Abstract
The effect of curing conditions on the early age and long-term shrinkage of ultra high-performance fiber-reinforced concrete (UHPFRC) was systematically studied. The shrinkage of the early age (0–168 h) and long-term age (0–90 d) of UHPFRC material was measured based on three kinds of humidity conditions (dry, sealed, and soaked) and curing temperatures (25°C, 40°C, and 75°C), respectively. In this paper, the hydration degree of different shrinkage stages was studied in combination with chemical-bound water experiment. Meanwhile, the influencing mechanism of curing condition on the shrinkage of UHPFRC was analyzed. The results show that the early shrinkage rate of UHPFRC is accelerated with the increase of temperature, and the rate of shrinkage development at the latter stage is suppressed with the increase of temperature. With the increase of humidity, the early age shrinkage of UHPFRC and its increasing rate gradually decrease, which means drying condition > sealing condition > soaking condition. According to the long-term shrinkage results, increasing temperature has very significant inhibiting effect on the UHPFRC shrinkage in the sealed condition. Due to the majority of the in-site components of UHPFRC cured in the sealed condition, high-temperature curing has evident inhibition of early age shrinkage of UHPFRC. Therefore, promoting curing temperature is fairly effective at inhibiting the early age shrinkage of UHPFRC for the in-site structures.
Highlights
As a kind of typical fiber-reinforced concrete material, ultra high-performance fiber-reinforced concrete (UHPFRC) is known for the high strength, high durability, high toughness, and low defection
Studies have shown that the autogenous shrinkage of cement hydration was only 50–100 με after 5 years [3], while the early age shrinkage of UHPFRC material reached up to 400 με at the age of 14 d [4]
Since the early strength and shrinkage of UHPFRC grow rapidly, the shrinkage stress will be generated inside concrete by constraint effect. en the probability of cracking increases, which causes negative effect on mechanical properties and durability of the structure. erefore, it is of great significance to further study the shrinkage mechanism of UHPFRC
Summary
As a kind of typical fiber-reinforced concrete material, ultra high-performance fiber-reinforced concrete (UHPFRC) is known for the high strength, high durability, high toughness, and low defection. E shrinkage mechanism of ordinary concrete is quite different from that of UHPFRC. Studies have shown that the autogenous shrinkage of cement hydration was only 50–100 με after 5 years [3], while the early age shrinkage of UHPFRC material reached up to 400 με at the age of 14 d [4]. Since the early strength and shrinkage of UHPFRC grow rapidly, the shrinkage stress will be generated inside concrete by constraint effect. Studies showed that [5] the shrinkage of UHPFRC among 14 d age reached up to 400–800 με in the standard curing condition, while that of 28 d was only about 100–300 με in the curing condition of high-temperature steam. Bouziadi et al [7] studied the effect of different curing temperatures
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