Microstructural Aspects of Stress Corrosion of Cementitious Materials

1986 ◽  
Vol 85 ◽  
Author(s):  
U. Schneider ◽  
E. Nagele ◽  
N. Dujardin
Keyword(s):  
Corrosion Resistance ◽  
Flexural Strength ◽  
Stress Corrosion ◽  
Cement Mortar ◽  
Cementitious Materials ◽  
Strength Reduction ◽  
Time Dependent ◽  
Hardened Cement ◽  
Chemical Attack ◽  
Comprehensive Study

ABSTRACTStress corrosion phenomena, i.e. significant effects of mechanical stresses on the corrosion resistance of materials, have been reported for a large variety of materials, including metals, oxides and halides. Recently it has been shown [1,2] that cementitious materials are also sensitive to stress corrosion. The time dependent decrease in the flexural strength of chemically stressed concrete and mortar depends significantly on the mechanical stress acting simultaneously with the chemical attack.For cementitious materials a comprehensive study of the stress corrosion phenomena has been started. In this paper the latest results from the current research program are presented and the interrelations between the microstructure of hardened cement mortar and the strength reduction caused by stress corrosion, are briefly discussed.

scholarly journals Stress-Strain Behavior of Cementitious Materials with Different Sizes

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Jikai Zhou ◽  
Pingping Qian ◽  
Xudong Chen
Keyword(s):  
Flexural Strength ◽  
Size Effect ◽  
Cement Mortar ◽  
Strain Curve ◽  
Cementitious Materials ◽  
Test Results ◽  
Stress Strain ◽  
Strain Behavior ◽  
Modified Equation ◽  
Good Agreement

The size dependence of flexural properties of cement mortar and concrete beams is investigated. Bazant’s size effect law and modified size effect law by Kim and Eo give a very good fit to the flexural strength of both cement mortar and concrete. As observed in the test results, a strong size effect in flexural strength is found in cement mortar than in concrete. A modification has been suggested to Li’s equation for describing the stress-strain curve of cement mortar and concrete by incorporating two different correction factors, the factors contained in the modified equation being established empirically as a function of specimen size. A comparison of the predictions of this equation with test data generated in this study shows good agreement.

Initiation of stress corrosion cracking in cold-drawn prestressing steel in hardened cement mortar exposed to chlorides

CORROSION ◽  
10.5006/3730 ◽  
2021 ◽  
Author(s):  
Dyana Joseline ◽  
Radhakrishna Pillai ◽  
Lakshman Neelakantan
Keyword(s):  
Stress Corrosion ◽  
Passive Film ◽  
Stress Corrosion Cracking ◽  
Cement Mortar ◽  
High Strength ◽  
Corrosion Cracking ◽  
Hardened Cement ◽  
Electrochemical Characteristics ◽  
Residual Tensile Stress ◽  
Prestressing Steel

Cold-drawn, high strength, prestressing (PS) steel strands are widely used in pretensioned concrete (PTC) structures. This paper discusses the stress corrosion cracking (SCC) of PS steel embedded in cement mortar and gradually exposed to chlorides. Various stages of the passive to active (P-to-A) transition, which marks the onset of SCC, were investigated using EIS technique. The key mechanisms were identified and confirmed using SEM/EDAX, XRD and Confocal Raman Spectroscopy. It was found that the passive film on unstressed PS steel has better electrochemical characteristics than that on conventional steel rebars. However, the residual tensile stress at the surface of PS steels can assist passive film cracking after chloride attack - contrary to the pitting corrosion without cracking of passive film in conventional steels. Further, tests indicated that the concentration of chlorides required to crack the passive film in PS steels can reduce by about 50% when prestressed – as in field structures. Chemical composition, stress state and microstructural features at the PS steel surface were identified as possible factors influencing the initiation of SCC in PTC structures.

scholarly journals Challenges and Benefits of Utilizing Carbon Nanofilaments in Cementitious Materials

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Ardavan Yazdanbakhsh ◽  
Zachary Grasley ◽  
Bryan Tyson ◽  
Rashid Abu Al-Rub
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Carbon Nanofibers ◽  
Experimental Research ◽  
Cementitious Materials ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
The Past ◽  
The Poor ◽  
Drying Conditions

Carbon nanofibers/tubes (CNF/Ts) are very strong and stiff and as a result, are expected to be capable of enhancing the mechanical properties of cementitious materials significantly. Yet there are practical issues concerning the utilization of CNF/Ts in cementitious materials. This study summarizes some of the past efforts made by different investigators for utilizing carbon nanofilaments in cementitious materials and also reports recent experimental research performed by the authors on the mechanical properties of CNF-reinforced hardened cement paste. The major difficulties concerning the utilization of CNF/Ts in cementitious materials are introduced and discussed. Most of these difficulties are related to the poor dispersibility of CNF/Ts. However, the findings from the research presented in this work indicate that, despite these difficulties, carbon nanofilaments can significantly improve the mechanical properties of cementitious materials. The results show that CNFs, even when poorly dispersed within the cementitious matrix, can remarkably increase the flexural strength and cracking resistance of concrete subjected to drying conditions.

Effect of Multi-Walled Carbon Nanotubes on Mechanical Properties and Durability of Latex-Modified Cement Mortar

2016 ◽  
Vol 711 ◽  
pp. 232-240 ◽  
Author(s):  
Ling Shi Meng ◽  
Christopher K.Y. Leung ◽  
Geng Ying Li
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Cement Mortar ◽  
Cement Composite ◽  
Cementitious Materials ◽  
Chloride Diffusion ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

This paper studies the effects of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and durability of polymer latex-modified cement mortar. Latex-modified cementitious materials possess many advantages. However, reduction of mechanical properties due to the introduction of an amorphous structure within the cement composite has limited its application. In this study, multi-walled carbon nanotubes functionalised with carboxyl group (MWCNTs-COOH), ranging from 0% to 0.15% by weight, are added into mortar modified with 0.6 wt.% polyvinyl alcohol (PVA) latex. Mechanical properties including compressive strength and flexural strength are measured. Water absorption test and rapid chloride diffusion test are performed to assess durability performance. Results indicate considerable increase of compressive strength and flexural strength, as well as improvement in durability, by the addition of MWCNTs-COOH. With Scanning Electron Microscopy conducted on both the latex solution and cement composite, the microstructural changes resulted from MWCNT addition are revealed.

Resistance to Nitric Acid Corrosion of Latex Modified Sulphoaluminate Cement Mortar

2011 ◽  
Vol 382 ◽  
pp. 404-407 ◽  
Author(s):  
Wei Dong Hua ◽  
Hong Yi Jiang ◽  
Zi Xia Zhou
Keyword(s):  
Compressive Strength ◽  
Corrosion Resistance ◽  
Nitric Acid ◽  
Flexural Strength ◽  
Weight Change ◽  
Cement Mortar ◽  
Acid Corrosion ◽  
Change Rate ◽  
Cement Ratio ◽  
Correlation Performance

The correlation performance between polymer/cement ratio and corrosion resistance to nitric acid of latex modified sulphoaluminate (SA) cement mortar was investigated by testing the compressive strength, flexural strength and weight change rate of latex modified SA cement mortar in the nitric acid solution at different ages. In addition, considering the appearance of the specimen, the results show that the corrosion resistance to nitric acid of latex modified SA cement mortar is influenced positively by the polymer/cement ratio. With the ratio of emulsion to cement increasing, the corrosion resistance to nitric acid was enhancement. when the polymer/cement ratio was 0.2, the latex modified SA cement mortar showed the best performance in compressive strength, flexural strength, weight change rate and the appearance.

scholarly journals Rheological, mechanical, and abrasion characteristics of polymer-modified cement mortar and concrete

2020 ◽  
Vol 47 (11) ◽  
pp. 1226-1237
Author(s):  
Changjun Zhou ◽  
Liangliang Chen ◽  
Shaopeng Zheng ◽  
Yunxi Xu ◽  
Decheng Feng
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Abrasion Resistance ◽  
Cement Mortar ◽  
Concrete Pavement ◽  
Styrene Butadiene Rubber ◽  
Hardened Cement ◽  
Butadiene Rubber ◽  
Polymer Modified Concrete ◽  
Styrene Butadiene

The settlement of fresh concrete or improper operation during construction usually makes the water to cement (w/c) ratio of the cement mortar on the concrete pavement surface higher than designed, which may influence the abrasion resistance of concrete pavement. This study firstly tried to establish relationships between abrasion of hardened cement mortar and rheological characteristics of fresh cement mortar in the laboratory. Secondly, a polymer-modified cement mortar was developed with carboxyl styrene butadiene rubber latex added to the cement mortar. Its rheological properties in mixing, mechanical properties, and abrasion were investigated. It is found that the polymer-modified cement mortar has a much better abrasion resistance and flexural strength while lower compressive strength than cement mortar. A stronger correlation was observed between flexural strength rather than compressive strength and abrasion resistance of cement mortar. The proposed polymer-modified concrete also exhibited good abrasion resistance.

scholarly journals The Effect of Bacteria on Early Age Strength of CEM I and CEM II Cementitious Composites

2022 ◽  
Vol 14 (2) ◽  
pp. 773
Author(s):  
Tsz Ying Hui ◽  
Lorena Skevi ◽  
Bianca Reeksting ◽  
Susanne Gebhard ◽  
Kevin Paine
Keyword(s):  
Flexural Strength ◽  
Surface Morphology ◽  
Cementitious Materials ◽  
Strength Reduction ◽  
Cement Matrix ◽  
Early Age ◽  
Bacterial Cells ◽  
Strength Gain ◽  
Strength Tests ◽  
Lower Carbon

Despite being associated with lower carbon emissions, CEM II cementitious materials exhibit reduced early age strength compared to that of CEM I. Several studies have demonstrated early age strength improvements by incorporating bacterial cells in concrete. In this study, live vegetative bacteria and dead bacteria killed in two different ways were used to explore whether changes in strength are related to the bacteria’s viability or their surface morphology. Compressive and flexural strength tests were performed at mortars with and without bacteria for both CEM I and CEM II cement. Their microstructure, porosity and mineralogy were also examined. No net strength gain was recorded for either CEM I or CEM II bacterial mortars compared to non-bacterial controls, although changes in the porosity were reported. It is proposed that two phenomena, one causing strength-reduction and one causing strength-gain, took place in the bacterial specimens, simultaneously. It is suggested that each phenomenon is dependent on the alkalinity of the cement matrix, which differs between CEM I and CEM II mortars at early age. Nevertheless, in neither case could it be recommended that the addition of bacteria is an effective way of increasing the early age strength of mortars.

Research on Nitric Acid Corrosion Resistance of Latex Modified Ordinary Portland Cement Mortar

2012 ◽  
Vol 485 ◽  
pp. 262-265
Author(s):  
Wei Dong Hua ◽  
Hong Yi Jiang ◽  
Zi Xia Zhou
Keyword(s):  
Compressive Strength ◽  
Corrosion Resistance ◽  
Nitric Acid ◽  
Flexural Strength ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cement Mortar ◽  
Acid Corrosion ◽  
Cement Ratio ◽  
Acrylic Latex

The relationship between the ratio of styrene-acrylic latex to ordinary Portland cement (OPC) and the nitric acid corrosion resistance of latex modified ordinary Portland cement mortar was studied. The compressive strength and flexural strength of latex modified cement mortar in the nitric acid solution at different ages were tesed and the samples appearance was observed. The results show that the nitric acid corrosion resistance of latex modified OPC mortar is influenced positively by the latex/cement ratio. With the ratio of emulsion to cement increasing, the nitric acid corrosion resistance ability of OPC mortar was enhanced firstly and then decreased. When the polymer/cement ratio was 0.2, the latex modified cement mortar showed the best performance in compressive strength, flexural strength, and the appearance.

AMBRONZE 413

Alloy Digest ◽  
1969 ◽  
Vol 18 (6) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Surface Treatment ◽  
Stress Corrosion ◽  
Tensile Properties ◽  
Stress Corrosion Cracking ◽  
Electrical Contact ◽  
Heat Treating ◽  
Corrosion Cracking ◽  
Tin Bronze

Abstract AMBRONZE 413 is a copper-tin bronze recommended for plater's plates and electrical contact springs. It is relatively immune to stress-corrosion cracking. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Cu-201. Producer or source: Anaconda American Brass Company.

INCO ALLOY G-3

Alloy Digest ◽  
1986 ◽  
Vol 35 (10) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Heat Affected Zone ◽  
Iron Alloy ◽  
Heat Treating ◽  
Minor Elements ◽  
Nickel Chromium ◽  
Inco Alloy

Abstract INCO Alloy G-3 is a nickel-chromium-iron alloy with additions of molybdenum and copper. Some of the minor elements are controlled to provide increased resistance to weld heat-affected zone corrosion. The alloy has exceptional stress-corrosion cracking resistance in chloride-containing environments. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-341. Producer or source: lnco Alloys International.

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