Search

In response to the dilemma of the scarcity of mineral additions and the high cost of long-distance transport in Hotan, Xinjiang, China, this paper presented an activation process study on the feasibility of volcanic rock powders unique to this region as mineral additions. This study explored the activity-enhancing effects of volcanic rock powder via three methods: physical activation process, chemical activation process, and thermal activation process. The results showed that physical grinding improved the particle size distribution and enhanced the 'microaggregate' effect. For every 80 m2/kg increase in specific surface area, the particle size decreased by approximately 0.7 μm, and the 28-day activity index increased by up to 4%. In the chemical activation process, the optimal combination scheme of 6% CaO, 2% CaCO3, and 2% CaSO4·2H2O increased the 28-day strength of volcanic rock powder mortar specimens by approximately 20%, achieving an activity index of 82%. Thermal activation studies showed that the low-temperature heat treatment interval of 300 °C to 700 °C increased the 28 d activity index of volcanic rock powders by 12 to 22 percent. However, when the temperature reached the high-temperature interval of 800 °C to 1400 °C, it, rather, inhibited the activity enhancement. A combination of the three activation methods (physical milling with a specific surface area of 560 m2/kg after heat treatment at 600 °C, chemical activation with 6% CaO, 2% CaCO3, and 2% CaSO4·2H2O) resulted in an activity of up to 86% for the volcanic rock powder. The activity enhancement by different activation methods provided a theoretical basis and practical reference for the application of volcanic rock powder as a mineral additions in Hotan, Xinjiang. [ABSTRACT FROM AUTHOR]

Self-leveling mortars are a product that stands out in the market for optimizing production. Greater speed of application is achieved due to its high fluidity, and the ability to level without segregation. This paper approaches self-leveling mortars formulated with different types of cement and additions and evaluates these material's effect on the rheological behavior, physical–mechanical characteristics, and environmental aspects of this type of mortar. The results indicate that rheological aspects can be achieved regardless of the type of cement and addition. With proper proportioning, the normative requirements in terms of mechanical properties are met. When using lower-fineness cement, the risk of cracking and the demand for water and chemicals increases. Mineral additions contributed to the mortars' cohesion and reduced shrinkage in mixtures with contents of up to 25% metakaolin and 15% silica fume. Regarding the decarbonization process, opting for cement with pozzolanic additions becomes a favorable solution as it presents a reduction in CO2 emissions of around 170 kg per m3 of mortar produced. [ABSTRACT FROM AUTHOR]

The aim of this experimental work is to analyze the effect of mineral additions fineness on the hydration of self-compacting mortars, as well as their behavior in the fresh and hardened states. To do this, cement was partially replaced with a fixed rate of 20% for natural pozzolan and 30% for slag. The additions were ground to three different fineness. The results showed that the use of slag is favourable to the formulation of self-compacting mortars, the workability has been considerably improved, the increase in its fineness, meanwhile, reduces the dosage of superplasticizer up to 46%. For the pozzolan, on the other hand, not only was the workability reduced, but the increase in fineness implies an additional demand for superplasticizer up to 16%. Mortars based on additions release less heat, nevertheless, this reduction is accompanied by a drop in compressive strength at a young age. However, the increase in fineness lets to accelerate the initial hydration, inducing additional strength, and to generate heat comparable to that of the reference mortar. Nonetheless, in the case of excessive grinding, the heat release must be taken into account in order to avoid the thermal cracking. [ABSTRACT FROM AUTHOR]

In addressing the dual challenges of sustainable waste management and environmental conservation in the construction industry, particularly the disposal of waste tire crumb rubber (CR) and the demand for eco-friendly building materials, this study explores a novel solution. It examines the sustainable incorporation of waste tire crumb rubber and mineral additions—namely silica fume (SF), marble slurry powder (MSP), and fly ash (FA)—as partial substitutes for natural fine aggregates and cement in concrete. Through comprehensive testing of seventeen concrete samples, the study reveals that the specific mix of R10S5M10F15 that contained 10% crumb rubber as replacement of fine aggregates, and 5% silica fume, 10% marble slurry powder and 15% fly ash as replacements of cement, not only achieves compressive and split tensile strength comparable to the control mix, while the 90 days flexural strength was improved by 4.48%; credited to SF's pozzolanic action and the filler effects of MSP and FA, but also that the inclusion of CR, while reducing compressive strength due to material variations, enhances ductility and improves resistance to sulfate and acid attacks, despite increasing water absorption. The primary goal of this research is to investigate the feasibility and effectiveness of using waste materials in concrete to foster more sustainable construction practices. The objectives include a detailed assessment of the mechanical properties and durability of concrete incorporating these waste materials, aiming to determine the optimal mix proportions for their effective utilization. This study's novelty lies in its detailed analysis of the synergistic effects of combining CR, SF, MSP, and FA in concrete, contributing to the field by offering a sustainable alternative approach to traditional concrete formulations and highlighting the delicate balance required for optimized concrete performance. [ABSTRACT FROM AUTHOR]

Abstract This research evaluated the use of industrial ash from eucalyptus chips in the biosorption of sodium dipyrone with the subsequent, study of its potential in Portland cement matrix. The biosorbent was characterized by the point of zero charge and the surface area. For comparison, before and after the biosorption process, scanning electron microscopy, energy dispersive x-ray spectroscopy, and Fourier transform infrared spectrometry were performed. Regarding the study of the potential of industrial ash after biosorption (AAB), it was characterized by analyzing specific mass, moisture, loss on fire, and X-ray fluorescence, as well as by X-ray diffraction, modified Chapelle, pozzolanic activity index with lime, and performance index with cement, compressive strength, and tensile strength by diametral compression. The biosorption tests were carried out in batch, it being possible to observe that at 298.15 K, 130 rpm, without pH adjustment approximately 93% of commercial dipyrone was removed. The pseudo-second-order kinetic model fitted better with the experimental data and the process was characterized as exothermic and spontaneous. The chemical composition of ash and AAB showed a predominance of CaO followed by MgO, without the presence of an amorphous halo. In the study of the filer effect, using cement pastes, both materials showed favorable results. Thus, it is concluded that the industrial ash studied has the potential to be applied as an alternative material in the removal of sodium dipyrone and for the replacement of cement in the composition of cement matrices, due to the filer effect they presented.

Research in innovative construction materials has focused on utilising supplementary materials in cementitious composites to promote sustainable development and reduce CO2 emissions. Within this context, this study aims to investigate the fresh properties and assess the pozzolanic activity of ternary blended cement by incorporating two industrial waste materials, namely waste glass (WG) and granulated blast furnace slag (GBS), as cement replacements up to 30%. A mixture design approach was employed for composition optimisation, and mathematical models were implemented to achieve this. XRD and SEM/EDS analyses were conducted to examine the structure and composition of the cementitious matrix. The results indicate that the setting time was prolonged compared to the reference mixture. Furthermore, based on the results of the SAI (Strength Activity Index) test, an acceptable level of strength development was demonstrated, confirming that WG and GBS possess the potential to replace cement while meeting the minimum strength requirements outlined in the specifications. Microstructure analyses revealed good adhesion between WGP, GGBS, and the cementitious binder. This research contributes to the development of eco-efficient binders that exhibit increased cement replacement ratios and qualities comparable to, or even superior to, traditional cement systems.

In response to the dilemma of the scarcity of mineral additions and the high cost of long-distance transport in Hotan, Xinjiang, China, this paper presented an activation process study on the feasibility of volcanic rock powders unique to this region as mineral additions. This study explored the activity-enhancing effects of volcanic rock powder via three methods: physical activation process, chemical activation process, and thermal activation process. The results showed that physical grinding improved the particle size distribution and enhanced the ‘microaggregate’ effect. For every 80 m2/kg increase in specific surface area, the particle size decreased by approximately 0.7 μm, and the 28-day activity index increased by up to 4%. In the chemical activation process, the optimal combination scheme of 6% CaO, 2% CaCO3, and 2% CaSO4·2H2O increased the 28-day strength of volcanic rock powder mortar specimens by approximately 20%, achieving an activity index of 82%. Thermal activation studies showed that the low-temperature heat treatment interval of 300 °C to 700 °C increased the 28 d activity index of volcanic rock powders by 12 to 22 percent. However, when the temperature reached the high-temperature interval of 800 °C to 1400 °C, it, rather, inhibited the activity enhancement. A combination of the three activation methods (physical milling with a specific surface area of 560 m2/kg after heat treatment at 600 °C, chemical activation with 6% CaO, 2% CaCO3, and 2% CaSO4·2H2O) resulted in an activity of up to 86% for the volcanic rock powder. The activity enhancement by different activation methods provided a theoretical basis and practical reference for the application of volcanic rock powder as a mineral additions in Hotan, Xinjiang.

Gypsum, from either nature or industrial by-products, can be a lower-cost and cleaner alternative binder to Portland cement used in construction projects, such as affordable housing in developing countries. Although various building products have successfully used gypsum as the binder, some drawbacks of this material have still been claimed, for example, in the aspects of mechanical strength and some other physical properties. Using mineral additions to gypsum seems to be a possible solution to create composite gypsum with improved properties. This work has investigated the possibility of two common minerals (silica flour and talc powder) in modifying composite gypsum's physical and mechanical performance at elevated temperatures (100–1100 °C), including hydration, strength, thermal conduction and stability, and microstructure. The results suggest that 10% gypsum replacement by silica flour or talc powder modifies gypsum's physical and mechanical properties, with silica flour performing better than talc powder. The performance of composite gypsum at elevated temperatures depends on the treatment temperature and reflects the combined effects of gypsum phase change and the filler effects of silica flour or talc powder. Thermal treatment at ≤200 °C increased the thermal resistance of all gypsum boards but decreased their compressive strength. Thermal treatment at ≥300 °C significantly increased the compressive strength of gypsum with silica flour and talc powder but induced intensive microcracks and thus failed the thermal insulation. This investigation indicates that silica flour can potentially raise the mechanical performance of gypsum. At the same time, talc powder can hold water and lubricate, which may help with the continuous hydration of gypsum phases and the rheology of its mixtures. [ABSTRACT FROM AUTHOR]

Research in innovative construction materials has focused on utilising supplementary materials in cementitious composites to promote sustainable development and reduce CO2 emissions. Within this context, this study aims to investigate the fresh properties and assess the pozzolanic activity of ternary blended cement by incorporating two industrial waste materials, namely waste glass (WG) and granulated blast furnace slag (GBS), as cement replacements up to 30%. A mixture design approach was employed for composition optimisation, and mathematical models were implemented to achieve this. XRD and SEM/EDS analyses were conducted to examine the structure and composition of the cementitious matrix. The results indicate that the setting time was prolonged compared to the reference mixture. Furthermore, based on the results of the SAI (Strength Activity Index) test, an acceptable level of strength development was demonstrated, confirming that WG and GBS possess the potential to replace cement while meeting the minimum strength requirements outlined in the specifications. Microstructure analyses revealed good adhesion between WGP, GGBS, and the cementitious binder. This research contributes to the development of eco-efficient binders that exhibit increased cement replacement ratios and qualities comparable to, or even superior to, traditional cement systems. [ABSTRACT FROM AUTHOR]

In this investigation, the properties of ultra-high-performance concretes (UHPC) produced with different binders and aggregates were analyzed. Ternary and quaternary mixtures were tested, including structural white Portland cement (WPC), silica fume (SF), hydrated lime (HL), rice husk ash (RHA), fly ash (FA), and limestone filler (LF), in combination with industrial sand (IS) and discarded foundry phenolic sand (DFPS). The mixtures underwent two types of curing: moist curing until the testing age and moist combined with thermal curing. The concretes were evaluated for compressive strength and microstructure using thermogravimetric analysis (TG/DTG) and Fourier transform infrared spectroscopy (FTIR) techniques. The results showed that all mixtures achieved the desired levels of strength for UHPC (150 MPa). Up to 28 days, the mixtures with RHA exhibited higher strength compared to those with FA, regardless of the curing type. However, at 91 days, the mixtures with FA and thermal curing were more resistant than the mixtures with RHA. Among the quaternary mixtures, at 7 days, the strengths of the mixtures were equivalent, indicating that FA did not react at earlier ages.

This article focuses on the utilization of additions such as microsilica (MS), metakaolin (MK), and calcium carbonate (CaCO3) for the design of cementitious materials based on ordinary Portland cement (OPC) suitable for 3D printing (additive manufacturing). The additions were incorporated into the mixes as replacements for OPC in quantities of 5-10% (MS), 5-15% (MK), and 5-15% (CaCO3). The effect of the additions on the fresh and hardened state properties of the mixes was evaluated. The properties studied included extrusion capability, workability (mini slump), flowability (flow table test), setting time, open time, and printability. Additionally, microscopic inspection of the 3D printing mixes was conducted using scanning electron microscopy (SEM), and physical-mechanical characterization was performed through tests for density, absorption, porosity, flexural strength, and compressive strength. The results demonstrated that the additions directly influence the aforementioned properties. It was concluded that the mix 90%OPC-5%MS-5%CaCO3 (mixture 1) and the mix 90%OPC-5%MS-5%MK (mixture 2) exhibited the most suitable set of characteristics to be implemented as 3D printing cementitious materials. From these mixes, it was possible to 3D print beam-type specimens (160 x 40 x 40 mm), achieving flexural strength values at 28 days of 3.4 MPa (mixture 1) and 4.0 MPa (mixture 2), and compressive strength values of 44 MPa (mixture 1) and 50 MPa (mixture 2). These results are considered as a starting point for future research related to the use of these types of additions in 3D printing of OPC-based cementitious materials. [ABSTRACT FROM AUTHOR]

Efforts are made to alleviate thermal problems in buildings. The use of thermal mortars for coating with vermiculite as aggregate is used for this purpose, but the use with mineral additions is still scarce, especially the rheology through squeeze-flow. Thus, it was aimed to evaluate the behavior in fresh, hardened state and in the thermal conductivity of these mortars. Mortars containing Portland cement, lime, vermiculite, sand, and additions of metakaolin or ceramic brick waste, in the proportion of 1:1:6 (Cement: Lime: Sand), were evaluated. The sand was replaced by vermiculite in 40%, and the additions added in the proportion of 20% to the cement mass, and the water content determined with the spread obtained on the consistency table. Mixtures containing 20% mineral addition and 40% vermiculite proved to be feasible, reaching minimum values according to the respective standards.

In addressing the dual challenges of sustainable waste management and environmental conservation in the construction industry, particularly the disposal of waste tire crumb rubber (CR) and the demand for eco-friendly building materials, this study explores a novel solution. It examines the sustainable incorporation of waste tire crumb rubber and mineral additions—namely silica fume (SF), marble slurry powder (MSP), and fly ash (FA)—as partial substitutes for natural fine aggregates and cement in concrete. Through comprehensive testing of seventeen concrete samples, the study reveals that the specific mix of R10S5M10F15 that contained 10% crumb rubber as replacement of fine aggregates, and 5% silica fume, 10% marble slurry powder and 15% fly ash as replacements of cement, not only achieves compressive and split tensile strength comparable to the control mix, while the 90 days flexural strength was improved by 4.48%; credited to SF’s pozzolanic action and the filler effects of MSP and FA, but also that the inclusion of CR, while reducing compressive strength due to material variations, enhances ductility and improves resistance to sulfate and acid attacks, despite increasing water absorption. The primary goal of this research is to investigate the feasibility and effectiveness of using waste materials in concrete to foster more sustainable construction practices. The objectives include a detailed assessment of the mechanical properties and durability of concrete incorporating these waste materials, aiming to determine the optimal mix proportions for their effective utilization. This study’s novelty lies in its detailed analysis of the synergistic effects of combining CR, SF, MSP, and FA in concrete, contributing to the field by offering a sustainable alternative approach to traditional concrete formulations and highlighting the delicate balance required for optimized concrete performance.

In this paper, multi-ion transference numbers were determined throughout the chloride migration testing of low clinker cement-based materials. For this purpose, five cement pastes were studied: pure Portland paste (as a reference) and four other pastes, based on limestone filler, fly ash, slag or silica fume. The transference numbers were calculated from the concentration evolution in the three zones of the migration cell (catholyte, anolyte and sample), considering that: (i) ions moved in the catholyte and anolyte; (ii) ions leached from the sample; (iii) ions were generated from the electrode processes, and (iv) the pore solution of the sample evolved during the test. The chloride transference numbers of pastes with pure Portland cement, limestone filler, fly ash, slag or silica fume are almost zero at the beginning of the migration test but 0.23; 0.18; 0.06; 0.05 and 0.20 at the end of the test, respectively. The ion transference numbers obtained were used for the calculation of diffusion coefficients of chlorides, sodium and potassium using the Nernst-Einstein equation. [ABSTRACT FROM AUTHOR]

Self -compacting concrete composition results from several approaches to satisfy specific criteria. SCCs must be able to fill small, confined formwork without the need for vibration. To ensure the homogeneity and mechanical characteristics of the concrete, they must have good resistance to segregation throughout the setting time. The self-compacting aspect is controlled by a high volume of paste and an important fines content ensured by incorporating mineral additions that are expensive and not always available. The main objective of this paper is to utilize a new type of micronized limestone filler that may be characterized and incorporated into concrete to guarantee self-compacting quality. In the first part, a detailed characterization of the limestone filler was carried out to investigate its effects on the concrete properties. The identification has been physical, chemical, and specific to the concrete's formulation. The second part is devoted to the experimental tests on different SCCs mixed with various amounts of filler to determine the optimal incorporation percentage. Moreover, a parametric study, involving the content of filler, the granular structure, and the quantity of superplasticizer, allowed an evaluation of the effect of limestone filler incorporation on fresh and hardened concrete characteristics. Through this study, it was demonstrated that with a proportion of limestone filler of about 25% of the quantity of cement used, the quality of the concrete has recognized appreciable improvements. [ABSTRACT FROM AUTHOR]

In the 21st century, numerous numerical calculation techniques have been discovered and used in several fields of science and technology. The purpose of this study was to use an artificial neural network (ANN) to forecast the compressive strength of waste-based concretes. The specimens studied include different kinds of mineral additions: metakaolin, silica fume, fly ash, limestone filler, marble waste, recycled aggregates, and ground granulated blast furnace slag. This method is based on the experimental results available for 1303 different mixtures gathered from 22 bibliographic sources for the ANN learning process. Based on a multilayer feedforward neural network model, the data were arranged and prepared to train and test the model. The model consists of 18 inputs following the type of cement, water content, water to binder ratio, replacement ratio, the quantity of superplasticizer, etc. The ANN model was built and applied with MATLAB software using the neural network module. According to the results forecast by the proposed neural network model, the ANN shows a strong capacity for predicting the compressive strength of concrete and is particularly precise with satisfactory accuracy (R² = 0.9888, MAPE = 2.87%). [ABSTRACT FROM AUTHOR]

Prediction of carbonation progress in concrete exposed to ionizing radiation is important for the durability assessment of nuclear power plants, eventually needed for operational license extension. The objective of this work is to reveal the influence of gamma irradiation on the carbonation development and resulting microstructural features of cement mortar. The composition of mortar was varied by using mineral additions. Canned specimens at elevated CO2 concentration environment were exposed to gamma irradiation up to the absorbed dose of 1.6 MGy in the vicinity of spent nuclear fuel rods in pool of research reactor. Micromechanical properties of carbonation reaction products were determined using nanoindentation tests. The carbonation depth was found to increase with increasing absorbed γ dose. The size of calcite crystals was about three times greater in irradiated specimens. Gamma irradiation improved the micromechanical properties of carbonation products. Effects of mineral additives on the characteristics of irradiated mortar are discussed. [ABSTRACT FROM AUTHOR]

Cementitious mixtures for 3D printing require specific rheological properties in the fresh state, which is why it is necessary to incorporate admixtures and/or mineral additions (modifiers) into such mixtures. The objectives of this article were to compare the effects of bentonite (Ben) (1 %–5 %) and mineral additions, such as metakaolin (MK) (5 % and 10 %), microsilica (MS) (5 % and 10 %) and calcium carbonate (Ca) (5 % and 10 %), on the rheological properties in the fresh state and to determine the printability of cementitious mixtures based on ordinary Portland cement (OPC). Among the rheological properties, the static yield stress (τ 0), flow behavior, viscosity (η) and thixotropic of the mixtures were evaluated. Complementarily, the properties of materials in the fresh state, such as the settlement (minislump), flow rate (flow table) and buildability, were determined. The printability was evaluated through laboratory-scale additive manufacturing tests by printing from a hollow cylinder (unfilled) 50.8 mm in diameter and 208 mm in height (≈52 layers). The results showed that the incorporation of Ben between 1 % and 5 % had a significant effect on the rheological properties of the mixtures in the fresh state, increasing τ 0 to 203.8 % (5 % Ben) and structural regeneration (thixotropy) to 98.5 %. Ben decreased the fluidity of the mixtures while significantly increasing the buildability. Among the mineral additions used, MS and MK increased the rheological properties of the mixtures as a function of the amount incorporated (5 % and 10 %, respectively), while Ca had a fluidifying effect on the mixtures, thereby affecting the buildability during the 3D printing process. This phenomenon was corrected by simultaneous adding 3 % Ben. The results obtained were considered a starting point for the design of OPC-based 3D printing mixtures with these modifiers (Ben, MK, MS and Ca). • The effect of bentonite, metakaolin, microsilica and calcium carbonate was studied. • Bentonite had a significant effect on the rheological properties of the mixtures. • Bentonite and microsilica increase the buildability of the 3D printed mixes. • Calcium carbonate does not generate significant changes in the flow behavior. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study to evaluate the effect of local mineral additions (pozzolan, slag and limestone) on the rheological behaviour of based cement binder's pastes. The binary, ternary and quaternary binder pastes were prepared with the partial clinker cement replacement limited up to 20%, according with type CEM II specifications. The cements were characterized by their geometric shapes, the reactivity and the chemical composition. An experimental design plan was used to modelling the rheological behaviour of pastes. The relatives yield stress and plastic viscosity of binder's pastes, with normal consistency, were determined. The results showed that all the tested compositions with additions follow the same rheological behaviour law according to the Bingham model. The binder pastes rheological parameters (yield stress and viscosity) are affected by mineral additions. The highest values of the rheological parameters were measured in binary and ternary cements with limestone and pozzolan. On the other hand, the lower viscosity among the tested pastes was obtained with slag addition. The statistical approach allowed us to obtain a satisfactory modelling of viscosity and yield stress with a coefficient of determination R2 = 0.91 and 0.92, respectively and a satisfactory correlation between the viscosity and the water/binder ratio (W/B) for a normal consistency with a coefficient of determination R2 = 0.91. [ABSTRACT FROM AUTHOR]

The present work analyses the basic creep of concrete compositions for which 75% of Portland cement is substituted by limestone filler and/or blast furnace slag. Compressive creep tests are performed during and after the peak of hydration of the slag in order to track the effect of the slag on the development of the creep properties. An adapted version of the Model Code 2010 (MC2010) is used to model basic creep. It is observed that the high substitution rate of cement by limestone filler and/or slag leads to a significant change in the evolution of the viscoelastic properties of concrete till a significant degree of reaction of slag is reached. It corresponds to the end of the second peak of hydration due to slag. After the slag peak of hydration, the basic creep is similar to ordinary Portland cement concrete with equivalent water‐to‐binder ratio. For very early age, a new model is developed and is composed of two terms, which consider the hydration of (a) Portland cement and (b) slag in the aging of the specific creep function. [ABSTRACT FROM AUTHOR]

In this research the effect of the addition of silica fume (SF) and fly ash (FA) to the ordinary Portland cement (OPC), individually and in combination, on rheology, compressive strength and self-compacting capacity in mixtures of cement were evaluated. At the beginning, the physicochemical characterization of the raw materials was carried out using XRF, SEM and PSD. Subsequently the rheological analysis was done in order to determine yield stress and plastic viscosity, then the compressive strength was measured at 7 and 28 days of normal curing. Finally, the measurement of the selfcompacting capacity by means of a V-funnel was performed. It was found that the FA influences positively because it reduces yield stress and selfcompacting test times, but decreases the compressive strength in comparison to control sample. The addition of SF increases the yield stress and selfcompacting times, but positively influences the compressive strength. By analyzing the combinations of FA and SF additions the effects of each one are maintained allowing finding an addition range that delivered efficient values for the performance of fresh and hardened state of the blended cement pastes.

Variation in colors in lime base mortars by adding materials like clay, manufacturing brick ash, quarry powder, and maize starch have been analyzed in this research. Such additions were compared with a sample mortar made only of sand and clay. In order to quantify the color, Chromatic coordinates, expressed in coordinates C.I.E. (L*, a* and b*) were measured. These analyses determine the median chromatic coordinates which are between red and yellow, maybe as orange. To design a mortar in that original color the measured values L*, a* and b* were taken into account. The present work shows the results of color of lime mortars which provides acceptable aesthetic results according to the original colors of the monuments that is intended to be restored but without diminishing the mechanical resistance of them.

The use of mineral additions is a common practice in the production of cementitious materials. Recently proposed usage of high amounts of cement replaced by mineral additions requires the study of the chemical interaction of these additions with the cement. This study intends to evaluate, by means of TG/DTG techniques, XRD and compressive strength, the effect of high volume of mineral additions in the hydration of cementitious pastes. Pastes with 50–70% of cement replaced by mineral addition and with different combinations of fly ash and metakaolin were evaluated, two pastes without mineral addition and two other pastes with lime addition. Results showed TG/DTG and XRD techniques are more suitable for evaluating kinetics of reactions of hydration, making it possible to quantify the substantial reduction in the levels of portlandite in hydrated pastes containing high volumes of mineral additions. These techniques allowed to find important differences in the evaluation of calcium hydroxide, because its morphology can change in the presence of additions. Also showed that it is possible to achieve, enhanced or even high compressive strength (50–80 MPa) in concretes containing reduced cement contents. As well as more resistance against harmful agents and carbonation attack. [ABSTRACT FROM AUTHOR]

In this work, several reinforced self-compacting concretes were prepared by using three types of fibers made of steel, polypropylene and glass, and three different types of mineral additions (marble powder, metakaolin and limestone powder). The water to cement ratio was kept constant at 0.34 and fibers were used in combination, keeping the total fiber content constant at 60 kg/m3. Slump flow diameter, L-Box, stability and air content were performed to assess the fresh properties of the concrete. Compressive strength, flexural strength, splitting tensile strength and ultrasonic pulse velocity of the concrete were determined for the hardened properties. Noteworthy performances were generally obtained, particularly in hardened properties for the self-compacting concretes prepared with steel fibers in association with polypropylene fiber and marble powder as mineral addition.

Highlights • Resistivity is an expressive indicator of concrete durability regarding Cl− attack. • Concretes with pozzolanic additions have significantly high resistivities. • It has been found an inverse correlation between R p and ER before Cl− attack. • Concretes with pozzolans showed a better performance regarding the steel corrosion. • The impedance for systems with pozzolans was slightly altered after Cl− attack. Abstract In this article, the beneficial effects of pozzolanic mineral additions incorporated in concrete under the attack of chlorides are evaluated. Three different mineral additions incorporated in binary combinations with Portland cement (silica fume, metakaolin and fly ash) were studied. By monitoring and analyzing thermodynamic and kinetic parameters, the corrosion performances of reinforced test specimens were evaluated over an extended period of chloride attack (44 weekly cycles of wetting in a solution of NaCl and air drying, equivalent to 308 days of attack). The electrochemical techniques (E corr , R p and EIS) 1 Electrical resistivity (ER), corrosion potential (E corr), polarization resistance (Rp), electrochemical impedance spectroscopy (EIS), corrosion rate (i corr), control concrete (C), concrete with silica fume (SF), concrete with fly ash (FA), concrete with metakaolin (MK). 1 , added to the electrical resistivity technique (ER), are allowed to evaluate the protection capacity of the concretes under study, in relation to this strong attack on the reinforcement. They also allowed the production of subsidies capable of generating scientific discussion about the mechanisms of protection, imparted to concrete by mineral additions, in this specific aggressive medium rich in chlorides. The results showed that the used mineral additions produced significant increases in the resistivity of concretes, which is probably due to physical changes in the pore structure of cement paste, besides the improvement of paste-aggregate interface and the changes in the conductivity of pore solution. This higher resistivity certainly delayed the transport of chlorides and their attack on the reinforcement, seen by small changes in the values of E corr , R p and i corr in concretes with pozzolans. The EIS results showed that there was little change in the impedance values at the steel-concrete interface in these systems with mineral additions, in spite of the strong and prolonged attack. [ABSTRACT FROM AUTHOR]

In this research the effect of the addition of silica fume (SF) and fly ash (FA) to the ordinary Portland cement (OPC), individually and in combination, on rheology, compressive strength and self-compacting capacity in mixtures of cement were evaluated. At the beginning, the physicochemical characterization of the raw materials was carried out using XRF, SEM and PSD. Subsequently the rheological analysis was done in order to determine yield stress and plastic viscosity, then the compressive strength was measured at 7 and 28 days of normal curing. Finally, the measurement of the selfcompacting capacity by means of a V-funnel was performed. It was found that the FA influences positively because it reduces yield stress and selfcompacting test times, but decreases the compressive strength in comparison to control sample. The addition of SF increases the yield stress and selfcompacting times, but positively influences the compressive strength. By analyzing the combinations of FA and SF additions the effects of each one are maintained allowing finding an addition range that delivered efficient values for the performance of fresh and hardened state of the blended cement pastes. [ABSTRACT FROM AUTHOR]

The self-compacting concrete (SCC) has a high content of fine materials and has been widely used due to its characteristics of high fluidity and cohesion. Fines from industrial waste or by-products may be used for the sake of sustainability, considerably reducing the consumption of cement associated with the possibility of maintaining or improving mechanical or durability properties. In this way, this article aims to study the properties of concrete in the fresh state and hardened state, analyzing the feasibility of the development of SCC made with high levels of mineral additions. For this, the cement was replaced by mineral additions (sugar cane biomass residue or pozzolan from rice husk and metakaolin) in the 50% content, based on the reference trait, which consumes 442.6 kg/m3 of cement, giving new traits with cement consumption between 215.9 kg/m3 and 216.2 kg/m3. The SCC were characterized in the fresh state by the Slump-Flow Test, T500, J-ring, V-funnel and L-box assays, assessing the influence of the insertion of the additions on the rheological properties and the superplasticizer additive consumption. In order to evaluate the mechanical performance of the SCC, compressive strength tests were performed. The SCC with mineral additions presented satisfactory mechanical performance. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study aimed at evaluating the reactivity of natural and industrial local mineral additions (pozzolan, slag and limestone) by different microstructural and mechanical approaches. Binary, ternary and quaternary cement compositions were prepared with partial replacement of the clinker by additions limited to 20%, according to CEM II / A cement specifications. The reactivity during the hydration process is characterized by the hydraulic power of the additions to react with the water and the hydrates of the cement and the pozzolanic capability of fixing the portlandite to form new mineral phases which contribute to the resistance as much as the hydrated products of cement. An experimental methodology was established for the reactivity illustration of the additions by a microstructural approach based on a study of the physicochemical and microstructural properties realized by X-ray diffraction (XRD), the scanning electron microscopy (SEM) on pastes. Further, thermogravimetric analysis (TGA), mercury microporosity (MIP) on mortars at 28 days of age was performed. A mechanical approach based on compressive strength at 2, 7 and 28 days to determine the activity index according to ASTM C 618 has been undertaken. The results obtained show a good correlation between the microporosity, X-ray diffraction and the resistance activity index, in particular for the slag, as for the thermogravimetric analysis that clearly confirms the pozzolanic activity of the pozzolan addition. As for mechanical performance, a binary mortar with 20% slag showed a better compressive strength at 28 days (49.40 MPa) with a reactivity index (87.90%) compared to the control mortar. Further, the slag developed better resistance (49.53 MPa) in combination with the other additions for quaternary mortars (pozzolan, limestone and slag) with an optimal rate of 5, 5 and 10%, respectively. Nevertheless, the pozzolan showed better compressive strength values compared to the slag for the binary mortars at young age 2 and 7 days of 25.67 and 32.07 MPa, respectively. [ABSTRACT FROM AUTHOR]

The study of the hydration kinetics appears as a prerequisite for understanding the physical and mechanical phenomena that control the behavior of cementitious materials. This research is based on monitoring the evolution of the degree of hydration for ordinary cement and those containing 10% of limestone powder, 20% of natural pozzolana or 30% of the blast furnace slag under high temperatures. The results provide a better understanding the effect of cure temperature on the hydration kinetics and understand the contribution of mineral additions on improving the cement properties. A new model proposed gives the satisfaction results for predicting in later age the heat of hydration of cements blended kept under constant temperatures. The latter has a wider appreciation of the results, where it gives correlation coefficients very close of unity. This justifies the reliability of this new model proposed. [ABSTRACT FROM AUTHOR]

Reinforced concrete is the most widely used construction material in the world. The combination of high compressive strength, afforded by concrete and, and the excellent mechanical properties that characterise steel make it an ideal composite for all manner of structures. One of the main weaknesses of this material, however, is that when the concrete is exposed to aggressive environments, in particular high concentrations of chloride ions or carbon dioxide, reinforcing steel corrodes, shortening service life. This article reviews the state of the art on concrete durability, along with the conditions that affect its useful life by inducing reinforcing steel corrosion. It also discusses the prevention and control methods, in particular electrochemical prevention and rehabilitation techniques, that have been developed to mitigate the problem.

This study analyses the impact of substituting limestone fillers for cement on the rheological behaviour and drying shrinkage of microconcretes that are used for repair coatings. Three microconcretes were formulated with limestone filler contents of 80%, 60% and 20% by weight in relation of the total fines (cement and limestone filler). The total fines and water contents were kept constant in all of the formulations result in mixtures with similar volume of paste. The rheological behaviours of the mixtures were evaluated using a rheometer with planetary motion. The specimens were then moulded for mechanical characterisation and to measure the drying shrinkage. The porosity of the pastes was also evaluated using the mercury intrusion porosimetry (MIP). Rheological properties such as the yield stress and viscosity were influenced by the amount of cement that was replaced by fillers. Larger volumes of filler in the paste produced lower yield stresses and, consequently, higher slump values were obtained. However, the plastic viscosity increased with the filler content. In the hardened state, greater substitutions of cement by fillers decreased the drying shrinkage. This will cause lower differential shrinkage between the repair material and the existing substrate, generating lower tensile stresses in the repair material (repair coating) and therefore less potential for cracking of this. The experimental shrinkage results were compared to values that were obtained by the ACI 209, CEB-FIP90, B3 and GL2000 shrinkage prediction models. The models were found to overestimate the amount of shrinkage with increased substitution of cement by filler in the paste. Therefore, these models should be calibrated considering other factors such as the quantity of filler used in cement replacement. That consideration could optimize the use of these models in the design stage to verify if the values of expected shrinkage are within usually accepted limits for this application. [ABSTRACT FROM AUTHOR]

An experimental investigation is conducted to study the flexural fatigue performance of steel fibre reinforced concrete containing fly ash (FA), silica fume (SF), metakaolin (MK) and limestone powder (LP) as mineral additions in terms of theoretical fatigue lives. Seven mix combinations are prepared by replacing 30 % of cement by weight with FA, SF, MK and LP in different proportions to form binary and ternary blend systems. Rectangular corrugated steel fibres at 1.0 % volume fraction are incorporated in all seven mix combinations. Beam specimens are tested at four fatigue stress levels ranging from 0.90 to 0.75. The Weibull distribution is employed to incorporate the failure probabilities into the fatigue life data of all mix combinations. The theoretical fatigue lives of all mix combinations are calculated using single-logarithm fatigue equation. The theoretical fatigue lives of concretes containing mineral additions get enhanced in different extent as compared to control concrete. The concrete containing SF and FA in the amount of 10 and 20 % by weight of binder respectively has shown the best flexural fatigue performance, which is much better than that of the control concrete. [ABSTRACT FROM AUTHOR]

Environmental issues have led European stakeholders to join around an ambitious project, the reuse 70 % of inert wastes from construction and demolition by 2020. Among available solutions, the reuse of fine recycled aggregates as substitute of natural sand is somewhat problematic due to their high water absorption. The aim of the present research is to study a new way of recovery for fine recycled aggregates. We propose to use them as mineral addition, after a process of crushing and sieving resulting in powder (particles diameter lower than 80 µm). For this purpose, Recycled Crushed Concrete Fines (RCCF) were prepared from a 5 years old concrete and characterized by a physico-chemical approach. Attention was paid to assess the content of anhydrous cement. Mortars with different substitution levels of Portland cement by RCCF (Recycled Crushed Concrete Fines) or limestone filler were also studied at both fresh and harden states. The studied RCCF were found to have low content of anhydrous cement and thus low hydraulic properties. However, RCCF (Recycled Crushed Concrete Fines) was found to play a similar role than limestone filler on cement hydration. Portland cement could be substituted by RCCF (Recycled Crushed Concrete Fines) up to 25 % without altering properties of mortars. These results are encouraging and lead us to continue our research with inert wastes from real demolition sites. [ABSTRACT FROM AUTHOR]

The exact mechanisms of the phase transitions caused by a combined sulphate-chloride attack are discussed controversially. The main points concern the mutual influences of sulphate and chloride ions during the secondary binding processes of these anions within cement hydrate phases. We simulated combined sulphate-chloride attack under laboratory conditions using solutions containing NaCl and Na 2 SO 4 in different concentrations. Three sample compositions were used for the preparation of the specimens. In two of them, 30% of Portland cement was replaced by supplementary cementitious materials (fly ash, slag). The phase distribution in the samples was determined using synchrotron X-ray diffraction. The analysis with high spatial resolution allows the localisation of the secondary phase formation in the microstructural profile of the sample. A mechanism of the phase developments under combined sulphate-chloride attack is derived. [ABSTRACT FROM AUTHOR]

The complex matter of external sulphate attack on cement-based construction materials is still not completely understood. The concentration of sulphate is a crucial factor for the formation of secondary phases and phase transitions of cement hydrates due to sulphate ingress into the microstructure. The sulphate attack on building materials for high and low sulphate concentrations was monitored by laboratory experiments. Hardened cement paste consisting of ordinary Portland cement (CEM I) were exposed to aqueous solutions of sodium sulphate for 18 months. Three sample compositions were used for this research, including different supplementary cementitious materials (SCM). The phase composition was determined for different time spans by high resolution synchrotron X-ray diffraction. Cross sections of exposed cement prisms were investigated as a representation of the microstructural profile. Based on the data, a temporal and spatial determination of the stages of the sulphate attack and the deterioration course was possible. Cement matrices blended with slag showed the highest resistance against sulphate attack. [ABSTRACT FROM AUTHOR]