Chromate and amine contact allergies in workers manufacturing precast concrete elements

2016 ◽  
Vol 75 (6) ◽  
pp. 363-369 ◽  
Author(s):  
Martin Mowitz ◽  
Erik Zimerson ◽  
Inese Hauksson ◽  
Ann Pontén
Keyword(s):  
Precast Concrete ◽  
Concrete Elements

scholarly journals Modified mortar pad behavior in the transfer of compressive stresses

2016 ◽  
Vol 9 (3) ◽  
pp. 414-434
Author(s):  
J. D. Ditz ◽  
M. K. EL Debs ◽  
G. H. Siqueira
Keyword(s):  
Precast Concrete ◽  
Concrete Strength ◽  
Compressive Load ◽  
Stress Transfer ◽  
Compressive Stresses ◽  
Bonded Phase ◽  
Concrete Blocks ◽  
Load Tests ◽  
Styrene Butadiene ◽  
Concrete Elements

ABSTRACT This research aims to analyze the compressive stress transfer between precast concrete elements using cement mortar pads modified with polypropylene fibers, styrene-butadiene latex and heat-expanded vermiculite. The stress transfer analyses are performed interleaving a cementbearing pad between two concrete blocks, subjecting the entire specimen to different compressive load tests. The parameters analyzed in the tests are: surface roughness (using bosses on the bonded phase of different thicknesses), compressive strength with monotonic and cyclic loadings. The main results obtained in this study are: a) the presence of pad increased the strength in 24% for thicknesses of imperfections of 0.5 mm and approximately 12% for smooth faces blocks; b) gain of effectiveness of the bearing pad when the concrete strength was reduced; c) for cyclic loading, the bearing pad increased in 48% the connections strength.

Effect of Fly Ash and Activator on Performance of Steam-Cured Concrete

2010 ◽  
Vol 113-116 ◽  
pp. 1013-1016 ◽  
Author(s):  
Zhi Min He ◽  
You Jun Xie ◽  
Guang Cheng Long ◽  
Jun Zhe Liu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Precast Concrete ◽  
Early Age ◽  
Flexure Strength ◽  
Concrete Elements ◽  
Chemical Activator

In precast concrete elements manufacturing, steam-cured concrete incorporating 30% fly ash encountered the problem of a too low demoulding compressive strength. To resolve it, this paper developed a new steam-cured concrete (AFSC) incorporating fly ash and a chemical activator. Experiments were conducted to investigate the mechanical properties of AFSC. The corresponding mechanism was also discussed by testing the microstructure of concrete. Results indicate that the demoulding compressive strength of AFSC can meet production requirements, and compressive and flexure strength of AFSC at later ages increase well. Compared with that of ordinary steam-cured concrete, AFSC has a higher tensile strength, and the capability of AFSC to resist cracks is enhanced remarkably. At an early age, addition of the chemical activator can distinctly accelerate the extent of hydration of the fly ash cement systems, and thus the microstructure of concrete becomes denser.

Connections in Precast Concrete Elements

2016 ◽  
Vol 691 ◽  
pp. 376-387 ◽  
Author(s):  
Ivan Hollý ◽  
Ivan Harvan
Keyword(s):  
Structural Integrity ◽  
Precast Concrete ◽  
Concrete Structures ◽  
Structural Elements ◽  
Entire Structure ◽  
Engineering Department ◽  
Final Design ◽  
Structural Engineer ◽  
Concrete Elements

The structural integrity of precast concrete structures depends mainly on the connections between the precast structural elements. The purpose of a connection is to transfer loads, restrain movement, and/or to provide stability to a component or an entire structure. Therefore, the design of connections is one of the most important aspects in the design of precast concrete structures. All connections should design with valid codes. Every precasters have developed connection details over the years that suit their particular production and erection preferences. It is common, that the structural engineer to show loads and connection locations and allow the successful manufacturer’s engineering department to provide the final design and details of the connections.

scholarly journals Evaluación de elementos premoldeados de hormigón utilizados en instalaciones de crianza de ganado porcino en ambiente agresivo. Recomendaciones de fabricación

2013 ◽  
Vol 3 (2) ◽  
pp. 140-148
Author(s):  
M. Positieri ◽  
C. Baronetto ◽  
B. Raggiotti
Keyword(s):  
Ultrasonic Wave ◽  
Precast Concrete ◽  
Capillary Absorption ◽  
Aggressive Environment ◽  
Compression Speed ◽  
Intensive Rearing ◽  
Service Conditions ◽  
Precast Elements ◽  
Concrete Elements

RESUMENLas modernas instalaciones destinadas a la crianza intensiva de ganado porcino se construyen con elementos premoldeados de hormigón ensamblados in situ en grandes superficies techadas; están sujetas a un ambiente agresivo por los excrementos y vapores que el ganado porcino produce, produciéndose un recambio prematuro de piezas por la escasa durabilidad de las mismas. El trabajo presenta los resultados del estudio realizado sobre elementos premoldeados de hormigón (sin uso) que conforman la estructura, con el objetivo de verificar su comportamiento en las condiciones de servicio y realizar recomendaciones para asegurar su correcto desempeño. Se extrajeron testigos de las piezas y se midieron la resistencia a compresión, velocidad de pasaje de onda ultrasónica, absorción capilar, absorción y permeabilidad al aire. Los resultados obtenidos permiten calificar al hormigón entre regular y bueno y se presentan las recomendaciones que deberían considerarse al fabricar los elementos premoldeados para asegurar su durabilidad.Palabras Clave: hormigón; premoldeados; durabilidad; calidad; testigos.ABSTRACTThe modern installations for the intensive rearing of pigs are constructed based on precast concrete elements that are assembled on site in large areas covered and which are subject to an aggressive environment and in the feces they produce vapors, causing a premature replacement of parts by the low durability of the same. The paper presents the results of a study on precast concrete (unworn) that make up the structure in order to verify its performance in service conditions and make recommendations to assure its correct performance. Witnesses were extracted from the parts and measured the resistance to compression, speed of passage of the ultrasonic wave, capillary absorption, absorption and permeability to air. The results obtained allow us to qualify to the concrete between regular and good and presents the recommendations should be considered when manufacturing the precast elements to ensure their durability.Keywords: concrete; precast; durability; quality; witnesses.

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