J. L. Barroso de Aguiar

Cost-efficient one-part alkali-activated mortars with low global warming potential for floor heating systems applications

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.

Thermal mortars with incorporation of PCM microcapsules

The main purpose of this work is the production of a mortar with incorporation of Phase Change Materials (PCM) microcapsules, which must have a compromise between workability, mechanical strength and aesthetic appearance. The mortars studied in this work are mixed mortars of lime and gypsum. The proportion of PCM is 0 %, 10 %, 20 % and 30 %. In order to minimize some problems associated with shrinkage and consequent cracking of the mortars, the incorporation of nylon fibers, superplasticizer and gypsum was tested. A study of mechanical characteristics and some sensitivity tests for qualify the shrinkage of the fifteen compositions was realized. In this way, one composition for the application in tests cells was selected, with the aim of studying the thermal behaviour of these mortars. The test performed on test cells includes the study of a standard mortar without addition of PCM and a mortar with incorporation of an ideal percentage of PCM. Based on the obtained results it was possible to conclude that the incorporation of PCM microcapsules in the studied mortars causes an increase in mechanical strengths and shrinkage. The tests performed on test cells allowed to verify a time lag in maximum and minimum temperatures, as well as a slight attenuation in the temperature variation. It can be concluded that the use of PCM microcapsules in mixed mortars of lime and gypsum can be assumed as a viable solution for applications in the construction industry once these present a compromise between their resistance, aesthetic appearance and thermal behaviour.

A study of the adhesion between hydraulic mortars and concrete

Knowledge of the adhesion properties of materials is necessary for many applications. When one has to cover a wall or a concrete pavement with mortar, it is necessary to pay attention to the adhesion between the two materials, otherwise one can have some problems such as the delamination of the two materials after application. We present here a study of the adhesion between hydraulic mortars and concrete. Mortars with permeability-reducing admixtures were used. This type of mortar is used to reduce the possibility of water infiltration in construction. Mortars should be impermeable but this should not affect the adhesion. To measure the adhesion, we used the pull-off test. The results show a decrease in the adhesion strength with increasing permeability-reducing admixture dosage, except for one of the admixtures used. We believe that this result is a consequence of the decrease in porosity caused by the use of a more waterproofing admixture and that a higher dosage contributes to the increase of admixture...

Cost efficiency and resistance to chemical attack of a fly ash geopolymeric mortar versus epoxy resin and acrylic paint coatings

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.

Performance of alkali-activated mortars for the repair and strengthening of OPC concrete

Abstract Infrastructure rehabilitation represents a multitrillion dollar opportunity for the construction industry. In the United States alone, the rehabilitation needs are estimated to exceed 1.6 trillion dollars over the next five years. Since the majority of the existing infrastructure is concrete based, this means that concrete infrastructure rehabilitation is a hot issue. Besides, the sooner concrete deterioration is tackled, the lower are the rehabilitation costs. The majority of current commercial repair materials are not cost efficient and some even present both technical and worrying environmental limitations. This chapter provides a literature overview on concrete repair materials, highlighting current problems faced by them. The potential of alkali-activated mortars to overcome those limitations is analysed.

Comportamento térmico de argamassas com incorporação de Materiais de Mudança de Fase (PCM) no clima português

Os autores desejam expressar os seus agradecimentos a Fundacao para a Ciencia e Tecnologia (FCT) pelo nfinanciamento deste trabalho no âmbito da bolsa de doutoramento SFRH/BD/95611/2013.

Geopolymeric repair mortars based on a low reactive clay

Abstract This chapter discloses results of an investigation concerning the development of geopolymeric repair mortars based on a low reactive Tunisian clay. Geopolymeric mortars were studied for workability, compressive strength, adhesion, unrestrained shrinkage, and modulus of elasticity. Several concrete beams, rehabilitated with a metallic grid and geopolymeric mortars were also tested for flexural strength. The hydration products were studied using X-ray diffractograms (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR).