Effect of ground and classified fly ash on the properties of high performance concrete | |
| Author | Patoary, Md. Kabir Hossain |
| Call Number | AIT Thesis no. ST-99-14 |
| Subject(s) | Fly ash Aggregates (Building materials) Fly ash Aggregates (Building materials) |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering. |
| Publisher | Asian Institute of Technology |
| Abstract | Modern thermal power plants are producing large amounts of fly ash, which is lmown to exhibit pozzolanic properties and packing effect when mixed with concrete. But the inconsistency of fly ash prope1ties remains the major obstacle for its full utilization in concrete. With otherwise similar chemical and mineralogical composition of fly ash, it is its fineness, which has the most significant influence on the properties of concrete. The investigation presented in this study shows an example of the improvements of fly ash fineness achieved by a simple physical process, that is, air-classification and a rather mechanical process, that is, grinding. To make high performance concrete three different types of fly ash namely, original, classified and ground fly ash with different finenesses were used as cement replacement. The percentage replacements of cement by each type of fly ashes were used as 0, 10, 15 and 20% by weight of cementitious materials. The total cementitious material content, water to cementitious material ratio, fine to total aggregate ratio, aggregate to cementitious material ratio and the dosage of superplasticizer were kept to be constant. The results showed that substitution of part of the cement with original or classified fly ash produces concrete mixtures with greater workability than the control as measured by slump and slump flow. On the contrary, it was found that the ground fly ash, having more or less the same degree of fineness as classified fly ash resulted in a lower workability due to the loss of its spherical shape and lubricant effect. The inclusion of original fly ash drastically reduced the early strength and this reduction was more significant with the increase of percentage replacements. Classified and ground fly ash improved the early strength significantly. The long-term strength development of classified and ground fly ash concrete was remarkable and the strength was found to be considerably higher than that of control concrete for all the percentage replacements. As a final conclusion it can be established that the very fine to ultra fine fly ash resulting from air classification and grinding is an excellent supplementary cementing materials which can be used as a replacement of silica fume to produce high performance concrete. It is, however, a challenge to produce these supplementary cementing materials commercially in an economical way. |
| Year | 1999 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pichai Nimityongskul.;Pichai Nimityongskul.; |
| Examination Committee(s) | Anil Wijeyewickrema;Kishi, Toshiharu; |
| Scholarship Donor(s) | Government of Japan; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1999 |