thermal properties (TGA/DTA) from both commercial and recycled gypsum plaster were analysed. The results show a recycled plaster with similarities with commercial plaster, showing the possibility to reuse this waste in construction works.

Assessment of the Material Loss in Walls Renderings with β-Hemihydrate Paste

In civil construction, β-hemihydrate pastes have been used as decorative ornaments, plasterboards, dry-wall and renderings. The application procedure of β-hemihydrate pastes for rendering generates large amounts of waste due to its hydration kinetics. Waste production also occurs due to the technique of preparation and application of this material. It is essential to minimize gypsum waste. The aim of this work was to quantify the amount of gypsum waste produced by the process of using it as renderings. It was observed the influence of workers applying pastes rendering on gypsum waste production. The application process of plaster renderings was followed measuring the waste generated and the time for finishing the process was also observed. Results pointed out waste production values in the range between 16% and 47%. The application technique influences the amount of waste production.

Curing Effects on Air Permeability of Concrete

The kinetics of cement hydration can be accelerated by steam curing and this kind of curing can be responsible for increasing concrete porosity, since a greater portion of non hydrated cement particles can be present. The increased porosity results can result in increased permeability. The aim of this work was to investigate the influence of curing on concrete quality by air permeability and compressive strength test. It was measured by means of a non steady state air permeameter. Concretes were produced with Portland cements containing 0%, 27% and 53% of ground granulated blastfurnace slag. The amount of slag in cement influenced concrete performance and steam curing increased air permeability of concrete.

Properties of Cellular Concrete for Filters

Considering the trends of new materials in Construction, the lightweight concrete with a density between 400 and 1800 kg/m³ has been the subject of several studies with emphasis on particle size distribution of aggregates and their raw materials. Some of the advantages of cellular concrete are its lightness, resistance to freezing and thawing, good thermal insulation and acoustics. It can be used as blocks, precast masonry panels, filling and regularization of slabs to be waterproofed. The aim of this work is to study the material proportion that composes the cellular concrete, such as cement, sand, admixtures and water. It was analyzed the composite in the fresh and hardened state. Properties, such as compressive strength, water permeability of the plates, water absorption by immersion and by capillary rise were determined. The tests followed the Brazilian Standards and took place in cylindrical, prismatic and cubic specimens. It was made seven mixtures with four different admixtures, TecFoam, TecFill, CO 436 and Less S. The cellular concrete with TecFoam and Less S obtained strength and porosity for filtering water.

Microstructure of recycled gypsum plaster by SEM

Gypsum waste from building constructions is a material which can contaminate the soil and groundwater if is disposed directly in the soil or landfill without any control. In Brazil, these wastes are considered a recycle and/or recovery material, but the research of gypsum plaster recycling are very few at this moment. In this way, this work presents the microstructural characterization of two types of recycled plaster. The recycled plaster was produced by a grinding and calcination the building construction waste. Microstructural characteristics were evaluated by SEM observations. The results show similarities between crystals of recycled and commercial plasters.

Methods to Measure the Transfer Properties of Mortars

The search for techniques and materials able to improve structure quality and durability has lead to research some methods that are able to measure the transfer properties of composites. Cement type has an important influence on mortar performance, and chemical and physical deteriorations modify microstructure, and thereby transfer properties. The aim of this work is to evaluate two methods which can measure the transfer properties of cement based materials: capillary absorption and air permeability tests in mortars produced with blastfurnace slag Portland cement. The relationship between these two methods was investigated. The mortars were submitted to steam curing (60 °C) and standard curing. Results show that steam curing improved initial compressive strength. At 28 days all mortars had the same performance. Water absorption coefficient and air permeability was higher for steam cured mortars. There was a significant correlation between both tests results.

Gypsum Plaster Waste Recycling: Analysis of Calcination Time

The gypsum plaster is a material widely used in constructions around the world. It is a material with high versatility that can be applied from wall coverings to decorative ornaments. However, during its application in buildings, large amounts of waste materials are generated. The average values of waste during its application are higher than 45% of the gypsum amount used. A series of tests were conducted to develop a feasible methodology to reuse this waste material. The results collected at this stage indicated that it is possible to obtain a recycled product with low energy consumption. It was noted that after a certain number of procedures in which gypsum was subjected to recycling, there was a loss of workability; however, it did not present relevant changes in mechanical properties. This lack of workability avoids the recycled material maintain its properties in the fresh state as it is subjected to recycling. This work evaluates the calcination time of gypsum plaster waste for the production of a gypsum plaster with binder properties for using as components. The temperature of calcination was kept constant (150 °C), but the residence time in the stationary kiln was modified. The properties in the powder state (bulk density, fineness modulus, specific mass and sieve analysis), fresh state (mini-slump, setting times and kinetics of temperature) and in the hardened state (compressive strength and hardness) were analysed in order to have some answers about the performance of the recycled gypsum. In the fresh state, the recycled material showed good results for precast components. The initial setting times were good for all residence times and the final setting times for the material calcined in periods of 5 and 6 hours. In the hardened state, the best compressive strength results were obtained for all residence times, and hardness for calcination for 3, 4, 5 and 6 hours. All these results were satisfactory when compared to the commercial plaster took as reference. On the other hand, there was a lack of workability in those pastes indicating that an admixture is needed to adjust this property of the recycled material.