scholarly journals Rehabilitation of buildings in winter conditions

2011 ◽  
Vol 9 (3) ◽  
pp. 357-366
Author(s):  
Slavko Zdravkovic ◽  
Dragoslav Stojic ◽  
Dragana Turnic
Keyword(s):  
Water Absorption ◽  
Porous Materials ◽  
Hardened Concrete ◽  
Freezing And Thawing ◽  
Volume Changes ◽  
Winter Conditions ◽  
Volume Measure ◽  
Solidification Processes ◽  
Freezing And Thawing Cycles

Various factors are taken as the criteria for determining the susceptibility of materials to frost, such as: porosity and water absorption, volume changes, the number of freezing and thawing cycles. Mortars as a mixture of binder, water and sand, after placing and undergoing bonding and solidification processes, represent extremely porous materials, and the same holds for concrete. When the water turns into ice, it changes its volume measure unit from (V?) into Vt = 1.09 V?. If the concrete that has not completed bonding is exposed to frost, the process is likely to be suspended, and later when the warming starts, followed by the thawing of concrete, it will need the repeated vibrating in order to bind again and harden up without the detrimental effects on its strength. However, there are cases of devastating effects of frost on the hardened concrete. All the mentioned strategies should be kept in mind when performing remediation.

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.

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 Macro Photography as an Alternative to the Stereoscopic Microscope in the Standard Test Method for Microscopical Characterisation of the air-void System in Hardened Concrete: Equipment and Methodology

2018 ◽  
Author(s):  
Fernando Suárez ◽  
José J. Conchillo ◽  
Jaime C. Gálvez ◽  
María J. Casati
Keyword(s):  
Standard Test ◽  
Test Method ◽  
Hardened Concrete ◽  
Large Set ◽  
Alternative Procedure ◽  
Freezing And Thawing ◽  
Point Count ◽  
Void System ◽  
Freezing And Thawing Cycles ◽  
Air Void

The determination of the parameters that characterise the air-void system in hardened concrete elements becomes crucial for structures under freezing and thawing cycles. The ASTM C457 standard describes some procedures to accomplish this task, but they are not easy to apply, require specialised equipment such as a stereoscopic microscope and result in highly tedious tasks to be performed. This paper describes an alternative procedure to the modified point-count method described in the Standard that makes use of macro photography. This alternative procedure is successfully applied to a large set of samples and presents some advantages over the traditional method, since the required equipment is less expensive and provides a more comfortable and less tedious procedure for the operator.

scholarly journals Macro Photography as an Alternative to the Stereoscopic Microscope in the Standard Test Method for Microscopical Characterisation of the Air-Void System in Hardened Concrete: Equipment and Methodology

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1515
Author(s):  
Fernando Suárez ◽  
José Conchillo ◽  
Jaime Gálvez ◽  
María Casati
Keyword(s):  
Standard Test ◽  
Test Method ◽  
Hardened Concrete ◽  
Large Set ◽  
Alternative Procedure ◽  
Freezing And Thawing ◽  
Point Count ◽  
Void System ◽  
Freezing And Thawing Cycles ◽  
Air Void

The determination of the parameters that characterize the air-void system in hardened concrete elements becomes crucial for structures under freezing and thawing cycles. The ASTM C457 standard describes some procedures to accomplish this task, but they are not easy to apply, require specialised equipment, such as a stereoscopic microscope, and result in highly tedious tasks to be performed. This paper describes an alternative procedure to the modified point-count method that is described in the Standard that makes use of macro photography. This alternative procedure uses macro-photographic images that can be obtained with a quite standard photo camera and it is successfully applied to a large set of samples and presents some advantages over the traditional method, since the required equipment is less expensive and provides a more comfortable and less tedious procedure for the operator.

scholarly journals Effect of Hydrophobic Treatments on Improving the Salt Frost Resistance of Concrete

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5361
Author(s):  
Guo Li ◽  
Chunhua Fan ◽  
Yajun Lv ◽  
Fujun Fan
Keyword(s):  
Water Absorption ◽  
Frost Resistance ◽  
Contact Angles ◽  
Water Repellent ◽  
Freezing And Thawing ◽  
Ordinary Water ◽  
Salt Scaling ◽  
Mass Losses ◽  
Hydrophobic Treatment ◽  
Freezing And Thawing Cycles

Hydrophobic treatment is an important method to improve the waterproof properties of concrete. To evaluate the effectiveness of hydrophobic treatments on improving the salt frost resistance of concrete, two representative commercial ordinary water repellent agents of silane and organosilicone emulsion were selected, and concrete specimens with three water/cement ratios were fabricated. After the application of repellent agents on concrete surfaces, accelerated saline (5% MgCl2) freeze-thaw cycles were conducted on the specimens. The mass losses and relative dynamic modulus of elasticity (RDME) of concrete were tested periodically. The contact angles and water absorption ratios of concrete with and without hydrophobic treatments were also tested. Results showed that the repellent agents could substantially enhance the hydrophobicity of concrete and greatly reduce its water absorption. Different repellent agents exerted diverse improvements on concrete hydrophobicity. Meanwhile, the repellent agents could improve concrete resistance against salt scaling and RDME losses to a certain degree, and concrete with strong hydrophobicity showed relatively high salt frost resistance. However, the ordinary water repellent agents cannot achieve the same enhancement on salt frost resistance of concrete as that on the water hydrophobicity of concrete. With saline freezing and thawing cycles, the hydrophobic layer formed by the repellent agents on superficial concrete was destroyed gradually. As a result, the salt frost resistance of concrete from the hydrophobic treatments was ultimately lost.

scholarly journals Effect of Expanded Perlite Aggregate Size on Physical and Mechanical Properties of Ultra Lightweight Concrete Produced with Expanded Perlite Aggregate

2019 ◽  
Author(s):  
Mucip Tapan ◽  
Celil Engin
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Water Absorption ◽  
Bending Strength ◽  
Lightweight Concrete ◽  
Unit Weight ◽  
Ultra Sound ◽  
Expanded Perlite ◽  
Freezing And Thawing ◽  
Freezing And Thawing Cycles

In this study, ultra-light weight concrete (ULWC) with heat-insulating properties is produced by using different size expanded perlite aggregates and various admixtures. The compressive strength, 4 point bending strength, freezing and thawing resistance, water absorption, dry unit weight, ultra sound velocities and thermal conductivity of the samples were determined by applying appropriate tests. The effect of different size expanded perlite aggregate on the properties of ULWC were also investigated in this study and it was found that as the expanded perlite aggregate diameter increased, the void volume uniformity, water absorption percentage and freezing-thawing resistance increased while the unit volume weight of ULWC samples, ultrasound speed velocities, thermal conductivity and compressive strength were decreased. The changes in the masses and compressive strength of ULWC samples subjected to freezing and thawing cycles were examined. The compressive strength loss was found to be between 5 % and 47 % while the weight loss was between 1 % and 3.5 % after 15 freezing and thawing cycles. Finally, the effects of the admixtures on the fresh properties of ULWC were examined and it was determined that the use of 4.5 kg of air-entraining material in one cubic meter of concrete mix is the most ideal ratio and the use of more than 0.01 % by volume of polypropylene fiber is caused settlements in fresh concrete mixtures.

Performance of temporary tie-backs under winter conditions

1981 ◽  
Vol 18 (4) ◽  
pp. 566-572 ◽  
Author(s):  
N. R. Morgenstern ◽  
D. C. Sego
Keyword(s):  
Air Temperature ◽  
Earth Pressure ◽  
Pressure Measurements ◽  
Sheet Pile ◽  
Freezing And Thawing ◽  
Railway Line ◽  
Winter Conditions ◽  
Design Requirements ◽  
The City ◽  
Sheet Pile Wall

The construction of an underpass in the City of Edmonton required the temporary relocation of the CNR main-line prior to the construction of a permanent bridge. The line was placed close to the underpass excavation which was supported by a tie-back sheet pile wall. Because of the stringent requirements associated with the presence of the railway line, the supports were designed on a conservative basis and observations of tie-back loads were taken over a period of 7 months.This note presents the observations of tie-back loads from January to July, 1977. Following installation in accordance with the design requirements, substantial fluctuations in tie-back load were observed for about 3 months. Then the loads fell off gradually to about 50% of the originally applied values. The variation of the load with time bears a strong correlation with average air temperature and is accounted for by the alternate freezing and thawing of the ground adjacent to the sheet pile wall. The ultimate decline in load is attributed to relaxation of the soil behind the wall during spring thaw. The case history draws attention to special requirements associated with interpretation of earth pressure measurements during winter con struction.

scholarly journals DEVELOPMENT OF LIGHTWEIGHT CONCRETE FROM EXPANDED CLAY MODIFIED WITH TIRE RUBBER WASTE

2021 ◽  
Author(s):  
Herbet Alves Oliveira
Keyword(s):  
Water Absorption ◽  
Lightweight Concrete ◽  
Experimental Program ◽  
Size Analysis ◽  
Mechanical Resistance ◽  
Hardened Concrete ◽  
Fine Aggregate ◽  
Specific Mass ◽  
Tire Rubber ◽  
Rubber Waste

Lightweight concrete has as main characteristic its low density due to the incorporation of light materials such as expanded clay, or even the incorporation of air whose function is to reduce the density, characteristic of cellular concrete. In Aracaju city, there are companies that promote tire reconditioning, generating large amounts of waste dust. The aim of this work is to study the reuse of tire rubber waste in light concrete from expanded clay. An experimental program was developed for the analysis of these concretes, varying the percentage of 1%, 2.5% and 5% of the tire rubber waste to replace the natural fine aggregate and 100% replacing the natural coarse aggregate by expanded clay (50% of expanded clay C1506 and 50% of C2215). The materials (cement, sand, expanded clays and tire rubber waste) were characterized through tests of particle size analysis and unit mass. The hardened concrete was evaluated through mechanical tests of axial compression strength, modulus of elasticity and tensile strength by diametrical compression, physical tests of water absorption and specific mass, in addition to image analysis by scanning electron microscopy. The use of expanded clay with incorporation of 1% of tire rubber waste guaranteed better results in mechanical resistance, lower water absorption and greater specific mass than the mixtures with 2.5 and 5%, reaching values close to the reference concrete. Thus, the residue can be an alternative for reuse, avoiding disposal.

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.

Grip of Mature and Fresh Concrete with Heat Treatment in Winter Conditions

2020 ◽  
Vol 992 ◽  
pp. 111-117
Author(s):  
V.V. Molodin ◽  
S.E. Sarafyan ◽  
D.S. Kasyanova
Keyword(s):  
Sea Water ◽  
Fresh Concrete ◽  
Protective Layer ◽  
Cement Clinker ◽  
Hardened Concrete ◽  
Climatic Zones ◽  
Winter Conditions ◽  
Sulfide Corrosion ◽  
Port Infrastructure ◽  
Mixing Water

Port infrastructure facilities, located in cold climatic zones in contact with sea water, are destroyed due to carbonation of concrete and sulfide corrosion. The restoration of the reinforcement protective layer by standard methods does not provide high-quality grip of the concrete structures that has undergone destruction and the repair concrete. The study of the “old” and “new” concrete grip using forced heating of the “new” one shows that mixing water with cement clinker components dissolved in it penetrates through the pores and capillaries deep into the “old” concrete to a depth of 60–70 mm under the temperature factor influence. After hardened concrete got its standard strength, it exceeds concrete grip, hardened under normal conditions by 30%.

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