No abstract

No abstract

The properties of structural concrete which incorporates recycled coarse concrete aggregates (RCCA) may be affected by the RCCA's properties, especially in terms of water absorption, if no technological control methods are adopted in its production. Based on the knowledge of RCCA's water absorption behaviour, this research is aimed at determining the influence of the pre-saturation of the RCCA method on concrete's fresh and hardened properties, compared with a conventional concrete and a recycled aggregates concrete produced using the mixing water compensation method. Both methods can be easily adopted at concrete plants or construction sites. For the establishment of the pre-saturation method procedure, RCCA absorption was thoroughly characterised. A reference concrete and three mixes with replacement ratios of 20%, 50% and 100% of natural coarse aggregates by RCCA were produced, for each method. Tests were performed to determine slump, density, compressive strength, elasticity modulus, shrinkage, water absorption by immersion and capillary water absorption; the surfaces of the mixes were also observed with a magnifying glass. Results showed that mixes produced with the pre-saturation method exhibited slightly worse fresh and hardened properties, and therefore it is concluded that both the pre-saturation method and the mixing water compensation method can be adopted.

Bottom ash from municipal solid waste incinerator plants in Catalonia was characterised to investigate some alternatives for its utilisation and their potential environmental impact. After a detailed chemical and mineralogical characterisation, physical and geotechnical properties were investigated. The study focused on the use of bottom ash as an aggregate substitute in pavement applications. The results show that

With the aim of gaining a better understanding of the phenomena responsible of the loss of durability of cement mortar composites reinforced with vegetable fibers, this paper focuses on the analysis of the fiber-matrix interactions. More specifically we analyze the effects of the vegetable fibers on the cementitious matrix after their mixture for different periods of time and vice versa. Three kinds of cellulosic fibers with differences on its physicchemical properties were studied: bamboo fibers, kraft pulp and cotton linters. The results show that the cellulosic fibers modify the total amount of heat released during the hydration process in the cement paste, this effect differing depending on the purity of the fibers. The high alkalinity of the cementitious matrix causes the partial dissolution of chemical components of the fibers and a harmful precipitate of the inorganic particles on its surface and/or lumen, damaging the fibers and hence decreasing its reinforcement capacity.