Search

Ternary blended cements, made with silica fume and limestone, provide significant benefits such as improved compressive strength, chloride penetration resistance, sulfates attack, etc. Furthermore, they could be considered low-carbon cements, and they contribute to reducing the depletion of natural resources in reference to water usage, fossil fuel consumption, and mining. Limestone (10%, 15%, and 20%) with different fineness and coarse silica fume (3%, 5%, and 7%) was used to produce ternary cements. The average size of coarse silica fume used was 238 μm. For the first time, the carbonation resistance of ternary Portland cements made with silica fume and limestone has been assessed. The carbonation resistance was assessed by natural carbonation testing. The presence of coarse silica fume and limestone in the blended cement led to pore refinement of the cement-based materials by the filling effect and the C-S-H gel formation. Accordingly, the carbonation resistance of these new ternary cements was less poor than expected for blended cements.

The alkali-silica reaction has been studied in depth due to the evolution in the knowledge of the expansive phenomenon. One of its most important aspects is the reaction rate of the aggregates. In Spain, at the early 90s of the 20th century, aggregates were considered almost non-reactive. However, the use of accelerated curing and other environmental factors revealed that there were potentially reactive siliceous aggregates. Nevertheless, there are several siliceous and limestone aggregates with siliceous inclusions that show reactivity over long period. In the present work, open porosity, expansion and petrography with quartz reactivity index have been determined, in 68 siliceous, limestone and dolomitic aggregates, from quarries located in areas with diagnostic reactivity. Based on these parameters and their interrelation, a classification method is proposed to detect slow-reacting aggregates.

Through this research it is intended to catalogue different environmental scenarios taking into account extreme climatic actions and what is their mechanical, chemical and physical impact on the main materials used in construction (reinforced concrete, bricks, lime repair mortars, etc.). For this, a qualification of these material deterioration processes will be carried out after having done the data collection, the analysis of the different scenarios and a structural study. To move towards sustainability, where building is better described as a process than a product, a new integrated-design approach that accounts for durability is deemed to be essential. This approach will allow building assessment in a multi-performance perspective. The Sustainable Structural Design (SSD) methodology is presented based on environmental and structural performance parameters in a life-cycle approach. The concept of reuse is a sustainable perspective for extremely durable structures (ESD), new structures and existing structures. In this work we will focused in different building materials characteristics and their potential degradation under extreme events conditions. This work is framed in a research project of the National Plan of Spain, whose purpose is the development of a decision support system based on intelligent management tools for the maintenance of existing buildings and the design of new buildings, in order to extend its working life to cope with climate change and extreme events.

The deterioration of built heritage is a major concern for many countries. In the specific case of brick heritage buildings, degradation depends on several factors such as the chemical and mineralogical composition and the porosity of the bricks, floor insulation and exposure to environmental conditions. This paper applies a probabilistic Bayesian approach to identifying the pattern of recession of the brick walls using digital photogrammetry data. Two cases studies are presented corresponding to two buildings classified as Assets of Cultural Interest by the Spanish Ministry of Culture. The analysis of physico-chemical factors and photogrammetric descriptions allow a holistic understanding of the deterioration process to be developed. The degradation patterns and degradation velocities obtained are used for the structural assessment of the buildings. The comparison of the degradation patterns of both buildings considering their individual features allows the most critical factors in the degradation process of brick walls to be identified.

Portland cement production is an energy-intensive process that releases carbon dioxide into the atmosphere. To reach carbon neutrality by 2050, it would be necessary to implement innovative measures in the cement industry to deliver carbon neutrality. In this respect, it is striking that the new cement types made with high contents of industrial by-products will act as a lever to combat climate change. Accordingly, the purpose of this study is to assess coal–ash blended cements in light of climate change mitigation. In particular, ground coal bottom ash could be considered as a novel constituent for common cement production. The performance of these coal–ash mortars was assessed by measuring pozzolanic reactivity, mechanical strength gain, and microstructural characteristics. Mortars were made with 10%, 25%, or 35% of coal ash (fly ash and/or bottom ash). Therefore, by considering an emission intensity factor of 830 kgCO2/kg of clinker, a reduction in carbon dioxide emissions for all coal fly ash cements is expected, which will be about 83 kgCO2/kg of cement, 208 kgCO2/kg of cement, and 290 kgCO2/kg of cement, respectively. Ground coal bottom ash presented similar characteristics to the coal fly ash. Consequently, ground coal bottom ash is a promising Portland cement constituent with properties comparable to coal fly ash, and its increased usage can contribute to the climate change mitigation.

Within the PARTNER project (2002–2006) concrete cubes were exposed for 13 years at different exposure sites in Europe. Subsequently, cores were extracted from these cubes for further investigation within the framework of RILEM TC 258-AAA. The aim of the microstructural study is to relate the microstructural features to cube expansion and to investigate a possible relation between aggregate type and chemical composition of ASR product. Both the Damage Rating Index (DRI) determined on polished sections and the Qualitative Damage Assessment (QDA) performed on thin sections show a relation to cube expansion. However, damage characteristics depend on the texture and composition of the aggregates, affecting the results of both used methods. The composition of ASR products formed in aggregate particles varies in a very small range showing no systematic influence of aggregate type or exposure site.

The influence of the effects of the degradation of materials on the seismic fragility of Cultural Heritage buildings in Granada (Spain) is investigated. The degradation of the material, which mainly happens at the lower levels of the façades, is obtained by using 3D photogrammetry data. Fragility curves for three cultural heritage constructions in Granada are calculated by using FE nonlinear dynamic analyses for both non-deteriorated and deteriorated geometries. The Finite Elements (FE) models, based on the macro-modelling technique, are subjected to ground motions for the city of Granada, which were selected by considering Probabilistic Seismic Hazard Analysis (PSHA) methodology with their probability of occurrence. The response of each model is analyzed for different seismic Intensity Measure (IM) levels, which, in this study, correspond to average pseudo-acceleration. The procedure is applied to three monuments in Granada that were built with two different constructions materials: calcarenite and rammed earth. The damage mechanisms considered are roof displacement or maximum compressive principal stress, depending on each case. The results show that the restoration works that have been carried out has prevented structural failures in the rammed earth construction studied, and that, during future seismic events, special attention must be paid to the level of compressive strengh reached in the Santa Pudia calcarenite used at the San Jerónimo monastery.

Ternary Portland cements composed of coarse silica fume (SF), limestone (LS), and Portland cement (PC) can afford some environmental advantages by reducing the clinker content in Portland cements. These cements will help to reduce the clinker factor target from 0.78 to 0.60 by 2050 with the aim to be climate neutral. Silica fume (SF) possesses pozzolanic properties that enhance mechanical strength and durability. By contrast, limestone powder has three main outcomes, i.e., filler, dilution, and chemical effects. The first reduces porosity and refines the microstructure of mortars and concretes. The second decreases the amount of hydration products and increases the porosity; the third one promotes the appearance of carboaluminates and reduces porosity. This paper covers the mechanical properties of Portland cement-limestone-coarse silica fume ternary cements, and its synergetic mechanism. Compressive and flexural strength of mortar at 2, 7, 14 and 28 days was performed. Coarse silica fume has a minor contribution on the nucleation effect compared to ground limestone at early ages. The nucleation and filler effects, at early ages, are less pronounced in coarse and very fine limestone powder. The highest compressive strength at 28 days is reached with the lowest content of coarse silica fume (3%). Mortar mixes made with a high level of limestone presented a delay in the compressive strength development.

[EN] To create an international recommendation concerning the release of alkalis, test method AAR-8 was developed within the scope of RILEM TC 258-AAA activities. The first round robin test was performed using five aggregate types, and further investigation was conducted as RRT2, leading to the final version of the AAR-8 recommendation. Five aggregates with different mineralogies and origins were immersed in specific volumes of NaOH or KOH solutions with excess calcium hydroxide maintained 38 °C and 60 °C respectively. Samples of the immersion test solution were removed at intervals of 2, 6, 13, 26, and 52 weeks by pipetting and chemically analyzed for NaOH or KOH test solutions. The amount of alkali released was expressed in grams of Na2O, K2O, and Na2Oe per kilogram of the respective aggregate. The results obtained are presented. Based on the data, several changes to the original version of the test method are proposed., [ES] Con el fin de crear una recomendación internacional sobre la lixiviación de álcalis de los áridos, se desarrolló el método de ensayo AAR-8 en el ámbito de las actividades de RILEM TC 258-AAA. El primer Round Robin Test (RRT1) de AAR-8 se realizó utilizando cinco tipos áridos y se llevó a cabo una investigación adicional como RRT2 que condujo a la versión final de la recomendación AAR-8 publicado recientemente. Se sumergieron cinco áridos con diferente mineralogía y origen (fonolita, cataclasita, granodiorita, granito y una arena dragada de mar) en volúmenes específicos de soluciones de NaOH o KOH con exceso de hidróxido de calcio mantenido a 38 ° C y 60 ° C. A las 2, 6, 13, 26 y 52 semanas, se extrajeron muestras de la solución de prueba de inmersión mediante pipeteo y se analizaron químicamente para determinar el potasio (solución de prueba de NaOH) o sodio (solución de prueba de KOH). La cantidad de álcalis lixiviados se expresó en gramos de Na2O, K2O y Na2Oe por kilogramo de áridos. En este artículo, se presentan los resultados obtenidos de los álcalis lixibiables por los áridos probados se presentan en los cinco laboratorios participantes. A partir de los datos obtenidos, se proponen varios cambios en la versión original del método de prueba para mejorarlo.

An indication about the expansion of the concrete can be derived from the crack-index [1]. The crack-index is determined by measuring the crack width along pre-drawn lines, Fig. 2.1 and is expressed as crack-width per measured length. However, it has to be kept in mind that the formation of the cracks may not be attributable solely to AAR. Still, the crack index indicates a concrete expansion at the studied location in mm/m.

This paper studies the durability of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) with high Blast Furnace Slag content (BFS) and nanoadditives such as crystalline admixture (CA), alumina nanofibres (ANF) and cellulose nanocrystals (CNC), exposed to different aggressive environmental conditions: 1) three aggressive media: a) deionized water (dw), b)sulphate rich solution (ss) and c) simulated geothermal water (sgw) containing sulphate and chloride; 2) two water interactionconditions: a) static and b) dynamic (water impact); and 3) with and without the presence of cracks. Durability was analysed over24 months, measuring several physical and chemical parameters of the system, recording changes in both the aggressive mediaand the concrete. All UHPFRC types demonstrate good durability, showing high resistance to expansion and deformation in thesulphate-rich media. A leaching process occurs in all water interaction systems, the dynamic interaction in sgw being the mostaggressive. The interaction of sgw inside the crack favours the formation of solid phases such as calcium carbonates and ettringite, while the presence of nanoadditives affects the response of both the matrix and the formation of precipitates within the crack.

Coal fly ash (CFA), coal bottom ash (CBA) are residues produced in thermo-electrical power stations as result of the coal combustion in the same boiler. Therefore, some characteristics of the coal fly ash (CFA) are comparable with those of the coal bottom ash (CBA). Nevertheless, coal bottom ash size is larger than coal fly ash one. Consequently, it was found that it is necessary to grind the coal bottom ash (CBA) to reach a similar size to that one of the CFA. The objective of this paper is to evaluate the performance of Portland cement mortars made with coal fly ash (CFA), coal bottom ash (CBA) or mixes (CFA+CBA), against sulphate attack. The methodology is based on the expansion of slender bars submerged in a sodium sulphate solution (5%) according to the ASTM C-1012/C1012-13 standard. It has been found that mortars elaborated with CEM I 42.5 N (without ashes) presented the largest expansion (0.09%) after a testing period of 330 days. Mortars made with CEM II/A-V exhibited lower expansion (0.03%). Summing up, it can be established that mortar expansion decreases when the coal ash amount increases, independently of the type of coal ash employed. The novelty of this paper relies on the comparison between the performances of Portland cement mortars made with coal fly ash (CFA) or coal bottom ash (CBA) exposed to external sulphate attack.

Alkali–silica reaction (ASR) is a swelling reaction that occurs in concrete structures over time between the reactive amorphous siliceous aggregate particles and the hydroxyl ions of the hardened concrete pore solution. The aim of this paper is to assess the effect of pozzolanic Portland cements on the alkali–silica reaction (ASR) evaluated from two different points of view: (i) alkali-silica reaction (ASR) abatement and (ii) climatic change mitigation by clinker reduction, i.e., by depleting its emissions. Open porosity, SEM microscopy, compressive strength and ASR-expansion measurements were performed in mortars made with silica fume, siliceous coal fly ash, natural pozzolan and blast-furnace slag. The main contributions are as follows: (i) the higher the content of reactive silica in the pozzolanic material, the greater the ASR inhibition level; (ii) silica fume and coal fly ash are the best Portland cement constituents for ASR mitigation.

The giant gypsum crystals of Naica cave have fascinated scientists since their discovery in 2000. Human activity has changed the microclimate inside the cave, making scientists wonder about the potential environmental impact on the crystals. Over the last 9 years, we have studied approximately 70 samples. This paper reports on the detailed chemical¿structural characterization of the impurities present at thesurfaceofthesecrystals and theexperimentalsimulationsoftheir potential deterioration patterns. Selected samples were studied by petrography, optical and electronic microscopy, and laboratory X-ray diffraction. 2D grazing incidence X-ray diffraction, X-ray ¿-¿uorescence, and X-ray ¿-absorption near-edge structure were used to identify the impurities and their associated phases. Theseimpuritiesweredepositedduringthelatest stageofthegypsumcrystalformationandhaveafterward evolved with the natural high humidity. The simulations of the behavior of the crystals in microclimaticchambersproducedcrystaldissolutionby1¿4%weightfractionunderhighCO2 concentration and permanent fog,andgypsumphasedehydrationunderairandCO2 gaseousenvironment.Ourwork suggests that most surface impurities are of natural origin; the most signi¿cant anthropogenic damage on the crystals is the extraction of water from the caves.

The increased use of industrial wastes and by-products to produce concretes and blended cements is a lever to achieve carbon neutrality. Furthermore, they could improve their durability. Some pozzolanic additions can minimize the alkali-silica reaction (ASR), which is a well-known deleterious process that occurs between some reactive aggregates and the alkaline pore solution found in mortars and concretes. This work quantifies the efficiency of four pozzolanic materials (natural pozzolan, P, siliceous coal fly ash, V, silica fume, D, and blast-furnace slag, S) assessed by means of compressive strength testing, open porosity, ASR-expansion measurements, and SEM microscopy. Accelerated expansion tests were performed in mortar bars with a cement/sand ratio of 1/2.25 and a water/cement ratio of 0.47, two reactive aggregates and a non-reactive one. The major contributions of this paper are: (i) The more aggregate reactivity is, the higher ASR mitigation level was found when additions were added and (ii) The best additions for ASR inhibition are silica fume and fly ash.

Siliceous coal bottom ash is a residue originated in thermo-electrical power stations as a result of the hard coal combustion. It is expected that some characteristics of the coal bottom ash would be similar to those of the coal fly ash formed together in the same boiler. Coal bottom ash has a larger size than coal fly ash. Then, the first one was ground to achieve a particle size similar to the cement size. Therefore, to assess the sulphate resistance of cement-based materials made of ground coal bottom ash, sixteen Portland cement mixes were prepared by combining a cement CEM I 42.5 N according to the European standard EN 197-1:2011, a ground coal bottom ash and a coal fly ash. Both ashes were formed in the same boiler. The expansion measurements are considered to be an adequate parameter to assess damage due to sulphate attack of continuously submerged specimens. This procedure is the basis of the American standard ASTM C-1012/C1012 to evaluate the resistance of Portland cement and other cementitious materials to sulphate attack wherein the expansion measurements are taken with a standardized length comparator along the time. In this research program, the extent of sulphate attack was quantified by the percentage expansion of slender bars submerged in 5% sodium sulphate solution according to the ASTM C-1012 standard. This standard specifies an expansion limit of 0.01% for ordinary Portland cements CEM I and 0.035% for blended cements after a period of one year of exposure. The Portland cement CEM I 42.5 N made without ashes exhibited the largest expansion at 330 days (0.09%); whereas a cement with 10% of coal ash, CEM II/A-V, the expansion was much lower (0.03%) for both types of ashes. The expansion decreases when the ash content increases. In this property, no difference was found between ground coal bottom ash and coal fly ash provided by the same thermo-electrical power station.

In this research, an analysis of the damage caused by sulphate attack in various hardened concrete structures, located in Spain, is carried out. This work is showing a summarization of field concretes affected by sulphate attack (external or internal) in the last twenty years based on the experience of the Eduardo Torroja Institute. For the damage assessment, a set of parameters that directly influence the degree of aggressiveness of the attack are taken into account. Parameters related to risks are assessed, such as the environmental conditions of exposure and the characteristics of the materials of the structure itself. The effects of degradation, related to the consequences of this damage, are also analysed. Likewise, these parameters are also related to the type of structures affected. In several regions of Spain, geological characteristics of the soils and climatic conditions that directly influence the processes of attack by sulphates in concrete structures and promote the occurrence of cases of concrete structures attacked by sulphates are presented. These conditions are well known and sulphate resistant cements are commonly used in Spain. Even so, in Spain there are several concrete structures affected by sulphate attack. A number of 17 cases have been analysed according to the experience with sulphate attack in structures and concrete elements at IETcc-CSIC team in the last 20 years.