scholarly journals Effects of freezing and thawing cycles on over-consolidated reconstituted structural loess

2021 ◽  
Vol 861 (2) ◽  
pp. 022035
Author(s):  
Y Zheng ◽  
Y W Lu ◽  
J B Zhu ◽  
W Hu ◽  
B Hu ◽  
...  
Keyword(s):  
Freezing And Thawing ◽  
Freezing And Thawing Cycles

scholarly journals EXPERIENCE OF APPLICATION HIGH PERFORMANCE CEMENT COMPOSITES FOR CREATING DURABLE SCULPTURAL ELEMENTS

2017 ◽  
Vol 3 ◽  
pp. 286
Author(s):  
Genadijs Sahmenko ◽  
Sandis Aispurs ◽  
Aleksandrs Korjakins
Keyword(s):  
Water Absorption ◽  
High Performance ◽  
Cement Composite ◽  
Cement Composites ◽  
Freezing And Thawing ◽  
Initial Water ◽  
Good Potential ◽  
Freezing And Thawing Cycles ◽  
Material Ductility ◽  
And Control

Traditionally, sculptural and decorative elements of building facades are created from mortar mixes based on lime, gypsum or Portland cement. Generally these materials have porous and permeable structure, which determines their accelerated degradation, especially in the aggressive environment of modern cities. High performance cement composites (HPCC) have been considered for production and restoration of sculptural elements in historical buildings. For this purpose, fine-graded, multi-component and highly workable mixes were elaborated. Mix compositions were modified with micro-fillers, plasticizing and stabilizing admixtures, as well as fibers to improve material ductility and control shrinkage cracking. Basic mechanical properties and durability (such as water absorption, frost resistance) were determined and two types of HPCC were compared (>50 MPa: HPCC and >120 MPa: UHPCC). It has been confirmed that cement composite mixes are characterized by self-consolidating effect, high compressive strength, extremely high resistance versus freezing and thawing cycles and low water absorption. Surface quality was evaluated and initial water absorption (tube tests) were performed for laboratory samples and real sculptural elements after 5 years of exploitation. The results confirmed good potential for using HPCC for creating more attractive and durable architectural shapes and façade elements compared to elements made using traditional cement and lime mortar.

scholarly journals Experimental Study on Freezing and Thawing Cycles of Shrinkage-Compensating Concrete with Double Expansive Agents

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1850
Author(s):  
Jinjun Guo ◽  
Ting Guo ◽  
Shiwei Zhang ◽  
Yan Lu
Keyword(s):  
Frost Resistance ◽  
Large Scale ◽  
Mass Loss Rate ◽  
Test Results ◽  
Freezing And Thawing ◽  
Expansive Agent ◽  
Hydraulic Concrete ◽  
Mix Proportion ◽  
Three Stages ◽  
Freezing And Thawing Cycles

The freezing and thawing of construction concrete is becoming an increasingly important structural challenge. In this study, a shrinkage-compensating concrete based on a double expansive admixture was developed and its frost resistance was assessed through rapid freezing and thawing cycling. The frost resistance of the concrete was derived through the measurement and calculation of the relative dynamic modulus of elasticity (RDME) and the mass loss rate (MLR), and the freezing- and thawing-cycle microstructures and products of concretes with different expansive agents were analyzed using scanning electron microscopy (SEM). It was shown that changes in the properties of the concrete under freezing and thawing could be divided into three stages: slow-damage stage, fast-damage stage, and stable stage. Compared to concrete without an expansive agent, a single-expansive-agent concrete demonstrated excellent frost resistance during the slow-damage stage, but the frost resistance rapidly decreased during the fast-damage age. After 150 cycles (the stable-damage stage), the concrete with a U-type expansive agent (UEA): MgO expansive agent (MEA) mix proportion of 2:1 had the best frost resistance, with RDME and MLR values 17.35% higher and 25.1% lower respectively, than that of an expansive-agent-free concrete. These test results provide a basis for the study of frost resistance in large-scale hydraulic concrete structures.

Permeability and volume changes in till due to cyclic freeze/thaw

1998 ◽  
Vol 35 (3) ◽  
pp. 471-477 ◽  
Author(s):  
Peter Viklander
Keyword(s):  
Soil Structure ◽  
Void Ratio ◽  
Vertical Direction ◽  
Rigid Wall ◽  
Freezing And Thawing ◽  
Volume Changes ◽  
Freeze Thaw ◽  
Fine Grained ◽  
Loose Soil ◽  
Freezing And Thawing Cycles

A fine-grained nonplastic till was compacted in the laboratory in three types of rigid wall permeameters, having a volume of 0.4, 1.5, and 25 dm3, respectively, and, was thereafter exposed to a maximum of 18 freezing and thawing cycles. The permeabilities in the vertical direction of saturated samples were measured in unfrozen soil as well as in thawed soil. The results show that the permeabilities changed after freezing and thawing. The magnitude of the changes in this study were in the range 0.02-10 times after freeze/thaw compared with the unfrozen soil. Soil exhibited volume changes subsequent to freeze/thaw. The volume typically decreased for an initially loose soil and increased for a dense soil. Independent of whether the initial soil structure was loose or dense, a constant "residual" void ratio, eres, was obtained after 1-3 cycles. For the soil investigated, the residual void ratio ranged from 0.31 to 0.40.Key words: till, fine-grained, non plastic, permeability, freeze/thaw, residual void ratio.

scholarly journals Characterization and Structural Determination of Cold-Adapted Monodehydroascorbate Reductase, MDHAR, from the Antarctic Hairgrass Deschampsia Antarctica

Crystals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 537 ◽  
Author(s):  
Ae Kyung Park ◽  
Il-Sup Kim ◽  
Hackwon Do ◽  
Hyun Kim ◽  
Woong Choi ◽  
...  
Keyword(s):  
Oryza Sativa L ◽  
Extreme Temperature ◽  
Biochemical Properties ◽  
Yeast Cells ◽  
Monodehydroascorbate Reductase ◽  
Deschampsia Antarctica ◽  
Freezing And Thawing ◽  
Freezing And Thawing Cycles ◽  
The Antarctic

Ascorbic acid (AsA) is an abundant component of plants and acts as a strong and active antioxidant. In order to maintain the antioxidative capacity of AsA, the rapid regeneration of AsA is regulated by dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR). To understand how MDHAR functions under extreme temperature conditions, this study characterized its biochemical properties and determined the crystal structure of MDHAR from the Antarctic hairgrass Deschampsia antarctica (DaMDHAR) at 2.2 Å resolution. This allowed for a structural comparison with the mesophilic MDHAR from Oryza sativa L. japonica (OsMDHAR). In the functional analysis, yeast cells expressing DaMDHAR were tolerant to freezing and thawing cycles. It is possible that the expression of DaMDHAR in yeast enhanced the tolerance for ROS-induced abiotic stress.

scholarly journals The analysis of influence of polymer admixtures on properties of lightweight concrete

2019 ◽  
Vol 252 ◽  
pp. 08007 ◽  
Author(s):  
Jacek Góra ◽  
Danuta Barnat-Hunek ◽  
Paweł Wlaź ◽  
Monika Garbacz
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Statistical Analysis ◽  
Lightweight Concrete ◽  
Strength Properties ◽  
Freezing And Thawing ◽  
Factors Of Influence ◽  
Freezing And Thawing Cycles ◽  
Acetate Copolymer

The article presents the results of testing physical and strength properties of concrete with the addition of lightweight perlite in the amount of 10 and 20%. The additive was introduced by volume substituting a part of the sand. In addition, the effect of using siloxane admixtures and a vinyl acetate copolymer with different degree of dosing, as well as applied simultaneously, were analysed. The tests were carried out in the field of bulk density and proper density, determination of tightness and porosity, compressive strength and tensile strength after 28 days of maturation. In terms of durability of concrete, absorption and resistance of concretes to the freeze-up effects after 100 freezing and thawing cycles were tested. The results of the study were subjected to statistical analysis using the analysis of variance. The analysed factors of influence were the amount of perlite addition, as well as the type and amount of the added admixture

Engineering properties of rubberized concrete

1992 ◽  
Vol 19 (5) ◽  
pp. 912-923 ◽  
Author(s):  
Neil N. Eldin ◽  
Ahmed B. Senouci
Keyword(s):  
Plain Concrete ◽  
Crumb Rubber ◽  
Engineering Properties ◽  
Unit Weight ◽  
Rubberized Concrete ◽  
Portland Cement Concrete ◽  
Freezing And Thawing ◽  
Scrap Tire ◽  
Plastic Energy ◽  
Freezing And Thawing Cycles

Growing piles of discarded tires are potential sources of fire and health hazards. The current disposal methods are wasteful and costly. As a possible solution to the problem of scrap-tire disposal, an experimental study was conducted to examine the potential use of rubber aggregate (tire chips and crumb rubber) as mineral aggregate substitute in Portland cement concrete mixes. The research focused on determining the strength characteristics of rubberized concrete and examined the relationship between the size, percentage, and shape of rubber aggregate and the strength measured.Rubberized concrete was found to possess good esthetics, acceptable workability, and a smaller unit weight than plain concrete. However, it exhibited low compressive and tensile strengths and lower resistance to repeated freezing and thawing cycles than that of plain concrete. A statistical analysis of the experimental data suggested that only the percentage by volume of rubber in the mix has a significant effect on strength. The size and shape was found insignificant. Unlike plain concrete, rubberized concrete did not demonstrate the typical brittle failure. It exhibited a ductile, plastic failure, and showed the ability to absorb a large amount of plastic energy under compressive and tensile loads. Key words: rubberized concrete, concrete properties, compression, durability, failure, modulus of elasticity, slump, tension, toughness, workability.

Real-Time Monitor Method of Soil Slope Stability in Seasonal Frozen Area

2013 ◽  
Vol 303-306 ◽  
pp. 777-781
Author(s):  
Ping Jiang ◽  
Meng Su Zhang
Keyword(s):  
Shear Strength ◽  
Slope Stability ◽  
Real Time ◽  
Evaluation System ◽  
Landslide Hazard ◽  
Soil Slope ◽  
Freezing And Thawing ◽  
The Neural Network ◽  
Neural Network Algorithm ◽  
Freezing And Thawing Cycles

Soil slope in seasonal frozen area subject to rainfall or freezing and thawing cycles, the shear strength of soil damage and lead to landslide hazard. In order to predict the landslide hazard through monitoring the soil slope stability real-time, the soil slope stability evaluation system is established. The Neural Network Algorithm can simulate elastic-plastic finite element method well, and using Genetic Algorithm to search cohesion(c) and internal friction angel(φ) which meet the accuracy requirements. And the intelligent parameter inversion model of soil shear strength (c, φ) based on displacement is established. So, the slope stability can be evaluated real –time based on displacement monitor. Application of this method in actual project shows that this method is accurate and effective.

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