The Early Age Strength Improvement of the High Volume Fly Ash Mortar

Abstract

In the last decade, the use of Fly ash as replacement to improve the strength and performance of the cement has become a part of mortar and concrete manufacturing. When the used amount of fly ash ranges from 20 to 25%, the proprieties of concrete and mortars such as strength and durability are improved, which also reduce the Portland cement consumption and its impact on environment. For some special applications the High-Volume Fly Ash (HVFA) (up to 50%) is recommended, but the use of HVFA is still limited because of the low early age strength. The aim of this study is to overcome the constraints caused by the use of the High-Volume Fly Ash, by upgrading the mortar using grinding to reduce the particle size, and by the application of an upsetting force to modify the behavior of swelling and to modify the crystal structure of ettringite in order to increase the early age strength of the mortar. The results show an increase in the rupture resistance at 7 days and 28 days by 60% and 30% respectively. Which will make the use of HVFA mortar possible in construction industry and therefore reduce more CO2 emissions from the cement production. Doi: 10.28991/cej-2021-03091731 Full Text: PDF

Mechanical properties and microstructure of brick aggregate concrete with raw fly ash as a partial replacement of cement

“…At 7 days, the control concrete achieved 0.2%, 8.5%, 20%, and 23.8% higher strength compared to BAC containing 10%, 15%, 20%, and 25% FA, respectively. This may be due to the dilution effect and delayed pozzolanic action of FA [ [53] , [54] , [55] ]. At 28 days, BAC containing 10% and 15% FA achieved 7.9% and 1.8% higher strength compared to control concrete, respectively.…”

“…At 90 days, BAC with 10% and 15% FA developed 13.7% and 4.2% higher strength, respectively. This improved behavior may be attributed to the pozzolanic and filler effect of FA [ [53] , [54] , [55] ]. BAC containing 10% FA showed the maximum strength at 28 and 90 days, possibly due to the ideal replacement of FA in BAC.…”

“…This may be due to the increase in silica (contained in FA) and the gradual reduction of calcium oxide (contained in OPC) in the concrete, leading to unavailability of CaO for pozzolanic reaction. The strength development of concrete containing FA is slow at early ages but shows superior strength at later ages compared to the control concrete [ [53] , [54] , [55] ]. Sun et al [ 55 ] used 40% FA in stone aggregate concrete and stated that high-volume FA concrete exhibited lower strength at early ages but higher strength at later ages.…”

Engineering Properties of Concrete Made with Coal Bottom Ash as Sustainable Construction Materials

“…Several recent research has discovered that organic and inorganic waste can be used as cementitious material since they are similar to cement. Fly ash [8][9][10] and blast furnace slag [11][12][13] are two commodities that have been successfully commercialized for construction materials and received positive feedback. Meanwhile, rice husk ash [14][15][16], bagasse ash [17][18][19], palm oil waste [20][21][22], and Kaolin [23][24][25] are among the materials being researched as alternatives for cement replacement.…”