Evaluation of key aggregate parameters on the properties of ordinary and high strength concretes

[EN] This paper reports the results of a study conducted to determine the influence of coarse aggregate type on the workability, compressive strength, and flexural strength of normal and high strength concretes with target 28-day compressive strengths of 30 and 60 MPa and two water/cement ratios of 0.44 and 0.27. The concretes were prepared using four types of natural coarse aggregates, namely diabase, calcareous, river gravel, and basalt, with maximum particle sizes of 12.7 and 19.1 millimeters. Silica fume was added to the high-strength concretes at a replacement ratio to Portland cement of 10% by mass. The results showed that among all aggregates, basaltic aggregate with a maximum particle size of 12.7 millimeters produced concrete with the highest compressive and flexural strength, followed by limestone and river aggregate, indicating that particle size, surface texture, structure and mineralogical composition play a dominant role in the behavior of concretes, especially high strength concretes. Normal strength concretes showed similar compressive strengths, while the concrete containing limestone gave slightly higher strength. These results show that for a given water/cementitious material ratio, the influence of the type of coarse aggregate on the compressive strength of the concrete is more important for high strength concrete than for normal strength concrete.Salas-Montoya, A.; Mira-Rada, BE. (2023). Evaluation of key aggregate parameters on the properties of ordinary and high strength concretes. VITRUVIO - International Journal of Architectural Technology and Sustainability. 8:76-85. https://doi.org/10.4995/vitruvio-ijats.2023.195967685

Evaluation of key aggregate parameters on the properties of ordinary and high strength concretes

This paper reports the results of a study conducted to determine the influence of coarse aggregate type on the workability, compressive strength, and flexural strength of normal and high strength concretes with target 28-day compressive strengths of 30 and 60 MPa and two water/cement ratios of 0.44 and 0.27. The concretes were prepared using four types of natural coarse aggregates, namely diabase, calcareous, river gravel, and basalt, with maximum particle sizes of 12.7 and 19.1 millimeters. Silica fume was added to the high-strength concretes at a replacement ratio to Portland cement of 10% by mass. The results showed that among all aggregates, basaltic aggregate with a maximum particle size of 12.7 millimeters produced concrete with the highest compressive and flexural strength, followed by limestone and river aggregate, indicating that particle size, surface texture, structure and mineralogical composition play a dominant role in the behavior of concretes, especially high strength concretes. Normal strength concretes showed similar compressive strengths, while the concrete containing limestone gave slightly higher strength. These results show that for a given water/cementitious material ratio, the influence of the type of coarse aggregate on the compressive strength of the concrete is more important for high strength concrete than for normal strength concrete

Molecular, Neuronal, and Behavioral Effects of Ethanol and Nicotine Interactions

Ethanol and nicotine can modulate the activity of several neurotransmitter systems and signalling pathways. Interactions between ethanol and nicotine can also occur via common molecular targets including nicotinic acetylcholine receptors (nAChRs). These effects can induce molecular and synaptic adaptations that over time, are consolidated in brain circuits that reinforce drug-seeking behavior, contribute to the development of withdrawal symptoms during abstinence and increase the susceptibility to relapse. This chapter will discuss the acute and chronic effects of ethanol and nicotine within the mesolimbic reward pathway and brain circuits involved in learning, memory, and withdrawal. Individual and common molecular targets of ethanol and nicotine within these circuits are also discussed. Finally, we review studies that have identified potential molecular and neuronal processes underlying the high incidence of ethanol and nicotine co-use that may contribute to the development of ethanol and nicotine co-addiction

Potato consumption does not increase blood pressure or incident hypertension in 2 cohorts of Spanish adults

5 TablasBackground: Potatoes have a high glycemic load but also antioxidants, vitamins, and minerals. It is unclear what mechanisms are involved in relation to their effect on blood pressure (BP) and hypertension. Objectives: This study aimed to assess the association between potato consumption, BP changes, and the risk of hypertension in 2 Spanish populations. Methods: Separate analyses were performed in PREDIMED (PREvención con DIeta MEDiterránea), a multicenter nutrition intervention trial of adults aged 55-80 y, and the SUN (Seguimiento Universidad de Navarra) project, a prospective cohort made up of university graduates and educated adults with ages (means±SDs) of 42.7±13.3 y for men and 35.1± 10.7 y for women. In PREDIMED, generalized estimating equations adjusted for lifestyle and dietary characteristics were used to assess changes in BP across quintiles of total potato consumption during a 4-y follow-up. Controlled BP values (systolic BP < 140 mm Hg and diastolic BP < 90 mm Hg) during follow-up were also assessed. For SUN, multivariateadjusted HRs for incident hypertension during a mean 6.7-y follow-up were calculated. Results: In PREDIMED, the total potato intake was 81.9 ± 40.6 g/d. No overall differences in systolic or diastolic BP changes were detected based on consumption of potatoes. For total potatoes, the mean difference in change between quintile 5 (highest intake) and quintile 1 (lowest intake) in systolic BP after multivariate adjustment was 20.90 mm Hg (95% CI: -2.56, 0.76 mm Hg; P-trend = 0.1) and for diastolic BP was 20.02 mm Hg (95% CI: -0.93, 0.89 mm Hg; P-trend = 0.8). In SUN, the total potato consumption was 52.7 ± 33.6 g/d, and no significant association between potato consumption and hypertension incidence was observed in the fully adjusted HR for total potato consumption (quintile 5 compared with quintile 1: 0.98; 95% CI: 0.80, 1.19; P-trend = 0.8). Conclusions: Potato consumption is not associated with changes over 4 y in blood pressure among older adults in Spain or with the risk of hypertension among Spanish adults.Supported by the official funding agency for biomedical research of the Spanish Government, Instituto de Salud Carlos III through grants provided to research networks specifically developed for the trial (RTIC G03/140, to RE; RTIC RD 06/0045, to MAM-G) and through Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBERobn), and by grants from Centro Nacional de Investigaciones Cardiovasculares (CNIC 06/2007), Fondo de Investigación Sanitaria–Fondo Europeo de Desarrollo Regional [Proyecto de Investigación (PI) 04-2239, PI 05/2584, CP06/00100, PI07/0240, PI07/1138, PI07/0954, PI 07/0473, PI10/01407, PI10/02658, PI11/01647, P11/02505 and PI13/00462], Ministerio de Ciencia e Innovación [Recursos y teconologia agroalimentarias (AGL)-2009-13906-C02 and AGL2010-22319-C03 and AGL2013-49083-C3-1-R], Fundación Mapfre 2010, the Consejería de Salud de la Junta de Andalucía (PI0105/2007), the Public Health Division of the Department of Health of the Autonomous Government of Catalonia, Generalitat Valenciana [Generalitat Valenciana Ayuda Complementaria (GVACOMP) 06109, GVACOMP2010-181, GVACOMP2011-151], Conselleria de Sanitat y AP; Atención Primaria (CS) 2010-AP-111 and CS2011-AP-042, and Regional Government of Navarra (P27/2011)