Investigation of use of coal fly ash in eco-friendly construction materials: fired clay bricks and silica-calcareous non fired bricks

The use of coal fly ash (CFA) as raw material for the manufacture of two construction materials, fired clay bricks and silica-calcareous non-fired bricks, was investigated. Fired clay bricks were manufactured using a commercial clay and different waste ratios (0–50 wt%), moulded at 10 MPa and fired at 1000 ºC (4 h). Silica-calcareous non-fired bricks were prepared using two wastes as raw material: CFA and “geosilex”(G), a hidrated lime residue which comes entirely from acetylene industry waste. Different proportions CFA (80–30 wt%) – G (20–70 wt%) were investigated. Raw materials were moulded at 10 MPa and cured in water at room temperature during 28 days. The results indicated that the incorporation of up to 20 wt% of CFA produced fired clay bricks with physical and mechanical properties similar to control bricks without waste. However, additions of a higher amount (30–50 wt%) of residue resulted in a more pronounced decrease in mechanical properties (between 25–50%) due to an increase in open porosity. The technological characterization of the silica-calcareous non-fired bricks showed a reduction in the values of bulk density and water absorption when the coal fly ash content decreases. Silica-calcareous non-fired bricks containing between 40 and 60 wt% of CFA had the highest values of compressive strength in the range 46–43 MPa. These silica-calcareous non-fired bricks, 60CFA-40 G, 50CFA-50 G and 40CFA-60 G, presented the optimum amount of pozzolanic materials (SiO and AlO) in the coal fly ash and calcium hydroxide in the geosilex to give rise to the formation of calcium silicate hydrates and calcium aluminate hydrates, the phases responsible for the mechanical resistance increase of the construction materials. Therefore, CFA-clay fired bricks and silica-calcareous CFA-Geosilex non-fired bricks presented optimal technological properties that attain the quality standards.This work has been funded by the Project “Valuation of various types of ash for the obtaining of new sustainable ceramic materials” (UJA2014/06/13), Own Plan University of Jaen, sponsored by Caja Rural of Jaen. The authors thank the companies “Thermal Power Plant Litoral SS” and “Geosilex Trenza Metal S.L.” for supplying the ashes and geosilex, respectively. Technical and human support provided by CICT of Universidad de Jaén (UJA, MINECO, Junta de Andalucía, FEDER) is gratefully acknowledged

Menadione Sodium Bisulphite (MSB): beyond seed-soaking. Root pretreatment with MSB primes salt stress tolerance in tomato plants

Salinity and drought are considered significant abiotic plant stressors with major impact on plant development that causes serious agricultural yield losses. Amongst the strategies to face this problem, the use of compounds capable of inducing abiotic stress tolerance is still little explored. Menadione sodium bisulphite (MSB), a water-soluble vitamin K3 derivative, was previously shown to prime salt stress tolerance when Arabidopsis seeds were pre-soaked with this compound. However, this method has some technical problems regarding seed storage and longevity. In order to overcome these handicaps, we assessed the effect of supplying MSB to roots to prime the response to salinity stress, analysing the effect of two NaCl concentrations (100 and 150¿mM). We selected tomato plants, the most economically important horticultural crop, as our biological model. In this new system, MSB primes salt tolerance in tomato plants by improving net photosynthesis, regulating stomatal aperture and maintaining water balance. Furthermore, MSB induces a faster proline accumulation and ion homeostasis by up-regulating several ion transporter genes, and increases antioxidant activity. As a result, a clear positive effect on plant growth was observed, indicated by the relative growth rate (RGR), These findings again highlight the potential usefulness of MSB as a priming agent for enhancing crop tolerance in the field under adverse environmental conditions.This work was supported by Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad SAF2013-48399-R from Ministerio de Economía y Competitividad (Spain), and by Proyecto RESALM 2016TUR02 supported by Fundación Caja Canarias. F.J.G-M., PhD fellowship of Universidad de La Laguna, was supported by a research contract from Cajasiete. The authors also thank Guido Jones, who copy-edited the manuscript.Peer Reviewe