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Nguyen, Khoa Tan,Le, Tuan Anh,Lee, Kihak Elsevier 2018 Construction and Building Materials Vol.169 No.-
<P><B>Abstract</B></P> <P>Portland cement concrete is a major construction and building material used all over the world. It is a composite material comprising Portland cement, coarse aggregate, fine aggregate, and water. But its increased use in construction is exhausting natural resources used in its production, making it necessary to find alternative materials. One potential method is to use sea sand as fine aggregate to produce fly ash based geopolymer concrete. In this paper, the mechanical properties of geopolymer concrete prepared with sea sand as the fine aggregate, and the corrosion of steel bar embedded in the concrete subjected to accelerated corrosion tests, were investigated. The test data revealed that for sea sand based geopolymer concrete, the compressive strength reached high values at an alkaline to fly ash ratio of 0.35–0.45. The geopolymer concrete exhibited highcompressive strength with a low aggregate to fly ash ratio. Also, there was an increase in compressive strength when the Si/Al ratio changed from 1.16 to 1.67. Furthermore, very little difference was observed between the mechanical properties of geopolymer concrete using sea sand, and river sand. Measurements of the corrosion of steel bar using a half-cell potential survey indicated that the steel in geopolymer concrete with sea sand was attacked and corroded like normal concrete. However, the potential of steel bar in geopolymer concrete was higher than in Portland cement concrete.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The compressive strength of geopolymer concrete using sea sand as fine aggregate reaches the highest value at an alkaline to fly ash ratio of 0.35–0.45. </LI> <LI> For sea sand based geopolymer concrete, when the ratio of aggregate to fly ash is low, the compressive strength enhances high value. </LI> <LI> The difference in strength between specimens using river sand and sea sand is not significant. </LI> <LI> It takes more time for steel bar in geopolymer concrete using sea sand to be attacked and corroded, compared with the steel bar in normal concrete. </LI> </UL> </P>
Nguyen, Khoa Tan,Le, Tuan Anh,Lee, Jaehong,Lee, Dongkyu,Lee, Kihak Elsevier 2017 Construction and Building Materials Vol.130 No.-
<P><B>Abstract</B></P> <P>Heat curing in an oven is the traditional method to obtain mechanical properties of geopolymers. This characteristic has significantly affected operations in terms of construction and energy consumption. The target of this paper is proposing alternative curing methods namely self-cured technologies for fly ash based geopolymer materials that are cured in ambient conditions without use of a heat resource. Two alternative methods are to use three different mixing processes with preheated materials and to use two thermogenetic admixtures (hot pack material and quicklime). The results show that for the mixing processes, a larger amount of provided heat energy results in a higher compressive strength of the geopolymer mortar (GM). For the use of a thermogenetic admixture, the results from compressive strength testing, Scanning Electron Microscope (SEM), energy dispersive X-ray analysis (EDX) micrographs and X-ray diffraction (XRD) analysis confirm that quicklime is more efficient than hot pack material. In the case of using quicklime, the suggested amount is about 3–5% of fly ash by mass.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Proposing two new alternative curing method are using preheated materials and thermogentic admixtures. </LI> <LI> For using preheated materials, a larger amount of preheated materials results in a higher compressive strength. </LI> <LI> For using thermogentic admixtures, quicklime is more efficient than hot pack material. </LI> <LI> The suggested amount of quicklime is about 3–5% of fly ash by mass. </LI> </UL> </P>