High strength concrete

مقدم أطروحة جامعية

Naim, Mustafa

مشرف أطروحة جامعية

Kazim, Ayyad

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم هندسة البناء و الإنشاءات

دولة الجامعة

العراق

الدرجة العلمية

دكتوراه

تاريخ الدرجة العلمية

1999

الملخص الإنجليزي

The objective of this report was to present static-of the art information on concrete with strengths in excess of about 6000 psi (41 Mpa) but not including concrete made using exotic materials or techniques.

This section of the report presents a summary of the material contained in the previous chapters.

All materials for use in high-strength concrete must be carefully selected using all available techniques to insure uniform success ; items to be considered in selecting materials include cement characteristics! Aggregate size, aggregate strength, particle shape and texture, and the effects of set-controlling admixtures, water reducers, silica fume, and pozzolans.

Trial mixtures are essential to insure that required concrete strengths will be obtained and that all constituent materials are compatible, Mix proportions for high-strength concrete generally have been on achieving a required compressive strength at a specified age.

Depending on the appropriate application, a specified age other than 28 days has been used.

Factors included in selecting concrete mix proportions have included availability of materials, desired workability, and effects of temperature rise.

All materials must be optimized in concrete mix proportioning Lo achieve maximum strength.

High-strength concrete mixes have usually used high cement contents, low water-cement ration, and normal weight aggregate, and chemical and pozzolanic admixtures.

Required strength, specified age, material characteristics, and type of application have strongly influenced mix design.

High-strength concrete mix proportioning has been found to be a more critical than the proportioning of lower-strength concrete mixes.

Laboratory trial batches have been required in order to generate necessary data on mix design.

In many cases; laboratory mixes have been followed by field production trial batches.

Batching, mixing, transporting, placing, and control procedures for high-strength concrete are not essentially different from procedures used for lower-strength concrete.

However, special attentions are required to insure a high-strength uniform material.

Special consideration should be given to minimizing the length of time between concrete batching and final placement in the forms.

Delay in concrete placement can result in a subsequent loss of long-term strength or difficulties in concrete placement.

Special attention should also be paid to the testing of high-strength concrete cylinders since any deficiency will result in an apparent lower strength than that actually achieved by the concrete.

Items deserving specific attention include manufacture, curing, and capping of control ; specimens for compressive strength measurement ; characteristics of testing machines ; type of mold used to produce specimens ; and age of testing.

In many instances, strength measurement at early ages have been made even though the compressive strength has been specified until 56 or 90 days, The economic advantage of using high-strength concrete in the columns or high-rise buildings have been clearly demonstrated by applications in many cities.

The ability to reduce the amount of reinforcing steel in columns without sacrificing strength and to keep the columns to an acceptable size has been an economic benefit to owners of high-rise buildings.

Consequently, concrete with compressive strength in excess of 6000 psi (41 Mpa) has been used in the columns of high-rise Advantages in the use of high strength concrete in long - span concrete bridges-However ; this application has yet to be fully implemented.

There have also been applications where high-compressive-strength concrete has been needed to satisfy special local requirements.

Theses have included dame, prestressed concrete poles, grandstand roofs, marine foundations, and industrial manufacturing applications.

Although high-strength concrete is often considered a relatively new material.

At the same time, material producers are responding to the demands for the material and are learning production techniques.

As with many developments of new materials, research data supporting is still needed in the cars shear strength, torsion, bond and development length, and the effects of repeated loading.

Some research projects are underway to satisfy these needs.

However, further work is needed to fully use the advantages of high-strength concrete and to affirm its capabilities.

This report has documented existing of high-strength concrete so that the direction for future development may be ascertained.

التخصصات الرئيسية

الهندسة المدنية

الموضوعات

• الخرسانة
• الخرسانة المسلحة

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-306264