Abstract
The use of fly ash (FA) limestone and powder (LP) in combination with cement in concrete has several practical, ecological, and economic advantages by reducing carbon dioxide emissions, reducing the excessive consumption of natural resources, and contributing to a cleaner production of self‐compacting concrete (SCC). A mix design method for SCC based on paste rheological threshold theory can guide the SCC mix design by paste tests. This method can be visualized by the self‐compacting paste zone (SCP zone), a plane area where all the mix points meet the paste threshold theory, and SCC zone, a plane area consisting of all the mix points satisfying the criteria of qualified SCC. In the case of cement SCC, the SCP zone coheres with the SCC zone. However, in the case of the addition of FA or LP with different granulometry and shape characteristics from cement, experimental results indicate that the SCP zone is separated from the SCC zone. This work quantitatively studied the influence of FA and LP on the movement of the SCP zone by introducing the improved powder equivalence model. The improved model was obtained by powder equivalence coefficients calculated through the mortar test results with or without FA or LP, instead of SCC tests in the former method. The equivalence coefficients by volume of FA and LP are 0.55 and 0.79, respectively, which means that 1.82 unit volume of FA or 1.27 unit volume of LP is equivalent to one unit volume of cement. The improved powder equivalence model was verified by the successful preparation of SCC incorporating FA or LP simply and effectively. The equivalent SCP zone cohered better with the SCC zone than the former SCP zone, which could guide the quick mix design of SCC without SCC premix tests.
Highlights
IntroductionAs a kind of high-performance concrete, self-compacting concrete (SCC) can flow through the gaps of dense reinforced bars under its gravity without vibration and fill up the voids without segregation and excessive bleeding, to ensure the compaction of the structure, shorten the construction period, and eliminate vibration noise [1, 2]
The obtaining of the coefficients was based on a trial-anderror process and at least 9 groups of self-compacting concrete (SCC), leading to a lot of experiments. To solve this weak point, this paper works on the improved powder equivalence coefficients for fly ash (FA) and limestone and powder (LP), which can be obtained by conducting mortar experiments instead of the time-consuming SCC experiments
According to the frequently used sand ratio and superplasticizer dosage recommended by the manufacturer, the sand ratio was fixed at 45% and the polycarboxylate-based superplasticizer was fixed at 1% by mass
Summary
As a kind of high-performance concrete, self-compacting concrete (SCC) can flow through the gaps of dense reinforced bars under its gravity without vibration and fill up the voids without segregation and excessive bleeding, to ensure the compaction of the structure, shorten the construction period, and eliminate vibration noise [1, 2]. Based on the paste rheological threshold theory, Nie [36] carried out several paste experiments by using different FA proportions and obtained SCP zones. Based on the SCP zone and SCC zone, they conducted concrete experiments to validate the SCP zone and found the separation of the SCP zone and the SCC zone [37] To deal with this problem, Zhang et al [37] studied the difference of cement, FA, and LP from the perspective of powder equivalence. The powder equivalence coefficients are obtained by comparing the equivalent SCP zone with the SCC zone until they coincide mostly, and some time-consuming concrete experiments have to be conducted inevitably [37, 38]. To deal with this problem, the powder equivalence model will be enhanced from the perspective of obtaining powder equivalence coefficients by comparing the results of mortars with/without FA/LP instead of the comparison of the equivalent SCP zone and the SCC zone in the previous study
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