Prefabricados de micro-hormigón y su empleo como ligante hidráulico

Research was directed, in its early stage, towards the application of micro-concrete, compounds of industrial wastes or minerals which can be chemically reactivated, cement and water, in order to obtain paving and bricks. Subsequently, tests were started to use it as hydraulic binding for organic particles. Conglomerating resins with organic particles, proceeding from agriculture and the farming industry, has resulted in obtaining plates of mechanical resistance under the structural demands of construction, which are generally permeable and fire-spreading, and are only acceptable as materials for interior finish. In the quest for improving resistance and lowering costs, research has been undertaken to use pastes or hydraulic mortars to replace these resins, without the objective being achieved due to the low percentage of particles which these accept. On observing the physical qualities of micro-concrete, an attempt was made to test it as a hydraulic binding and obtain pre-casts for housing, Monolithic paving and bricks did not offer any advantages over traditional ones as far as resistance and cost were concerned; their application could only be justified on account of their better appearance in texture and coloring. Tiles in 20 x 20 cm to 30 X 30 cm modules with the same resistance work out at 51 % cheaper than traditional ones and bricks for walling turned out having conditions similar to those currently being mechanized. Panels obtained by using micro-concrete as a binding for sawn wood measuring 230 x 50 x 6 cm, resulted in structural modular elements that are easy to assemble and have thermal, acoustic and water-proof characteristics which comply with standards and costs less than similar ones of widest use in construction. Thus they constitute a new material, which, along with continued testing for other pre-casts, may improve the characteristics of those already known, particularly in cheap housing.La investigación estuvo destinada, en su primera parte, a la aplicación de micro-hormigones, compuestos de desechos industriales o minerales químicamente reactivables, cemento y agua, para obtener pavimentos y ladrillos. Posteriormente se iniciaron ensayos para emplearlo como ligante hidráulico de partículas orgánicas. El conglomerar con resinas partículas orgánicas, provenientes de la agricultura y la agro-industria, ha dado como resultado la obtención de placas de resistencias mecánicas bajo las exigencias estructurales de la edificación, comúnmente permeables y propagadoras del fuego, siendo sólo aceptables como materiales de terminación interior. En la búsqueda de mejorar resistencias y bajar costos, se ha ensayado ocupar pastas o morteros hidráulicos para reemplazar estas resinas, no llegando al objetivo por el bajo porcentaje de partículas que estos aceptan. Observando las cualidades físicas de los micro-hormigones, se intentó ensayarlo como ligante hidráulico y obtener prefabricados para viviendas. Los pavimentos monolíticos y ladrillos, en cuanto a resistencia y costo, no presentaron ventajas sobre los tradicionales. Se podría justificar su aplicación sólo por mejor aspecto de textura y colorido. Las baldosas en módulos de 20 x 20 cm, a 30 X 30 cm a iguales resistencias, resultante un costo 51 % menor a las tradicionales y los ladrillos para muros resultaron de condiciones similares a los mecanizados actuales. Los paneles obtenidos usando el micro-hormigón como ligante de aserrín de madera, de 230 x 50 x 6 cm, dieron como resultado elementos modulares estructurales, de fácil montaje y cualidades térmicas, acústicas e hidrófugas de acuerdo a las normas y a menor costo que sus similares más usados en la construcción, constituyendo así un material nuevo que, continuando en su ensayo para otros prefabricados, puede mejorar las características de los ya conocidos especialmente en viviendas económicas

Evolution over Time of Ventilatory Management and Outcome of Patients with Neurologic Disease∗

OBJECTIVES: To describe the changes in ventilator management over time in patients with neurologic disease at ICU admission and to estimate factors associated with 28-day hospital mortality. DESIGN: Secondary analysis of three prospective, observational, multicenter studies. SETTING: Cohort studies conducted in 2004, 2010, and 2016. PATIENTS: Adult patients who received mechanical ventilation for more than 12 hours. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among the 20,929 patients enrolled, we included 4,152 (20%) mechanically ventilated patients due to different neurologic diseases. Hemorrhagic stroke and brain trauma were the most common pathologies associated with the need for mechanical ventilation. Although volume-cycled ventilation remained the preferred ventilation mode, there was a significant (p < 0.001) increment in the use of pressure support ventilation. The proportion of patients receiving a protective lung ventilation strategy was increased over time: 47% in 2004, 63% in 2010, and 65% in 2016 (p < 0.001), as well as the duration of protective ventilation strategies: 406 days per 1,000 mechanical ventilation days in 2004, 523 days per 1,000 mechanical ventilation days in 2010, and 585 days per 1,000 mechanical ventilation days in 2016 (p < 0.001). There were no differences in the length of stay in the ICU, mortality in the ICU, and mortality in hospital from 2004 to 2016. Independent risk factors for 28-day mortality were age greater than 75 years, Simplified Acute Physiology Score II greater than 50, the occurrence of organ dysfunction within first 48 hours after brain injury, and specific neurologic diseases such as hemorrhagic stroke, ischemic stroke, and brain trauma. CONCLUSIONS: More lung-protective ventilatory strategies have been implemented over years in neurologic patients with no effect on pulmonary complications or on survival. We found several prognostic factors on mortality such as advanced age, the severity of the disease, organ dysfunctions, and the etiology of neurologic disease