Development of foam one-part geopolymers with enhanced thermal insulation performance and low carbon dioxide emissions

Buildings are responsible for more than 40% of the energy consumption and greenhouse gas emissions. Thus, increasing building energy efficiency is one the most cost-effective ways to reduce emissions. The use of thermal insulation materials could constitute the most effective way of reducing heat losses in buildings by minimising heat energy needs. These materials have a thermal conductivity factor, k (W/m.K) lower than 0.065 while other insulation materials such as aerated concrete can go up to 0.11. Current insulation materials are associated with negative impacts in terms of toxicity. Polystyrene, for example contains anti-oxidant additives and ignition retardants. In addition, its production involves the generation of benzene and chlorofluorocarbons. Polyurethane is obtained from isocyanates, which are widely known for their tragic association with the Bhopal disaster. Besides current insulation materials releases toxic fumes when subjected to fire. This paper presents experimental results on one-part geopolymers. It also includes global warming potential assessment and cost analysis. The results show that only the use of aluminium powder allows the production mixtures with a high compressive strength however its high cost means they are commercially useless when facing the competition of commercial cellular concrete. The results also show that one-part geopolymer mixtures based on 26%OPC +58.3%FA +8%CS +7.7%CH and 3.5% hydrogen peroxide constitute a promising cost efficient (67 euro/m3), thermal insulation solution for floor heating systems with low global warming potential of 443 KgCO2eq/m3

Eco-concrete: one-part geopolymer mixes

The geopolymerization of alumino-silicate materials is a complex chemical process evolving dissolution of raw materiais, transportation or orientation and polycondensation of the reaction products. Publications on the field of geopolymeric binders, state that this new material is likely to have high potential to become an altemative to Portland cement composites, Classical two part geopolymers could be made more eco-efficient with a lower carbon dioxide footprint if the use of sodium silicate is avoided. Besides current geopolymeric mixes can suffer from efflorescence originated by the fact that alkaline and/or soluble silicates that are added during processing cannot be totally consumed during geopolymerisation. Therefore new geopolymer mixes are needed. This paper presents experimental results on a novel kind of mixes termed one-part geopolymers. Compressive strength results and efflorescences observations show that the new mixes already analyzed are promissing

Foam geopolymers: state of the art and preliminary experimental results

Buildings are responsible for more than 40% of the energy consumption and greenhouse gas emissions. Thus increasing building energy efficiency is the most cost effective way to reduce emissions. The use of thermal insulation materials constitutes the most effective way of reducing heat losses in buildings thus reducing heat energy needs. These materials have a thermal conductivity factor, k (W/m.K) lower than 0.065 while other insulation materials like for instance aerated concrete can go up to 0.11. Current insulation materials are associated with negative impacts in terms of toxicity. Polystyrene, for example contains anti-oxidant additives and ignition retardants, additionally, its production involves the generation of benzene and chlorofluorocarbons. Polyurethane is obtained from isocyanates, which are widely known for their tragic association with the Bhopal disaster. Besides current insulation materials releases toxic fumes when subjected to fire. This paper reviews literature on foam geopolymers that could constitute a lower toxicity alternative to current commercial insulator. Current methods use foaming agents (blowing agents) such as hydrogen peroxide (H2O2), sodium perborate (NaBO3), silica fume, powder alumina. Results of an experimental research on foam hybrid alkaline cements are reported

Argamassas fotocatalíticas: influência da composição na resistência mecânica e na capacidade de auto-limpeza

O presente artigo apresentam-se resultados relativos ao estudo conjunto de diversos parâmetros na resistência mecânica e na capacidade de auto-limpeza de argamassas fotocatalíticas. Os resultados obtidos mostram que a fim de manter a mesma consistência em todas as argamassas se torna necessário aumentar a razão w/b com a percentagem de TiO2 o que se traduz numa redução acentuada da resistência mecânica das argamassas. Os resultados mostram ainda que que as composições com 2% de TiO2 são as que apresentam uma maior capacidade de auto-limpeza

Genetics and expected selection gain for growth traits in Eugenia dysenterica DC populations.

The objective of this study was to estimate genetic parameters of quantitative traits in a living germplasm collection of Eugenia dysenterica. The genetic material consisted of 110 progenies derived from 10 natural Eugenia dysenterica subpopulations sampled in the southeastern region of the state of Goiás. The experiment was established in a complete randomized block design, with 110 treatments, four replications and one tree per plot. The study variables were total height, stem diameter and respective growth rates. After the analysis of variance some genetic parameters were estimated. The levels of genetic variation in the collection were high and the highest proportion was found within subpopulations. Highest coefficients of heritability and genetic variation were observed in subpopulations from the counties Catalão, Três Ranchos, Cristalina and Senador Canedo. Considering the promising expected progress for growth traits, this collection can be converted into an unrogued seedling seed orchard, aiming the production of improved seed

Previsão da resistência de geopolímeros monofásicos

The discovery of one-part geopolymers is considered a key event on the evolution of geopolymer technology because emulates one of the most important properties of Portland cement, the just add water concept. This materials are not associated with the known problems of two part geopolymers, namely the use of caustic solutions that have poor workability and make the handling and application of geopolymers difficult and the fact that alkaline or soluble silicates are not consumed during geopolymerization leading to severe efflorescence phenomena. However, so far very few investigations were published on this field and some report low mechanical strength. This paper discloses results regarding the numerical modelling of one part-geopolymers compressive strength.A descoberta dos geopolímeros monofásicos é considerado um importante acontecimento no âmbito da tecnologia dos geopolímeros porque mimetizam uma das mais importantes propriedades do cimento Portland, o conceito relativo à simples adição de água. Estes materiais não estão associados aos conhecidos problemas dos geopolímeros correntes nomeadamente a utilização de soluções cáusticas, baixa trabalhabilidade que dificultam a sua colocação e o facto das espécies alcalinas e silicatos solúveis não reagirem na sua totalidade durante a reacção de geopolímerização originando o aparecimento de elevada quantidade de eflorescências. Contudo muito poucas investigações foram publicadas neste domínio e algumas apresentam baixa resistência mecânica. Este artigo apresenta resultados relativos à modelação numérica da resistência à compressão de geopolímeros monofásicos.info:eu-repo/semantics/publishedVersio

Concrete retrofitting using CFRP and geopolymer mortars

A new development in the repair and strengthening of reinforced concrete systems is the use of carbon fiber reinforced polymers (CFRP) strips bonded to concrete substrate with epoxy resins. It has been reported that epoxy adhesive are extremely sensitive to high temperatures. Some authors conclude that the epoxy temperature should not exceed 70 ºC in order to safeguard the adhesiveness of the epoxy and, thus, the integrity and adequate functioning of CFRP. It is noted that even frequently exposure to direct sunlight causes temperatures higher than 70 ºC. Since geopolymers are known to possess high stability at high temperature, these materials can be an alternative to epoxy resins. This papers presents results about the use of metakaolin based geopolymers mortars to insure the adhesion between the CFRP and the concrete substrate. Several compositions of geopolymer mortars were executed by varying the percentage of binder, sand/binder ratio and the concentration of sodium hydroxide. It was found that geopolymer mortars demonstrate very promising performances, having obtained a high mechanical resistance and a good adhesion to concrete. On the other hand the adhesion between CFRP and geopolymer mortars proved to be smaller than expected which could be due, to the fact that the composition of the mortar was not optimized or even to the nature of the CFRP