Abstract
This research aimed to investigate the effect of fine aggregate particles on mechanical properties of fly ash-based geopolymer mortar. In this work, seven kinds of river sand particles were designed based on different fine aggregate characteristics. The fineness modulus was adopted to quantitatively describe the gradation of sands. The fluidity, compressive, flexural, and tensile strengths of geopolymer mortar with different sand gradations were analyzed by laboratory tests. Furthermore, the composition and morphology of fly ash-based geopolymer mortar was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reasonable gradation range and filling effect of sand were obtained. The results show that fluidity and compressive and flexural strengths of geopolymer mortar both improve with the increase of the fineness modulus, while specific surface area and voidage are opposite. The tensile strength of mortar largely lies on the interface properties between the geopolymer binder and fine aggregates. When the pass rate of the key sieving size 1.18 mm is 75–95%, the pass rate of the key sieving size 0.15 mm is 15–25%, the fineness modulus is 2.2–2.6 and the appropriate filling coefficient of geopolymer paste is around 1.0–1.15, the comprehensive performance of geopolymer mortar is the best. This research paper could provide a basis for the design of geopolymer mortar based on fly ash, and it is of great significance for its popularization and application.
Highlights
Cement is one of the most popular building materials in civil construction
Geopolymer binder is one of such alternative cementing materials which are produced by mixing high alkali solutions and aluminosilicate material together [6,7,8]
Compressive, flexural and tensile strengths of geopolymer mortar with different sand gradations were analyzed by laboratory tests
Summary
Cement is one of the most popular building materials in civil construction. In 2014, China’s cement output reached 2.182 billion tons, accounting for 60% of the total world production [1]. Geopolymer binder is one of such alternative cementing materials which are produced by mixing high alkali solutions and aluminosilicate material together [6,7,8]. The CO2 emission of producing one ton of geopolymer is only about 1/6 of cement production [10]. The researchers used different raw materials to prepare the geopolymer binder. Many raw materials, including zeolite or bentonite [20], palm oil fuel ash, granulated blast furnace slag [23,24], metakaolin [25,26,27], or flue gas desulfurization gypsum [28], were used to composite fly ash as the preparation materials of geopolymer binder. A range of gelation properties of inorganic polymer are formed under a certain temperature [29]
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