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Abstract: Some investigations about conservation actions in historical buildings points out that lime–cement mortars should be avoided and lime–pozzolan mortars should be use instead. Nevertheless this type of mortar is still under investigation and the absolute rejection of the use of Portland cement even with just a minimum amount appears to be a dogmatic position that is not fully grounded in scientific terms. Besides the use of lime–pozzolan mortars requires skilled craftsmanship and at least in the case of the majority of Portuguese construction enterprises operating in the field of building conservation these conditions are not assured. These facts can influence the decision about the mortars choice for conservation purposes, since in certain circumstances it may be preferable to apply lime–cement mortars instead of an incorrect application of lime–pozzolan mortars. [Copyright &y& Elsevier]

Abstract: This study has investigated the joint effect of several factors on the workability and mechanical strength of alkali-activated metakaolin based mortars. The factors analysed through a laboratory experiment of 432 specimens, pertaining to 48 different mortar mixes were, sodium hydroxide concentration (10M, 12M, 14M, 16M), the superplasticizer content (1%, 2%, 3%) and the percentage substitution of metakaolin by calcium hydroxide in the mixture (5%, 10%). The results show that the workability decreases with the concentration of sodium hydroxide and increases with the amount of calcium hydroxide and superplasticizer. The results also show that the use of 3% of superplasticizer, combined with a calcium hydroxide content of 10%, allows improving the mortar flow from less than 50% to over 90%, while maintaining a high compressive and flexural strength. [Copyright &y& Elsevier]

Energy efficiency is not only the most cost-effective way to reduce carbon dioxide emissions but also a way to improve competitiveness and create employment. EU aims to achieve nearly zero-energy (public) building (NZEB) by the end of 2018 (2020 for private buildings). This very ambitious target would be more easily fulfilled if high-performance thermal materials like phase change materials-PCMs are to be used. This paper reports experimental results on the properties of fly ash-based alkali-activated binder-AACB mortars in which a minor percentage of aggregates were replaced by PCMs. These include compression strength, at normal temperature and also at high temperatures, flexural strength, density, water absorption, unrestrained shrinkage as well as cost analysis. Several AACB mixtures showed an increase in compressive strength after being exposed to high temperatures. Since PCMs are made of flammable materials and AACB mortars show a much higher stability at high temperature than Portland cement-based mortars this means that AACB mortars are more suitable for PCM incorporation. This is a very important feature because flammable insulation materials were reported to be the cause of the recent Grenfell Tower fire tragedy that made 71 victims. [ABSTRACT FROM AUTHOR]

Carbon dioxide sequestration is crucial for targets for limiting global warming could be achieved. This paper discloses results of an investigation concerning the performance of fly ash/waste glass alkaline-based mortars with recycled aggregates reinforced by hemp fibres exposed to accelerated carbon dioxide curing. Compressive strength, freeze-thaw resistance, carbon footprint and cost were studied. The results show that hemp fibres lead to a reduction of mechanical properties of alkali-activated materials. A high correlation was found between compressive and flexural strength. The results also show that accelerated curing provides a high carbon sequestration. Furthermore, the use of at least 8% hemp fibres leads to carbon negative emissions −19.7 kgCO 2 eq/m 3 for fly ash/waste glass alkaline-based mortars with recycled aggregates based composites. [ABSTRACT FROM AUTHOR]

Increasing building energy efficiency is one the most cost-effective ways to reduce emissions. The use of thermal insulation materials mitigates heat loss in buildings, therefore minimising heat energy needs. In recent years, several papers were published on the subject of foam alkali-activated cements with enhanced thermal conductivity. However, on those papers cost analysis was strangely avoided. This paper presents experimental results on one-part alkali-activated cements. It also includes global warming potential assessment and cost analysis. Foam one-part alkali-activated cements cost simulations considering two carbon dioxide social costs scenarios are also included. The results show that one-part alkali-activated cements 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. This mixture presents a low global warming potential of 443 KgCO2eq/m3. The results confirm that in both carbon dioxide social cost scenarios the mixture 26 OPC + 58.3 FA + 8 CS + 7.7 CH with 3.5% hydrogen peroxide foaming agent is still the most cost efficient. [ABSTRACT FROM AUTHOR]

This article presents results of an experimental investigation on the resistance to chemical attack (with sulphuric, hydrochloric and nitric acid) of several materials: OPC concrete, high-performance concrete, epoxy resin, acrylic painting and a fly ash-based geopolymeric mortar). Three types of acids with three high concentrations (10, 20 and 30%) were used to simulate long-term degradation. A cost analysis was also performed. The results show that the epoxy resin has the best resistance to chemical attack independently of the acid type and the acid concentration. However, the cost analysis shows that the epoxy resin-based solution is the least cost-efficient solution being 70% above the cost efficiency of the fly ash-based geopolymeric mortar. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents results about the use of metakaolin based geopolymers mortars for retrofitting purposes. Two main situations are addressed, the use of geopolymeric mortars as a repairing layer or as a binding agent to insure the adhesion between CFRP sheets and the concrete substrate. Several compositions of metakaolin geopolymer mortars were executed by varying the percentage of sand/binder mass ratio and the concentration of sodium hydroxide. It was found that metakaolin geopolymer mortars show a high mechanical resistance and a relevant adhesion to the concrete substrate. Although their adhesion strength is lower than the one present by commercial pre-pack repair mortars, they are very cost-effective (5–10 times less expensive). On the other hand, the adhesion strength between CFRP and geopolymer mortars proved to be lower than expected which could be due to the fact that the composition of the geopolymeric mortars was not optimized and also to the fact that the CFRP used was not prone to this kind of application. [Copyright &y& Elsevier]