copy of concrete quality-final.ppt 2

BEC 201 - CONCRETE TECHNOLOGY

Group Members


Mohd Hafiez Bin Akib 093005307

Asif Sher Khan 092904304

Siti Khadijah bte Hassan 102006553

Mohammed Mahmood Thabit Khan 101905672

Abdo Al Alwahed Muhammad Saleh KI091030

What is Concrete?What is Concrete? Concrete is the most widely used construction

material, commonly made by mixing Portland cement with sand, crushed rock, and water. In many countries the ratio of concrete consumption to steel consumption exceeds ten to one.


What is Concrete ?

For a building structure to be durable, more strength and also for aesthetic, accomplishing a quality concrete is of supreme importance. This is because the vital factor which determines or makes a building look elegant, gives a building more strength and durability is the concrete’s quality.

Low strength and low durable concrete structures have damaged millions of lives and properties in the past decades. So, in order to achieve a quality and a durable building structure, maintaining the quality and standard of concrete is paramount.


Definitions Definitions

QUALITY CONCEPTS:

Quality is perceived differently by different people. Yet, everyone understands what is meant by “quality.” In a manufactured product, the customer as a user recognizes the quality of fit, finish, appearance, function, and performance. The quality of service may be rated based on the degree of satisfaction by the customer receiving the service. The relevant dictionary meaning of quality is “the degree of excellence.”


mechanical properties of the reinforcement to be used dimensions of the reinforcement location of the reinforcement in the construction before

concrete is poured location of pre-stressing ducts properties of the cement used in the concrete properties of the concrete mix designed for use in the

structure control of the aggregates and sand going into the concrete


mixing of the concrete transport of the concrete to the construction site slump of the concrete pouring of the concrete control of water additions vibration/compaction of the concrete preparation of areas where different concrete pours are

done control of compression test samples control of formwork removal.


QUALITY CONTROL: Quality control is a technical function that includes all

the scientific precautions, such as calibrations and duplications, that are needed to acquire data of known and adequate quality.

QUALITY ASSURANCE: is a management or oversight function; it deals with

setting policy and running an administrative system of management controls that cover planning, implementation, and review of data collection activities and the use of data in decision making.


It begins in the production of materials used in concrete (sampling and testing): Portland cement Pozzolan Coarse and fine aggregates

Uniformity of concrete production will be no greater than the uniformity of materials used in that concrete


Handling and stockpiling Batching and mixing Sampling and testing fresh concrete

Slump Air content Unit weight Temperature

Transporting and placing the freshly mixed concrete


The most common measurement is the uniformity of the compressive strength specimens determined from statistical concepts (ACI 214)

These same statistical concepts can also be applied to test results on materials used in the concrete, on the fresh concrete, and on other properties of the hardened concrete.



TO KNOW THE QUALITY OF CONCRETE,

WE CAN DO SEVERAL TESTS

a) THE SLUMP TEST


KEY POINT:

The mould for the slump test has the shape of frustum of a cone, 300mm high.

The diameter at the base is 200mm and at the top is 100mm


b) THE VEBE CONSISTOMETER TEST


Procedure to determine workability of fresh concrete by Vee-Bee consistometer..

A conventional slump test is performed, placing A conventional slump test is performed, placing the slump cone inside the cylindrical part of the the slump cone inside the cylindrical part of the consistometer.consistometer.ii) The glass disc attached to the swivel arm is ii) The glass disc attached to the swivel arm is turned and placed on the top of the concrete in turned and placed on the top of the concrete in the pot.the pot.iii) The electrical vibrator is switched on and a iii) The electrical vibrator is switched on and a stop-watch is started, simultaneously.stop-watch is started, simultaneously.iv) Vibration is continued till the conical shape of iv) Vibration is continued till the conical shape of the concrete disappears and the concrete the concrete disappears and the concrete assumes a cylindrical shape.assumes a cylindrical shape.v) When the concrete fully assumes a cylindrical v) When the concrete fully assumes a cylindrical shape, the stop-watch is switched off shape, the stop-watch is switched off immediately. The time is noted. The consistency immediately. The time is noted. The consistency of the concrete should be expressed in VB-of the concrete should be expressed in VB-degrees, which is equal to the time in seconds degrees, which is equal to the time in seconds recorded above.recorded above.

c) THE COMPACTING FACTOR TESTc) THE COMPACTING FACTOR TEST


KEY POINT:

a) COMPRESSION TESTa) COMPRESSION TEST


KEY POINT:

b) Indirect Tensile Strength testb) Indirect Tensile Strength test


KEY POINT:

c) Flexural Strength Testc) Flexural Strength Test


d) Shrinkage and Creep Testsd) Shrinkage and Creep Tests


PRINCIPLE AND STANDARD OF QUALITY CONTROL

Principal of quality control is a validity of diagnostic test results produced in each laboratory is entirely dependent on the measures employed before, during, and after each assay. Consistency in the production of good results requires an overall program that includes quality assurance, quality control, and quality assessment.

Quality control standards provide the mathematical and statistical procedures instrumental in the evaluation of experiments and test methods. These procedures encompass the information-gathering stage of an experiment where variation is present, and includes the probability sampling process, the determination of the precision and bias of an experiment, and the measurement of the reliability and degree of uncertainty of test results and data.


Quality control of any manufactured product may beachieved though the following stages :

Specification of raw materials Testing of raw materials and use of the results to modify ( c )

below ; Specification of processing Testing at intermediate stages of production and use of the

results to modify ( c ) above, to modify the product at the intermediate stage, or, if necessary, to reject the product at this stage and avoid further financial loss

Testing of the final product for pass/fail and use of results to modify ( c ) above.


QUALITY SCHEMESQUALITY SCHEMES

Quality assessment scheme Quality assessment scheme in the laboratory can be by an internal which can be used to monitor the quality of the work more frequently and accurately than EQA schemes,

EQA samples are usually received infrequently and they are usually treated differently from the routine specimens.

Experience at laboratories that have an internal quality assessment scheme has generally been that internal schemes are much better at identifying quality problems in the laboratory than external schemes.


THIRD PARTY CAPABILITY ASSESSEMENTTHIRD PARTY CAPABILITY ASSESSEMENT

Quality assessment (also known as proficiency testing) is a means to determine the quality of the results generated by the laboratory. It is usually an external evaluation of the laboratory's performance. Internal quality assessment programs can also be instituted.

Quality assessment is a challenge to the effectiveness of the QA and QC programs generated by the test are correct.

However, quality assurance is concerned with much more: that the right test is carried out on the right specimen, and that the right result and right interpretation is delivered to the right person at the right time"


QUALITY ASSESSMENT SCHEMES FOR MATERIALSQUALITY ASSESSMENT SCHEMES FOR MATERIALS

Materials used in concrete:

Cement Water Aggregates Admixture


1) Cement: A mixture of compounds made by burning limestone and

clay together at very high temperature ranging from 1400 to 1500°C. the production of Portland cement begins with the quarrying of limestone, CaCO3. Then mixed with clay (or shale), sand and iron ore and ground together to form a homogenous powder.

Portland cement


2) Water: It is the key ingredient. When mixed with cement, forms a paste that binds the aggregates

together Water causes the hardening of concrete through process call

hydration. The water needs to be pure in order to prevent side reaction from

occurring which may weaken the concrete or otherwise interfere with hydration process.

The ratio of cement and water is the most critical factor in the production of ‘perfect’ concrete.

Too much water can reduces concrete strength but high workability

Too little water will make the concrete unworkable but high strength


3) Aggregates: Chemically inert, solid bodies, held together by the cement. Come in various shapes, sizes and materials ranging from fine

particles of sand to large, coarse rock. Soft, porous aggregates can result in weak concrete with low wear

resistance. Hard aggregates can make strong concrete with high resistance to

abrasion Should be clean, hard and strong. Usually washed to remove any dust

silt, clay, organic matter. coarse aggregate


4) Admixtures: A material, other than aggregates, cement, or water, added

in small quantities to the mix in order to produce some desired modifications, either to the physical or chemical properties of the mix or of the hardened product.

The most common admixtures affect plasticity, air entrainment and curing time.


READY MIX CONCRETE AND PRECAST CONCRETEREADY MIX CONCRETE AND PRECAST CONCRETE

READY MIX CONCRETE:READY MIX CONCRETE: Ready-mix concrete is a type of concrete that is

manufactured in a factory or batching plant, according to a set recipe, and then delivered to a worksite, by truck mounted transit mixers .


This results in a precise mixture, allowing specialty concrete mixtures to be developed and implemented on construction sites. The first ready-mix factory was built in the 1930s, but the industry did not begin to expand significantly until the 1960s, and it has continued to grow since then Ready-mix concrete is sometimes preferred over on-site concrete mixing because of the precision of the mixture and reduced worksite confusion.


HOW TO CONTROL THE QUALITY OF READY MIX / PRECAST HOW TO CONTROL THE QUALITY OF READY MIX / PRECAST QUALITY?QUALITY?

Quality Control for Ready Mix Concrete:Quality Control for Ready Mix Concrete:

Quality is optimum in the ready mix concrete for the followingreasons:

The materials which are to be used for the concrete are subject to strict quality requirement. (i.e. if the quality of the materials are not up to the standard level, then the materials would not be accepted in carrying out a respective work.)

Quality control is carried out throughout the manufacturing and delivery process; The formulation and manufacturing of the concrete are covered by the numerous

national quality standards.


PRODUCT CONFORMITYPRODUCT CONFORMITY

Precast Concrete Products Agricultural Products : Products include bunker silos, cattle feed bunks, cattle grid, agricultural fencing, H-bunks, J-bunks, livestock slats, livestock watering troughs.

Building and Site Amenities : Precast concrete building components and site amenities are used architecturally as cladding, trim products, accessories and in structural applications such as foundations, beams, floors, walls and other structural components.

Cemetery Products : Underground vaults or mausoleums - calls for quality watertight structures that withstand the tests of time and the forces of nature.

Transportation and traffic related products : Products include: box culverts, 3-sided culverts, bridge systems, railroad crossings, railroad ties, sound walls/barriers, Jersey barriers, tunnel segments and other transportation products


QUALITY OF MIXED CONCRETEQUALITY OF MIXED CONCRETE

Concrete production :Concrete production :The processes used vary dramatically, from hand tools to heavy

industry, but result in the concrete being placed where it cures

into a final form Mixing concrete: High-Energy Mixed Concrete (HEM concrete) is

produced by means of high-speed mixing of cement, water and sand with net specific energy consumption at least 5 kilojoules per kilogram of the mix.

Workability: Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (vibration) and without reducing the concrete's quality.


OUTLINE OF PROBLEMS INVOLVED IN QUALITY OUTLINE OF PROBLEMS INVOLVED IN QUALITY CONTROLCONTROL

Quality assurance is the process of verifying or

determining whether products or services meet or exceed customer expectations. Quality assurance is a process-driven approach with specific steps to help define and attain goals


CONTROL TECHNIQUE :Histograms Check Sheets • Pareto Charts • Cause and Effect Diagrams • Defect Concentration Diagrams • Scatter Diagrams • Control Charts

SELECTION OF TECHNIQUES:SELECTION OF TECHNIQUES: Specific inspection techniques Specific testing techniques Work process sampling Random product sampling Tick sheets – frequency by category Check list


Concrete is the most rapidly used engineering material in the world of construction business. To achieve a high standard, high durability and an attractive building structure, the key is to obtain a quality concrete during a construction project.

Too much water occupies space in concrete and on evaporation, voids are created in concrete, which reduces the concrete’s strength and durability.


The volume change in concrete results in crack formation and the factor which contributes the volume change is the permeability.

Permeability is the contributing factor for volume change and water-cement ratio is the fundamental cause of higher permeability. Thus, the use of higher water-cement ratio – permeability – volume change – cracks – disintegration – failure of concrete is a cyclic process in concrete. Hence, for a durable and a high strength concrete, use of lowest possible water-cement ratio is the fundamental requirement to produce dense and impermeable concrete.

Quality control can be expressed as the application of the operational techniques and activities, which sustain the quality of a product or service to satisfy given needs.


copy of concrete quality-final.ppt 2

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