The influence of air content on sprayed concrete quality and sprayability in a civil tunnel

Shotcrete ◽  
2010 ◽  
pp. 119-124 ◽  
Author(s):  
C Hauck ◽  
G Kristiansen
Keyword(s):  
Sprayed Concrete ◽  
Air Content ◽  
Concrete Quality

scholarly journals Review of Sprayability of Wet Sprayed Concrete

2020 ◽  
Vol 63 (2) ◽  
pp. 21-41
Author(s):  
Nicholas Trussell ◽  
Stefan Jacobsen
Keyword(s):  
Pore Structure ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Spray Application ◽  
Sprayed Concrete ◽  
Factors Affecting ◽  
Production Factors ◽  
Concrete Quality ◽  
Cast Concrete ◽  
Definition Of

AbstractWet sprayed concrete quality is affected by more production factors than cast concrete, particularly due to the propulsion through the nozzle and the flash set caused by the set accelerator. Practitioners often use the term “sprayability” to describe these factors. We propose a definition of “sprayability” that relates the application to the final properties of the hardened sprayed concrete and review factors affecting it: concrete constituents, proportioning, and application mechanics. These factors affect the hardening and the structure of the hardened sprayed concrete – the porosity, permeability and durability. We consider improving sustainability through proportioning with increased share of supplementary cementitious materials, calculate the placed composition and focus on factors that affect water transport, and hence durability. Due to the spray application and flash-set, irregular compaction voids dominate the macro pore structure of sprayed concrete. Studies of permeability of sprayed concrete have shown that it is possible to obtain low permeabilities given adequate composition and curing. Presumably these samples have been well-cured, uncracked and with non-percolating macro voids. Given observations of cracks in sprayed concrete linings and the macro voids, important further studies will be on the effect of accelerator, compaction porosity and cracking on permeability.

Establishment of Dedicated Concrete Plant in Site and Efforts to Improve the Concrete Quality

2018 ◽  
Vol 56 (2) ◽  
pp. 144-149
Author(s):  
T. Mukohara ◽  
N. Kanasaki ◽  
K. Watanabe ◽  
K. Kobayashi
Keyword(s):  
Concrete Quality

A Rule-Breaking Approach to a Better Understanding of the Method of Tests for Slump, Air Content and Compressive Strength

2019 ◽  
Vol 57 (6) ◽  
pp. 433-440
Author(s):  
S. Komatsu ◽  
Y. Kondo ◽  
N. Ikawa ◽  
C. Hashimoto
Keyword(s):  
Compressive Strength ◽  
Air Content ◽  
Rule Breaking

scholarly journals Use of Ecofriendly Glass Powder Concrete in Construction of Wind Farms

2021 ◽  
Vol 11 (7) ◽  
pp. 3050
Author(s):  
Eva M. García del Toro ◽  
Daniel Alcala-Gonzalez ◽  
María Isabel Más-López ◽  
Sara García-Salgado ◽  
Santiago Pindado
Keyword(s):  
Wind Farm ◽  
Glass Powder ◽  
Wind Farms ◽  
Main Element ◽  
Partial Replacement ◽  
Surface Protection ◽  
Air Content ◽  
Concrete Mixtures ◽  
Strength Tests ◽  
Rate Of Substitution

Silicon is the main element in the composition of glass and it has been seen that it can be used as a partial replacement for cement in the manufacture of concrete. Different dosages of glass powder and cement were applied to manufacture the concrete mixes. Initially, the characteristics of fresh concrete were studied, such as consistency, air content, apparent density and workability. Secondly, compressive strength tests were performed on the different concrete mixtures produced. The consistency tests allowed us to classify these concretes within the group of fluids. The air content of these concretes increased with the rate of substitution of cement by glass powder, resulting in lighter concretes. Density tests showed that this parameter decreased as the rate of substitution of cement increased. A coefficient k has been calculated for the substitution of glass powder by cement in the binder, using the Bolomey formula. Also, a mathematical model has been proposed to further analyze the experimental data. Major contributions of this work were to study the possible application of this concrete in different dispersions as a surface protection layer against the action of corrosion, in wind turbine foundations as well as the stabilization of the wind farm roads.

scholarly journals Absorption and Strength Properties of Short Carbon Fiber Reinforced Mortar Composite

Buildings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 300
Author(s):  
Md. Safiuddin ◽  
George Abdel-Sayed ◽  
Nataliya Hearn
Keyword(s):  
Tensile Strength ◽  
Carbon Fiber ◽  
Water Absorption ◽  
Carbon Fibers ◽  
Strength Properties ◽  
Fiber Content ◽  
Test Results ◽  
Air Content ◽  
Entrapped Air ◽  
Short Carbon

This paper presents the water absorption and strength properties of short carbon fiber reinforced mortar (CFRM) composite. Four CFRM composites with 1%, 2%, 3%, and 4% short pitch-based carbon fibers were produced in this study. Normal Portland cement mortar (NCPM) was also prepared for use as the control mortar. The freshly mixed mortar composites were tested for workability, wet density, and entrapped air content. In addition, the hardened mortar composites were examined for compressive strength, splitting tensile strength, flexural strength, and water absorption at the ages of 7 and 28 days. The effects of different carbon fiber contents on the tested properties were observed. Test results showed that the incorporation of carbon fibers decreased the workability and wet density, but increased the entrapped air content in mortar composite. Most interestingly, the compressive strength of CFRM composite increased up to 3% carbon fiber content and then it declined significantly for 4% fiber content, depending on the workability and compaction of the mortar. In contrast, the splitting tensile strength and flexural strength of the CFRM composite increased for all fiber contents due to the greater cracking resistance and improved bond strength of the carbon fibers in the mortar. The presence of short pitch-based carbon fibers significantly strengthened the mortar by bridging the microcracks, resisting the propagation of these minute cracks, and impeding the growth of macrocracks. Furthermore, the water absorption of CFRM composite decreased up to 3% carbon fiber content and then it increased substantially for 4% fiber content, depending on the entrapped air content of the mortar. The overall test results suggest that the mortar with 3% carbon fibers is the optimum CFRM composite based on the tested properties.

scholarly journals Reinforced Concrete Bridge Deck Model Considering Delayed Exposure to Chlorides

2019 ◽  
Author(s):  
Petr Konečný ◽  
Petr Lehner ◽  
David Pustka
Keyword(s):  
Reinforced Concrete ◽  
Bridge Deck ◽  
Concrete Bridge ◽  
Reinforced Concrete Bridge ◽  
Corrosion Initiation ◽  
Chloride Induced Corrosion ◽  
Concrete Quality ◽  
Concrete Type ◽  
Concrete Bridge Deck ◽  
Delayed Exposure

The paper is focused on the model of the effect of delayed chloride exposure on the chloride induced corrosion initiation on ideal reinforced concrete bridge. The Finite Element-based numerical model is applied. The effect of concrete quality is expressed in the form of time dependent diffusion coefficient in order to evaluate the effect of concrete type as well as the effect of aging. The influence of extended chloride exposure on the corrosion initiation is introduced.

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