scholarly journals Freeze-Thaw Durability and Digital Hardened Air Void Analysis of Self Consolidating Concrete

2013 ◽  
Author(s):  
Bryan M. Surface
Keyword(s):  
Self Consolidating Concrete ◽  
Freeze Thaw ◽  
Air Void

scholarly journals Freeze–Thaw Resistance and Air-Void Analysis of Concrete with Recycled Glass–Pozzolan Using X-ray Micro-Tomography

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 154
Author(s):  
Marija Krstic ◽  
Julio F. Davalos ◽  
Emanuele Rossi ◽  
Stefan C. Figueiredo ◽  
Oguzhan Copuroglu
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
The United States ◽  
Adsorption Method ◽  
X Ray ◽  
Freeze Thaw ◽  
Void System ◽  
Spatial Parameters ◽  
Micro Tomography ◽  
Air Void

Recent studies have shown promising potential for using Glass Pozzolan (GP) as an alternative supplementary cementitious material (SCM) due to the scarcity of fly ash and slag in the United States. However, comprehensive studies on the freeze–thaw (FT) resistance and air void system of mixtures containing GP are lacking. Therefore, this study aimed to evaluate GP’s effect on FT resistance and characterize mixtures with different GP contents, both macro- and microscopically. In this study, six concrete mixes were considered: Three mixes with 20%, 30% and 40% GP as cement replacements and two other comparable mixes with 30% fly ash and 40% slag, as well as a mix with 100% Ordinary Portland cement (OPC) as a reference. Concrete samples were prepared, cured and tested according to the ASTM standards for accelerated FT resistance for 1000 cycles and corresponding dynamic modulus of elasticity (Ed). All the samples showed minimal deterioration and scaling and high F/T resistance with a durability factor of over 90%. The relationships among FT resistance parameters, air-pressured method measurements of fresh concretes and air void analysis parameters of hardened concretes were examined in this study. X-ray micro-tomography (micro-CT scan) was used to evaluate micro-cracks development after 1000 freeze–thaw cycles and to determine spatial parameters of air voids in the concretes. Pore structure properties obtained from mercury intrusion porosimetry (MIP) and N2 adsorption method showed refined pore structure for higher cement replacement with GP, indicating more gel formation (C-S-H) which was verified by thermogravimetric analysis (TGA).

Effect of Pumping on Air Characteristics of Conventional Concrete

1996 ◽  
Vol 1532 (1) ◽  
pp. 9-14 ◽  
Author(s):  
M. Lessard ◽  
M. Baalbaki ◽  
P.-C. Aïtcin
Keyword(s):  
Specific Surface ◽  
Freezing And Thawing ◽  
Conventional Concrete ◽  
Freeze Thaw ◽  
Pump Line ◽  
Spacing Factor ◽  
Void System ◽  
The Stability ◽  
Air Void ◽  
Frost Durability

The stability of the air content of concrete during pumping has been the subject of a number of recent investigations. Because increasing volumes of concrete are placed with the aid of pumps and the durability of such concrete to freezing and thawing (ASTM C666) as well as the scaling resistance (ASTM C672) preoccupy engineers, a study concerning the stability of the air-void system of a concrete with 45 to 50 MPa compressive strength was carried out. The slump of the three tested concretes ranged between 85 and 115 mm. Three pumping setups were studied. In the first, the concrete was pumped horizontally; in the second the concrete was pumped upward and then downward. In the third, the vertical setup was used but a reduced section was placed at the end of the pump line, and the concrete was allowed to free fall a short distance. For each pump setup, the concrete was sampled before being placed in the pump and after leaving the pump. The results clearly show that when the concrete is pumped horizontally, the spacing factor (L) and the specific surface of the air-void system are barely altered. On the other hand, after pumping the concrete vertically without a reduced end section, it was impossible to obtain an L less than 230 μm, the maximum spacing factor allowed by Canadian standards (CSA A23.1) to ensure good frost durability. Furthermore, the specific surface of the air bubbles fell to 20 mm−1, which is inferior to the 25-mm−1 value recommended in Canadian standards. By placing a reduced section at the end of the vertical pump line, it was possible to enhance the air-void system but that procedure still fell short of ensuring a system that satisfies the air-void system recommended by Canadian standards to ensure proper frost durability. Although the pumped concrete mixtures did not always satisfy the requirements of CSA A23.1 regarding air-void systems, they satisfied the requirements of ASTM C666 (Procedure A) for resistance to freeze-thaw cycles. Freeze-thaw resistance in the presence of deicing salts was evaluated according to ASTM C672. After 50 frost cycles, all but one concrete exhibited mass losses that were lower than the maximum permissible limit of 0.50 kg/m2 required by BNQ 2621-900, the standard currently enforced in the province of Quebec. Placing a reduced section at the end of the pump line creates a light counterpressure in the descending section of the pump line, which allows the conservation of an acceptable air-void system. Considering the appreciable improvement in the preservation of air-void characteristics when a reduced section was placed at the end of the pump line, it was decided to proceed with further experimental work using four 90-degree elbows placed at the end of the vertically hanging pump line.

Material Characteristics Evaluation of Existing Pre-Stressed Concrete Railroad Ties After Service Period

2018 ◽  
Author(s):  
Aref Shafiei Dastgerdi ◽  
Kyle Riding ◽  
Robert J. Peterman ◽  
B. Terry Beck
Keyword(s):  
Service Life ◽  
High Speed ◽  
Current Status ◽  
Polished Surface ◽  
Material Characteristic ◽  
Freeze Thaw ◽  
Material Characteristics ◽  
Void System ◽  
Different Types ◽  
Air Void

As an important element in track, pre-stressed concrete railroad ties in the high-speed rail industry must meet the safety and performance specifications of high-speed trains. Systematic destructive and non-destructive evaluation of existing concrete ties can lead to a better understanding of the effect of prestressed concrete tie material design on performance and failure within their service life. It has been evident that environmental and climate conditions also have a significant impact on concrete railroad ties, causing various forms of deterioration such as abrasion and freeze-thaw damage. Understanding of the material characteristics that cause failure in different types of existing concrete railroad ties taken from different places is the main focus of this paper. Observing the current status and damages of railroad ties taken from track might give a correlation between the material characteristic and type of distress and cracking seen. Although it has been seen by previous works that effective factors such as air void system and material composition directly affect the performance of concrete ties such as freeze-thaw, material evaluation of existing ties after service life has not been addressed in previous publications. In this research, the authors have investigated the material characteristic such as aggregate and air-void system of existing pre-stressed concrete railroad ties taken from track. However, compressive and splitting tensile strength and fractured surface of samples cored from the ties were acquired. In order to obtain the strength of concrete materials of existing ties, six samples were cored from six different types of ties taken from tracks across the U.S., according to ASTM C42-16, and tested using ASTM C39 and ASTM C496 methods. However, the concrete air-void system (ASTM C457) was measured on saw-cut samples extracted from the ties to evaluate the influence air content and distribution on mechanical properties of the ties. Regarding the history and service life condition of the ties, it seems that material properties of the ties effectively alter the performance of the ties. Aggregate sources used at each location may have different properties such as texture, angularity, and mineralogy, contributing either propagation or resistance in splitting cracking in concrete. Furthermore, the polished surface of samples extracted from the ties show the uniformity and air void system in some ties which demonstrate their superiority in terms of resistance to freeze-thaw damage. Considering the results of this research, comprehensive evaluation of material characteristics might give a better view of existing concrete railroad ties situation, providing a worthwhile background for future tie design considerations.

scholarly journals Research on the Corrosion Damage Mechanism of Concrete in Two Freeze–Thaw Environments

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xianhua Yao ◽  
Min Zhang ◽  
Junfeng Guan ◽  
Lielie Li ◽  
Weifeng Bai ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Erosion Resistance ◽  
Corrosion Damage ◽  
Damage Mechanism ◽  
Resistance Coefficient ◽  
Dynamic Elastic Modulus ◽  
Freeze Thaw ◽  
Environment Temperature ◽  
Performance Deterioration ◽  
Air Void

This study aims to investigate the effects of two freeze–thaw environments (i.e., maintenance freeze-thaw (MFT) environment and immersion freeze-thaw (IFT) environment) on the durability performance, deterioration rules, and mechanisms of concrete. In MFT, the concrete specimens were firstly cured in the standard curing environment (temperature, 20 ± 3, humidity, not less than 95%, and ages, 28 d) and then were carried out in freeze–thaw environment, while in IFT, the concrete specimens were firstly cured in the salt (NaHCO3, NaCl, and Na2SO4) immersion environment for 90 d and then were carried out in freeze–thaw environment. In this study, the damage features, relative dynamic elastic modulus, mass changes, and erosion-resistance coefficient of concrete have been measured. Thereafter, using the scanning electron microscopy (SEM) and the mercury intrusion porosimetry (MIP), the air-void structure parameters and the microstructures have been measured, respectively. The results show that the relative dynamic elastic modulus and the erosion-resistance coefficient of the compressive strength of the concrete in the IFT environment are, respectively, 14.3% and 21.0% higher than those of the concrete in the MFT environment. In addition, the results of the microstructure analyses show that the corrosion damages of the concrete are mainly caused by the combined action of the corrosion products of ettringite and freeze–thaw environment. However, the damage to the concrete in the MFT environment is more serious than that in the IFT environment. The results of the MIP analysis show that the harmful pore value for the concrete in the MFT environment is almost two times larger than that for the concrete in the IFT environment.

scholarly journals Experimental Study on the Performance Decay of Permeable Asphalt Mixture in Seasonally Frozen Regions under Freeze-Thaw Cycles

2020 ◽  
Vol 12 (7) ◽  
pp. 2966 ◽  
Author(s):  
Chao Chai ◽  
Yong-Chun Cheng ◽  
Yuwei Zhang ◽  
Yu Chen ◽  
Bing Zhu
Keyword(s):  
Acoustic Emission ◽  
Asphalt Mixture ◽  
Temperature Stability ◽  
High Temperature Stability ◽  
Air Voids ◽  
Particle Loss ◽  
Seasonal Freezing ◽  
Freeze Thaw ◽  
Splitting Test ◽  
Air Void

This paper focuses on the freeze-thaw cycles (F-T cycles) resistance of porous asphalt mixture (PAM) with different air voids in order to explore the gradation of the PAM suitable for seasonal freezing regions. Three sets of PAMs with 18%, 21%, and 25% air voids were designed. After 0–20 F-T cycles, the effects of F-T cycles on the performance degradation of three groups of PAMs were studied by performing a low-temperature splitting test with acoustic emission technology, a normal temperature splitting test, a compression test, a Cantabro particle loss test, and a dynamic creep test. The results show that the damage process of PAM caused by multiple F-T cycles could be more clearly defined by acoustic emission parameters. In addition, the larger the air void, the smaller its indirect tensile strength and compression strength, and the worse its particle loss resistance and high-temperature stability, which made the adverse effect of F-T cycles more significant. Therefore, the air void of PAM used in seasonal freezing regions is suggested to be less than 21%.

Effect of fine fly ash and calcium hydroxide on air void structure in very-early-strength latex-modified concrete

2015 ◽  
Vol 42 (10) ◽  
pp. 797-807
Author(s):  
Pangil Choi ◽  
Sung Il Jeon ◽  
Kyong-Ku Yun
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Bridge Decks ◽  
Time Frame ◽  
Early Age ◽  
Freeze Thaw ◽  
Void Structure ◽  
Early Strength ◽  
Air Void ◽  
Air Void Structure

Very-early-strength latex-modified concrete (VES-LMC) was developed for rapid repairs of distresses in concrete bridge decks and pavements, with the emphasis on early-age strength gain so that the repaired bridges and pavements can be opened to traffic within the time frame required in the specifications. However, there are two main concerns in the use of VES-LMC — early-age cracking and poor air void structure. The main objective of this study was to further improve VES-LMC to minimize early-age cracking and improve freeze–thaw durability, which included the use of fine fly ash (FFA) and calcium hydroxide (CH). Laboratory experiments were conducted on VES-LMC materials with cement replaced with FFA as well as CH, and various tests performed. Early-age drying shrinkages of VES-LMC containing both FFA and CH in the amounts evaluated in this study were smaller than that of VES-LMC with no replacements. It is expected that the use of FFA and CH in the range evaluated in this study will reduce the cracking potential of VES-LMC. Overall, the replacement of cement with FFA and CH improved the characteristics of entrained air void system, which will enhance the durability of VES-LMC against freeze–thaw damage. Scanning electron microscope and energy dispersive spectroscopy analysis indicate the primary mechanism of the generation of small sized air voids in concretes containing adequate amount of FFA and CH is the gas formation reaction between citric acid solutions and CH during concrete mixing. It is expected that the inclusion of adequate amounts of FFA and CH in VES-LMC will improve the performance of repaired bridge decks and pavements in terms of reduced cracking and improved freeze-thaw durability.

Study on Volume Performance of Conductive Asphalt Concrete Based on Freeze-Thaw Cycle

2013 ◽  
Vol 303-306 ◽  
pp. 2501-2504 ◽  
Author(s):  
Pan Pan ◽  
Chang Jun Sun ◽  
Ning Tang ◽  
Ming Yu Chen ◽  
Shao Peng Wu
Keyword(s):  
Asphalt Concrete ◽  
Asphalt Mixture ◽  
Material Composition ◽  
Moisture Resistance ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Volume Properties ◽  
Freeze Thaw Cycle ◽  
Air Void ◽  
Weight Loss Ratio

Conductive asphalt concrete, a kind of intelligent materials, can serve as asphalt solar collector, asphalt heater and self monitor. And moisture damage is one of the most common performance degradation of asphalt concrete. This paper investigates the volume properties of conductive asphalt concrete based on Freeze-thaw cycles. Marshall specimen was frozen and thawed repeatedly and a cycle consists 16h at -18oC and 8h at 60oC. The change of air void and weight loss ratio were chosen to evaluate the moisture resistance of conductive asphalt concrete. Three types of asphalt mixture (control, CAC 1 and CAC 2) were used to study the effect of initial void and material composition on moisture resistance. The results show that both the framework structures and the material composition have a great effect on antifreeze-thaw property of asphalt concrete, which provides an efficient guidance for application of this technology in pavement.

scholarly journals Image-based Restoration of the Concrete Void System Using 2D-to-3D Unfolding Technique

2020 ◽  
Author(s):  
Yu Song ◽  
Chuanyue Shen ◽  
Robbie Damiani ◽  
David Lange
Keyword(s):  
Air Entrainment ◽  
Void Size ◽  
Essential Information ◽  
Air Voids ◽  
Freeze Thaw ◽  
Void System ◽  
Void Structure ◽  
Unfolding Analysis ◽  
Air Void ◽  
2D To 3D

Hardened air void analysis provides essential information of concrete freeze-thaw durability based on the size and spacing of air voids in the material. As the physical freeze-thaw experiment is time-consuming and costly, the characteristics of concrete air voids are often deemed as a proxy of the freeze-thaw performance. This analysis is typically done by measuring the 2D air void intersections on polished samples, but the current interpretation of the 2D void characters does not accurately represent the actual void structure in 3D. To solve this problem, a 2D-to-3D unfolding technique has been proposed in the field of stereology. However, the unfolding analysis is known to be sensitive to several factors, such as void population and size along with a binning scheme, where improper unfolding can considerably bias the prediction of the actual concrete void system. This study investigates the optimal strategy of conducting the unfolding analysis for concrete. The investigation is carried out on both idealized void systems to interrogate the influence of the critical factors individually, and real concrete samples with varying levels of air entrainment to assess the concrete-specific impacts. The concrete void system is studied based on a stereological model emulating the intersected 3D air voids on the surface of polished concrete. The results highlight that, for unfolding concrete voids, logarithmic binning scheme is far more accurate to linear binning. The low unfolding error of the concrete samples indicates that the proposed methodology enables an accurate restoration of 3D void size distribution.

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