scholarly journals Comparison of Analytical Methods for Estimation of Early-Age Thermal-Shrinkage Stresses in RC Walls

2013 ◽  
Vol 59 (1) ◽  
pp. 97-117 ◽  
Author(s):  
B. Klemczak ◽  
A. Knoppik-Wróbel
Keyword(s):  
Thermal Shrinkage ◽  
Engineering Practice ◽  
Early Age ◽  
Concrete Element ◽  
University Of Technology ◽  
Wide Range ◽  
Early Age Concrete ◽  
The Comparative Study ◽  
Analytical Approaches ◽  
Concrete Elements

Abstract The volume changes caused by coupled temperature and moisture variations in early-age concrete elements lead to formation of stresses. If a restraint exists along the contact surface of mature concrete against which a new concrete element has been cast, generated stresses are mostly of a restraint origin. In engineering practice a wide range of externally restrained concrete elements can be distinguished such as tank walls or bridge abutments cast against an old set foundation, in which early-age cracking may endanger their durability or functionality. Therefore, for years methods were being developed to predict early-age stresses and cracking risk of externally restrained concrete elements subjected to early-age thermal-moisture effects. The paper presents the comparative study of the most recognised analytical approaches: the method proposed in EC2, the method proposed by ACI Committee 207 and the method developed at the Luleå University of Technology.

Monitoring of concrete curing using the electromechanical impedance technique: review and path forward

2019 ◽  
pp. 147592171989306 ◽  
Author(s):  
Yee Yan Lim ◽  
Scott T Smith ◽  
Ricardo Vasquez Padilla ◽  
Chee Kiong Soh
Keyword(s):  
State Of The Art ◽  
Research Field ◽  
Strength Development ◽  
Early Age ◽  
Remote Monitoring System ◽  
Electromechanical Impedance ◽  
Wide Range ◽  
Impedance Technique ◽  
Technology Modeling ◽  
Early Age Concrete

The ability to monitor the strength development of early-age concrete is an important capability in the laboratory and in the field. Accurate and reliable in situ measurements can inform the appropriate time for removal of formwork and loading of structural elements, as well as determination of batch quality. The piezoelectric-based electromechanical impedance technique is emerging as a viable option for such monitoring needs. The first research articles on the topic started to appear in 2005, and since then, the research field has advanced and has grown in popularity. This article therefore presents the first state-of-the-art review of the topic to date. In this article, existing research is reviewed and sorted into key themes while critical developments as well as knowledge gaps are identified. The topics addressed range from miniaturization of hardware, methods of installation, incorporation of wireless technology, modeling, data interpretation, signal processing, influence of curing, and environmental conditions to a wide range of other practical issues. Previous studies have indicated that the electromechanical impedance technique has the potential to be developed into an autonomous and remote monitoring system, capable of predicting the strength development of early-age concrete structures in real time. An end game is therefore the realization of this capability. Appropriate comments are therefore also provided in this article about this goal. Researchers interested in venturing into this research area shall find this article a useful introduction as well as a state-of-the-art assessment. In addition, the identified research gaps can inform projects for more experienced research teams.

Effect of Very Early Prestressing on Ultimate Geometry of Precast Concrete Element

2016 ◽  
Vol 677 ◽  
pp. 49-52
Author(s):  
Lukáš Černosta ◽  
Petr Štemberk
Keyword(s):  
Experimental Investigation ◽  
Bearing Capacity ◽  
Precast Concrete ◽  
Small Scale ◽  
Early Age ◽  
Concrete Element ◽  
Load Bearing Capacity ◽  
Shrinkage And Creep ◽  
T Beam ◽  
Concrete Elements

This paper describes an experimental investigation of the effect of early age prestressing on the ultimate geometry and the load bearing capacity of precast concrete elements. The experimental is performed with a small-scale T-beam which are prestress at three different ages. The experimental results obtained after seven days after prestressing are compared with calculated estimations on the shrinkage and creep according to B3 model.

Very early age concrete hydration characterization monitoring using piezoceramic based smart aggregates

2013 ◽  
Vol 22 (8) ◽  
pp. 085025 ◽  
Author(s):  
Qingzhao Kong ◽  
Shuang Hou ◽  
Qing Ji ◽  
Y L Mo ◽  
Gangbing Song
Keyword(s):  
Early Age ◽  
Concrete Hydration ◽  
Early Age Concrete

scholarly journals Characterization of Moisture Diffusion in Cured Concrete Slabs at Early Ages

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Xiao Zhang ◽  
Hongduo Zhao
Keyword(s):  
Process Model ◽  
Model Simulation ◽  
Moisture Diffusion ◽  
Experimental Results ◽  
Concrete Slabs ◽  
Model Parameters ◽  
Early Age ◽  
Water Curing ◽  
Early Age Concrete

The objective of this paper is to investigate the characterization of moisture diffusion inside early-age concrete slabs subjected to curing. Time-dependent relative humidity (RH) distributions of three mixture proportions subjected to three different curing methods (i.e., air curing, water curing, and membrane-forming compounds curing) and sealed condition were measured for 28 days. A one-dimensional nonlinear moisture diffusion partial differential equation (PDE) based on Fick’s second law, which incorporates the effect of curing in the Dirichlet boundary condition using a concept of curing factor, is developed to simulate the diffusion process. Model parameters are calibrated by a genetic algorithm (GA). Experimental results show that the RH reducing rate inside concrete under air curing is greater than the rates under membrane-forming compound curing and water curing. It is shown that the effect of water-to-cement (w/c) ratio on self-desiccation is significant. Lower w/c ratio tends to result in larger RH reduction. RH reduction considering both effect of diffusion and self-desiccation in early-age concrete is not sensitive to w/c ratio, but to curing method. Comparison between model simulation and experimental results indicates that the improved model is able to reflect the effect of curing on moisture diffusion in early-age concrete slabs.

Durability of Cement Stabilized Cold-Recycled of Asphalt Pavement Materials

2012 ◽  
Vol 174-177 ◽  
pp. 1188-1192 ◽  
Author(s):  
Lian Yu Wei ◽  
Zhi Yu Guo
Keyword(s):  
Asphalt Pavement ◽  
Base Material ◽  
Road Construction ◽  
Thermal Shrinkage ◽  
Construction Process ◽  
Pavement Materials ◽  
Road Base ◽  
Wide Range ◽  
Dry Shrinkage ◽  
Recycled Material

In recent years, due to the dual pressures of resources and the environment,the clod recycled technology renovation and expansion of the old road and new road construction process increasingly attention increasingly wide range of applications. In this paper, the water stability of the cold recycled materials in asphalt pavement on cement additives, frozen stability, thermal shrinkage resistance, dry Shrinkage thefour indicators of experiments to evaluate its durability, and compared with the typical semi-rigid material. To verify the feasibility of the cold recycled material as road base material.

scholarly journals Monitoring of the ultrasonicP-wave velocity in early-age concrete using Smart Aggregates

2012 ◽  
Vol 1 ◽  
pp. 01001 ◽  
Author(s):  
Cédric Dumoulin ◽  
Grigoris Karaiskos ◽  
Jérôme Carette ◽  
Stéphanie Staquet ◽  
Arnaud Deraemaeker
Keyword(s):  
Wave Velocity ◽  
Early Age ◽  
Early Age Concrete
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