Stabilization of sulphidic mine tailings with MgO activated blast furnace slag

The mining industry is the biggest producer of waste materials in the form of waste rock and tailings. Tailings ponds create potential ecological risks due to hazardous substances the tailings themselves and the toxic additives used in the metal processing phase include (1). For example, in China, tailings storage is rated to be 18/93 among the most dangerous environmental risk sources (2). Serious environmental accidents worldwide, increased public awareness and increasingly stringent environmental regulations have promoted research to develop new innovative approaches to mitigate the risks caused by tailings. The Pyhäsalmi mine in Finland is one of the largest massive sulphidic ore mines in the world. The tailings potentially generate acid, mostly due to oxidation of iron sulphides (58 %). The total area of the tailings ponds is 150 ha which has mainly been covered with conventional methods at the beginning of the millennium. The mine will be closed in the near future, and the principal aim of the tailings recovery plan is to decrease environmental risks in the long-term by restricting acid generation caused by water and oxygen ingress. Several tailings pond cover liner options are currently under consideration. This study compares tailings stabilization with two alternative binder materials; alkali activated blast furnace slag (AAC) and Portland cement (PC). Stabilization is a commonly used technology to prevent the leaching of hazardous substances into the natural environment. Stabilization encapsulates hazardous substances both chemically and physically. In the research, MgO-activated blast furnace slag was compared with PC as a stabilization binder using a dosage of 10 w%. According to the literature, MgO activated BFS binder has not been studied or used earlier in the stabilization of tailings while PC is the most commonly used stabilization binder. However, the long-term durability of PC, especially in highly sulphidic environments, is questionable due to its vulnerability to sulphate attack and ecological impacts. These vulnerabilities are significant due to the need for high binder amounts and consequently required investments. In addition, commonly used liquid alkali activators, for example sodium and potassium hydroxides and silicates, have safety, cost and ecological issues. In this research, by-product based MgO was used as an activator in BFS instead of liquid alkali activators. The laboratory studies tested hydraulic conductivity, compression strength, oxygen diffusion, leaching, freeze-thaw resistance and water resistance, in addition to chemical, mineralogical, microscopic and thermal analysis. The Life Cycle Assessment (LCA) method was used to compare environmental impacts of the used binder materials. A stabilized tailings layer with a thickness of 300 mm was constructed as a part of the advanced hardpan cover pilot structure of 100 m2 in the tailings pond area. According to the tests, the hydraulic conductivity (6.08E-09 m/s) and compressive strength (11.5 MPa/28 days) of AAC were better than when using the corresponding amount of PC (2.04E-08 m/s and 10.3 MPa/28 days) indicating better immobilization efficiency and thus improved technical performance, in addition to competitive costs. LCA shows clear ecological benefits when using AAC instead of PC: a 35 % lower amount of generated greenhouse gas emissions due to the use of waste based binders. In addition, using the stabilization method in tailings storage reduces the need for natural moraine in the cover structure. The video script illustrates the use of AAC binder in the pilot structure. References (1) Manjunatha L.S. & Sunil B.M. (2013) Stabillization/solidification of iron ore mine tailings using cement, lime and fly ash, International Journal of Research in Engineering and Technology, Vol.02,12:625-636 Xie X., Tian W., Wang Y., Zhan G.X. (2009) The safety analysis of current situation and management countermeasure on tailing reservoir in China. Journal of Safety Science and Technology, 5(2): 5−9

Modification of Alkali Activated Blast Furnace Slag for Pothole Repairs

Potholes denote small, typically sharp edged holes in the pavement. The aim of this research was to study the usability of alkali activated (AA) blast furnace slag based material in the repair of paved roads, especially during the cold winter and spring seasons when such repairs are needed most and the use of hot asphalt is not possible. The objective was to a find material which is both more cost-efficient and durable than plain cold asphalt. Properties like rapid strength development, good bonding with old paving material, weather resistance, abrasion resistance, and low shrinkage were required. The influence of the chosen factors on the performance of the material was studied applying the multi-attribute optimization method. The impact of different additives, such as Portland cement, fibers and crushed tire rubber were studied. The results indicated that the AA slag based materials studied can be improved by suitable additives to make them reach desired performance. According to the tests, adding Portland cement increased compressive strength threefold after 3 hours and reduced shrinkage by 34% but should be a negative impact on higher levels related to freeze-thaw resistance. In addition, crushed rubber was indicated to have a positive impact related to all the studied performance properties

Leisure-time physical inactivity and association with body mass index : a Finnish Twin Study with a 35-year follow-up

Background: We investigated the stability and change of leisure-time physical inactivity in adult men and women during a 35-year follow-up. We also analysed the impact of long-term physical inactivity on the development of body mass index (BMI). Methods: In this population-based cohort study, 5254 Finnish twin individuals (59% women) participated in four surveys in 1975, 1981, 1990 and 2011. Mean age at baseline was 23.9 years. Individual long-term leisure-time physical activity (LTPA) was categorized into seven classes varying from 'persistently inactive' to 'persistently active'. We used the multivariate multilevel mixed-effects linear regression model and paired-sample t-test in the analyses. Co-twin control design was used for examining within-pair associations. Results: Of men 11%, and of women 8%, were persistently inactive. Among both sexes, the mean BMI slope trajectories were steeper among the persistently inactive and those who became inactive than among those who were persistently active. Overall, the inactive participants gained 1.4 kg/m(2) [95% confidence interval (CI) 1.2 to 1.7] more in weight than did the active participants from 1975 to 2011. Among twin pairs discordant for LTPA, the corresponding difference was 1.4 kg/m(2) (95% CI 0.83 to 2.0) in dizygotic pairs and 0.68 kg/m(2) (95% CI 0.05 to1.3) in monozygotic pairs. Conclusions: Over a 35-year time span from young adulthood, persistently inactive participants and those who had become inactive had greater weight increases than those who were persistently active. This association was also found in twin-pair analyses, although attenuated in monozygotic pairs. This may support the importance of LTPA in weight management, although further causal inference is required.Peer reviewe

Objectively measured physical activity profile and cognition in Finnish elderly twins

Introduction We studied whether objectively measured physical activity (PA) and sedentary behavior (SB) are associated with cognition in Finnish elderly twins. Methods This cross-sectional study comprised twins born in Finland from 1940 to 1944 in the Older Finnish Twin Cohort (mean age, 72.9 years; 726 persons). From 2014 to 2016, cognition was assessed with a validated telephonic interview, whereas PA was measured with a waist-worn accelerometer. Results In between-family models, SB and light physical activity had significant linear associations with cognition after adjusting for age, sex, wearing time, education level, body mass index, and living condition (SB: β-estimate, −0.21 [95% confidence intervals, −0.42 to −0.003]; light physical activity: β-estimate, 0.30 [95% confidence intervals, 0.02–0.58]). In within-family models, there were no significant linear associations between objectively measured PA and cognition. Discussion Objectively measured light physical activity and SB are associated with cognition in Finnish twins in their seventies, but the associations were attributable to genetic and environmental selection.Peer reviewe

Chronic diseases and objectively monitored physical activity profile among aged individuals - a cross-sectional twin cohort study

Introduction: High physical activity (PA) at old age indicates good functional capacity enabling independent living. We investigated how different disease conditions are associated with measured PA indicators in old women and men, and whether they recognize this association. Materials and methods: This cross-sectional twin cohort study in Finland comprised 779 individuals (276 complete twin pairs, including 117 monozygotic pairs), who participated in hip-worn accelerometer monitoring of PA and responded to questions on diseases and mobility limitations at mean age of 73 (range 71-75). Results: Of the participants, 23.2% reported having a disease restricting mobility. With sex and age in the regression model, the reported disease restricting mobility explained 11.8% of the variation in moderate-to-vigorous PA (MVPA) and 10.4% of the variation in daily steps. Adding stepwise other self-reported diseases and body mass index to the model increased the explanatory power for MVPA up to 18.5% and 25.5%, and for daily steps up to 16.0% and 20.7%, respectively. In the co-twin control analysis the PA differences were smaller in disease-discordant monozygotic than dizygotic pairs. Conclusions: Chronic disease conditions are associated with low PA, which individuals may not always recognize. Shared genetic factors may explain part of the associations.Key messages Among community-dwelling older men and women one-fourth of the variation in objectively measured moderate-to-vigorous physical activity is accounted for by age, sex, body mass index and self-reported diseases. Occurrence of chronic diseases is associated with low physical activity and individuals do not always recognize this. Healthcare professionals should pay attention to the low physical activity and mobility of individuals with chronic disease conditions before these result in limitations in independent living.Peer reviewe

Long-term leisure-time physical activity and other health habits as predictors of objectively monitored late-life physical activity - A 40-year twin study

Moderate-to-vigorous physical activity (MVPA) in old age is an important indicator of good health and functional capacity enabling independent living. In our prospective twin cohort study with 616 individuals we investigated whether long-term physical activity assessed three times, in 1975, 1982 and 1990 (mean age 48 years in 1990), and other self-reported health habits predict objectively measured MVPA measured with a hip-worn triaxial accelerometer (at least 10 hours per day for at least 4 days) 25 years later (mean age of 73 years). Low leisure-time physical activity at younger age, higher relative weight, smoking, low socioeconomic status, and health problems predicted low MVPA in old age in individual-based analyses (altogether explaining 20.3% of the variation in MVPA). However, quantitative trait modeling indicated that shared genetic factors explained 82% of the correlation between baseline and follow-up physical activity. Pairwise analyses within monozygotic twin pairs showed that only baseline smoking was a statistically significant predictor of later-life MVPA. The results imply that younger-age physical activity is associated with later-life MVPA, but shared genetic factors underlies this association. Of the other predictors mid-life smoking predicted less physical activity at older age independent of genetic factors.Peer reviewe

Association between education and future leisure-time physical inactivity: a study of Finnish twins over a 35-year follow-up

Peer reviewe

Chronic diseases and objectively monitored physical activity profile among aged individuals – a cross-sectional twin cohort study

Introduction: High physical activity (PA) at old age indicates good functional capacity enabling independent living. We investigated how different disease conditions are associated with measured PA indicators in old women and men, and whether they recognize this association.Materials and methods: This cross-sectional twin cohort study in Finland comprised 779 individuals (276 complete twin pairs, including 117 monozygotic pairs), who participated in hip-worn accelerometer monitoring of PA and responded to questions on diseases and mobility limitations at mean age of 73 (range 71–75).Results: Of the participants, 23.2% reported having a disease restricting mobility. With sex and age in the regression model, the reported disease restricting mobility explained 11.8% of the variation in moderate-to-vigorous PA (MVPA) and 10.4% of the variation in daily steps. Adding stepwise other self-reported diseases and body mass index to the model increased the explanatory power for MVPA up to 18.5% and 25.5%, and for daily steps up to 16.0% and 20.7%, respectively. In the co-twin control analysis the PA differences were smaller in disease-discordant monozygotic than dizygotic pairs.Conclusions: Chronic disease conditions are associated with low PA, which individuals may not always recognize. Shared genetic factors may explain part of the associations.</p

Objectively measured physical activity profile and cognition in Finnish elderly twins

Introduction: We studied whether objectively measured physical activity (PA) and sedentary behavior (SB) are associated with cognition in Finnish elderly twins.Methods: This cross-sectional study comprised twins born in Finland from 1940 to 1944 in the Older Finnish Twin Cohort (mean age, 72.9 years; 726 persons). From 2014 to 2016, cognition was assessed with a validated telephonic interview, whereas PA was measured with a waist-worn accelerometer.Results: In between-family models, SB and light physical activity had significant linear associations with cognition after adjusting for age, sex, wearing time, education level, body mass index, and living condition (SB: β-estimate, −0.21 [95% confidence intervals, −0.42 to −0.003]; light physical activity: β-estimate, 0.30 [95% confidence intervals, 0.02–0.58]). In within-family models, there were no significant linear associations between objectively measured PA and cognition.Discussion: Objectively measured light physical activity and SB are associated with cognition in Finnish twins in their seventies, but the associations were attributable to genetic and environmental selection.</p

FinnTwin16 : A Longitudinal Study from Age 16 of a Population-Based Finnish Twin Cohort

The purpose of this review is to provide a detailed and updated description of the FinnTwin16 (FT16) study and its future directions. The Finnish Twin Cohort comprises three different cohorts: the Older Twin Cohort established in the 1970s and the FinnTwin12 and FT16 initiated in the 1990s. FT16 was initiated in 1991 to identify the genetic and environmental precursors of alcoholism, but later the scope of the project expanded to studying the determinants of various health-related behaviors and diseases in different stages of life. The main areas addressed are alcohol use and its consequences, smoking, physical activity, overall physical health, eating behaviors and eating disorders, weight development, obesity, life satisfaction and personality. To date, five waves of data collection have been completed and the sixth is now planned. Data from the FT16 cohort have contributed to several hundred studies and many substudies, with more detailed phenotyping and collection of omics data completed or underway. FT16 has also contributed to many national and international collaborations.Peer reviewe