Vanderley Moacyr John

Fungal colonization and succession on newly painted buildings and the effect of biocide

This report describes the sequence of fungal colonization and the influence of biocide incorporation on paint films, determined using quantitative methods. Two buildings were painted with an acrylic paint, with and without an experimental biocide formulation containing a carbamate (carbendazin), N-octyl-2H-isothiazolin-3-one and N-(3,4-dichlorophenyl)N,N-dimethyl urea (total biocide concentration 0.25% w/w). One week after painting, the major groups of organisms detected were yeasts and Cladosporium. The yeast population fell to undetectable levels after the third week and this microbial group was not detected again until the 31st week, after which they increased to high levels on the 42nd week. Aureobasidium showed a pattern similar to the yeasts. The main fungal genera detected over the 42-week period were Alternaria, Curvularia, Epicoccum, Helminthosporium, Coelomycetes (mainly Pestalotia/Pestalotiopsis), Monascus, Nigrospora, Aureobasidium and Cladosporium. The latter was the main fungal genus detected at all times. The physiological factors controlling colonization are discussed. Cladosporium, Aureobasidium, Tripospermum and yeasts on the painted surfaces were all able to grow on mineral salts agar containing 10% sodium chloride. This is the first time that the genus Tripospermum has been reported on painted buildings. The fungal population on biocide-containing surfaces was significantly lower than on non-biocide-containing paint after 13 weeks and continued so to 42 weeks after painting, but there was no statistically significant difference in the level of fungal biodiversity.

Pore size distribution of hydrated cement pastes modified with polymers

Mercury intrusion porosimetry (MIP) tests were performed on pure and polymer-modified cement pastes in order to evaluate the influence of hydroxyethyl cellulose (HEC polymer) and vinyl acetate/ethylene copolymer (EVA) on the pore size distribution. Cement pastes containing 0%, 10%, and 20% of EVA and 0%, 0.5%, and 1.0% of HEC of the weight of cement were prepared and the water/cement ratio was kept constant (0.4). The effects of two curing methods (dry cure: 27 days at 23°C and 75% relative humidity (RH); mixed cure: 7 days at 23°C under sealed conditions and 20 days at 23°C and 75% RH) were also evaluated. Analysis of variances (ANOVA) showed that the most important factors affecting pore size distribution are the curing method and EVA content.

Chemical–mineralogical characterization of C&D waste recycled aggregates from São Paulo, Brazil

This study presents a methodology for the characterization of construction and demolition (C&D) waste recycled aggregates based on a combination of analytical techniques (X-ray fluorescence (XRF), soluble ions, semi-quantitative X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTG) and hydrochloric acid (HCl) selective dissolution). These combined analytical techniques allow for the estimation of the amount of cement paste, its most important hydrated and carbonated phases, as well as the amount of clay and micas. Details of the methodology are presented here and the results of three representative C&D samples taken from the São Paulo region in Brazil are discussed. Chemical compositions of mixed C&D aggregate samples have mostly been influenced by particle size rather than the visual classification of C&D into red or grey and geographical origin. The amount of measured soluble salts in C&D aggregates (0.15-25.4mm) is lower than the usual limits for mortar and concrete production. The content of porous cement paste in the C&D aggregates is around 19.3% (w/w). However, this content is significantly lower than the 43% detected for the C&D powders (<0.15 mm). The clay content of the powders was also high, potentially resulting from soil intermixed with the C&D waste, as well as poorly burnt red ceramic. Since only about 50% of the measured CaO is combined with CO(2), the powders have potential use as raw materials for the cement industry.

Research & development methodology for recycling residues as building materials--a proposal.

This article presents a proposal of methodology for conducting such research and development. The data/statistics waste collection statistics phase must cover geographical distribution, seasonal variations on production rates, waste management practices, current applications and their related costs and revenues. Waste characterisation must be comprehensive with physical, environmental and chemical aspects, including waste variability and waste contamination from shipping, handling and storage activities. Based on the previous results a broad forecast of potential applications must be developed based on very simple rules like minimisation of transportation distances and energy consumption, etc. Marketing evaluation is a very important step, frequently neglected when choosing the best applications for a particular waste. Other steps are product development and performance evaluation. Environmental evaluation of the new technology is very important because not all recycling is environmentally sound. This evaluation must be based on the life cycle assessment (LCA) and has to consider the environmental benefit of avoiding landfill disposal of the waste, and could include leaching or other specific tests or simulations. Also, the technological transference phase must be carefully planned and developed. Each proposed step is discussed, examples are given and needs for further research emphasised.

Eco-efficient concrete

Part 1 Eco-efficiency of Portland cement concrete: Environmental impact of Portland cement production Low binder intensity eco-efficient concretes Life cycle assessment (LCA) aspects of concrete. Part 2 Concrete with supplementary cementitious materials (SCMs): Natural pozzolans in eco-efficient concrete Artificial pozzolans in eco-efficient concrete Tests to evaluate pozzolanic activity in eco-efficient concrete Properties of concrete with high volume pozzolans Influence of supplementary cementitious materials (SCMs) on concrete durability Performance of self- compacting concrete (SCC) with high volume SCMs High volume ground granulated blast furnace slag (GGBFS) concrete Recycled glass concrete. Part 3 Concrete with non-reactive wastes: Municipal solid waste incinerator (MSWI) concrete Concrete with polymeric wastes Concrete with construction and demolition wastes (CDW) An eco-efficient approach to concrete carbonation Concrete with polymers. Part 4 Future alternative binders and use of nano and biotech: Alkali-activated based concrete Sulfoaluminate cement Reactive magnesia cement Nanotechnology for eco-efficient concrete Biotechconcrete: An innovative approach for concrete with enhanced durability.

Climate as the most important factor determining anti-fungal biocide performance in paint films

The effect of Pigment Volume Content (PVC) on fungal growth on acrylic paint formulations with and without biocide, exposed to weathering in three different climatic regions in Brazil for four years, was studied. Latex paints, with PVC of 30%, 35% and 50%, were applied to autoclaved aerated concrete blocks pre-covered with acrylic sealer and acrylic plaster. They were exposed to equatorial, tropical and temperate climates in north, south-east, and south Brazil. Cladosporium was the most abundant fungal genus detected in the biofilm on the surfaces of all paint formulations at all sites after four years. Heaviest fungal colonization occurred in the tropical south-east and lightest in the temperate south of the country, but more phototrophs, principally cyanobacteria, were detected in the equatorial region. PVC and presence of biocides were shown to be of less importance than environmental conditions (irradiance, humidity and temperature) for biofilm formation and consequent discolouration. These results have important implications for testing of paint formulations.

Durability evaluation of vegetable fibre reinforced materials

The tests carried out in Brazil indicate that a composite material including vegetable fibres of the coir type are suitable for outdoor use in environments similar to that found in Sao Paulo.

Hybrid Reinforcement of Sisal and Polypropylene Fibers in Cement-Based Composites

Several studies using vegetable fibers as the exclusive reinforcement in fiber-cement composites have shown acceptable mechanical performance at the first ages. However, after the exposure to accelerated aging tests, these composites have shown significant reduction in the toughness or increase in embrittlement. This was mainly attributed to the improved fiber-matrix adhesion and fiber mineralization after aging process. The objective of the present research was to evaluate composites produced by the slurry dewatering technique followed by pressing and air curing, reinforced with combinations of polypropylene fibers and sisal kraft pulp at different pulp freeness. The physical properties, mechanical performance, and microstructural characteristics of the composites were evaluated before and after accelerated and natural aging. Results showed the great contribution of pulp refinement on the improvement of the mechanical strength in the composites. Higher intensities of refinement resulted in higher modulus of rupture for the composites with hybrid reinforcement after accelerated and natural aging. The more compact microstructure was due to the improved packing of the mineral particles with refined sisal pulp. The toughness of the composites after aging was maintained in relation to the composites at 28 days of cure.

Thermo-Mechanical Treatment to Improve Properties of Sisal Fibres for Composites

The cross section variation, mechanical properties and moisture absorption of vegetable sisal fibres compressed at temperatures of 120, 160 and 200 °C were determined and compared with values obtained in non-compressed fibres. The thermo-mechanical treatment carried out resulted in a relevant increasing of fibre stiffness (elastic modulus) and decreasing of fibre moisture absorption.

Rationalizing the impact of aging on fiber–matrix interface and stability of cement-based composites submitted to carbonation at early ages

The objective of this work is to show the effect of carbonation at early stages on fiber–cement composites and impact on hydration, chemical and dimension stability. Carbonation increased the content of CaCO3 polymorphs and consumed Ca(OH)2 and other hydrated calcium phases. Micrographs and energy-dispersive spectrometry showed the CaCO3 formed is precipitated in the pore structure of the matrix, decreasing diffusion of Si, S, and Al during hydration. Therefore, a refining process of pore sizes is produced, and fiber–matrix interface in carbonated composites was improved, leading to volume stabilization of the composite, as indicated by lower drying shrinkage and lower porosity.