Potasyum humat ilaveli laboratuvar ortamında hazırlanan akışkanlaştırıcı kimyasal katkılar ile üretilen harçların mekanik ve durabilite özelliklerinin incelenmesi

Abstract

Medeniyetin ilerlemesi ve dünya nüfüsünün artması sonucunda beton teknolojisinde son 100 yılda önemli ilerlemeler olmuştur. 90'lı yıllarda başlayan çimento-agrega ara bölgesinin özelliklerinin araştırmalar, ekonomik ve durabil beton üretimi sektörde önemli bir yer almıştır. Beton üretiminde kullanılan agregaların, hacim olarak beton tasarımının % 70-80 kadarını oluşturmaktadır. Beton üretiminde kullanılan agrega bileşiminde ise en yüksek pay ise maliyetin avantajlı olması nedeniyle kırma kuma aittir. Bu sebeple kırma kumun ihtiva ettiği kirlilik düzeyi, betonun kalitesini etkileyen başlıca parametrelerden biri olmakla beraber, kimyasal katkı üretimi yapan firmalar için de katkı dizaynını oluşturmak açısından son derece önemli bir değerdir. Türkiye'de, kırma ve eleme tesislerinde yıkama sistemi yaygın olarak kullanılmadığından, beton içerisindeki agregalarda kirlilik önemli bir sorun oluşturmaktadır. Ülkemizin birçok bölgesinde temiz agrega temininde zorluk çekildiğinden, metilen değeri yüksek agregalarla beton üretimi yapılmakta, bu da beraberinde bazı sıkıntılar getirmektedir. Bu sebeple, agrega üreticilerinin kil ve silt gibi ince malzemelerin agregaya karışmasını önlemeye yönelik tedbirler almaları gerekmektedir. Bu yüksek lisans tezinde potasyum humat içeren 16 farklı dizayna sahip akışkanlaştırıcı kimyasal katkılar Kırklareli Üniversitesi Mühendislik Fakültesi İnşaat Mühendisliği Bölümü Yapı Malzemesi Laboratuarında hazırlanmıştır. Bu çalışmada iki farklı tip potasyum humat kullanılmıştır. Aynı zamanda akışkanlaştırıcı kimyasal katkı üretiminde kullanılan diğer hammaddeler de katkı üretiminde kullanılmıştır. Hazırlanan kimyasal katkıların pH ve sıcaklık değerleri de ölçülmüştür. Kimyasal katkıların pH ve sıcaklık değerleri sunulmuştur. Katkı 01'den Katkı 08'e kadar olan kimyasal katkılar bir kimyasal katkı firmasının kullandığı hammaddeler kullanılarak laboratuvar ortamında hazırlanmıştır. Katkı 09'dan Katkı 16'ya kadar olan katkılar ise bir başka kimyasal katkı firmasının kullandığı hammaddeler kullanılarak laboratuvar ortamında hazırlanmıştır. Potasyum humat ilaveli akışkanlaştırıcı katkıların laboratuvar ortamında üretiminden sonra 40*40*160 mm boyutlu kalıplara her bir katkı ile üretilen harçlar yerleştirilmiştir. Harç üretiminde iki farklı yöntem izlenmiştir. İlk yöntem ile üretilen harçlarda %100 standart kum kullanılmış ve mekanik, durabilite özellikleri test edilmiştir. İkinci yöntem ile üretilen harçlarda ise %50 standart kum + %50 dolomit kırma kum kullanılmış ve mekanik, durabilite özellikleri test edilmiştir. Aynı zamanda Potasyum humat ilaveli akışkanlaştırıcı katkıların performanslarını belirlemek için şahit harç üretimleri yapılmıştır. Şahit harç karışımının yayılma değeri 15 cm olarak alınmıştır ve her bir katkı tasarımı ile denemeler yapılarak katkının hangi oranda su kesme yüzdesine sahip olduğu test sonuçları ile belirlenmiştir.

As a result of civilization and increase of word population, remarkable improvents in concrete industry have been recorded in the past 100 years. Following concentrated studies regarding the features of cement-aggregate transition areas since 90's, durable and economical concretes have achieved an important place in field of concrete technology. During to production of durable and economical concrete aggregates play an important role because by volume of concrete design, proportion of aggregates used in concrete is % 70-80. In the aggregate composition used in concrete production, the crushing sand has the highest proportion because of the advantage of its cost. For economically efficient concrete production needs local sources. Regarding to local codes concrete must be durable. Thus, the dirtiness of crushed sand is one of the main parameters affecting the quality of the concrete, and it is an extremely important value in terms of forming admixture design for the companies producing chemical additives. In Turkey, washing of aggregates is not widely used due to this reason dirtiness of crushed sand creates significant problem for concrete production. Since it is difficult to supply clean aggregates in many regions of our country, concrete production is carried out with high methylene value aggregates, which brings some diffıculties together. Vey fine material in fine aggregate is limited with % 3 respect to TS 706 EN 12620. If fine aggregate contents more that % 3 very fine material, methylene blue test should perform on fine aggregate according to Turkish Standard TS EN 933-9. For this reason, aggregate produces should take some precautions to stepping fine materials such as silt and clay in aggregate. In this sense, quality and content of fine materials passing from 0.063 mm sieve such as clay, silt and very fine stone powder, directly affects the quality of concrete. Clay is a laminar or fiber formed hydrated aluminum or magnesium silicate based material that holds water and has a great ion exchange capability, having particles smaller than 0.02 mm. Activity of clay minerals depends on its characteristic patterns. It is known that some types of clay are relatively affectless and do not change aggregate performance, but other types are moist sensitive, expansive and have significant effects on aggregate performance even in small amounts. The existence of clay and silt in aggregates reduce the bond between coarse aggregates and cement paste, and enlarge the specific surface area of aggregates. As a consequence, the amount of mixing water and water/cement ratio (w/c) change in negative direction. This causes serious problems such as low strength, durability and volume stability of concrete. An additional important property of clay and silt is water holding or water adsorption capability. Adsorbing water by clay and silt bring out volume expansion and shrinkage follows this phenomenon, which increases tensile stress on surface. Clay and silt reduce the adherence by reacting with binder material, and delay hydration and setting of concrete. On the other hand, very small amounts of fine material improve workability and impermeability of concrete. It is preferred to be in minimum level due to their negative effects. Concrete admixtures are liquid or powder additives. They are added to the concrete mix in small quantities to meet specific requirements such as fixing fresh concrete behavior, controlling, setting or hardening, increasingthe durability properties. The effect of admixtures is always to improve the concrete properties. Superplasticizers (mid-range and high-range water reducers) and plasticizers (water reducers) represent more than half of all the admixtures generally used. Although conventional polycarboxylate based chemical admixtures reduce water requirement and provide consistency, they have limited usage because of being sensitive to dirtiness of aggregate. Some special chemical admixtures can be developed to eliminate negative effects of clay-bearing aggregates. This will be useful for producers which can't find clean aggregates in concrete production. Humic substances are organic materials which are originated from physical, chemical and microbiological transformation of dead animals and plants. Humic substances can be found in soil, sediments and aqueous medium, and include carbon, hydrogen, oxygen, sulphur and nitrogen. These elements exist in all humic substances independently from origin and country. In this study, aggregates with high methylene blue value were used. To eliminate negative effects of aggregates having high fine material content, chemical admixtures with clay-mitigating properties were prepared. For this purpose, potassium humate, which is the potassium salt of humic acid, was used in preparation of chemical admixtures. In this Ms thesis, sixteen different potassium humate based chemical admixtures were prepared in Kırklareli University, Faculty of Civil Engineering, Construction Materials Laboratory. Before using each potassium based admixture to determine its performance, two study group were built up in this study with different types of potassium humate. Raw materials required for the production of potassium humate base plasticizer admixtures prepared in the laboratory conditions obtained from two major companies which are manufacturing and marketing chemical admixture in the construction sector. In this study, companies were coded as Firm A and Firm B. After production of potassium humate based chemical admixtures in laboratory conditions, the mortars were produced and placed in 40*40*160 mm mould by using each potassium humate based chemical admixture. Two study groups were built up during mortar production. For the production of first group chemical admixture, Firm A raw material was used and chemical admixtures were coded as admixture 01, admixture 02, admixture 03, admixture 04, admixture 05, admixture 06, admixture 07 and admixture 08. In the production of mortars, 100 % standard sand was used and mechanical and durability properties of mortar specimens were investigated. For the production of second group chemical admixtures, Firm B raw material was used and coded as admixture 09, admixture 10, admixture 11, admixture 12, admixture 13, admixture 14, admixture 15 and admixture 16. In the production of mortars, 50 % standard sand + 50 % crushed dolomite sand were used and mechanical and durability properties of mortar specimens were investigated. At the same time, control mortar specimens were produced. The slump value of the control mortar was selected as 15 cm and water reduction percentage values were determined for each chemical admixture. The percentage of potassium humate based chemical admixture was % 1 per cent by the weight of cement. Cement dosage was 450 kg/m3 for all groups. All samples were unmolded after 24 hours and stored in water at 20±1 °C. Fresh unit weight, compressive strength and split tensile strength test results were applied for 3, 7 and 18-day specimens. Also, sulfate resistance test was applied. Prepared samples were immersed in 150 gram/ litre Na2SO4 solution prepared according to ASTM C1012. Sulfate resistance test was performed on the produced samples and the weight change percentage, flexural strength and compressive strength properties for 3, 7 and 28-day specimens were determined. As a consequence of, it was found that potassium humate based chemical admixtures eliminated the negative effects of veryfine materials in aggregates by providing the intended slump and compressive strength of concrete. Regarding, further research is needed to optimize the cost for design of potassium humate based clay mitigating chemical admixtures and the cost of production.