Synthesis and behavior of Belite-Alite-Ye’elimite (BAY) cement

Ye’elimite based cements have been studied since 70’s years in China, due to the irrelevant characteristics from a hydraulic and environmental point of view. One of them is the reduced fuel consumption, related to the lower temperature reaction required for this kind of cement production as compared to Ordinary Portland Cement (OPC), another characteristic is the reduced requirement of carbonates as a typical raw material, compared to OPC, with the consequent reduction in CO2 releases (~22%)from combustion. Thus, Belite-Ye’elimite-Ferrite (BYF) cements have been developed as potential OPC substitutes. BYF cements contain belite as main phase (>50 wt%) and ye´elimite as the second content phase (~30 wt%). However, an important technological problem is associated to them, related to the low mechanical strengths developed at intermediate hydration ages (3, 7 and 28 days). One of the proposed solutions to this problem is the activation of BYF clinkers by preparing clinkers with high percentage of coexisting alite and ye'elimite. These clinkers are known Belite-Alite-Ye’elimite (BAY) cements. Their manufacture would produce ~15% less CO2 than OPC. Alite is the main component of OPC and is responsible for early mechanical strengths. The reaction of alite and ye´elimite with water will develop cements with high mechanical strengths at early ages, while belite will contribute to later curing times. Moreover, the high alkalinity of BAY cement pastes/mortars/concretes may facilitate the use of supplementary cementitious materials with pozzolanic activity which also contributes to decrease the CO2 footprint of these ecocements. The main objective of this work was the design and optimization of all the parameters evolved in the preparation of a BAY eco-cement that develop higher mechanical strengths than BYF cements. These parameters include the selection of the raw materials (lime, gypsum, kaolin and sand), milling, clinkering conditions (temperature, and holding time), and clinker characterization The addition of fly ash has also been studied. All BAY clinker and pastes (at different hydration ages) were mineralogically characterized through laboratory X-ray powder diffraction (LXRPD) in combination with the Rietveld methodology to obtain the full phase assemblage including Amorphous and Crystalline non-quantified, ACn, contents. The pastes were also characterized through rheological measurements, thermal analyses (TA), scanning electronic microscopy (SEM) and nuclear magnetic resonance (NMR). The compressive strengths were also measured at different hydration times and compared to BYF.

Impact of HydroPolymers on the soil biological components in mediterranean drylands

Soil degradation affects more than 52 million ha of land in counties of the European Union. This problem is particularly serious in Mediterranean areas, where the effects of anthropogenic activities (tillage on slopes, deforestation, and pasture production) add to problems caused by prolonged periods of drought and intense and irregular rainfall. Soil microbiota can be used as an indicator of the soil healthy in degraded areas. This is because soil microbiota participates in the cycle elements and in the organic matter decomposition. All this helps to the young plants establishment and in long term protect the soils against the erosion. During dry periods in the Mediterranean areas, the lack of water entering the soil matrix leads to a loss of soil microbiological activity and it turns into a lower soil production capabilities. Under these conditions, the aim of this study was to evaluate the positive effect on soil biological components produced by an hydro absorbent polymer (Terracottem). The aim of the experiment was to evaluate the impact assessment of an hydropolymer (Terracottem) on the soil biological components. An experimental flowerpot layout was established in June 2015 and 12 variants with different amount of Terracottem were applied as follow: i) 3.0 kg.m3 ; ii) 1.5 kg.m3 and; iii) 0 kg.m3. In all the variants were tested the further additives: a) 1% of glucose, b) 50 kg N.ha-1 of Mineral nitrogen, c) 1% of Glucose + 50 kg N.ha-1 of Mineral nitrogen d) control (no additive). According to natural conditions, humidity have been kept at 15% in all the variants. During four weeks, mineral nitrogen leaching and soil respiration have been measured in each flowerplot. Respiration has been quantified four times every time while moistening containers and alkaline soda lime has been used as a sorbent. The amount of CO 2 increase has been measured with the sorbent. Leaching of mineral nitrogen has been quantified by ion exchange resins (IER). IER pouches have been placed on the bottom of each container, and after completion of the experiment mineral nitrogen leaching has been evaluated by distillation and titration method. Results from respiration have shown statistically significant differences between the variants. According to control, soil with polymers have shown significant difference when comparing respiration with independence of the additive used. CO 2 production in the first week has exceeded the sum of the outputs of the following weeks. Mineral nitrogen leaching measurement has shown statistically significant differences. The lowest leaching has been occurred in control variant, while the highest in variant containing only the addition of mineral nitrogen. Research results may conclude that the biological part of the test soil is not limited by a lack of components, the only thing that suppresses its activity is the lack of moisture. After moistening it leads to a rapid growth of soil activity, without causing the nutrients loss. Besides, Terracottem has affected soil activity neither positively nor negatively, but it considers being a suitable tool for reducing the drought impact in arid and semi-arid areas.