Influence of Cement Replacement with Fly Ash and Ground Sand with Different Fineness on Alkali-Silica Reaction of Mortar.

Suwat Ramjan,Chai Jaturapitakkul,Teewara Suwan,Cheah Chee Ban,Peerapong Jitsangiam,Weerachart Tangchirapat

doi:10.3390/ma14061528

Abstract

The alkali-silica reaction (ASR) is an important consideration in ensuring the long-term durability of concrete materials, especially for those containing reactive aggregates. Although fly ash (FA) has proven to be useful in preventing ASR expansion, the filler effect and the effect of FA fineness on ASR expansion are not well defined in the present literature. Hence, this study aimed to examine the effects of the filler and fineness of FA on ASR mortar expansion. FAs with two different finenesses were used to substitute ordinary Portland cement (OPC) at 20% by weight of binder. River sand (RS) with the same fineness as the FA was also used to replace OPC at the same rate as FA. The replacement of OPC with RS (an inert material) was carried out to observe the filler effect of FA on ASR. The results showed that FA and RS provided lower ASR expansions compared with the control mortar. Fine and coarse fly ashes in this study had almost the same effectiveness in mitigating the ASR expansion of the mortars. For the filler effect, smaller particles of RS had more influence on the ASR reduction than RS with coarser particles. A significant mitigation of the ASR expansion was obtained by decreasing the OPC content in the mortar mixture through its partial substitution with FA and RS.

Highlights

Fly ash (FA) is one of main by-products from coal combustion in thermal power plants.Currently, the Mae Moh power plant in Thailand produces about 2.1 million tons of fly ash, increasing annually
4, the mortar (CT), in which(CT), the crushed coarsereactive c aggregate was used as a fine reactive aggregate, had an expansion aggregate was used as a fine reactive aggregate, had an alkali-silica reaction (ASR) expansion of 0.234 ± 0.013%ofat0.234 ± 0
The extent of the reduction depended on the replacement of ordinary Portland cement (OPC) by FA rather than on the fineness of FA

Summary

Introduction

Fly ash (FA) is one of main by-products from coal combustion in thermal power plants.Currently, the Mae Moh power plant in Thailand produces about 2.1 million tons of fly ash, increasing annually. Fly ash (FA) is one of main by-products from coal combustion in thermal power plants. Fly ash (FA) is a well-known mineral admixture and has been widely accepted for use as a pozzolanic material to partially replace ordinary Portland cement (OPC) in concrete. The use of fly ash as a pozzolanic material is constantly increasing because it improves the properties of mortar and concrete, namely the workability, durability, and strength in the long term. The size and shape of fly ash particles vary depending on the source and combustion conditions. In 2010, Sharma et al [1] studied the influence of FA characteristics from 14 thermal power plants and found that calcium content and particle size are the main parameters affecting the compressive strength of concrete. The use of FA can significantly improve the elementary properties of paste and mortar, such as normal consistency, setting time, and water requirements [7]

Objectives

Results

Conclusion