681 research outputs found
Alkali release from aggregates in long-service concrete structures. Laboratory test evaluation and ASR prediction
Il lavoro propone un semplice modello per la previsione dello sviluppo di espansione deleteria da reazione alcali-silice (ASR) in strutture di calcestruzzo progettate per lunga vita di servizio. Il modello è basato su parametri di composizione e di reattività legati alla ASR, compreso il contributo in alcali a lungo termine da parte degli aggregati. Questo contributo è stato stimato attraverso una prova di estrazione di laboratorio, appositamente sviluppata con lo scopo di massimizzare il rilascio in tempi di prova relativamente brevi e con basso rapporto soluzione lisciviante/aggregato. Il metodo di prova proposto è basato sullo standard italiano riportato nella norma UNI 11417-2 e consiste nel sottoporre l'aggregato a lisciviazione con una soluzione satura di idrossido di calcio a 105°C, in autoclave. Sono stati sottoposti a prova nove aggregati (sette sabbie e due aggregati grossi), il rapporto in peso lisciviante/aggregato era pari a 0,6, il rapporto Ca(OH)2 solida/aggregato era pari a 0,05 ed il tempo di prova 120 ore. I risultati delle prove sono stati utilizzati nel modello di previsione dell'espansione deleteria a lungo termine, ottenendo delle previsioni del tutto congruenti con le informazioni sul comportamento reale dei materiali, nonché con le raccomandazioni riportate nel CEN/TR 16349:2012.This paper proposes a simple model for predicting the development of deleterious expansion from alkali-silica reaction (ASR) in long-service concrete structures. This model is based on some composition and reactivity parameters related to ASR, including the long-term alkali contribution by aggregates to concrete structures. This alkali contribution was estimated by means of a laboratory extraction test, appositely developed in this study in order to maximize the alkali extraction within relatively short testing times and with low leaching solution/aggregate ratios. The proposed test is a modification of the Italian Standard test method UNI 11417-2 (Ente Nazionale Italiano di Normazione) and it consists of subjecting an aggregate sample to leaching with saturated calcium hydroxide solution in a laboratory autoclave at 105 degrees C. Nine natural ASR-susceptible aggregates (seven sands and two coarse aggregates) were tested and the following optimized test conditions were found: leaching solution/aggregate weight ratio = 0.6; solid calcium hydroxide/aggregate weight ratio = 0.05; test duration = 120 h. The results of the optimized alkali extraction tests were used in the proposed model for predicting the potential development of long-term ASR expansion in concrete dams. ASR predictions congruent with both the field experience and the ASR prevention criteria recommended by European Committee for Standardization Technical Report CEN/TR 16349: 2012 were found, thus indicating the suitability of the proposed model
Residual capability of alkali binding by hydrated pozzolanic cements in long-service concrete structures
An experimental procedure was developed and applied to cement pastes made with two different pozzolanic cements (CEM IV/B (P) and CEM IV/B (V)) in order to ascertain the existence of a residual capability of alkali binding by long-term hydrated pozzolanic cements and, at the same time, to evaluate the alkali retention capability and the concentration of OH- ions in the pore solution of such cementitious matrices. The developed procedure consisted of accelerated curing of cement paste specimens (150 days at 60°C and 100% RH), subsequent leaching tests at 60°C for 30 days by using deionized water or basic solutions (NaOH or KOH at different concentrations) as leaching media, and correlation of the leaching test results with a simple mass balance equation for sodium and potassium ions. The developed procedure was found to be appropriate for evaluating both the pore liquid alkalinity and the alkali retention capability by long-term hydrated pozzolanic cement pastes. A residual capability of alkali binding was also identified for both tested pozzolanic cements, thus indicating their potential ability to prevent (CEM IV/B (V)) or minimize (CEM IV/B (P)) the risk of deleterious expansion associated to alkali-aggregate reaction in long-service concrete structures, like concrete dams
Desarrollo de señalética sustentable
A partir de técnicas sustentables se desarrolló una placa con desechos de denim del sector confeccionista de la ciudad de Pergamino. El material obtenido se utilizó para realizar la señalética del edificio Presidente Raúl R. Alfonsín de la UNNOBA. Condicionando los procesos de producción a los requerimientos estéticos propuestos por el CEDi CCentro de Edición y Diseño) de la universidad.Área: Ciencias Sociales y Humana
Urine sampling and collection system
This specification defines the performance and design requirements for the urine sampling and collection system engineering model and establishes requirements for its design, development, and test. The model shall provide conceptual verification of a system applicable to manned space flight which will automatically provide for collection, volume sensing, and sampling of urine
Automated biowaste sampling system urine subsystem operating model, part 1
The urine subsystem automatically provides for the collection, volume sensing, and sampling of urine from six subjects during space flight. Verification of the subsystem design was a primary objective of the current effort which was accomplished thru the detail design, fabrication, and verification testing of an operating model of the subsystem
Automated biowaste sampling system improved feces collection, mass measurement and sampling
The capability of the basic automated Biowaste Sampling System (ABSS) hardware was extended and improved through the design, fabrication and test of breadboard hardware. A preliminary system design effort established the feasibility of integrating the breadboard concepts into the ABSS
The dimensional analysis of the bricks. The case study of Lucera between the thirteenth and fourteenth century
In a project aimed to the historic reconstruction of the medieval landscape of Capitanata,
particularly of fortified sites, the swabian – angevin fortification of Lucera was the subject of
targeted archaeological investigation in order to identify the material parameters present in
the walls. This investigation allowed to outline the production dynamics, in relation to the
resources of 'landscape', the design choices, and the social and cultural implications of the
building work organization. The dimensional analysis carried out on the brick buildings in the
center of Lucera has contributed to identify the role that the Angevin fortification may have
played in the development of reactivated clay cycle. It also helped to focus on typical
relationship between dimensional features and production, circulation and use of bricks,
starting from to late middle age to early modern age
Postemergence Control of Palmer Amaranth with Mesotrione-Based Herbicide Mixtures and the Impact of Lactofen and Planting Date on the Growth, Development, and Yield of Indeterminate Soybean
Research was conducted in 2013 and 2014 to evaluate the postemergence control of Palmer amaranth [Amaranthus palmeri (S.) Wats.] with mesotrione alone and in mixtures with fomesafen and/or glyphosate and to evaluate the impact of lactofen and planting date on growth, development, and yield of indeterminate soybean [Glycine max (L.) Merr.]. Studies included a greenhouse evaluation of different rates of mesotrione on the control of 5- and 10-cm Palmer amaranth and field studies evaluating the control of 5- to 10-cm Palmer amaranth with three rates of mesotrione applied alone and in mixtures with fomesafen and/or glyphosate. Lactofen studies include a planting date study evaluating one rate of lactofen applied at V2 soybean stage with planting dates of April 15, May 1, May 15, and June 1 and a lactofen timing study where one rate of lactofen was applied at soybean growth stages ranging from V1 to R5
Automated biowaste sampling system, solids subsystem operating model, part 2
The detail design and fabrication of the Solids Subsystem were implemented. The system's capacity for the collection, storage or sampling of feces and vomitus from six subjects was tested and verified
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