Süper akışkanlaştırıcı katkı maddelerinin portland çimento harçlarının rötresine etkisi
The Effect of superplasticizers on drying shrinkage of portland cement mortars
- Tez No: 39248
- Danışmanlar: PROF.DR. MEHMET UYAN
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1993
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 93
Özet
ÖZET Bu çalışmada dozajları 400, 4S0 ve SOO kg/m olarak değişen üç farklı bileşimde harç numuneleri üretilmiştir. Üretilen harçların tümünde en büyük agrega boyutu S mm olarak seçilmiştir. Agrega karışım granülometresi sabittir ve üretilen harçlarda Portland Çimentosu CPÇ 32. 5Z> kullanılmıştır. 3 400, 450 ve 500 kg/m dozajlı olarak üretilen harçlarda sabit i şl enebi 1 meyi sağlamak için her dozaj için ayrı ayrı su/çimento oranı bulunmuş ve tüm dozlarda katkı maddesi olarak; modi fi ye edilmiş linyosülf onat, mel amin ve naftalin olmak üzere üç farklı süperakışkanlaştırıcı katkı maddesinden yine işlenebilme sabit kalmak üzere iki farklı oranda katkı kullanılmıştır. üretilen harç numunelerinin 3, 7, 28 ve 90. günlük rötre ve ağırlık kaybı değerleriyle 7 ve 28. gün ultrases hızı, basınç ve eğilme mukavemetleri incelenmiştir. Yapılan deneyler sonucunda süper ak ışk ani aştı - rıcılardan linyosülf onat ve naftalin kökenli katkı maddeleri her dozaj ve katkı oranında harçların rötresini arttırken, melamin kökenli katkı tipinde ise çimento dozajına ve kullanılan katkı oranına bağlı olarak rötreyi azaltıcı yada arttırıcı etkisi tespit edilmiştir. Basınç ve eğilme mukavemetle - rinde ise tüm katkı tipleri her doz için kontrol numunelerinden büyük değerler vermiştir. XII
Özet (Çeviri)
SUMMARY "THE EFFECT OF SUPERPLASTI CI ZERS ON DRYING SHRINKAGE OF PORTLAND CEMENT MORTARS- INTRODUCTION The development of super pi asti ci zer s has contributed to the easy execution of work with concretes of low water -cement ratio. Many reports have been published on various properties of superpl asti ci zer admixed concretes, however, little information is available on the drying shrinkage characteristic of high-strength concrete and the information that is available is inconclusive. The purpose of the present work is to investigate the effect of superpl asti ci zer admixtures Chigh range water reducer sD on drying shrinkage of Portland cement mortars The superpl asti ci zer admixtures can be used to significantly increase slump without adding more water» or to greatly reduce water content without a loss in slump. They are roper ly categorized as a high-range water -reducing admixture CHRWRAD, meeting requirements of ASTM C 494 Type F or G. The superpl asti ci zer s currently in use may be divided into four categories: 1. sulfonated mel amine -formaldehyde condensates 2. sulfonated naphthalene-formaldehyde condensates 3. modified 1 i gni nsul f onates 4. other super pi ast i ci zer s such as sulfonic acid esters or other carbohydrate esters. Mode of action of superplasticizing admixtures: These admixtures are thought to be adsorbed onto cement particles, causing them to become mutually repulsive as a result of the anionic nature of superpl asti ci zer s, which causes the xiiicement, particles to become negatively charged and as a result dispersed. In principle, this adsorption and dispersing effect is similar to that found for normal plasticizers. Superplasticizers are being used for three principal purposes: 1. control of the consistency of fresh cocrete without modifying the properties of the hardened cocrete, 2. production of flowing cocrete from stiff cocrete, 3. production of high quality cocrete at a low water/ cement ratio. The review indicates that incorporation of superplasticizers does not adversely affect the properties of fresh concrete, though superplasti- cized concretes lose slump rapidly with time and this is accentuated at elevated temperatures. All superplasticizers appear to have no significant retarding effect on time of initial set of concrete. The primary effects of superplasticizers on concrete compressive strength are derived from their effect on the water /cement ratio. When a super pi astici zer is used to lower water requirements at the same slump and cement content, the resulting decrease in water /cement ratio will significantly increase concrete strength at all ages. Superplasticizers are beneficial in producing concretes with compressive strengths greater than 41 MPa at 28 days, which are defined as high strength concretes Some laboratory studies indicate that adding superplasticizers to a cement paste increases the drying shrinkage of the paste. Some laboratory data confirm that superplasticizers can increase concrete drying shrinkage at a given water /cement ratio and cement content Cgiven paste content!), but this effect has not been definitively established. Therefore, the drying shrinkage of flowing concrete should be greater than, that of the same concrete mixture without any super pi ast i ci zer. xivIf there is a simultaneous reduction in cement content and water /cement ratio when the super pi astici zer is added, drying shrinkage can be reduced. LABORATORY INVESTIGATIONS In the experiments, PC 32.5 Portland cement was used. The mix dosages were produced 400, 4S0 and 500 kg/m. Different water /cement ratio was found for each dosages to provide same workability of al 1 mi xes. Three kinds of super pi astici zer s ; sulfonated mel ami ne- formaldehyde condansates, sulfonated naphthalene-formaldehyde condansates and modified lignin sulfonates were examined. Two different admixtures were used for each super pi astici zer type to provide same workability. Natural sand and crushed stone having maximum size of 8 mm were used as aggregates. All the tests were performed on 40*40*160 mm prismatic specimens in a room where the temperature and the humidity were kept constant at 20±1 C and 60±5 R. H., respectively. Shrinkage testing was performed on mortar specimens after moist curing for 3, 7, 28 and 90 days, while flexural, ultrasonic pulse velocity and compressive strengths testing were performed on specimens after moist curing for 7 and 28 days. CONCLUSIONS The most important conclusions derived from this study can be summarized as follows: 1. When cement content of the control mix increases the drying shrinkage also increases. 2. The drying shrinkage of super pi astici zer produced from high amount modified 1 i gnosul f onate, is greater than the other drying shrinkage of super pi ast i ci zer s. xv3. The drying shrinkage of mixes, which were produced by using a from mel ami n-based admixture, is lower -than that of the control mixes in the 400 and 450 dosages..4. The drying shrinkage of superplasticizer mortars which was napt hal ene -based, showed some changes with cement dosages. 5. If there is a simultaneous reduction in cement content and water /cement ratio when superplasticizer is added drying shrinkage can be reduced. 6. Generally, superplasticizer s which were used in this work, increase the drying shrinkage of mor tar s. 7. Moisture loss amount of mortars with superplasticizer s are lower than that of the control mixes. 8. Moisture loss amount of samples for all dosages showed slightly increase between 28 and 90 days. But the drying shrinkages amount much increased between the same days. 9. In the same shrinkage, control mixes took the maximum moisture looss 10. In the same moisture loss, modified 1 i gnosul f onated mixes took the maximum shrinkage. 11. When cement dosage increases, compressive strength also increases. 12. Compressive strength of the mixes with superplasticizer s are higher than that of the control mixes. Showing that uses of superplasticizer admixtures are very important to achieve the high strength concrete. 13. Increase rate of compressive strength of all the samples with admixture for 28. day are bigger than for 7. day. 14. With respect to compressive strength, mel ami ne -based samples take bigger amount in the 400 and 450 dosages. However, take high amount into 500 dosage sample which is producted modified xvi1 i gnosul f onate-based. 15. Effect of superplasticizers on the flexural strength is lower than that on the compressive strength xvii
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