Understanding the Limits of Deleterious Materials of ...€¦ · 4 2.3.2.4 Deleterious Materials...
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Understanding the Limits of Deleterious Materials of Aggregates for Airfield Pavement Job Specifications ACPA 54 th Annual Meeting November 30, 2017
Transcript of Understanding the Limits of Deleterious Materials of ...€¦ · 4 2.3.2.4 Deleterious Materials...
Understanding the Limits of Deleterious Materials of Aggregates for Airfield Pavement Job Specifications
ACPA 54th Annual MeetingNovember 30, 2017
Presenter
Presentation Notes
Good morning. My name is Joni Jones and I am a project manager at CTLGroup. Our corporate office is located in Skokie, IL which is 20 minutes north of Chicago. As a project manager working with concrete for the past 12 years. I’ve sorted concrete in three categories: I mostly work with LABCRETE. This is were we fabricate specimens using precise measuring tools. If the design says 14 pounds of cement, we will weight out 14.00 lbs of cement. We have multiple curing environments where temperature and humidity hardly changes. This is quite different when it comes to FIELDCRETE; it’s what is produced in the field. It doesn’t come out what we design on paper or in the lab, but it’s close enough. Then there’s something people like to call as LEGALCRETE. This is the stuff that people say when “we have a problem” and our consultants have to do some intense investigation to figure out a solution to your tough problem. So in a sense CTLGroup provides services all three types of concrete. Today’s topic, it’s all about LABCRETE because testing for deleterious materials in the lab will produce great FIELDCRETE and will help avoid LEGALCRETE.
Three Types of Concrete
• Labcrete• Fieldcrete• Legalcrete
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Definition of Deleterious
[del-i-teer-ee-uh s] adjective
• Causing harm or damage• Harmful often in a subtle or unexpected way
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2.3.2.4 Deleterious Materials – Airfield Pavements The amount of deleterious material in each size group of coarse
aggregate shall not exceed the limits shown in Table 5, determined in accordance with the test methods shown.
Section 32 13 14.13 – Concrete Pavement forAirfields and Other Heavy-Duty Pavements
Presenter
Presentation Notes
The section that I work with is 2.3.2.4 Deleterious materials – Airfield Pavements. Is anyone here familiar with this job specification? The amount of deleterious materials in each size group of coarse aggregate shall not exceed the limits shown in Table 5, determined in accordance with the test methods shown. I’ll show the table in a minute, but I have to point out that it states that each size group must be tested. So if a blend of two coarse aggregates are used, contractors need to understand that both must be tested even through they are from the same lithology.
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2.3.2.4 of Section 32 13 14.13Table 5 – Limits of Deleterious Materials in Coarse Aggregate for Airfield Pavements
Material Percentage by Mass (Severe Weather)
Clay Lumps & Friable Particles (ASTM C142) 0.2
Shale (ASTM C295) 0.1
Material Finer than 0.075 mm (No. 200 sieve) (ASTM C117) 0.5
Lightweight Particles (ASTM C123) 0.2
Clay Ironstone (ASTM C295) 0.1
Chert & Cherty Stone (less than 2.4 Sp. Gr.) (ASTM C123 & ASTM C295)
0.1
Claystone, Mudstone, and Siltstone (ASTM C295) 0.1
Shaly and Argillaceous Limestone (ASTM C295) 0.2
Other Soft Particles (COE CRD-C130) 1.0
Total of all deleterious substances exclusive of material finer than 0.075 mm (No. 200 sieve)
1.0
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Presenter
Presentation Notes
About half the tests are physical aggregate tests and the other have is petrography. On the left lists the tests required by the spec and the right is the limit. There used to be just a category for Severe Weather, but there is a Moderate Weather Category. The only differences in Moderate Weather is that the shale limit is increased to 0.2, and the clay ironstone, chert, and cherty stone are increased to 0.5.
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ASTM C117, Material Finer than 0.075 mm (No. 200 sieve)
Silt, clay, and loose dust may form a coating the aggregate particles.
Weaken the bond between the cement paste and aggregate.
Increases water demand
Presenter
Presentation Notes
During a sieve analysis we obtain the material finer than the No. 200 Sieve This material looks like dust. The silt, clay, and loose dust may form a coating the aggregate particles. This can weaken the bond between the cement paste and aggregate and can also increase water demand due to a the higher surface area.
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ASTM C142, Clay Lumps & Friable Particles
Clay lumps present in concrete may absorb some of the mixing water
Cause pop outs in hardened concrete
Affect durability and wear resistance
Can break up during mixing and increase the mixing water demand
Captions should be smaller and set in blue or orange.
Presenter
Presentation Notes
The first test mentioned is the clay lumps and friable particles. This test involves picking up every particle that has been soaking in water and rubbing the particles between your fingers. The sample is weighed before and after Clay lumps present in concrete may absorb some the of mixing water. These can cause pop outs in hardened concrete, it affects durability and wear resistance, and can break up during mixing and increase the mixing water demand.
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ASTM C123, Lightweight Particles
Coal, lignite, chert
Low density materials such as wood or fibrous materials
Excessive amounts will affect durability
If impurities are near the surface, pop outs or staining can occur
Presenter
Presentation Notes
This is the test for the lightweight particles. Particles like coal, lignite, and chert will float to the top if the particles are submerged in Zinc Cloride or Zinc Bromide. This also will show if low density materials such as wood or fibrous materials are present. Excessive amounts will affect the overall durability in concrete. If these impurities are near the surface, pop outs or staining can occur.
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Shale
Identified by ASTM C295 Fine-grained, thinly laminated
or fissile sedimentary rock. It is commonly composed of clay or silt or both. It has been indurated by compaction or by cementation, but not so much as to have become slate.
Presenter
Presentation Notes
For the analysis of each aggregate, a microscopist performs an intense version of ASTM C295 by looking for particles that fall under different particles of potential deleterious particles. The first type is Shale. Shale is fine-grained, thinly laminated or fissile sedimentary rock It is commonly composed of clay or silt or both It has been indurated by compaction or by cementation, but not so much as to have become slate.
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Clay ironstone Identified by ASTM C295 Defined as an impure variety of
iron carbonate, iron oxide, hydrous iron oxide, or combinations thereof, commonly mixed with clay, silt, or sand.
It commonly occurs as dull, earthy particles, homogeneous concretionary masses, or hard-shell particles with soft interiors.
Other names are commonly used for clay ironstone are “chocolate bars” and limonite concretions.
Presenter
Presentation Notes
Clay ironstone is defined as an impure variety of iron carbonate, iron oxide, hydrous iron oxide, or combinations thereof, commonly mixed with clay, silt or sand. It commonly occurs as dull, earthy particles, or hardned shell particles with soft interior Other names are common names are chocolate bars and limonite concretions. Here in the photo you can see what one of the chocolate bars has done It almost looks like corrosion, but the iron has oxidized and stained the concrete.
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Chert and Cherty Stone Identified by ASTM C295 Chert is defined as a rock
composed of quartz, chalcedony or opal, or any mixture of these forms of silica.
It is variable in color. The texture is so fine that the individual mineral grains are too small to be distinguished by the unaided eye.
Its hardness is such that it scratches glass but is not scratched by a knife blade.
It may contain impurities such as clay, carbonates, iron oxides, and other minerals.
Cherty stone is defined as any type of rock (generally limestone) that contains chert as lenses and nodules, or irregular masses partially or completely replacing the original stone.
Presenter
Presentation Notes
Chert is defined as a rock composed of quartz, chalcedony or opal, or any mixture of these forms of silica. It’s variable in color The texture is so fine that the individual mineral grains are too small to be distinguished by the unaided eye Its hardness is such that it scratches glass but is not scratched by a knife blade. It may contain impurities such as clay, carbonate, iron oxides, and other minerals. Cherty stone is defined as any type of rock (generally limestone) that contains chert as lenses and nodules, or irregular masses partially or completely replacing the original stone.
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Claystone, mudstone, and siltstone
Identified by ASTM C295 Defined as a massive fine-
grained sedimentary rock that consists predominantly of indurated clay or silt without laminations or fissility.
It may be indurated either by compaction or be cementation.
Presenter
Presentation Notes
Claystone, mudstone, and siltstone are defined as a massive fine grained sedimentary rock that consists predominantly of indurated clay or silt without laminations of fissility. It may be indurated either by compaction or be cementation.
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Shaly and argillaceous limestone
Identified by ASTM C295 Defined as limestone in which shale
occurs as one or more thin beds or laminae.
These laminae may be regular or very irregular and may be spaced from a few inches down to minute fractions of an inch.
Argillaceous limestone is defined as limestone in which clay minerals occur disseminated in the stone in the amount of 10-50 % by weight of the rock: when these make up from 50-90%, the rock is known as calcareous (or dolomitic) shale (or claystone, mudstone, or siltstone).
Presenter
Presentation Notes
Defined as limestone in which shale occurs as one or more thin beds or laminae. These laminae may be regular or very irregular and my be spaced from a few inches down to minute fractions of an inch. Argillaceous limestone is defined The job spec defines shaly and argillaceous stone as limestone in which clay minerals occur disseminated in the stone in the amount of 10-50% by weight of the rock; when these make up from 50-90% the rock is known as calcareous (or dolomitic) shale or claystone, mudstone or siltstone. All these definitions take a trained petrographer to accurately identify these different types of deleterious materials. In fact, I believe the spec requires that resumes must be submitted to the core who have to approve the petrographer.
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CRD-C 130, Soft Particles
Cause pop outs
Affects durability
Presenter
Presentation Notes
As part of the petrography process, a microcscopist will analysis each particle to look for soft particles. It was hard to find a picture of soft aggregate, so hence the soft fluffy bread. This test method involves taking each aggregate and scraping it against a large metal needle. If the needle leaves a scratch it’s considered a soft particle. Again, soft particles can cause pop outs and affects durability.
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Punch line – Prevent FOD
Foreign Object Debris
Presenter
Presentation Notes
The point of all this analysis is to prevent an airfield pavement that looks like swiss cheese. We’re trying to prevent pop outs. And we do not want any Foreign Object Debris Pop outs are different from spalling Pop outs occur from the aggregate failure and facture, where spalling occurs fracture between the aggregate and paste. It’s hard to believe that all this screening is to prevent a small but important factor to making concrete correctly. It’s to prevent any FOD flying into our expensive aircrafts. This is…to avoid LEGALcrete.
Section 32 13 14.132.3.2.5 Testing Sequence / Deleterious Materials – Airfields OnlyNo extension of time or additional payment due to any delays caused by the testing, evaluation, or personnel requirements is allowed. The minimum test sample size of the coarse aggregate is 90 kg [200 lb] for the 19 mm [3/4 in] and larger maximum size and 12 kg [25 lbs] for the 4.75 to 19 mm [No. 4 to 3/4 in] coarse aggregate.
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Presenter
Presentation Notes
One the paragraphs within the spec states, The Contractor will not be entitled to any extension of time or additional payment due to any delays caused by the testing, evaluation, or personnel requirements. What contractors don’t understand that the sequential testing can take about 2 months to complete the testing. I’ll explain in the moment why it takes this long. One of the reasons is from the next statement. Also those weights should indicate dry weights. Test samples in the referenced methods are listed as dry weights.
Section 32 13 14.132.3.2.5 Testing Sequence / Deleterious Materials – Airfields OnlyNo extension of time or additional payment due to any delays caused by the testing, evaluation, or personnel requirements is allowed. The minimum test sample size of the coarse aggregate is 90 kg [200 lb] for the 19 mm [3/4 in] and larger maximum size and 12 kg [25 lbs] for the 4.75 to 19 mm [No. 4 to 3/4 in] coarse aggregate.
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Presenter
Presentation Notes
The size of the coarse aggregate sample shall be at least 200 pounds for the ¾ inch and larger maximum size and 25 pounds for the No. 4 to ¾ inch coarse aggregate and 10 pounds for the fine aggregate. Everytime I’ve managed one of these test programs, one of the samples is 200 lbs. 200 lbs is a lot of material. It’s about 4 full 5 gallon buckets of material to test. Remember C142 and CRD C130? The technician or microscopist has to examine and pick up every particle and exam it. It takes more time to analyze the sample than the normal sample size requirement. The hardest or the longest top sizes to analyze is a #57 stone. Since these particles have a smaller top size when compared to a #4 aggregate. 200 lbs of #57 stone has more particles than 200 lbs of a #4 aggregate.
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Testing Sequence
Step 1: Wash each full sample of coarse aggregate for material finer than the 0.075 mm No. 200 sieve. Discard material finer than the 0.075 mm No. 200 sieve.
Step 2: Test remaining full sample for clay lumps and friable particles and remove.
Step 3. Test remaining full sample for chert and cherty stone with SSD density of less than 2.40 specific gravity. Remove lightweight chert and cherty stone. Retain other materials less than 2.40 specific gravity for Step 4.
Step 4: Test the materials less than 2.40 specific gravity from Step 3 for lightweight particles (Sp. GR. 2.0) and remove. Restore other materials less than 2.40 specific gravity to the sample.
Step 5: Test remaining sample for clay-ironstone, shale, claystone, mudstone, siltstone, shaly and argillaceous limestone, and remove.
Step 6: Test a minimum of one-fifth of remaining full sample for other soft particles.
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Presenter
Presentation Notes
The sequence has changed since the last time I gave this presentation. Thank you!! Steps 3 and 4 used to be switched. It’s so much easier when you’re dealing with 200 lbs of material to obtain the lightweight particles with the ZnBr first. Whatever material floats in the ZnBr can be used in the ZnCl since the specific gravity of ZnCl is less than the specific gravity of the ZnBr. We used to have to do the lighter specific gravity first, wash all the aggregates and then take the whole 200 lbs sample in the ZnBr.
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Pros & Cons
Pros Careful and strict testing will minimize pop
outs.
Lower water demand during fabrication.
Strong aggregate to paste bond to increase stiffness
Cons More stringent than most specs
More expensive
Longer turn around time for results
More labor intensive
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BUILDING KNOWLEDGE. DELIVERING RESULTS.
© CTLGroup 2011. The information contained in this document is intended only for use by the individual or entity it was issued to. No part of this work may be disseminated, distributed, or reproduced in any form or by any graphic, electronic or mechanical means (including photocopying, photographing, taping, or retrieval systems) without the written permission of the author, CTLGroup, or its duly designated representatives.
