Mortar compressive strength is a standard requirement and should be tested on stand-ardized specimens with a 40 mm square cross section. However, these specimens with only one type of mortar (base-coat layer) do not represent the render traditionally ap-plied to façades since that must consist of at least two layers (base coat and top coat, with different formulations and thicknesses).The in-service compressive strength of the render is therefore currently evaluated on-site by means of indirect methods (e.g. pendulum rebound hammer or ultrasound). Addi-tionally, studies on evaluating the compressive strength in multilayer coating systems, based on the laboratory analysis of the mortar samples collected in situ, are few and far between. This paper intends to discuss the method of assessing in-service compressive strength of applied multi-coat renders systems, by testing cores collected after pull-off tests. Therefore, 422 compressive strength tests were carried out to establish a relation-ship between the compressive strength of single- and multi-coat renders and identify which render layers influence the system’s compressive strength. The experimental cam-paign results have shown the great influence of the top coat on multi-coat renders’ per-formance and the feasibility of studying the in-service compressive strength after a pull-off test; and also allowed identifying relevant parameters to evaluate the strength of samples collected in-situ.

Resumen: Esta investigación presenta el análisis de 801 daños relativos a las cubiertas de edificios, los cuales han sido clasificados cualitativa y cuantitativamente. Se han correlacionado los mismos según el tipo de cubierta donde se daban, así como determinado cuáles eran las situaciones más recurrentes. Se informan e indican de los valores porcentuales de las causas que han provocado dichos daños, incluyendo una discusión técnica para cada una de ellas. Con todos estos resultados se ofrece a los promotores, proyectistas y responsables de obras cuáles son los puntos críticos de las cubiertas como forma de minimizar los defectos en sus obras. El análisis de estos fallos nos proporcionará una serie de lecciones aprendidas para mejorar la calidad de la construcción en general.

AbstractThis paper presents the results of a study on the behaviour of self-compacting concrete (SCC) in the fresh and hardened states, produced with binary and ternary mixes of fly ash (FA) and limestone filler (LF), using the method proposed by Nepomuceno. His method determines the SCC composition parameters in the mortar phase (self-compacting mortar - SCM) easily and efficiently, whilst guaranteeing the SCC properties in both the fresh and hardened states.For this, 11 SCMs were studied: one with cement (C) only; three with FA at 30%, 60% and 70% C substitution; three with LF at 30%, 60% and 70% C substitution; four with FA + LF in combinations of 10-20%, 20-10%, 20-40% and 40-20% C substitution. Once the composition of these mortars was defined, 18 SCC mixes were produced: 14 binary SCC mixes were produced with the seven binary mortar mixes, and four ternary SCC mixes were produced with the four ternary mortar mixes. In addition to the methodology proposed by Nepomuceno, the combined use of FA and LF in ternary mixtures was tested. The results confirmed that the method could yield SCC with adequate properties in both the fresh and hardened states. It was also possible to determine the SCC composition parameters in the mortar phase (self-compacting mortar - SCM) that will guarantee the SCC properties in both the fresh and hardened states, as confirmed through the optimized behaviour of the SCC in the fresh state and the promising results in the hardened state (compressive strength). The potential demonstrated by the joint use of LF and FA through the synergetic interaction of both additions is emphasized.

This paper provides a literature review and analysis of the various influencing aspects related to the use of recycled aggregates, sourced from construction and demolition waste, on the chloride ion penetration of concrete. A statistical analysis on the effect of incorporating increasing amounts of recycled aggregates of different type, size, and class on the chloride ion migration and total charge passed of concrete is also presented. The paper also presents the relationship between these properties and the corresponding compressive strength. The results show strong correlations between these parameters, which are independent of other aspects related to recycled aggregate use and made it possible obtaining a relationship between the values acquired via NT Build 492 and ASTM C1202.

The waste resulting from marble extraction process is usually disposed of in landfills or dumps and its accumulation is causing serious environmental and landscaping problems. One way of reusing marble waste is to consider its incorporation in structural concrete as a non-primary aggregate. This research work attempts to alleviate the situation and provide information on the mechanical performance of concrete as a function of the replacement ratio of primary aggregates (PA) with coarse waste marble aggregates (CMA). Three concrete families, including reference concrete (RC) mixes, were studied that were made with primary aggregates of basalt (BCA), limestone (LCA) and granite (GCA) (these are the main sources of primary aggregates in the southern and central parts of Portugal), and concrete mixes with replacement ratios of 20%, 50% and 100% of PA by CMA. To evaluate their quality and mechanical performance mixes were tested for: slump (in the Abrams cone test), specific density, compressive strength, splitting tensile strength, Young's modulus of elasticity and resistance to abrasion. The results suggest a tendency for the values of all mechanical properties to decline. However, this tendency is clearly weaker than those observed for the majority of the research involving other types of non-primary recycled aggregates, which are already used in certain proportions in structural concrete, according to the limits imposed by the standards and specifications. The mechanical properties of concrete made with CMA were assessed within the scope of concurrent work also undertaken at Instituto Superior Técnico (Lisbon, Portugal), concerning the durability-related materials of the same type of concrete.

This research assessed the performance of mortars in which recycled concrete aggregates (RCA) was a component. It replaced natural sand but kept the same particle size distribution. Three mortars were produced with replacement ratios of 20%, 50% and 100% as well as a reference mortar containing no recycled aggregate. The compressive and flexural strength, water absorption by capillarity, drying capacity and susceptibility to cracking of these mortars were analyzed first. Then, based on these results, the most satisfactory replacement ratio was chosen and the following properties were analyzed: water retentivity, shrinkage, adhesive strength, modulus of elasticity, and water vapor permeability. Somewhat surprisingly the best results in the first stage occurred for 20% and 100% replacement ratios, leading to a cautious choice of the 20% ratio for the second stage. Generally the mortar with 20% replacement ratio performed better than the reference mortar, except for adhesive strength and dimensional stability.

The construction industry keeps on demanding huge quantities of natural resources, mainly minerals for mortars and concrete production. The depletion of many quarries and environmental concerns about reducing the dumping of construction and demolition waste in quarries have led to an increase in the procuring and use of recycled aggregates from this type of waste. If they are to be incorporated in concrete and mortars it is essential to know their properties to guarantee the adequate performance of the end products, in both mechanical and durability-related terms. Existing regulated tests were developed for natural aggregates, however, and several problems arise when they are applied to recycled aggregates, especially fine recycled aggregates (FRA). This paper describes the main problems encountered with these tests and proposes an alternative method to determine the density and water absorption of FRA that removes them. The use of sodium hexametaphosphate solutions in the water absorption test has proven to improve its efficiency, minimizing cohesion between particles and helping to release entrained air.

This paper reports the strength behaviour of concrete containing three types of recycled polyethylene terephthalate (PET) aggregate. Results are also analysed to determine the PET-aggregate's effect on the relationship between the flexural and splitting tensile strengths and compressive strength and to know whether the relationships between compressive strength and other strength characteristics given in European design codes are applicable to concrete made with PET-aggregates. The compressive strength development of concrete containing all types of PET-aggregate behaves like in conventional concrete, though the incorporation of any type of PET-aggregate significantly lowers the compressive strength of the resulting concrete. The PET-aggregate incorporation improves the toughness behaviour of the resulting concrete. This behaviour is dependent on PET-aggregate's shape and is maximised for concrete containing coarse, flaky PET-aggregate. The splitting tensile and flexural strength characteristics are proportional to the loss in compressive strength of concrete containing plastic aggregates.

A indústria da construção representa um dos maiores e mais activos sectores da União Europeia (UE), consumindo mais matérias-primas e energia do que qualquer outra actividade económica. Da mesma forma, os resíduos das suas actividades corespondem a uma elevada parcela dos resíduos produzidos em toda a UE. A actual legislação na UE visa criar condições para a implementação de medidas de prevenção e reciclagem de RCD. No entanto, carece de instrumentos que acelerem o desenvolvimento de um sector tão tradicional como o da construção. O presente trabalho tem por objectivo determinar indicadores que possibilitem estimar a quantidade de RCD gerados, ao nível da obra, tanto globalmente como por fluxo de resíduos. A geração de RCD foi estimada para seis sectores específicos: nova construção residencial, nova construção não residencial, demolição residencial, demolição não residencial, reabilitação residencial e reabilitação não residencial. Neste artigo, apresentam-se os resultados para a nova construção residencial. Os dados necessários ao desenvolvimento dos indicadores foram obtidos através de um levantamento exaustivo dos dados de estudos anteriores.

The construction industry is one of the largest and most active sectors of the European Union (EU), consuming more raw materials and energy than any other economic activity. Likewise waste from its activities corresponds to a large share of those produced in the EU. The present EU legislation aims at creating conditions to implement construction and demolition waste (CDW) prevention and recycling measures. However, there is a lack of tools to accelerate the development of a sector as traditional as construction. The main objective of this research work is to propose indicators for estimating the amount of CDW generated on site, both globally and by waste stream. CDW generation was estimated for six specific sectors: new residential construction, new non-residential construction, residential demolition, non-residential demolition, residential rehabilitation, and non-residential rehabilitation. This paper presents the results for new residential construction. The data used to develop the indicators was obtained through an extensive analysis of data from previous international studies.