scholarly journals Damage of shotcrete under freeze-thaw loading

2017 ◽  
Vol 23 (5) ◽  
pp. 583-593 ◽  
Author(s):  
Jianxun CHEN ◽  
Pengyu ZHAO ◽  
Yanbin LUO ◽  
Xianghui DENG ◽  
Qin LIU
Keyword(s):  
Computed Tomography ◽  
Mass Loss ◽  
Pore Structure ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Cement Mortar ◽  
Ct Scanning ◽  
Freeze Thaw ◽  
Internal Pore Structure ◽  
Internal Pore

The freeze-thaw durability of shotcrete can be improved by adding an air-entraining agent in cold areas. The main focus of this paper is to investigate the changes in the internal pore structure of C25 ordinary shotcrete and shot­crete mixed with a RM-YQ air-entraining agent using computed tomography (CT) scanning technique during freeze-thaw cycles. The macroscopic tests were conducted, including mass loss, dynamic modulus of elasticity and ultrasonic wave velocity tests. Results were compared, and the freeze-thaw durability characteristics of shotcrete mixed with the air-entraining agent were revealed. Adding an air-entraining agent could reduce the number of pores largely that ranged mainly from 0.01 mm2 to 1.00 mm2 (excluding the pores or bubbles < 0.01 mm2 because of the precision of the CT scan­ning system), and could therefore improve the initial pore structure of the formed shotcrete. During first few freeze-thaw cycles, just few small pores formed. After cement mortar fragmentations appeared, the number of small pores (0.01 mm2 to 0.50 mm2) in ordinary shotcrete increased significantly. The pore structure deteriorated largely. However, this could be prevented effectively by adding an air-entraining agent. Therefore, the freeze–thaw durability of shotcrete was improved.

Performance Deterioration of High Strength Concrete under Mixed Erosion and Freeze-Thaw Cycling

2010 ◽  
Vol 163-167 ◽  
pp. 1655-1660
Author(s):  
Jian Zhang ◽  
Bo Diao ◽  
Xiao Ning Zheng ◽  
Yan Dong Li
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Mass Loss ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
High Strength Concrete ◽  
High Strength ◽  
Freeze Thaw ◽  
Strength Concrete ◽  
Dynamic Modulus Of Elasticity

The mechanical properties of high strength concrete(HSC) were experimentally investigated under mixed erosion and freeze-thaw cycling according to ASTM C666(Procedure B), the erosion solution was mixed by weight of 3% sodium chloride and 5% sodium sulfate. The mass loss, relative dynamic modulus of elasticity, compressive strength, elastic modulus and other relative data were measured. The results showed that with the increasing number of freeze-thaw cycles, the surface scaled more seriously; the mass loss, compressive strength and elastic modulus continued to decrease; the relative dynamic modulus of elasticity increased slightly in the first 225 freeze-thaw cycles, then decreased in the following 75 cycles; the corresponding strain to peak stress decreased with the increase of freeze-thaw cycles. After 200 cycles, the rate of deterioration of concrete accelerated obviously.

Assessing Freeze-Thaw Damage in Segmental Retaining Walls Units by Mass Loss, Moisture Gain, and Relative Dynamic Modulus

2019 ◽  
Vol 2673 (11) ◽  
pp. 309-318
Author(s):  
Cesar T. Chan ◽  
Kenneth C. Hover
Keyword(s):  
Moisture Content ◽  
Mass Loss ◽  
Dynamic Modulus ◽  
Moisture Absorption ◽  
Surface Damage ◽  
Mass Gain ◽  
Retaining Walls ◽  
Freeze Thaw ◽  
Cast Concrete ◽  
The Relationship

Segmental retaining walls (SRWs) constructed of dry-cast concrete masonry units are used in transportation-related applications for which freeze-thaw (FT) durability is evaluated on the basis of percent mass-loss accumulated after multiple FT cycles as per ASTM C1262. This study compared mass loss, mass gain owing to absorption during (FT) exposure, and relative dynamic modulus (RDM) as per ASTM C215. Application of RDM required accounting for the influence of the shape and moisture content of SRW coupons on resonant frequency, with corrections that are likewise applicable to ASTM C666 for ordinary concrete. It was demonstrated that mass loss does not exclusively indicate surface damage, and the relationship between mass loss and RDM is unique to each specimen. Mass gain (as moisture absorption) during testing emerged as a key index of damage, with rapid escalation of mass loss and reduction in RDM at the number of FT cycles required to increase the moisture content of the residual coupon by about 1%.

Change of internal/pore structure in alumina green body during initial sintering

1992 ◽  
Vol 27 (24) ◽  
pp. 6609-6614 ◽  
Author(s):  
Jin-Young Kim ◽  
Masayori Miyashita ◽  
Nozomu Uchida ◽  
Keizo Uematsu
Keyword(s):  
Pore Structure ◽  
Green Body ◽  
Internal Pore Structure ◽  
Internal Pore

scholarly journals The influence of type of cement on the degradation of microstructure and transport properties of cement mortars exposed to frost induced damage

2018 ◽  
Vol 174 ◽  
pp. 01014
Author(s):  
Alicja Wieczorek ◽  
Marcin Koniorczyk
Keyword(s):  
Absorption Coefficient ◽  
Pore Structure ◽  
Water Absorption ◽  
Transport Properties ◽  
Cement Mortar ◽  
Gas Permeability ◽  
Water Absorption Coefficient ◽  
Freeze Thaw ◽  
Cement Mortars ◽  
Small Pore

The purpose of the study is to understand how the cyclic water freezing (0, 25, 50, 75, 100 and 150 freeze-thaw cycles) impacts microstructure and transport properties of cement-based materials. Tests were conducted on cement mortars with different water/cement ratios (w/c=0.45 and 0.40) and on two types of cement (CEM I and CEM III) without air-entraining admixtures. The changes of pore size distribution and open porosity were investigated by means of mercury intrusion porosimetry. Additionally, the relationship between intrinsic permeability and the water absorption coefficient of cement mortar samples was analysed. The water absorption coefficient and gas permeability were determined using capillary absorption test and the modified RILEMCembureau method. The evolution of transport coefficients with growing number of freeze-thaw cycles were determined on the same sample. It was also established that change of pore structure (a decrease of small pore volume <100nm and increase of larger pores >100nm) induces an increase of water transport parameters such as permeability and water absorption coefficient. The higher gas permeability corresponds to the higher internal damage. In particular, it is associated with the change of cement mortar microstructure, which indicates damage of narrow channels in the pore structure of cement mortars.

scholarly journals Pore Structure Analysis of Mortar Under Freeze-Thaw Cycles Using X-Ray Computed Tomography

◽  
2016 ◽  
Author(s):  
Katsufumi Hashimoto ◽  
◽  
Hiroshi Yokota ◽  
Takafumi Sugiyama ◽  
◽  
...  
Keyword(s):  
Computed Tomography ◽  
Pore Structure ◽  
Structure Analysis ◽  
X Ray ◽  
Freeze Thaw ◽  
X Ray Computed ◽  
Pore Structure Analysis

Deterioration of Concrete Freezing-Thawing in Different Salts Solution

2009 ◽  
Vol 405-406 ◽  
pp. 315-321 ◽  
Author(s):  
Yong Ge ◽  
Wen Cui Yang ◽  
Jie Yuan ◽  
Bao Sheng Zhang ◽  
Ai Ling Xiong
Keyword(s):  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Frost Resistance ◽  
Nacl Solution ◽  
Freezing And Thawing ◽  
Lower Strength ◽  
Internal Damage ◽  
Freeze Thaw ◽  
Concrete Deterioration ◽  
All Solutions

The frost resistance of concrete subjected to 3.5% NaCl solution, 5%, 7%, and 10% Na2SO4 solution and seawater were investigated by quick freeze-thaw test. There were two criteria, the relative dynamic modulus of elasticity (RDME) and the mass of scaling, for evaluating the frost resistance of concrete. The results showed that scaling was the main characteristic of deterioration when concrete subjected to freeze-thaw cycles in 3.5% NaCl solution and seawater, whereas RDME had little change. When freezing and thawing in Na2SO4 solution, concrete failed because of internal damage and surfaces of lower strength concrete specimens appeared local swelling and scaling before failure. Concentration of Na2SO4 solution had influence on frost resistance of concrete: deterioration of concrete in 5% or 7% Na2SO4 solution was severe but slower when the concentration reached to 10%. Entraining air into concrete was the best method to improve the durability of concrete subjected to freeze-thaw cycles in all solutions.

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