Study On New Fly Ash Composite Materials And Its Influence On The Compressive And Flexural Strength Of Concrete

Fly ash can be considered as the world’s fifth largest raw material resource, which is widely used in cement based composite materials. Fly ash substituting same amount of cement results in the decrease of the early compressive and flexural strength of concrete. And the late flexural and compressive strength of concrete decrease ultimately with the percentage of blended fly ash increasing. In order to improve the early strength of fly ash concrete and the utilization of fly ash, in this study, we prepare polymer-modified fly ash by chemical means (grafting the highly hydrophilic polymer directly on the surface of fly ash), and the polymer on the surface of fly ash can improve the interfacial bonding between fly ash and other aggregate and prevent the concrete cracking, resulted in improving the strength of fly ash concrete. The main content of this dissertation is as follows:1. The surface of the fly ash was hydroxylated by acid and alkali neutralization method. Copolymer of acrylic acid (AA) and methyl allyl polyoxyethylene ether (HPEG) was preparated by solution polymerization, which was grafted in organic silane coupling agent KH-566. Hydroxylated fly ash was modified with organic silane coupling agent above to obtain target products. A series of tests indicated that the AA-HPEG modified fly ash composite materials were successfully prepared, which can significantly improve the early strength of fly ash concrete.2. Hydroxylated fly ash was modified with organic silane coupling agent KH-570 which finally polymerized with Poly(itaconic acid-co-acrylic acid) (AA-IA) (Poly(itaconic acid-co-acrylic acid) was preparated by solution polymerization) to obtain target products to obtain target products. A series of tests indicated that the IA-AA modified fly ash composite materials were successfully prepared, which can significantly improve the early strength of fly ash concrete.3. Polyacrylic acid (PAA) was preparated by solution polymerization, which was grafted in organic silane coupling agent KH-566. Hydroxylated fly ash was modified with organic silane coupling agent above to obtain target products. A series of tests indicated that the PAA modified fly ash composite materials were successfully prepared, which can significantly improve the early strength of fly ash concrete.