scholarly journals Diagnostic Reliability in the Assessment of Degradation in Precast Concrete Elements

2021 ◽  
Vol 6 (11) ◽  
pp. 164
Author(s):  
Antonio Bossio ◽  
Giuseppe Faella ◽  
Giorgio Frunzio ◽  
Mariateresa Guadagnuolo ◽  
Roberto Serpieri
Keyword(s):  
Precast Concrete ◽  
Construction Material ◽  
Concrete Strength ◽  
Research Area ◽  
Past Century ◽  
Concrete Core ◽  
Diagnostic Reliability ◽  
Core Sampling ◽  
Long Span ◽  
Concrete Elements

In the past century, precast reinforced concrete has become the most widely used construction material in infrastructure engineering, especially for long-span structures. Nowadays, a growing research area concerns the assessment of concrete strength degradation due to environmental exposure and reinforcement corrosion. This paper reports an experimental campaign on some prefabricated concrete elements that were exposed to atmospheric agents for approximately 20 years. The campaign took the uncommon opportunity to access the full inspection and sampling of rebar. The included activities had different invasiveness and encompassed inspections, core sampling, corrosion potential mapping, compressive strength tests, as well as neutralization depth assays on cored surfaces, on chisel-split surfaces, and on drilling powders. The results bring together a global diagnostic picture of very limited degradation and of elements that are fully able to attend their design service life; the latter is estimated to be considerably higher than 20 years and to exceed 75 years if the concrete mix does not show quality issues. Results also permit drawing considerations on a hierarchy of diagnostic reliability in the evaluation of RC degradation, in which concrete core sampling plays the role of golden standard.

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.

scholarly journals Effects of Concrete Core Technological Defects on the Strength of Tube Confined Concrete Elements

2018 ◽  
Vol 7 (3.2) ◽  
pp. 376
Author(s):  
Oleksandr Semko ◽  
Olga Gukasian ◽  
Serhii Skliarenko
Keyword(s):  
Concrete Strength ◽  
Experimental Studies ◽  
Fracture Pattern ◽  
Confined Concrete ◽  
Concrete Core ◽  
Different Types ◽  
Technological Defects ◽  
Concrete Elements ◽  
Core Production ◽  
Physical And Mechanical Characteristics

The paper sums up a series of experimental studies describing the influence of most types of concreting common defects, such as core weakening: weak compression inclusions, voids, height heterogeneity of concrete. The basis of the experimental study is the research on the concrete core production conditions influence on tube confined concrete elements and the change in physical and mechanical characteristics of the elements. The concrete strength is estimated based on the results of the study of specially shaped samples with given dimensions. According to the results of concreting samples with different types of modeled defects (abnormalities) inspection, the most dangerous damages of the concrete core were identified and different variants of the height strength retrogression of the elements under study were analyzed. As a result, the degree and type of damage to the tube confined concrete elements core of the samples, which affect the fracture pattern, was established. 

scholarly journals Choice Recommendations for Rational Concreting Technology of Steel Reinforced Concrete Structures

2018 ◽  
Vol 7 (3.2) ◽  
pp. 275
Author(s):  
Тatiana Nikiforova ◽  
Olga Gukasian ◽  
Nataliia Mahas
Keyword(s):  
Reinforced Concrete ◽  
Experimental Research ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Work Conditions ◽  
Reinforced Concrete Structures ◽  
Concrete Core ◽  
Steel Reinforced Concrete ◽  
Research Cycle ◽  
Concrete Elements

In this work the experimental research cycle is described. This cycle is an affect studying of the most widespread concrete defect types, such as concrete core weakening is an inclusion of the "weak" concrete, the presence of emptiness, concrete heterogeneous by the height. The research of the manufacturing conditions affect of combine concrete core structures and the elements of physical and mechanical characteristics changing are on the experimental research base. On the researches testing base of samples with special form and given sizes the concrete strength value is appreciated. The different variants of strength decreasing on the researched element height are analyzed by the conducted testing results of the steel reinforced concrete structures. As a result of the conducted tests, the work conditions coefficient and the steel reinforced concrete elements concreting technology were formulated.  

scholarly journals COMPARISON OF CONCRETE COMPRESSIVE STRENGTH VALUES OBTAINED USING REBOUND HAMMER AND DRILLED CORE SPECIMENS

2015 ◽  
Author(s):  
Raimondas SADZEVICIUS ◽  
Tatjana SANKAUSKIENE ◽  
Petras MILIUS
Keyword(s):  
Reinforced Concrete ◽  
Concrete Strength ◽  
Hydraulic Structures ◽  
Test Results ◽  
Concrete Compressive Strength ◽  
Main Attention ◽  
Concrete Core ◽  
Rebound Hammer ◽  
Concrete Elements ◽  
Non Destructive

Durability of reinforced concrete structures depends on the maintenance conditions, surveillance, and well-timed repair of structures or reconstructions. Usually, the main attention falls on the durability determination based on the evaluation of change of main physical –mechanical properties, especially, on the compression strength of concrete. In this study, tests with the rebound hammer and concrete cores extracted from the existing reinforced concrete elements in hydraulic structures are presented. The comparison of strength values obtained with the rebound hammer and the concrete core specimens of reinforced concrete in hydraulic structures is carried out. The research was performed during the scientific expedition in the period of 2010–2014. The investigated objects are allocated in hydroschemes of Druskininkai, Marijampolė, Klaipėda districts. It was established that the results obtained using the non-destructive method were by 17 % higher than the ones obtained by performing the destructive test. However, it can be said that despite this fact, the non-destructive method offers simplicity and rapidity in use: test results are readily available on site and there is a possibility to test concrete strength of those structures where cores cannot be drilled due to thin-walled or densely reinforced structures.

Precast Core Wall System for High-Rise Buildings

2019 ◽  
Author(s):  
Juan E. Carrion ◽  
William F. Baker ◽  
Charles Besjak
Keyword(s):  
New York ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Attractive Alternative ◽  
Lateral Loads ◽  
Concrete Core ◽  
High Rise ◽  
The Core ◽  
Steel Shapes ◽  
Wall System

<p>The design of high-rise buildings is usually governed by lateral forces (e.g., wind or seismic). One of the most efficient structural systems to resist lateral loads is the core wall system. Traditionally high-rise concrete cores have been constructed using cast-in-place concrete, however precast systems offer an attractive alternative to cast-in-place construction. A precast concrete core wall system has been developed for high-rise buildings and will be presented in this paper. The main components of the system are the core walls, which are composed of multiple precast panels. The panel layout is determined based on the geometry of the tower and the capacity of the transportation and lifting equipment, while the wall thickness, concrete strength, and reinforcement are determined to satisfy strength and serviceability requirements. Several methods for connecting the panels have been developed, including combinations of embedded steel shapes, bolts, welds, and continuous reinforcing bars or post-tensioning. An application of the system to a 296 m (972 feet) tower in New York City is presented in this paper. This application demonstrates that the precast core wall system is an attractive and viable alternative to cast-in-place construction, capable of resisting the large forces associated with high-rise buildings, and with several advantages, including speed of erection, cost, as well as the high quality of precast concrete.</p>

Flexural Resistance of Steel-Coconut Shell Concrete-Steel Composite Beam with Normal and J-Hook Shear Studs

2020 ◽  
Vol 12 (9) ◽  
Author(s):  
Lakshmi Thangasamy ◽  
◽  
Gunasekaran Kandasamy ◽  
Keyword(s):  
Concrete Strength ◽  
Steel Plates ◽  
Coconut Shell ◽  
Core Material ◽  
River Sand ◽  
Concrete Core ◽  
Conventional Concrete ◽  
Moment Capacity ◽  
The Moment ◽  
Core Concrete

Many researches on double skin sandwich having top and bottom steel plates and in between concrete core called as steel-concrete-steel (SCS) were carried out by them on this SCS type using with different materials. Yet, use of coconut shell concrete (CSC) as a core material on this SCS form construction and their results are very limited. Study investigated to use j-hook shear studs under flexure in the concept of steel-concrete-steel (SCS) in which the core concrete was CSC. To compare the results of CSC, the conventional concrete (CC) was also considered. To study the effect of quarry dust (QD) in its place of river sand (RS) was also taken. Hence four different mixes two without QD and two with QD both in CC and CSC was considered. The problem statement is to examine about partial and fully composite, moment capacity, deflection and ductility properties of CSC used SCS form of construction. Core concrete strength and the j-hook shear studs used are influences the moment carrying capacity of the SCS beams. Use of QD in its place of RS enhances the strength of concrete produced. Deflections predicted theoretically were compared with experimental results. The SCS beams showed good ductility behavior.

scholarly journals Influence of Rapid Heat Treatment on the Shrinkage and Strength of High-Performance Concrete

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4102
Author(s):  
Jan Stindt ◽  
Patrick Forman ◽  
Peter Mark
Keyword(s):  
Heat Treatment ◽  
High Performance ◽  
High Performance Concrete ◽  
Treatment Time ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Shrinkage Strain ◽  
Temperature Treatment ◽  
Production Flow ◽  
Steel Fibres

Resource-efficient precast concrete elements can be produced using high-performance concrete (HPC). A heat treatment accelerates hardening and thus enables early stripping. To minimise damages to the concrete structure, treatment time and temperature are regulated. This leads to temperature treatment times of more than 24 h, what seems too long for quick serial production (flow production) of HPC. To overcome this shortcoming and to accelerate production speed, the heat treatment is started here immediately after concreting. This in turn influences the shrinkage behaviour and the concrete strength. Therefore, shrinkage is investigated on prisms made from HPC with and without steel fibres, as well as on short beams with reinforcement ratios of 1.8% and 3.1%. Furthermore, the flexural and compressive strengths of the prisms are measured directly after heating and later on after 28 d. The specimens are heat-treated between 1 and 24 h at 80 °C and a relative humidity of 60%. Specimens without heating serve for reference. The results show that the shrinkage strain is pronouncedly reduced with increasing temperature duration and rebar ratio. Moreover, the compressive and flexural strength decrease with decreasing temperature duration, whereby the loss of strength can be compensated by adding steel fibres.

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 Experimental Study of a New Precast Prestressed Concrete Joint

2018 ◽  
Vol 8 (10) ◽  
pp. 1871 ◽  
Author(s):  
Xueyuan Yan ◽  
Suguo Wang ◽  
Canling Huang ◽  
Ai Qi ◽  
Chao Hong
Keyword(s):  
Energy Dissipation ◽  
Seismic Performance ◽  
Prestressed Concrete ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Frame Structure ◽  
Loading Test ◽  
Concrete Frame ◽  
Concrete Joints ◽  
Precast Prestressed Concrete

Precast monolithic structures are increasingly applied in construction. Such a structure has a performance somewhere between that of a pure precast structure and that of a cast-in-place structure. A precast concrete frame structure is one of the most common prefabricated structural systems. The post-pouring joint is important for controlling the seismic performance of the entire precast monolithic frame structure. This paper investigated the joints of a precast prestressed concrete frame structure. A reversed cyclic loading test was carried out on two precast prestressed concrete beam–column joints that were fabricated with two different concrete strengths in the keyway area. This testing was also performed on a cast-in-place reinforced concrete joint for comparison. The phenomena such as joint crack development, yielding, and ultimate damage were observed, and the seismic performance of the proposed precast prestressed concrete joint was determined. The results showed that the precast prestressed concrete joint and the cast-in-place joint had a similar failure mode. The stiffness, bearing capacity, ductility, and energy dissipation were comparable. The hysteresis curves were full and showed that the joints had good energy dissipation. The presence of prestressing tendons limited the development of cracks in the precast beams. The concrete strength of the keyway area had little effect on the seismic performance of the precast prestressed concrete joints. The precast prestressed concrete joints had a seismic performance that was comparable to the equivalent monolithic system.

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