fresh concrete properties & its standard tests

MaHmoud Khlifa Almoghazy AliraQi2nd CiViL Engineering

Section 21

Properties OF Fresh ConcreteIntroduction

The potential strength and durability of concrete of a given mix proportion is very dependent on the degree of its compaction.

It is vital, therefore, that the consistency of the mix be such that the concrete can be transported, placed, and finished sufficiently early enough to attain the expected strength and durability.

Significance The first 48 hours are very important for the performance of

the concrete structure. It controls the long-term behavior, influence f'c (ultimate

strength), Ec (elastic modulus), creep, and durability.

Properties OF Fresh ConcreteElasticity and Strength Of Concrete

The elastic properties of materials are a measure of their resistance to deformation under an applied load (but the elastic strain is recovered when the load is removed).

Strength usually refers to the maximum stress that a given kind of sample can carry.

Understanding these properties and how they are measured is essential for anyone wishing to use materials

Main Prop. OF Fresh Concrete

Consistency or fluidity of concrete is an important component of workability and refers in a way to the wetness of the concrete.

However, it must not be assumed that the wetter the mix the more workable it is. If a mix is too wet, segregation may occur with resulting honeycomb, excessive bleeding, and sand streaking on the formed surfaces

Concrete Consistency

On the other hand, if a mix is too dry it may be difficult to place and compact, and segregation may occur because of lack of cohesiveness and plasticity of the paste.

Concrete Consistency

3 Ways to determine Consistency of Fresh Concrete

Slump TestDefinition

A slump test is a method used to determine the consistency of concrete. The consistency, or stiffness, indicates how much water has been used in the mix. The stiffness of the concrete mix should be matched to the requirements for the finished product qualitySlump is a measurement of concrete’s workability, or fluidity.It’s an indirect measurement of concrete consistency or stiffness.

PrincipleThe slump test result is a measure of the behavior of a compacted inverted cone of concrete under the action of gravity. It measures the consistency or the wetness of concrete.

Slump TestApparatus

Slump cone : frustum of a cone, 300 mm (12 in) of height. The base is 200 mm (8in) in diameter and it has a smaller opening at the top of 100 mm

Scale for measurement,Temping rod(steel) 15mm diameter, 60cm length.

Slump TestProcedure

The base is placed on a smooth surface and the container is filled with concrete in three layers, whose workability is to be tested .

Each layer is temped 25 times with a standard 16 mm (5/8 in) diameter steel rod, rounded at the end.

When the mold is completely filled with concrete, the top surface is struck off (leveled with mold top opening) by means of screening and rolling motion of the temping rod.

The mold must be firmly held against its base during the entire operation so that it could not move due to the pouring of concrete and this can be done by means of handles or foot – rests brazed to the mold.

Slump TestProcedure

Immediately after filling is completed and the concrete is leveled, the cone is slowly and carefully lifted vertically, an unsupported concrete will now slump.

The decrease in the height of the center of the slumped concrete is called slump.

The slump is measured by placing the cone just besides the slump concrete and the temping rod is placed over the cone so that it should also come over the area of slumped concrete.

The decrease in height of concrete to that of mould is noted with scale. (usually measured to the nearest 5 mm (1/4 in).

Slump TestPrecautions

In order to reduce the influence on slump of the variation in the surface friction, the inside of the mold and its base should be moistened at the beginning of every test, and prior to lifting of the mold the area immediately around the base of the cone should be cleaned from concrete which may have dropped accidentally.

Slump TestTypes Of Slump

The slumped concrete takes various shapes, and according to the profile of slumped concrete, the slump is termed as;

Collapse Slump Shear Slump True Slump


Collapse SlumpIn a collapse slump the concrete collapses completely.A collapse slump will generally mean that the mix is too wet or that it is a high workability mix, for which slump test is not appropriate.

Shear SlumpIn a shear slump the top portion of the concrete shears off and slips sideways. ORIf one-half of the cone slides down an inclined plane, the slump is said to be a shear slump.If a shear or collapse slump is achieved, a fresh sample should be taken and the test is repeated.If the shear slump persists, as may the case with harsh mixes, this is an indication of lack of cohesion of the mix.


True SlumpIn a true slump the concrete simply subsides, keeping more or less to shapeThis is the only slump which is used in various tests.Mixes of stiff consistence have a Zero slump, so that in the rather dry range no variation can be detected between mixes of different workability.However , in a lean mix with a tendency to harshness, a true slump can easily change to the shear slump type or even to collapse, and widely different values of slump can be obtained in different samples from the same mix; thus, the slump test is unreliable for lean mixes.

Slump TestUses

The slump test is used to ensure uniformity for different batches of similar concrete under field conditions and to ascertain the effects of plasticizers on their introduction.

This test is very useful on site as a check on the day-to-day or hour- to-hour variation in the materials being fed into the mixer. An increase in slump may mean, for instance, that the moisture content of aggregate has unexpectedly increases.

Other cause would be a change in the grading of the aggregate, such as a deficiency of sand.

Too high or too low a slump gives immediate warning and enables the mixer operator to remedy the situation.

This application of slump test as well as its simplicity, is responsible for its widespread use.

Slump TestDegree of workability Slump (mm) Compacting

FactorUse for which

concrete is suitable

Very low 0 - 25 0.78Very dry mixes; used in road making. Roads vibrated by power operated machines

Low 25 - 50 0.85Low workability mixes; used for foundations with light reinforcement. Roads vibrated by hand operated Machines

Medium 50 - 100 0.92

Medium workability mixes; manually compacted flat slabs using crushed aggregates. Normal reinforced concrete manually compacted and heavily reinforced sections with vibrations

High 100 - 175 0.95

High workability concrete; for sections with congested reinforcement. Not normally suitable for vibration>Table : Workability, Slump and Compacting Factor of concrete with 19 or 38 mm (3/4 or 1 1/2 in) maximum size of aggregate.

Slump TestSlump (mm) 0 - 20 20 - 40 40 - 120 120 - 200 200 - 220

Consistency Dry Stiff Plastic Wet Sloppy

>Table : Relation between Consistency and Slump values

Slump TestDifference in Standards

The slump test is referred to in several testing and building code, with minor differences in the details of performing the test.United States

In the United States, engineers use the ASTM standards and AASHTO specifications when referring to the concrete slump test. The American standards explicitly state that the slump cone should have a height of 12-in, a bottom diameter of 8-in and an upper diameter of 4-in. The ASTM standards also state in the procedure that when the cone is removed, it should be lifted up vertically, without any rotational movement at all The concrete slump test is known as "Standard Test Method for Slump of Hydraulic-Cement Concrete" and carries the code (ASTM C 143) or (AASHTO T 119).

United Kingdom & Europe In the United Kingdom, the Standards specify a slump cone height of

300-mm, a bottom diameter of 200-mm and a top diameter of 100-mm. The British Standards do not explicitly specify that the cone should only be lifted vertically. The slump test in the British standards was first (BS 1881–102) and is now replaced by the European Standard (BS EN 12350-2)

Flow TestDefinition

The flow table test or flow test is a method to determine the consistence of fresh concrete.Application When fresh concrete is delivered to a site by a truck mixer it is sometimes necessary to check its consistence before pouring it into formwork.If the consistence is not correct, the concrete will not have the desired qualities once it has set, particularly the desired strength. If the concrete is too pasty, it may result in cavities within the concrete which leads to corrosion of the rebar, eventually leading to the formation of cracks (as the rebar expands as it corrodes) which will accelerate the whole process, rather like insufficient concrete cover. Cavities will also lower the stress the concrete is able to support.

Flow TestEquipment

Flow table with a grip and a hinge, 70 cm x 70 cm.Abrams cone, open at the top and at the bottom - 30

cm high, 17 cm top diameter, 25 cm base diameterWater bucket and broom for wetting the flow table.Tamping rod, 60 cm heightScale for measurement

Flow TestConducting

The flow table is wetted.The cone is placed on the flow table and filled with

fresh concrete in two layers, each layer 25 times tamp with tamping rod.

The cone is lifted, allowing the concrete to flow.The flow table is then lifted up several centimeters

and then dropped, causing the concrete flow a little bit further.

After this the diameter of the concrete is measured in a 6 different direction and take the average.

Flow Test

Flow Test

Percent of Flow 0 – 20 % 20 – 60 % 60 – 100

%100 – 120

%120 – 150

%

Consistency Dry Stiff Plastic Wet Sloppy

Ball Penetration Test (Kelly Ball)


DefinitionAnother method used in the field and

laboratory to measure the consistency of concrete is the ball penetration test (ASTM C360) which is also known as the Kelly ball test*.

ProcedureIt is performed by measuring the penetration, in inches, of a 6-in. diameter steel cylinder with a hemi spherically shaped bottom , weighing 30 lbs.


AdvantagesOne of the advantages of the ball penetration test

can be performed on the concrete in a hopper, buggy, wheelbarrow, or other suitable container.

Another advantage of this method is its simplicity and the rapidity with which the consistency of the concrete can be determined.

It is also not dependent on a procedure of filling and rodding a container like the slump test.

What Difference Between … ??

What Difference Between … ??Penetration Test (Kelly Ball)

This is a simple field test consisting of the measurement of the indentation made by15 cm diameter metal hemisphere weighing 13.6 kg. when freely placed on fresh concrete . The test has been devised by Kelly and hence known as Kelly Ball Test. This has not been covered by Indian Standards Specification. The advantages of this test is that it can be performed on the concrete placed in site and it is claimed that this test can be performed faster with a greater precision than slump test.

What Difference Between … ??Slump Test

Slump test is the most commonly used method of measuring consistency of concrete which can be employed either in laboratory or at site of work. It is not a suitable method for very wet or very dry concrete. It does not measure all factors contributing to workability, nor is it always representative of the placability of the concrete.

The apparatus for conducting the slump test essentially consists of a metallic mold in the form of a frustum of a cone having the internal dimensions as under: Bottom diameter : 20 cm

Top diameter : 10 cm Height : 30 cm

Concrete WorkabilityDefinition

The property of fresh concrete which is indicated by the amount of useful internal work required to fully compact the concrete without bleeding or segregation in the finished product.

Workability is one of the physical parameters of concrete which affects the strength and durability as well as the cost of labor and appearance of the finished product

Concrete is said to be workable when it is easily placed and compacted homogeneously i.e without bleeding or Segregation. Unworkable concrete needs more work or effort to be compacted in place, also honeycombs &/or pockets may also be visible in finished concrete.

Concrete WorkabilityFactors affecting workability

Water content in the concrete mix Amount of cement & its Properties Aggregate Grading (Size Distribution) Nature of Aggregate Particles (Shape, Surface

Texture, Porosity etc.) Temperature of the concrete mix Humidity of the environment Mode of compaction Method of placement of concrete Method of transmission of concrete

Concrete WorkabilityHow To improve the workability of concrete

increase water/cement ratio increase size of aggregate use well-rounded and smooth aggregate instead of

irregular shape increase the mixing time increase the mixing temperature use non-porous and saturated aggregate with addition of air-entraining mixtures

An on site simple test for determining workability is the SLUMP TEST.

Compacting Factor TestIntroduction

These tests were developed in the UK by Glanville ( 1947 ) and it is measure the degree of compaction For the standard amount of work and thus offer a direct and reasonably reliable assessment of the workability Of concrete . the test require measurement of the weight of the partially and fully compacted concrete and the ratio the partially compacted weight to the fully compacted weight, which is always less than one, is known as compacted factor .

For the normal range of concrete the compacting factor lies between 0.8 - 0.92

Compacting Factor TestApparatus

TrowelsHand Scoop (15.2 cm long) Rod of steel or other suitable material (1.6 cm diameter, 61 cm long rounded at one end ). Balance.

Compacting Factor TestProcedure

1) Ensure the apparatus and associated equipment are clean before test and free from hardened concrete and superfluous water .

2) Weigh the bottom cylinder to nearest 10gm , put it back on the stand and cover it up with a pair of floats .

3) Gently fill the upper hopper with the sampled concrete to the level of the rim with use of a scoop .

4) Immediately open the trap door of the upper hopper and allow the sampled concrete to fall into the middle hopper .

5) Remove the floats on top of the bottom cylinder and open the trap door of the middle hopper allowing the sampled concrete to fall into the bottom cylinder .

6) Remove the surplus concrete above the top of the bottom cylinder by holding a float in each hand and move towards each other to cut off the concrete across the top of cylinder

Compacting Factor Test7) Wipe clean the outside of cylinder of concrete and weigh to

nearest 10gm .8) Subtract the weight of empty cylinder from the weight of

cylinder plus concrete to obtain the weight of partially compacted concrete .

9) Remove the concrete from the cylinder and refill with sampled concrete in layers .

10) Compact each layer thoroughly with the standard Compacting Bar to achieve full compaction .

11) Float off the surplus concrete to top of cylinder and wipe it clean .

12) Weigh the cylinder to nearest 10gm and subtract the weight of empty cylinder from the weight of cylinder plus concrete to obtain the weight of fully compacted concrete .

Compacting Factor Test

Workability Slump (mm) C.F Uses

Very Low 0 - 25 0.78 Roads - Pavements

Low 25 - 50 0.85 Foundations Concrete

Medium 25 - 100 0.92 Reinforced Concrete

High 100 - 175 0.95Reinforced Concrete

(High Reinforcement)

VeBe Time Test

VeBe Time TestDefinition

It is based on measuring the time (Called VEBE time) needed to transfer the shape of a concrete mix from a frustum cone to a cylinder (these shapes are standardized by the apparatus of this test), by vibrating and compacting the mix. The more VEBE time needed the less workable the mix is. This method is very useful for stiff mixes.

Apparatus Cylindrical container with diameter = 240 mm, and height = 200 mm Mold: the same mold used in the slump test. Disc : A transparent horizontal disc attached to a rod which slides

vertically Vibrating Table : 380*260 mm, supported by four rubber shock

absorbers Tamping Rod Stop watch

VeBe Time TestProcedure

1) Slump test as described earlier is performed, placing the slump cone inside the sheet metal cylindrical pot of the consist meter.

2) The glass disc attached to the swivel arm is turn and place on the top of the concrete in the pot.

3) The electrical vibrator is then switched on and simultaneously a stop watch started.

4) The vibration is continued till such time as the conical shape of the concrete disappears and the concrete assume a cylindrical shape.

5) This can be judge by observing the glass disc from the top disappearance of transparency.

6) Immediately when the concrete fully assume a cylindrical shape, the stop watch is switched off.

VeBe Time Test7) The time required for the shape of concrete to change

from slump cone shape to cylindrical shape in second is known as Vibe Degree.

8) This method is very suitable for very dry concrete whose slump value cannot be measure by slump test, but the vibration is too vigorous for concrete with slump greater than about 50m.

The test fails if VeBe Time is less than 5 seconds .. And the test must be created when no collapse or shears slump in concrete

Concrete SegregationDefinition

Segregation is when the coarse and fine aggregate, and cement paste, become separated. Segregation may happen when the concrete is mixed, transported, placed or compacted

Segregation makes the concrete WEAKER, LESS DURABLE, and will leave A POOR SURFACE FINISH ^_*

Concrete SegregationBasic types of segregation

Coarse segregation : Occurs when gradation is shifted to include too much coarse aggregate and not enough fine aggregate. Coarse segregation is characterized by low asphalt content, low density, high air voids, rough surface texture, and accelerated rutting and fatigue failure (Williams et. al., 1996b). Typically, coarse segregation is considered the most prevalent and damaging type of segregation; thus segregation research has typically focused on coarse segregation. The term “segregation” by itself is usually taken to mean “coarse segregation.”

Fine segregation : Occurs when gradation is shifted to include too much fine aggregate and not enough course aggregate. High asphalt content, low density, smooth surface texture, accelerated rutting, and better fatigue performance characterize fine segregation (Williams, Duncan and White, 1996).

Concrete SegregationTo Avoid Segregation

Check the concrete is not 'too wet' or 'too dry'.Make sure the concrete is properly mixed. It is

important that the concrete is mixed at the correct speed in a transit mixer for at least two minutes immediately prior to discharge.

The concrete should be placed as soon as possible.When transporting the mix, load carefully.Always pour new concrete into the face of concrete

already in place.When compacting with a poker vibrator be sure to use it

carefully

Concrete SegregationTo Avoid Segregation

If placing concrete straight from a truck, pour vertically and never let the concrete fall more than one-and-a-half meters.

Concrete Bleeding

Concrete BleedingIntroduction

This refers to the appearance of water along with cement particles on the surface of the freshly laid concrete. This happens when there is excessive quantity of water in the mix or due to excessive compaction. Bleeding causes the formation of pores and renders the concrete weak. Bleeding can be avoided by suitably controlling the quantity of water in the concrete and using finer grading of aggregates.

A thorough knowledge of why concrete bleeds and how mix proportions affect it, is required to preventing the harmful effects of bleeding. Adoption of right finishing methods also helps to ensure that the bleeding problems won't ruin a slab surface.

Concrete BleedingBleeding Process

Almost all freshly placed concrete bleeds. As aggregate and cement particles settle, they force excess mixing water upward. The process continues until settlement stops, either because of solids bridging or because the concrete has set.

The total amount of bleeding or settlement depends on mix properties, primarily water content and amount of fines (cement, fly ash, fine sand). Increasing water content increases bleeding, and increasing the amount of fines reduces bleeding. Amount of bleeding is also proportional to the depth of concrete placed. More bleed water rises in deep sections than in thin ones.

Bleeding usually occurs gradually by uniform seepage over the whole surface, but sometimes vertical channels form. Water flows fast enough in these channels to carry fine particles of cement and sand, leaving "wormholes" in the interior or sand streaks at the form face. Channels are more likely to form when concrete bleeds excessively.

Channels that reach the surface are open paths for deicing solutions to penetrate the concrete. This leads to freezing and thawing damage and rebar corrosion.

Concrete BleedingEffects Of Excessive bleeding in Deep Section

Sometimes bleedwater can't entirely evaporate because it has been trapped near the top surface by setting. This raises the water-cement ratio, increases permeability, and lowers strength. Excessive bleeding also causes some other problems in deep sections: heavy laitance accumulation at horizontal construction joints; bond loss at aggregate and rebar surfaces; and unsightly sand streaks.

Bleeding Problems in Flatwork Never float or trowel concrete while there's bleedwater on the

surface. That's the cardinal rule of finishing. Finishing before bleedwater has evaporated can cause dusting, craze cracking, scaling, and low wear resistance. Working bleed-water into the surface also increases permeability.

Concrete BleedingHow to control bleeding

Excessive bleeding can be avoided. Don't add too much water to the concrete. Most of the water added to make placing easier bleeds out of the concrete. Any time saved during placement will be lost while waiting for the bleedwater to evaporate. Place concrete at the lowest possible slump. If you need a higher slump to speed placement, consider using a super plasticizer. Add additional concrete fines to reduce bleeding. The fines may come from a number of sources: Use a more finely ground cement. Concretes made with high early strength

(Type III) cement bleed less because the cement is ground finer than normal (Type I) cement.

Use more cement. At the same water content, rich mixes bleed less than lean mixes.

Use fly ash or other pozzolans in the concrete. If concrete sands don't have much material passing the No. 50 and 100 sieves,

blend in a fine blow sand at the batch plant. For air- entrained concrete, use the maximum allowable amount of entrained

air. Consider using an air- entraining agent whenever excessive bleeding is a problem. Entrained air bubbles act as additional fines. Air entrainment also lowers the amount of water needed to reach a desired slump.

Determination Of Bleeding Water For Fresh Concreteالطازجة للخرسانة النضح اختبار

رقم ) المصرى ( 8 – 6اختبار الكود

الهـــــــدفتعيين كمية المياه النسبية المنضوحة للخرسانة الطازجة ) الخرسانة العادية و

خرسانة الهواء المحبوس (وهو يتوقف على طريقة الدمك المستخدمة فى الموقع

أوال : العينات المدموكة بقضيب الدمكاالجهـــزة

إناء اـسطوانىميزانسحاحة ماءأنبوبة اختبارقضيب دمكمسطرينسخان كهـربيميزان حساـس


رقم ) المصرى ( 8 – 6اختبار الكود االولى بالطريقة االختبار اجراء خطوات

السطح يسوى ثم بالكامل بالخرسانة الوعاء ملء التجربة بداية وقت يسجل الخرسانى ومحتواه اإلناء كتلة يسجل النضح مياه سحب حالة فى إال العينة حول من األسطوانة اإلناء رفع يتم ال كل النضح مياه الـ 10تسحب خالل كل 40دقائق ثم األولى حتى 30دقيقة ذلك بعد دقيقة

المياه كمية وتسجل المدرجة االختبار أنبوبة فى المياه هذه وتوضع الخرسانة نضح يتوقفسحب مرة كل بعد األنبوبة فى المتراكمة

األستشارى بمعرفة المحدودة المياه كمية إلى الوصول عند الساعة إيقاف يتم السخان على وضعه ثم القدح فى بوضعه وذلك المنضوح للماء الصافى الماء وزن تحديد تم

المياه تبخر بعد القدح وزن يحسب القدح = – ثم وزن بالماء القدح وزن الصافى الماء وزنالمياه تبخر بعد

( حجم مياه النضحV)V1 ) حجم الماء المجمع عند أى زمن ) المنضوحA مساحة الخرسانة يحدد معدل النضح بمقارنة قيمةV فى كل مرحلة زمنية متساوية

يحسب وزن ماء النضح المتجمع كنسبة من وزن الماء الصافى الموجود بعينة االختبار W1وزن ماء النضح بالحجم )جم( = W2وزن الماء فى عينة االختبار =وزن الماء الكلى – وزن الماء الممتـص بالركام ( =) W3وزن الماء الصافى بالخلطة =

W4الوزن الكلى للخلطة = W5وزن عينة االختبار =



ثانياً : العينات المدموكة بالهزاالجهـــزة

منضدة اهتزازساعة ايقافإناء مخروطىميزانسحاحة ماء سم مكعب100انبوبة اختبار قضيب دمكمسطرينسخان كهربىميزان حساس


رقم ) المصرى ( 8 – 6اختبار الكود الثانية بالطريقة االختبار اجراء خطوات

وضع العينة فى اإلناء المخروطى حتى ارتفاع يساوى متوسط قطرىالمخروط

يوضع اإلناء المخروطى فوق المنضدة الهزازة ويثبت جيدا ويتم دمك العينةبالهز

يتم إيقاف عملية الهز بمجرد ظهور مياه النضح ( للتشغيل ثم فترة 3يغطى اإلناء المخروطى ويتم عمل هزات متتالية ) ثوانى

ثانية (30إيقاف بين كل هزة واألخرى ) يحدد الحجم الكلى للماء المنضوح كما سبق فى الطريقة األولى مع مراعاة أن نتائج االختبار تتأثر باختالف درجات الحرارة لذلك يفضل أن

تكون درجات الحرارة أثناء التجربة مماثلة لدرجة حرارة الموقع

Secondary Prop. OF Fresh Concrete

Determination Of Air Content (Volumetric Method)الحجمية بالطريقة المحبوس الهواء محتوى تعيين اختبار


الهـــــــدفتحديد محتوى الهواء المحجوز داخل الخرسانة الطازجة

)بالنسبة للخرسانات المـحتويةعلى إضافات أو مواد إحاللية لألسمنت )غبار السيليكا أو بدونها (

ويستخدم هذا االختبار للخرسانة المستخدم فيها أى نوع من الركاماالجهـــزة

عداد هوائى قياسىالقمعقضيب الدمككوب قياسسرنجةوعاء تفريغمسطرين تسوية ومغرفةكحول االيزوبوربيلمطرقة مطاطية

االختبار اجراء خطوات- 25مـرحلة الدمك ) يملء القدح على ثالث طبقات من الخرسانة الطازجة ـوتدمك كل طبقة

مرة ( ويتم الدق على جوانـب القدح بالمطـرقة المطاطية للتخلص من الهواء المحبوس) مـرحلة التسوية ) يتم تسوية ـالسطح مرحلة إضافة الماء ) يثبت القطاع العلوى فوق القدح ويضاف الماء بواسطة القمع حتى

يظهـر بالرقبة – ثم يرفع القمع ثم يضبط منسوب الماء حتى عالمة الصفر بواسطة السرنجة (

مرحلة الهـز )يتم قلب وهز الوحدات للتخلص من الهواء المحبوس حتى ثبات عمود الماءفى األنبوبة(

من الكحول بواسطة السرنجة للتخلص من أى فقاعات 3 سم1طرد الفقاقيع ) يتم إضافة متواجدة فوق سطح عمود الماء (

(0.01القــــراءة ) يتم قراءة ارتفاع السائل الموجود باالنبوبة المدرجة ألقرب %

النتائج نسبة الهواء فى الخرسانة = ارتفاع السائل باألنبوبة المدرجة + كمية الكحول المضافة

Determination Of Air Content (Volumetric Method)الحجمية بالطريقة المحبوس الهواء محتوى تعيين اختبار


Determination Of Air Content (Pressure Method)الضغط بطريقة المحبوس الهواء محتوى تعيين اختبار


الهـــــــدفهو تحديد مقدار الهواء المحجوز فى الخرسانة الطازجة والذى يمثل الهواء الموجود داخل الخرسانة فقط دون الركام ) الركام المستخدم ذو مسامية

صغيرة جدا (يستخدم هذا االختبار للخرسانة المحتوية على ركام عادى أو ثقيل فقط

االجهـــزـة عداد هوائى قياسى2عدد إناء معايره)انبوبة رشاشة )بخاخةمسطرينقضيب الدمك – الغز - التسويةمـطرقة من المطاطالقمعإناء لوضع الماء مم37.5هزاز + منخل

االختبار اجراء خطوات) أوال باستخدام العداد ) أ

- يجب التأكد من نظافة جميع األسطح المستخدمة فى االختبار1- يملء الجهاز بالماء حتى منتصف األنبوبة المدرجة2 درجة على المحور الرأسى ويترك للتخلص من الهواء المحبوس 30- يتم إمالة الجهاز 3- يعاد الجهاز لوضعه اإلصلى ثم يملء الجهاز بالماء حتى منسوب الصفر 4بسكال عند منسوب الصفر** تؤخذ قراءة عامود الماء p = 1380- يتم التاثير بضغط 5

H1باالنبوبة وليكن يخفض الضغط تدريجيا حتى يصل صفر خالل دقيقتين عن طريق فتح السدادة - 6

0.00عند الضغط H2العلوية للجهاز ويتم تحديد ارتفاع عمود الماء فى االنبوبة وليكن =P Aapكمية الهواء الظاهـرى - 7

تكرر الخطوة السابقة وتؤخذ المتوسطات بحيث تكون االختالف فى النتائج فى حدود 20 %



االختبار اجراء خطوات) ثانيـا باستخدام العداد ) ب

- يجب التأكد من نظافة جميع األسطح المستخدمة فى االختبار1- تثبيت الجهاز2- التخلص من الهواء الموجود عن طريق ) غلق صمام الهواء ( وملء القدح بالماء عن 3

طريق فتحتى الماء يتم خروج الماء من الفتحة األخرى مصاحبا مع الهواء مع مراعاة الرج أثناء مرور الماء

- قفل صمام الهواء ويسمح بمرور الهواء داخل الغرفة حتى تصل قراءة العداد إلى خط 4الضغط األبتدائى

- يبرد الهواء المضغوط5- يثبت العداد اليدوى عند خط الضغط اإلبتدائى 6- تغلق فتحتى الماء الموجودتين بغطاء الجهاز7- يفتح صمام الهواء بين القدح وغرفة الهواء مع الطرق على جوانب اإلناء 8- يتم قراءة قيم الضغط الموجودة بالعداد9

( A- كمية الهواء بالعينة المختبرة ) 10هى معامل التصحيح للركام Cfحيث

مم37.5عندما يكون المقاس اإلعتبارى للركام أكبر من Ac- كمية الهواء بالخليط الكلى 11



حيث V1 = 37.5الحجم المطلق لمكونات الخليط المار من منخل V2 = الحجم المطلق لكل مكونات الخليطVg = 37.5الحجم المطلق للركام الذى مقاسه االعتبارAm- كمية الهواء بالمونة الموجودة بالخرسانة 11

حيثVm = الحجم المطلق لمكونات المونة بالخليط

ويتم مقارنة النتائج بالقيم التالية حسب مقاس الركام مم10 % فى حالة استخدام ركام بمقاس اعتبار أكبر من 7 مم15 % فى حالة استخدام ركام بمقاس اعتبار أكبر من 6 مم20 % فى حالة استخدام ركام بمقاس اعتبار أكبر من 5 مم40 % فى حالة استخدام ركام بمقاس اعتبار أكبر من 4



Determination Of Densityالمدموكة الطازجة الخرسانة كثافة تعيين اختبار


الهـــــــدفتعيين كثافة الخرسانة الطازجة

) الكثافة = وزن كمية من الخرسانة المدموكة / حجم كمية الخرسانة(االجهـــزة

ميزانوعاءجاروف قياسىقضيب دمك – هزمسطرينمسطرة مدرجةسحاحة زجاجيةحوض لتجهيز العينةجاروف بفتحة مربعة

االختبار اجراء خطوات1 -ملء الوعاء بالخرسانة

- يتم التخلص من الهواء الموجود بقدر اإلمكان وذلك بوضع الخرسانة على 2ثالث طبقات متساوية وتدمك كل طبقة بقضيب الدمك أو الهزاز ثم يسوى

السطح- يتم وزن الوعاء بمحتوياته3- وزن الخرسانة المدموكة = وزن الوعاء بمحتوياته - وزن الوعاء فارغ4D- الكثـافة 5

Determination Of Densityالمدموكة الطازجة الخرسانة كثافة تعيين اختبار


Determination Of Setting Time (Penetration Resistance)للخرسانة الشك زمن لتعيين االختراق مقاومة اختبار


الهـــــــدفتحديد زمن شك الخرسانة االبتدائى والنهائى

زمن شك الخرسانة االبتدائىالزمن بين فترة إضافة الماء لالسمنت ووصول مقاومة الخرسانة لإلختراق إلى

2 نيوتن /مم3.50زمن سك الخرسانة النهائى

الزمن بين فترة إضافة الماء لالسمنت ووصول مقاومة الخرسانة لإلختراق إلى 2 نيوتن /مم27.6

االجهـــزةاالوعية القياسيةجهاز مقاومة االختراققضيب الدمكماصة

االختبار اجراء خطوات1 - درجة 15 – 10إزالة ماء النضح من العينة بواسطة الماصة ) وذلك بامالة العينة بزاوية

لمدة كافية2تثبيت إبرة االختراق والجهاز بحيث تالمس اإلبرة سطح العينة -3 مم ) عالمة اإلبرة (25- يتم الضغط على الجهاز تدريجيا حتى يصل اختراق اإلبرة إلى 4 ( ثوانى10- يجب أن يتم هذا االختراق خالل ) 5 تسجل القوة المطلوبة لالختراق ، ووقت االختراق محسوبا من لحظة إضافة الماء -

لألسمنت6 ساعات 3- تؤخذ القراءات كل ساعة للخلطات العادية وتؤخذ قراءة الشك االبتدائى بعد

من لحظة إضافة الماء للخلطة بالنسبة للخلطات سريعة التصلد يجب أخذ قراءة الشك االبتدائى خالل ساعة أو •

(2 – 1ساعتين) بالنسبة للخلطات بطيئـة التصلد يجب أخذ قراءة الشك االبتدائى خالل أربعةأو ستة •

(6–4ساعات ) قراءات ويجب االستمرار فى 6• مع مراعاة أال يقل عدد القراءات فى كل اختبار عن

2 نيوتن / مم27.6أخذ القراءات حتى تصل مقاومة االختراق يحسب زمن الشك بأخذ المتوسطات لالزمنة المحسوبة فى كل حالة •

Determination Of Setting Time (Penetration Resistance)للخرسانة الشك زمن لتعيين االختراق مقاومة اختبار


6 Tests to determine SCC Properties (Self Consolidating Concrete)

Slump Flow TestDefinition

The slump flow test aims at investigating the filling ability of SCC. It measures two parameters: flow spread and flow time T50 (optional). The former indicates the free, unrestricted deformability and the latter indicates the rate of deformation within a defined flow distance.

Apparatus Base plate of size at least 900 × 900 mm Abrams cone with the internal upper/lower diameter equal to 100/200

mm and the height of 300 mm Weight ring (>9 kg) for keeping Abrams cone in place during sample

filling Stopwatch Ruler (graduated in mm) Bucket with a capacity of larger than 6 liters Moist sponge or towel for wetting the inner surface of the cone

Slump Flow TestProcedure

Place the cleaned base plate in a stable and level position.Fill the bucket with 6~7 litres of representative fresh SCC and

let the sample stand still for about 1 minute (± 10 seconds)During the 1 minute waiting period pre-wet the inner surface

of the cone and the test surface of the base plate using the moist sponge or towel, and place the cone in the centre on the 200 mm circle of the base plate and put the weight ring on the top of the cone to keep it in place. (If a heavy cone is used, or the cone is kept in position by hand no weight ring is needed)

Fill the cone with the sample from the bucket without any external compacting action such as rodding or vibrating. The surplus concrete above the top of the cone should be struck off, and any concrete remaining on the base plate should be removed

Slump Flow TestProcedure

After a short rest (no more than 30 seconds for cleaning and checking the moist state of the test surface), lift the cone perpendicular to the base plate in a single movement, in such a manner that the concrete is allowed to flow out freely without obstruction from the cone, and start the stopwatch the moment the cone looses contact with the base plate.

Stop the stopwatch when the front of the concrete first touches the circle of diameter 500 mm. The stopwatch reading is recorded as the T50 value. The test is completed when the concrete flow has ceased

Measure the largest diameter of the flow spread, dmax, and the one perpendicular to it, dperp, using the ruler (reading to nearest 5 mm). Care should be taken to prevent the ruler from bending.

Slump Flow TestExpression Of Results

The slump flow spread S is the average of diameters dmax and dperp, as shown in Equation (1). S is expressed in mm to the nearest 5 mm

The slump flow time T50 is the period between the moment the cone leaves the base plate and SCC first touches the circle of diameter 500 mm. T50 is expressed in seconds to the nearest 1/10 seconds

Slump Flow TestPrecision

In accordance with ISO 5725, the repeatability r is defined as the difference between two consecutive test values by the same operator with the same apparatus that should be exceeded only once in 20 times, and reproducibility R is defined as the difference between two consecutive test values by different operators with different apparatus that should be exceeded only once in 20 times

Based on the inter-laboratory test organized in the EU-project “Testing-SCC” (GRD2-2000-30024/G6RD-CT-2001-00580) with 2 replicates and 16 operators from 8 laboratories, the values of repeatability and reproducibility of the slump flow spread and flow time T50 are listed in Table 1

Slump Flow Test

L-Box TestDefinition

The method aims at investigating the passing ability of SCC. It measures the reached height of fresh SCC after passing through the specified gaps of steel bars and flowing within a defined flow distance. With this reached height, the passing or blocking behavior of SCC can be estimated

Apparatus Two types of gates can be used, one with 3 smooth bars and one

with 2 smooth bars. The gaps are 41 and 59 mm, respectively Suitable tool for ensuring that the box is level i.e. a spirit level Suitable buckets for taking concrete sample

L-Box Test

L-Box TestProcedure

Place the L-box in a stable and level position Fill the vertical part of the L-box, with the extra adapter

mounted, with 12.7 liters of representative fresh SCC Let the concrete rest in the vertical part for one minute (± 10

seconds). During this time the concrete will display whether it is stable or not (segregation).

Lift the sliding gate and let the concrete flow out of the vertical part into the horizontal part of the L-box.

When the concrete has stopped moving, measure the average distance, noted as Δh, between the top edge of the box and the concrete that reached the end of the box, at three positions, one at the centre and two at each side

L-Box TestExpression Of Results

The passing ratio PL or blocking ratio BL is calculated using equation (2) or (2’), and expressed in dimensionless to the nearest 0.01

Precision The passing ratio PL or blocking ratio BL is calculated using equation

(2) or (2’), and expressed in dimensionless to the nearest 0.01 Based on the inter-laboratory test organised in the EU-project

“Testing-SCC” (GRD2- 2000-30024/G6RD-CT-2001-00580) with 2 replicates and 22 operators from 11 laboratories, the precision of the L-box passing or blocking ratio can be expressed by the following equations

or

where Hmax = 91 mm and H = 150 − Δh

L-Box TestPrecision

r = 0.474 – 0.463PL, with R2 = 0.996, when PL ≥ 0.65; and r = 0.18 when PL < 0.65 (3)

or r = 0.463BL – 0.011, with R2 = 0.996, when BL ≤ 0.35; and r = 0.18

when BL > 0.35 (3’)and R = 0.454 – 0.425PL, with R2 = 0.989, when PL ≥ 0.65; and R = 0.18

when PL < 0.65 (4)or R = 0.425BL – 0.029, with R2 = 0.996, when BL ≤ 0.35; and R = 0.18

when BL > 0.35 (4’)where R2 is the square correlation coefficient.

Some values are listed in Table 2 for convenience of use

L-Box Test

J-Ring TestDefinition

The J-ring test aims at investigating both the filling ability and the passing ability of SCC. It can also be used to investigate the resistance of SCC to segregation by comparing test results from two different portions of sample. The J-ring test measures three parameters: flow spread, flow time T50J (optional) and blocking step. The J-ring flow spread indicates the restricted deformability of SCC due to blocking effect of reinforcement bars and the flow time T50 indicates the rate of deformation within a defined flow distance. The blocking step quantifies the effect of blocking.

Apparatus J-ring with the dimensions as shown in Figure 6, where the

positions for the measurement of height differences are also given Straight rod for aligning the reference line in the measurement,

with a length of about 400 mm and at least one flat side having the flexure less than 1 mm.

J-Ring Test

J-Ring TestProcedure

Place the cleaned base plate in a stable and level position Fill the bucket with 6~7 litres of representative fresh SCC and

let the sample stand still for about 1 minute (± 10 seconds). Under the 1 minute waiting period pre-wet the inner surface of

the cone and the test urface of the base plate using the moist sponge or towel, and place the cone in the centre on the 200 mm circle of the base plate and put the weight ring on the top of the cone to keep it in place. (If a heavy cone is used, or the cone is kept in position by hand no weight ring is needed).

Place the J-ring on the base plate around the cone Fill the cone with the sample from the bucket without any

external compacting action such as rodding or vibrating. The surplus concrete above the top of the cone should be struck off, and any concrete remaining on the base plate should be removed


Check and make sure that the test surface is neither too wet nor too dry. No dry area on the base plate is allowed and any surplus of the water should be removed – the moisture state of the plate shall be ‘just wet’.

After a short rest (no more than 30 seconds for cleaning and checking the moist state of the test surface), lift the cone perpendicular to the base plate in a single movement, in such a manner that the concrete is allowed to flow out freely without obstruction from the cone, and start the stopwatch the moment the cone loose the contact with the base plate

Stop the stopwatch when the front of the concrete first touches the circle of diameter 500 mm. The stopwatch reading is recorded as the T50J value. The test is completed when the concrete flow has ceased.

lay the straight rod with the flat side on the top side of the J-ring and measure the relative height differences between the lower edge of the straight rod and the concrete surface at the central position (Δh0) and at the four positions outside the J-ring, two (Δhx1, Δhx2) in the x-direction and the other two (Δhy1, Δhy2) in the y-direction (perpendicular to x)


Measure the largest diameter of the flow spread, dmax, and the one perpendicular to it, dperp, using the ruler (reading to nearest 5 mm). Care should be taken to prevent the ruler from bending

NOTE For non-circular concrete spreads the x-direction is that of the largest spread diameter

Expression Of Results The J-ring flow spread SJ is the average of diameters dmax and

dperp, as shown in Equation (6). SJ is expressed in mm to the nearest 5 mm

J-Ring TestExpression Of Results

The J-ring flow time T50J is the period between the moment the cone leaves the base plate and SCC first touches the circle of diameter 500 mm. T50J is expressed in seconds to the nearest 1/10 seconds

The J-ring blocking step BJ is calculated using equation (7) and expressed in mm to the nearest 1 mm.

J-Ring TestPrecisions

Based on the inter-laboratory test organised in the EU-project “Testing-SCC” (GRD2- 2000-30024/G6RD-CT-2001-00580) with 2 replicates and 16 operators from 8 laboratories, the values of repeatability and reproducibility of the J-ring flow spread and flow time T50J are listed in Table 6

V-Funnel TestDefinition

The V-funnel flow time is the period a defined volume of SCC needs to pass a narrow opening and gives an indication of the filling ability of SCC provided that blocking and/or segregation do not take place; the flow time of the V-funnel test is to some degree related to the plastic viscosity.

Apparatus V-funnel, as shown in Figure 7, made of steel, with a flat, horizontal

top and placed on vertical supports, and with a momentary releasable, watertight opening gate

Stopwatch with the accuracy of 0.1 second for recording the flow time Straightedge for levelling the concrete Buckets with a capacity of 12∼14 litres for taking concrete sample Moist sponge or towel for wetting the inner surface of the V-funnel

V-Funnel TestProcedure

Place the cleaned V-funnel vertically on a stable and flat ground, with the top opening horizontally positioned

Wet the interior of the funnel with the moist sponge or towel and remove the surplus of water, e.g. through the opening. The inner side of the funnel should be ‘just wet’.

Close the gate and place a bucket under it in order to retain the concrete to be passed

Fill the funnel completely with a representative sample of SCC without applying any compaction or rodding

Remove any surplus of concrete from the top of the funnel using the straightedge.

Open the gate after a waiting period of (10 ± 2) seconds. Start the stopwatch at the same moment the gate opens

V-Funnel TestProcedure

Look inside the funnel and stop the time at the moment when clear space is visible through the opening of the funnel. The stopwatch reading is recorded as the V-funnel flow time, noted as tV

Do not touch or move the V-funnel until it is emptyExpression Of Results

The V-funnel flow time tV is the period from releasing the gate until first light enters the opening, expressed to the nearest 0.1 second

V-Funnel TestExpression Of Results

Based on the inter-laboratory test organised in the EU-project “Testing-SCC” (GRD2- 2000-30024/G6RD-CT-2001-00580) with 2 replicates and 20 operators from 10 laboratories, the precision of the V-funnel flow time can be expressed by the following equations

the precision of the V-funnel flow time can be expressed by the following equations:

r = 0.335 tV – 0.62, with R2 = 0.823, when 3 ≤ tV ≤ 15; and r = 4.4 when tV > 15 (8)

and R = 0.502 tV – 0.943, with R2 = 0.984, when 3 ≤ tV ≤ 15; and R = 6.6

when tV > 15 (9)where R2 is the square correlation coefficient.

Some values are listed in Table 5 for convenience of use.

V-Funnel Test

Orimet TestDefinition

The Orimet flow time is the period a defined volume of SCC needs to pass a narrow opening (a tube narrowed by an orifice). The flow time of the Orimet test is to some degree related to the plastic viscosity

Apparatus Orimet, made of steel, with the tube of a length of 600 mm and an

inner diameter of 120 mm. The orifice, which narrows the opening of the tube and shears SCC, is interchangeable; its diameter can be chosen according to the mixture composition and the criteria on SCC. Figure 8 shows the filling of the Orimet with a bucket

Stopwatch with the accuracy of 0.1 second for recording the flow time

Straightedge for levelling the concrete Buckets with a capacity of 10∼12 litres for taking concrete sample Moist sponge or towel for wetting the inner surface of the Orimet

Orimet Test

Orimet TestProcedure

Place the cleaned Orimet vertically on a stable and flat ground, with the top opening horizontally positioned and check whether the tripod is completely extended

Wet the interior of the Orimet with the moist sponge or towel and remove the surplus of water, e.g. through the opening. The inner side of the Orimet should be ‘just wet’.

Close the gate and place a bucket under it in order to retain the concrete to be passed

Fill the Orimet completely with a representative sample of SCC without applying any compaction or rodding

Remove any surplus of concrete from the top of the Orimet using the straightedge

Open the gate after a waiting period of (10 ± 2) seconds. Start the stopwatch at the same moment the gate opens

Orimet TestProcedure

Look inside the Orimet and stop the time at the moment when clear space is visible through the opening of the Orimet. The stopwatch reading is recorded as the Orimet flow time, noted as tO

Expression Of Results The Orimet flow time tO is the period from releasing the gate

until first light enters the opening, expressed to the nearest 0.1 second

Based on the inter-laboratory test organised in the EU-project “Testing-SCC” (GRD2- 2000-30024/G6RD-CT-2001-00580) with 2 replicates and 20 operators from 10 laboratories, the precision of the Orimet flow time (with the orifice 70 mm) can be expressed by the following equations

Orimet TestExpression Of Results

r = 0.433 tO – 0.594, with R2 = 0.996, when 3 ≤ tO ≤ 15; and r = 6.6 when tO > 15

(10)and R = 0.472 tO – 0.28, with R2 = 0.947, when 3 ≤ tO ≤ 15; and R = 6.8

when tO > 15 (11)where R2 is the square correlation coefficient.


Penetration TestDefinition

The test aims at investigating the resistance of SCC to segregation by penetrating a cylinder with a given weight into the fresh SCC sample. If the SCC has poor resistance to segregation, the cylinder will penetrate deeper due to the less amount of aggregate in the upper layer of the sample. Therefore the penetration depth indicates whether the SCC is stable or not

Apparatus Penetration apparatus, as illustrated in Figure 9, consisting of a

frame, slot and screw, reading scale and penetration head. The penetration head is assembled with an aluminium cylinder and rod. The rod should be able to move inside slot, as freely as possible. The inner diameter, height and thickness of the cylinder are 75 mm, 50 mm and 1 mm, respectively. The total weight of the penetration head is 54 g.

Penetration TestApparatus

Bucket with a capacity of 10~12 litres

Penetration TestProcedure

Place the bucket in a stable and level position Fill the bucket with (10 ± 0.5) litres of representative fresh SCC

and let the sample stand still for 2 minutes ± 10 seconds NOTE Care must be taken to avoid segregation caused by external

impacts 2 minutes after filling of the bucket, locate the penetration

apparatus on the top of the bucket, adjust the penetration cylinder until it just touches the upper surface of the concrete, and then let the cylinder penetrate freely into concrete

After the stabilisation of the cylinder (generally < 15~20 sec), the penetration depth of the cylinder head is recorded from the scale. Measure the penetration depths at the centre (noted as P1) and two sides (noted as P2 and P3) of the width of the bucket

NOTE The duration of the three measurements should be less than 3 minutes

Penetration TestExpression Of Results

The penetration depth P is the average value of the three measurements, rounded to 1 mm.

Precisions Based on the inter-laboratory test organised in the EU-project

“Testing-SCC” (GRD2- 2000-30024/G6RD-CT-2001-00580) with 2 replicates and 22 operators from 11 laboratories, the precision of the penetration depth can be expressed by the following equation r = R = 0.59 P + 1.7, with R2 = 1, when P ≤ 17; and r = R =

12 when tO > 17 (12)where R2 is the square correlation coefficient.


Penetration Test

MaHmoud Khlifa AliraQi2nd CiVil Engineering

Section 21

fresh concrete properties & its standard tests

Education

square correlation

flow time

laboratory

defined flow

vebe time

external compacting

compacting

ring flow