Miguel Bravo

Construction and demolition waste indicators

The construction industry is one of the biggest and most active sectors of the European Union (EU), consuming more raw materials and energy than any other economic activity. Furthermore, construction waste is the commonest waste produced in the EU. Current EU legislation sets out to implement construction and demolition waste (CDW) prevention and recycling measures. However it lacks tools to accelerate the development of a sector as bound by tradition as the building industry. The main objective of the present study was to determine indicators to estimate the amount of CDW generated on site both globally and by waste stream. CDW generation was estimated for six specific sectors: new residential construction, new non-residential construction, residential demolition, non-residential demolition, residential refurbishment, and non-residential refurbishment. The data needed to develop the indicators was collected through an exhaustive survey of previous international studies. The indicators determined suggest that the average composition of waste generated on site is mostly concrete and ceramic materials. Specifically for new residential and new non-residential construction the production of concrete waste in buildings with a reinforced concrete structure lies between 17.8 and 32.9 kg m−2 and between 18.3 and 40.1 kg m−2, respectively. For the residential and non-residential demolition sectors the production of this waste stream in buildings with a reinforced concrete structure varies from 492 to 840 kg m−2 and from 401 to 768 kg/m−2, respectively. For the residential and non-residential refurbishment sectors the production of concrete waste in buildings lies between 18.9 and 45.9 kg/m−2 and between 18.9 and 191.2 kg/m−2, respectively.

Mechanical Performance of Structural Concrete with the Incorporation of Coarse Recycled Concrete and Ceramic Aggregates

The paper presents the results of an experimental program to evaluate the viability of concrete made when various ratios of coarse natural aggregates (CNAs) are replaced with coarse recycled concrete aggregates (CRCAs), coarse recycled ceramic masonry and mortar aggregates (CRMMAs), or both. Results show that incorporation of CRCA and of CRCA and CRMMA simultaneously has no effect on compressive strength. However, this property decreases when only CRMMA is incorporated. A reduction of 23.6% in compressive strength was obtained when 50% of CRMMA was used. Splitting tensile strength is unaffected by incorporation of CRCA but it is affected by incorporation of CRMMA. The mixes with 50% of CRMMA showed a reduction of 20.1% in tensile strength. Every recycled aggregate concrete type suffered a linear decrease of modulus of elasticity as the replacement ratio of CNA by coarse recycled aggregates increased. The use of 100% CRCA caused a decrease in modulus of elasticity of 30%. In the mixes with 50% of CRMMA that decrease was 22.2%. Shrinkage was significantly affected by incorporation of course recycled aggregates, although the degree of shrinkage varied in accordance with their nature and incorporation ratio. For replacement ratios between 50 and 100%, the difference between a reference concrete (RC) and the mixes with CRCA remained constant, inside a 30% increase range.

Indicadores de resíduos de construção e demolição para construções residenciais novas

A industria da construcao representa um dos maiores e mais activos sectores da Uniao Europeia (UE), consumindo mais materias-primas e energia do que qualquer outra actividade economica. Da mesma forma, os residuos das suas actividades corespondem a uma elevada parcela dos residuos produzidos em toda a UE. A actual legislacao na UE visa criar condicoes para a implementacao de medidas de prevencao e reciclagem de RCD. No entanto, carece de instrumentos que acelerem o desenvolvimento de um sector tao tradicional como o da construcao. O presente trabalho tem por objectivo determinar indicadores que possibilitem estimar a quantidade de RCD gerados, ao nivel da obra, tanto globalmente como por fluxo de residuos. A geracao de RCD foi estimada para seis sectores especificos: nova construcao residencial, nova construcao nao residencial, demolicao residencial, demolicao nao residencial, reabilitacao residencial e reabilitacao nao residencial. Neste artigo, apresentam-se os resultados para a nova construcao residencial. Os dados necessarios ao desenvolvimento dos indicadores foram obtidos atraves de um levantamento exaustivo dos dados de estudos anteriores.

Performance of concrete made with recycled aggregates from Portuguese CDW recycling plants

The objective of this research is the production of concrete with recycled aggregates (RA) from various CDW plants around Portugal. The influence of the RA collection location and consequently of their composition on the characteristics of the concrete produced was analysed. In the mixes produced in this research RA from five plants (Valnor, Vimajas, Ambilei, Europontal and Retria) were used: in three of them coarse and fine RA were analysed and in the remaining ones only coarse RA were used. The experimental campaign comprised two tests in fresh concrete (cone of Abrams slump and density) and eight in hardened concrete (compressive strength in cubes and cylinders, splitting tensile strength, modulus of elasticity, water absorption by immersion and capillarity, carbonation and chloride penetration resistance). It was found that the use of RA causes a quality decrease in concrete. However, there was a wide results scatter according to the plant where the RAs were collected, because of the variation in composition of the RA. It was also found that the use of fine RA causes a more significant performance loss of the concrete properties analysed than the use of coarse RA.