A model for predicting evaporation from fresh concrete surface during the plastic stage

2019 ◽  
Vol 38 (16) ◽  
pp. 2231-2241 ◽  
Author(s):  
Ya Wei ◽  
Weiqiang Guo ◽  
Qianqian Zhang
2018 ◽  
Vol 760 ◽  
pp. 3-9
Author(s):  
Jiří Němeček ◽  
Rostislav Šulc ◽  
Jitka Němečková ◽  
Jaroslav Kruis

The paper summarizes utilization of nanoparticles (NP) in concrete for enhancing its mechanical, transport or other properties. The first part is devoted to review of NPs used in fresh concrete mixtures that have been reported previously in the literature while the second part shows original results from utilization of nanoparticles as healing agents for reparing of existing concrete structures. In the second case, nanoparticles are delivered to concrete via electrokinetic principle by using their surface charge provided in colloidal solutions. Particles are transported in the pore liquid of concrete due to electric field applied between the concrete surface and steel reinforcement. In this way, distressed concrete can be repaired, cracks sealed and risk of corrosion diminished. The injection of NPs can be complemented with extraction of chlorides that are the main deteriorating chemicals in reinforced concrete structures. Finally, the paper shows a framework developed for the electrokinetic transport of ionic species in concrete applied to chloride extraction from concrete and how it can be modified also for transport of nanoparticles.


2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Sandra Juradin ◽  
Goran Baloević ◽  
Alen Harapin

The self-compacting lightweight concrete (SCLC) is a combination of the Self compacting concrete (SCC) and the Lightweight concrete. It combines all the good properties of those two materials and is extremely convenient for the construction of buildings that require low mass and do not require high compressive strength, for example restoration works in old structures (e.g., replacement of wooden floors), prefabricated elements that require transportation, and for structures and elements where the concrete surface should be visible. In this paper the effect of the amount of fine particles on the properties of the self-compacting lightweight concrete (SCLC) in the fresh and hardened state was explored. For this purpose, sets of specimens with different combinations of admixtures of silica fume, fly ash, and filler were prepared and tested. Slump flow and flow time of fresh concrete, as well as the dynamic elastic modulus and compressive strength of hardened concrete, were measured at different ages of concrete. The processes of manufacturing and methods of testing are described, as well as the obtained results.


2015 ◽  
Vol 22 (1) ◽  
pp. 26-37 ◽  
Author(s):  
Samir BOUHAROUN

Concrete surface quality is generally linked to the development conditions of concrete close to the formwork. This work aims to study the influence of the nature of release agent and the quantity of fine elements on the chemical interactions at the concrete/oil/formwork interface. Five concretes were prepared at 28, 30, 32, 34, and 36% of paste to study the influence of paste volume on the friction between formwork and fresh concrete. The friction tests were performed using an apparatus which can reproduce the same conditions of construction sites. In addition, a physicochemical investigation was achieved to identify the effect of fine elements on the ability to form the interstitial mediums at the interface. The formation of soap in the vicinity of the formwork surfaces was also studied as a function of the content and the nature of oils. The results showed that the friction between fresh concrete and formwork depends on the pore solution content present at the interface.


10.29007/zw9k ◽  
2020 ◽  
Author(s):  
Kazuhide Nakata ◽  
Kazuki Umemoto ◽  
Kenji Kaneko ◽  
Ryusuke Fujisawa

This study addresses the development of a robot for inspection of old bridges. By suspending the robot with a wire and controlling the wire length, the movement of the robot is realized. The robot mounts a high-definition camera and aims to detect cracks on the concrete surface of the bridge using this camera. An inspection method using an unmanned aerial vehicle (UAV) has been proposed. Compared to the method using an unmanned aerial vehicle, the wire suspended robot system has the advantage of insensitivity to wind and ability to carry heavy equipments, this makes it possible to install a high-definition camera and a cleaning function to find cracks that are difficult to detect due to dirt.


2016 ◽  
Vol 54 (11) ◽  
pp. 1105-1110
Author(s):  
K. Watanabe ◽  
G. Sakai ◽  
N. Sakata ◽  
T. Ishida

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