Abstract
In this study, a new type of cement-based healing pellets (CHPs) were proposed to accelerate the healing efficiency of concrete, which was mainly based on the introduced Na2CO3 on promoting the formation of calcium carbonate (CaCO3) in cracks. The effects of Na2CO3 on the characteristics of CHPs were firstly investigated, and then the properties of cement mortar mixed with CHPs were studied quantitatively, including the workability, mechanical properties and healing ability. The results showed that higher dosages of Na2CO3 in CHPs decreased the size range of pellets and reduced the setting time, fluidity and heat of hydration of mortar. Still more, CHPs reduced the early strength of mortar but kept the intensity growth rate stable such that it had nearly no negative effect on the later strength. With the content of CHPs increasing, the strength of mortar showed a decreasing trend, while the pore-filling efficiency and strength healing rate of mortar were further improved. In addition, as a new type of self-healing pellets for concrete based on the “build-in” carbonation, CHPs improved the strength and healing effectiveness of cement mortar. When the dosage of Na2CO3 in CHPs and the content of CHPs in mortar were at 10% and 25%, respectively, mortar obtained highest strength in the later stage and the best healing effect.
Highlights
As an irreplaceable construction material, concrete is confronted with a potential threat to the durability after cracked [1]
Autogenous healing of cracks in concrete bridges was investigated in the 1930s [3,4], which mainly relied on the continued hydration and carbonization of cement mortar to fill cracks with hydrated gels and calcium carbonate crystals [5,6,7,8,9,10]
cement-based healing pellets (CHPs) present a circular granular form with a density of 25% lower than river sand, and the addition of Na2CO3 decreased the size range of pellets, promoting the production of calcite
Summary
As an irreplaceable construction material, concrete is confronted with a potential threat to the durability after cracked [1]. In order to improve the self-healing ability of cement structure, a common way is introducing a repairing substance into the mortar [6]. The pan-pelletizing technology was utilized to prepare mineral pellets by Alghamri [21,22], those prepared pellets were coated by PVA to reduce the invalid release of mineral These pellets showed a remarkable performance on crack sealing but forfeited the expected mechanical properties and strength healing rates of mortar. NaHCO3 and Na2 CO3 into mortar to investigate the cementitious recrystallization with expansive agents They affirmed that carbonates increased the self-healing ability of concrete, while the strength of mortar decreased in the alkalescent mix water. The effects of pellets on the mechanical properties and healing rates of mortar were investigated by the test of compressive and four-point bending, combined with the acoustic emission (AE) test
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