A comparative study of the evaluation methods for pozzolans

Abstract

The range of methodologies available for pozzolan classification, predicated on different viewpoints, may occasionally offer conflicting judgements regarding pozzolans. The present study compared the results obtained by assessing several natural pozzolans, silica fume and fly ash within the requirements of ASTM C618 and ASTM C1240. In addition, binary combinations of the pozzolans and Portland cement were investigated using EN 196-5. The outcomes manifested some anomalies between the different approaches. Complementary observations (such as environmental scanning electron microscope, insoluble residue and hardened concrete properties) were conducted to further clarify the results. The compressive strength and depth of water penetration of the concrete specimens containing the pozzolans revealed that EN 196-5 had superior compatibility with real concrete performance. This suggests that EN 196-5, which was originally developed for pozzolanic cements, can successfully determine the activity of Portland pozzolanic cements containing natural pozzolans, silica fume and fly ash.

Introduction of a mineral powder as a type of natural cementitious material in concrete: An experimental program

“…As given in Table , the SAI is about 82%. As stated in previous studies, it should be mentioned that SAI is not a powerful criterion for specifying the pozzolanic activity of a material. This parameter is mainly a useful initial criterion for concrete manufacturers, but it is just a qualitative parameter without sufficient detail which will not be complicated enough to assess the effectiveness of a pozzolan.…”

Evaluation of Ash Pozzolanic Activity by Means of the Strength Activity Index Test, Frattini Test and DTA/TG Analysis

“…Similarly to that observed for the SAI results, the greatest reactivity in the Frattini tests was detected in the two coal fly ashes K2 and K3, followed by K4, a pattern mostly related to the relatively high reactive SiO2 content of these particular ashes. It should be noted that as the test procedure assumes that no other source of soluble calcium is present in the system, any leaching of calcium would invalidate the results [22,34]. Significantly, all the studied ashes contained quite high amounts of CaO, as shown in Tab.…”

“…The values corresponding to the two fly ashes (K2, K3) are located below the saturation curve, indicating the removal of Ca 2+ from the solution, which is attributed to pozzolanic activity [22]; clear progress in the pozzolanic reaction is also apparent after 15 days. The majority of the studied ashes follow a reaction pathway shifting to higher alkalinity and lower Ca ion concentrations below the curve in the pozzolanicity assessment diagram, indicating that increasing alkali input in the aqueous solution reduces the solubility of Ca ions, a process that is characteristic of pozzolans associated with major alkali-calcium-ion exchange [34]. Since standard EN 196-5 [23] provides Ca(OH) 2 solubility data at 40 °C when the OHcontent is between 35 and 100 mmol/l, for materials within this range the theoretical maximum [CaO] concentration and CaO reduction can be calculated (Table 3).…”

Puzolanik Aktivite Tespit Yöntemleri: Fiziksel Metotlar

“…Diğer yandanyapılan başka bir araştırmada ise [31] dört farklı doğal puzolanın puzolanik aktivitesi ve puzolanik aktivite test yöntemleri incelenirken, puzolan ve kireç kombinasyonun kararlı bir iç yapı özelliği taşımasından dolayı puzolanik aktivite için kimyasal ölçüm teknikleriyle termal analizler arasında tam bir ilişkinin kurulamayacağı ve burada doğru kararlar için bir ölçüt bulunmadığı, dolayısıyla termogravimetrik metodun sıcaklığı işin içine dâhil ederek meselenin esası için elverişli bir yöntem sunmadığı şeklinde bir görüş ileri sürülmüştür. Benzer yöndeki görüşler yapılan başka araştırmalarda da [32], [33], [34] ifade edilmiştir. Termal yöntemlerle kimyasal içerikli testler arasında, yöntemlerin yönelik oldukları özelikler nedeniyle belki böyle bir ilişki kurulamayabilir, fakat, yukarıda genel içerikleri verilmiş bazı çalışmalardan [22,29,30] elde edilen sonuçlardan görüldüğü üzere, termal analizlerin, özellikle reaksiyon sonucu meydana gelen hidrate ürünlerin tespitinde faydalı bir teknik sunduğu, dolayısıyla bu durumun meydana gelebilmesi için kimyasal bir reaksiyonun gerçekleşmiş olmasının gerektiği de ortadadır.…”