Abstract
This research investigated the effect of fly ash content on the compressive strength development of ultra-high-performance concrete (UHPC) at different curing conditions, i.e., the standard curing condition and the heat curing. A total of 20 mixtures were prepared to cast specimens to measure the compressive strength at different ages from 3 days to 180 days. Additionally, 300 specimens were prepared to estimate the appropriate heat curing period at the early ages in terms of enhancing the 28-day compressive strength of UHPC with high content of fly ash (FA). From the regression analysis using test data, empirical equations were formulated to assess the compressive strength development of UHPC considering the FA content and maturity function. Test results revealed that the preference of the addition of FA for enhancing the compressive strength of UHPC requires the early heat curing procedure which can be recommended as at least 2 days under 90 °C. Moreover, the compressive strength of UHPC with FA under heat curing mostly reached its 28-day strength within 3 days. The proposed models based on the fib 2010 model can be a useful tool to reliably assess the compressive strength development of UHPC with high-volume fly ash (HVFA) (up to 70% fly ash content) under a heat curing condition that possesses a different performance from that of normal- and high-strength concrete. When 50% of the cement content was replaced by FA, the embodied CO2 emission for UHPC mixture reduced up to approximately 50%, which is comparable to the CO2 emission calculated from the conventional normal-strength concrete.
Highlights
Ultra-high-performance concrete (UHPC) has commonly been considered as a new class of concrete that has gained a strong interest in research and application since the late 1990s [1,2,3] with outstanding characteristics including high fluidity, compressive strength, high modulus of elasticity, low permeability, and excellent durability compared to conventional concrete and high strength concrete [5,6,7]
Portland cement PC50 Nghi Son, condensed silica fume (SF), and fly ash (FA) conforming to class F specified in ASTM C 618 [22] were used for the binder of the UHPC mixture
The compressive strength of specimens cured at the above conditions was tested at ages of 3, 7, 28, 90, and 180 days complying with ASTM C109 [24]
Summary
Ultra-high-performance concrete (UHPC) has commonly been considered as a new class of concrete that has gained a strong interest in research and application since the late 1990s [1,2,3] with outstanding characteristics including high fluidity, compressive strength (over 120 MPa [4]), high modulus of elasticity, low permeability, and excellent durability compared to conventional concrete and high strength concrete [5,6,7]. Because of these outstanding properties, application of UHPC can create.
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