Abstract
Accelerated curing is used for mass production in the precast concrete industry. Autogenous shrinkage and drying shrinkage occur in concrete, during and after accelerated curing. Thus, thermal cracks may occur in concrete due to both heating and cement hydration at early age, whereas drying shrinkage causes cracks after demolding. Ground granulated blast-furnace slag cement (GGBS), a byproduct in steel manufacture, has been used to improve concrete strength development during accelerated curing but poses a challenge of increased shrinkage. In this paper, two types of granulated blast-furnace slag cements were used to study mechanical and shrinkage properties of water cured and concrete subjected to accelerated curing. Limestone powder and gypsums, with two different types of fineness, were other additives used. An accelerated one day curing cycle was adopted that consisted of a 3 h delay period, heating to 65 °C, a peak temperature maintained for 3 h, and, finally, cooling. The results indicated that increment in gypsum fineness increased concrete expansion at one day for both sealed and accelerated cured concrete. In drying condition, similar shrinkage was observed. The addition of gypsum provided slightly lower shrinkage, and this may help to reduce cracking of concrete. Limestone powder improved concrete strength at early age. The difference in blast-furnace cement fineness did not have significant differences in compressive strengths, especially at 28 days.
Highlights
Ground granulated blast-furnace slag cement is a supplementary cementitious material (SCM) that is used in concrete, to reduce ordinary Portland cement (OPC) usage
This study investigated the fresh, mechanical, and shrinkage properties of concrete made with S3000 and S4000 cement as main mineral admixtures and subjected to accelerated curing by heating
On the basis of the results from the laboratory tests, conclusions were drawn and summarized as follows: 1. Fine gypsum contributed to higher expansion at early age in sealed and accelerated cured concrete
Summary
Ground granulated blast-furnace slag cement is a supplementary cementitious material (SCM) that is used in concrete, to reduce ordinary Portland cement (OPC) usage. Steam curing is a widely used accelerated curing method in the precast concrete industry In this method, it has been proven that there is a significant increase in early strength of concrete when GGBS is added [5]. Curing time plays an important role in concrete strength development as it affects the ultimate strength and other hardened concrete properties Mineral additives such as limestone powder or gypsum are incorporated in concrete to improve concrete workability, strength development, and durability in accelerated cured concrete [6]. GGBS with a specific surface area of at least 2750 cm2/g and less than 3500 cm2/g was developed This has been used for low heat slag cement as a concrete additive [8]. Autogenous shrinkage and drying shrinkage tests were conducted in order to provide experimental data sets on concrete crack resistance at early and later age
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