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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., This research was funded by the CSIC (Intramurales Projects PIE 201660E054 y PIE 202060E176).

The natural radioactivity in coal fly ash and natural pozzolan Portland cement samples produced in Spain was measured by gamma spectrometry. Activity concentrations of 226Ra, 232Th and 40K ranged from 15.7 to 88.3 Bq kg−1, from 12.8 to 81.0 Bq kg−1 and from 37.0 to 678.0 Bq kg−1, respectively. The radiological hazards samples owing to the mentioned natural radioactivity were inferred from determinations of the activity concentration index, I, absorbed dose rate, Dext, and annual effective dose, Ep, which falls within 0.20 mSv to 0.87 mSv (coal-cement) and 0.18 mSv to 0.50 mSv (pozzolan-cement) (≤ 1 mSv, threshold criterion). Therefore, these cements are proper to be used for building purposes as result of their radiological assessment.

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.

Activity concentration of 232Th, 226Ra and 40K was determined in 11 white and 63 grey Portland cements by using gamma spectrometry. The potential γ-ray radiation hazards due to mentioned activity concentrations were assessed by following five approaches: internal hazard index, Hin, external hazard index, Hex, activity concentration index, I, absorbed dose rate, D, and effective dose, Ep. All of these showed results falling below threshold limits. Particularly, white cements exhibited slightly lower values than grey ones. The annual effective dose estimated for all the Portland cements falls within 0.10 mSv to 0.47 mSv (≤ 1 mSv: threshold criterion for building materials).

The viability of ground coal bottom ash as a potential Portland cement constituent to be used in building materials is assessed. Currently, coal fly ash is used to produce Portland cements and concretes. However, coal bottom ash is mainly landfilled. Gamma spectrometry analysis, compressive strength, physical and chemical testing were performed. The ground coal bottom ash activity concentration index (I = 1.03) was compared to that of the coal fly ash (I = 1.11) provided from the same thermo-electrical power plant. Ground coal bottom ash could be used in building materials in the same way as coal fly ash as a Portland cement constituent.

The European parliament has declared a global &ldquo, climate and environmental emergency&rdquo, on 28 November 2019. Given that, climate change is a clear strategic issue all around the world. Then, greenhouse gas emissions are reported by each country to the United Nations Framework Convention on Climate Change (UNFCCC) every year. In addition, The Intergovernmental Panel on Climate Change (IPCC) in the &ldquo, 2006 IPCC Guidelines for National Greenhouse Gas Inventories&rdquo, give the procedure to calculate and manage the national greenhouse gases (GHG) emissions. However, these guidelines do not provide any method to consider the net carbon dioxide emissions to the atmosphere (released in clinker fabrication minus those due to concrete carbonation) by the Portland cement clinker industry. This topic should be implemented in the climatic models of the next IPCC assessment report. This paper provides an easy procedure of estimating net CO2 emissions proposed in the &ldquo, recarbonation project&rdquo, (simplified method), that is to say, carbon dioxide uptake during the service-life stage is considered as the 20% of the CO2 released by the calcination (process emissions), whereas the end-of-life and secondary usage is only the 3% of the CO2 released by calcination. The outcome of this study reveals that 31,290.753 tons of carbon dioxide will be absorbed by the cement-based materials produced in Spain with the cements manufactured from 2005 to 2015.

This article belongs to the Special Issue Properties and Novel Applications of Recycled Aggregates., Coal bottom ash is normally used as aggregate in mortars and concretes. When it is ground, its characteristics are modified. Therefore, the assessment of its long-term durability must be realized in depth. In this sense, an accelerated chloride ingress test has been performed on reinforced mortars made of Portland cement with different amounts of coal bottom ash (CBA) and/or coal fly ash (CFA). Corrosion potential and corrosion rate were continuously monitored. Cement replacement with bottom and fly ash had beneficial long-term effects regarding chloride penetration resistance. Concerning corrosion performance, by far the most dominant influencing parameter was the ash content. Chloride diffusion coefficient in natural test conditions decreased from 23 × 10−12 m2/s in cements without coal ashes to 4.5 × 10−12 m2/s in cements with 35% by weight of coal ashes. Moreover, the time to steel corrosion initiation went from 102 h to about 500 h, respectively. Therefore, this work presents experimental evidence that confirms the positive effect of both types of coal ashes (CBA and CFA) with regard to the concrete steel corrosion., This research was funded by the CSIC (Intramurales Projects PIE 201460E67 and PIE 201660E054).

Climate change is one of the most important issues affecting the future of the planet. Then, a lot of resources are being used to actively work on climate change issues and greenhouse gas reduction. Greenhouse gas (GHG) emissions are monitored by each country and reported yearly to the United Nations Framework Convention on Climate Change (UNFCCC). The Intergovernmental Panel on Climate Change (IPCC) published the document entitled “2006 IPCC Guidelines for National Greenhouse Gas Inventories” to provide the calculation rules and the way to inform the UNFCCC of the national GHG emissions. Currently, this document does not give a procedure to calculate the net carbon dioxide emissions to the atmosphere due to the Portland cement clinker production. The purpose of this paper is to get reliable relationships to better calculate the CO2 uptake by ground granulated blast-furnace slag (GGBFS) mortars. The application of this material cured under controlled conditions could help minimize environmental impact. Carbonation coefficient versus 28-day compressive strength relationship of mortars elaborated with GGBFS and cured underwater for 0, 1, 3, 7, 14, or 28 days were obtained. The main finding is the extreme sensitivity of the GGBFS mortars to the curing intensity and, therefore, they can be used cured under controlled conditions to minimize carbon footprints.

The Portland cement industry is presently deemed to account for around 7.4% of the carbon dioxide emitted annually worldwide. Clinker production is being reduced worldwide in response to the need to drastically lower greenhouse gas emissions. The trend began in the nineteen seventies with the advent of mineral additions to replace clinker. Blast furnace slag and fly ash, industrial by-products that were being stockpiled in waste heaps at the time, have not commonly been included in cements. Supply of these additions is no longer guaranteed, however, due to restrained activity in the source industries for the same reasons as in clinker production. The search is consequently on for other additions that may lower pollutant gas emissions without altering cement performance. In this study, bentonite, a very common clay, was used as such an addition directly, with no need for precalcination, a still novel approach that has been scantly explored to date for reinforced structural concrete with structural applications. The results of the mechanical strength and chemical resistance (to sulfates, carbonation and chlorides) tests conducted are promising. The carbonation findings proved to be of particular interest, for that is the area where cement with mineral additions tends to be least effective. In the bentonite-bearing material analysed here, however, carbonation resistance was found to be as low as or lower than that observed in plain Portland cement., This research was funded by the Spanish Ministry of Science, Innovation and Universities under project ADIMULT [ref. BIA-2015-70350-R], and Spain’s (Ministry of the Economy) training programme [ref. BES-2016-077157].

New additions to the cement are needed to achieve a more sustainable and durable construction material. Within this context, bottom ashes can be used as a main constituent of Portland cements when it is mixed in an optimized proportion with fly ashes. The mechanical characteristics of standarized mortars made of mixes of pulverized coal combustion bottom and fly ashes are studied. The mortars were made of ordinary Portland cement (CEM I 42.5 N) and mixes of bottom ashes with fly ashes in similar proportions to those of CEM II/A-V, CEM II/B-V and CEM IV/A (V). Summing up, it can be said that the utilization of bottom ashes mixed with fly ashes in replacement levels from 0% to 100% do not affect significantively on the mechanical caracteristics of the mortars considered in the present study which had an addition maximum content of 35%.

Because of industrialization growth, the amount of coal power plant wastes has increased very rapidly. Particularly, the disposal of coal bottom ash (CBA) is becoming an increasing concern for many countries because of the increasing volume generated, the costs of operating landfill sites, and its potential hazardous effects. Therefore, new applications of coal bottom ash (CBA) have become an interesting alternative to disposal. For instance, it could be used as a Portland cement constituent leading to more sustainable cement production by lowering energy consumption and raw material extracted from quarries. Coal fly and bottom ashes are formed together in the same boiler; however, the size and shape of these ashes are very different, and hence their effect on the chemical composition as well as on the mineralogical phases must be studied. Coal bottom ash was ground. Later, both ashes were compared from a physical, mechanical, and chemical point of view to evaluate the potential use of coal bottom ash as a new Portland cement constituent. Both ashes, produced by the same electrical power plant, generally present similar chemical composition and compressive strength and contribute to the refill of mortar capillary pores with the reaction products leading to a redistribution of the pore size.

Many investigations are realized to establish the basic mechanical properties of vegetable fibre reinforced composites (VFRC) but not their shrinkage and creep behaviour. Some works have been realized to establish the shrinkage of cement mortar matrices reinforced with cellulose fibres, but very few results has been published with regards to shrinkage of VFRC with short sisal and coconut fibres. In this paper a concise summary of several investigations is presented to establish the influence of sisal and coconut fibres on the free and restrained plastic shrinkage, early drying shrinkage cracking, crack self-healing and long-term drying shrinkage of mortar matrices. The free and restrained shrinkage were studied by subjecting the specimens to wind speed of 0.4–0.5 m/s at 40 °C temperature for up to 280 min. The self healing of cracks of the VFRC was studied by using the same specimens as for the study of restrained shrinkage which were kept further in a controlled environment with 100% relative humidity and temperature of 21 °C for up to 40 days. Drying shrinkage tests were carried out at room temperature with about 41% relative humidity for 320 days. The influence of curing method, mix proportions and partial replacement of ordinary Portland cement (OPC) by ground granulated blast-furnace slag and silica fume on the drying shrinkage of VFRC was also investigated. Finally, based on the obtained results on drying shrinkage an equation using the recommendation of ACI model B3 was adjusted and compared well with the obtained experimental data.