a brief research about permeability & durability of concrete with helpful images for civil engineering students
fully made by Amira Abdullah (civil engineering student in Ismailia - Egypt)
Permeability of concrete, chemical attack, acid attack, efflorescence, Corrosion in concrete. Thermal conductivity, thermal diffusivity, specific heat. Alkali Aggregate Reaction
Quality Control in Concrete and Durability factors : An overviewbybyRAJESH PRASAD,IRSE, CPM/M, RVNL. KOLKATA. An interesting and informative presentation....
a brief research about permeability & durability of concrete with helpful images for civil engineering students
fully made by Amira Abdullah (civil engineering student in Ismailia - Egypt)
Permeability of concrete, chemical attack, acid attack, efflorescence, Corrosion in concrete. Thermal conductivity, thermal diffusivity, specific heat. Alkali Aggregate Reaction
Quality Control in Concrete and Durability factors : An overviewbybyRAJESH PRASAD,IRSE, CPM/M, RVNL. KOLKATA. An interesting and informative presentation....
Concrete Construction: Batching of mixes; casting process, compaction and curing;
requirement of mix design and casting of test cubes – removing cubes from moulds and
curing for strength tests; bar-bending equipments and preparation of reinforcement for
R C C works
Hydration-Induced Stresses in Concrete Buttressing of Existing Concrete Gravi...Nihal Vitharana
The raising and/or stabilising of existing concrete gravity dams by continuous concrete buttressing is a viable solution and, in some cases, it is the only solution available. There are few medium-large dams in Australia currently under consideration for raising with continuous buttressing.
Two of the major issues to be surmounted are: (a) the existing dam should not be subjected to cracking (particularly on the upstream face) due to heat-hydration effects, and (b) the requirement for the two dam bodies to resist the hydrostatic and other loadings as a monolith (unified dam).
However, there is great need for understanding the mechanisms involved in selecting an appropriate heat-of-hydration model and in calculating thermal stresses rationally. Due to such lack of understanding, expensive precautions, mostly with compounding conservatisms, would be adopted in concept and detailed designs eg. shear-keys on the interface, artificial cooling, post-grouted interface, anchor bars at the interface, concrete with high cement contents. On the other hand, unsafe designs could be the result.
The paper discusses these issues highlighting that a rational approach can be adopted to economise the design and construction processes. An example is also presented to demonstrate how the potential for temperature-induced cracking in new and old dam bodies can be evaluated with reduced uncertainty by considering all the mechanisms involved in a holistic way.
Performance of Concrete at Elevated Temperatures: Utilizing A Blended Ordinar...IOSR Journals
This study aimed at investigating the effect of subjecting concrete, produced with cement being
partially replaced with saw dust ash (SDA) to elevated temperatures. The performance of the test concrete cubes
was done by exposing them to elevated temperatures of 200oC, 400oC, 600oC and 800oC, and allowed to cool
down to room temperature before testing for their properties. Both the physical and thermal properties of the
concrete cubes were determined. The concrete produced by blending cement with 10% SDA with an average
percentage loss of 23.04% retained more of its compressive strength when exposed to the different
temperatures, than concrete produced using only OPC, which has an average percentage loss of 29.11%. It is
also found that, at an elevated temperature of 800oC, concrete fail totally in flexure due to the effect of high
heat on binding elements. The flexural strength of both the control concrete (at 0% OPC replacement) and
OPC/SDA blended concrete (at 10% OPC replacement) decreased as the temperature is increased. The
replacement of OPC by 10% SDA increased the thermal shock resistance of the concrete by 11 cycles than the
0% OPC concrete at the same temperature. The concrete produced with OPC has better thermal conductivity
than the concrete produced by blending OPC with SDA, as a result, the dislodgement of the concrete edges is
relatively lower in the SDA blended cement concrete than in the OPC concrete. The result shows that, blending
OPC with SDA in concrete performed better at elevated temperatures than concrete produced with only OPC.
Therefore, the replacement of OPC with 10% SDA can be applied as a fire resisting bonding material in
concrete.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
6. De-Icing Chemicals Exposure
Cementitious
materials
Fly ash (Class C up to
35%) and natural
pozzolans
Slag
Silica fume
Total of fly ash, slag,
silica fume and
natural pozzolans
Maximum
replacement , %
25
50
10
50
Cementitious
Materials
Requirements for
Concrete Exposed
to Deicing
Chemicals (Ref
ACI 318)
7. Fly Ash and Natural Pozzolans
Reduced Permeability & Diffusivity
Resistance to ASR
Consumption of Ca(OH)2
Reduction in water mobility
Resistance to Sulfate (Low CaO pozzolans)
Dilution of C3A
Consumption of Ca(OH)2
10. Disintegration Mechanism
Surface disintegration in the form of pitting or
scaling
High degree of saturation in the concrete is
mainly responsible for their detrimental effect
due to lower vapor pressure
Development of disruptive osmotic and hydraulic
pressures during freezing, principally in the paste
Concentrations (3 to 4%) of deicing solutions
most severe
11. Recommended Solutions
Benefit from entrained air in concrete
exposure same as frost action
Concrete surface should have received some
drying, and minimum strength level specified
and concrete cover
Do not use in pre-stressed concrete or where
steel reinforcement has been used due to
corrosion effect
12. Mass Concrete
Mass concrete requires
minimizing heat
generation in massive
elements or structures
such as very thick
bridge supports, and
dams.
14. Mass Concrete Heat Generation
Control the generation of heat and resultant
volume change within the mass will require
consideration of temperature control
measures
Concrete temperature rise of 10 to 15 F per
100 lb of Portland cement/yd3 in 18 to 72
hours
Temperature rise of the concrete mass creates
thermal gradient causing Cracking
15. Thermal Cracking
May reduce the service life of a structure by
promoting early deterioration or excessive
maintenance
Selection of proper mixture proportions is
only one means of controlling temperature
rise
Additional aspects of the concrete work
should be studied and incorporated into the
design and construction requirements
16. Nominal Maximum Size Aggregate
Mass concrete is not necessarily larger aggregate
concrete
The minimum cross sectional dimensions of a
solid concrete member approach or exceed 2 to 3
ft or when cement contents above 600 lb/yd3 are
being used
Larger aggregate provides less surface area to be
coated by cement paste, a reduction in the
quantity of cement and water can be realized for
the same water-cement ratio
18. Cementitious Materials Impact
Reduction of heat of hydration, improved
workability, improved strength and/or
improved durability
Fly ash, natural pozzolans meeting ASTM C
618
Slag cement meeting ASTM C 989
19. Portland Cement Impact
Fineness of cement is an important factor affecting rate
of heat liberation, particularly at early ages
ASTM C150 contains optional limits for the heat of
hydration for Type IV and also includes Type II (MH)
moderate heat cement that limits the C3S and C3A
content
Chemical optional requirements are less restrictive in
ASTM C150, as compared to the optional Physical
requirement when evoked; 60.cal/g is the maximum
permitted for a Type V cement (7 days) or 70 cal/g (28
days)
20. Principle Phases of Portland Cement
Tricalcium aluminate (C3A) releases most of its
heat in the first day or so
Tricalcium silicate (C3S) in the first week
Dicalcium silicate (C2S) and calcium
aluminoferrite (C4AF) hydrate more slowly
21. Blended Cement Impact
Blended cements have lower heats of hydration
than Portland cements
Generally, most slag cements, fly ashes, and
natural pozzolans will hydrate after 28-day thus
lowering the maximum heat peak of a concrete
mixture
The volume occupy by supplementary materials
like slag cement, fly ashes, and natural pozzolans
is typically less than Portland cement.
22. Carbonation Affects
Carbon dioxide causes a reaction producing
carbonates accompanied by shrinkage
Carbonation during production can improve
the strength, hardness, and dimensional
stability of concrete products
Carbonation can result in deterioration and a
decrease in the pH of the cement paste
leading to corrosion of reinforcement near the
surface
23. Exposure to Carbon Dioxide (CO2)
During the hardening process can affect the
finished surface of slabs, leaving a soft,
dusting, less wear-resistant surface
During the hardening process, the use of
unvented heaters or exposure to exhaust
fumes from equipment or other sources can
produce a highly porous surface subject to
further chemical attack
25. Crazing Surface
Crazing surface due
to premature drying,
shrinkage of
concrete surface
caused by exhaust
fumes of heating
equipment in an
enclosed area
26. Reaction of Hydrated Portland Cement
with CO2
Highly dependent on the relative humidity of
the environment, temperature, permeability
of the concrete, and concentration of CO2
Highest rates of carbonation occur when the
relative humidity is maintained between 50%
and 75%
Below 25% relative humidity, the degree of
carbonation that takes place is considered
insignificant
27. Absorption of Ambient CO2
CO2 absorbed by rain enters the groundwater as
carbonic acid
CO2, together with humic, carbonic, acid, can be
dissolved from decaying vegetation, resulting in
high levels of free CO2
The rate of attack, similar to that by CO2 in the
atmosphere, is dependent upon the properties of
the concrete and concentration of the aggressive
CO2
28. Abrasion Resistance
“Ability of a surface to resist being worn away
by rubbing and friction”
Abrasion resistance of concrete is a
progressive phenomenon
Closely related to compressive strength at the
wearing surface
degradation that is related to aggregate-topaste
29. Concrete Mixture Quality
Avoiding segregation;
Eliminating bleeding;
Properly timed finishing;
Minimizing surface w/cm (forbidding any
water addition to the surface to aid finishing);
Hard toweling of the surface; and
Proper curing procedures.
32. Special Aggregates
Addition of high-quality quartz
Traprock, or emery aggregates
A blend of metallic aggregate
Use of two-course floors using a high-strength
topping is generally limited to floors where
both abrasion and impact are destructive
effects at the surface
33. Pavement Abrasion Resistance
Adequate texture and skid resistance for
proper vehicular control
Related to concrete’s compressive strength
and to the type of aggregate in the concrete;
harder aggregates resist wear better than
softer aggregates
Wear of pavement surfaces occurs due to the
rubbing action from the wheels of vehicular
traffic
34. Pavement Abrasion
Production Operations, or foot or vehicular
traffic
Wind or waterborne particles can also abrade
concrete surfaces
Abrasion is of little concern structurally, yet
there may be a dusting problem that can be
quite objectionable in some kinds of service
Abrasion resistance of concrete is a
progressive phenomenon
36. Testing for Abrasion Resistance
Los Angeles (LA) abrasion test (rattler method)
performed in accordance with ASTM C 131 or
ASTM C 535 / AASHTO T 96
ASTM C 418 subjects the concrete surface to airdriven silica sand, and the loss of volume of
concrete is determined
ASTM C 779, three procedures simulate different
abrasion conditions
ASTM C 944, a rotating cutter abrades the surface
of the concrete under load
37. Alkali-carbonate rock reaction
Detrimental reactions are usually associated
with argillaceous dolomitic limestones that
have somewhat unusual textural
characteristics
Some carbonate rocks occurs in which the
peripheral zones of the aggregate particles in
contact with cement paste are modified and
develop prominent rims within the particle
38. Alkali-Carbonate Reactivity
Brucite [Mg(OH)2], dedolomitization of
Magnesium
Feature is different from alkali-silica reactivity,
in which the alkali is combined in the reaction
product as the reaction proceeds
Presence of clay minerals appears significant
39. Affected Concrete Characteristics
A network of pattern or map cracks
Typically where the concrete has a constantly
renewable supply of moisture
Waterline in piers
Earth behind retaining walls wick action in posts
or columns
General absence of silica- gel exuding from cracks.
41. Evaluation of Affected Concrete
Damage can be the result of:
Poor Design
Faulty Workmanship
Mechanical Abrasive Action
Cavitation Or Erosion From Hydraulic Action
Leaching
Chemical Attack
Chemical Reaction Inherent In The Concrete Mixture
Exposure To Deicing Agents
Corrosion Of Embedded Metal Or
Another Lengthy Exposure To An Unfavorable Environment
Guidance for examining and sampling hardened concrete in
construction is found in ASTM C 823
42. D-Cracking Deterioration
D-cracking is damage that occurs in concrete
due to expansive freezing of water in some
aggregate particles
The damage normally starts near joints to
form a characteristic D-shaped crack
44. D-Cracking Reduction
Selecting aggregates that are less susceptible
to freeze-thaw deterioration
Reducing the maximum aggregate size for
marginal aggregates are used
Providing drainage for carrying water away
from the base may prevent saturation of the
pavement
45. D- Cracking Aggregates Characteristics
Aggregate particles with coarse pore structure
may be susceptible to freeze-thaw damage
Particles become saturated and the water
freezes, expanding water trapped in the pores
cannot get out
Aggregate particles cannot accom-modate the
pressure from the expanding water; the
particles crack and deteriorate
46. Identifying D-Cracking
Closely spaced cracks parallel to transverse
and longitudinal joints
Location where aggregate is most likely to
become saturated
Cracks multiply outward from the joints
toward the center of the pavement slab
47. D-Cracking Corrective Measures
Designing a mixture it is critical to select
aggregates that are not susceptible to freezethaw deterioration
If marginal aggregates must be used, you may
be able to reduce D-cracking susceptibility by
reducing the maximum particle size
Providing good drain-age for carrying water
away from the pavement base
48. Please return to Blackboard and watch
the following videos:
Video 1: Maximum Size
Video 2: Minimum Size