Abstract
The present study evaluated the addition of a 3% nopal cactus mucilage solution to cement pastes, in its effects on setting times, flow, hydration, and microstructure, as well as on capillary water absorption and chloride diffusion in concrete. Hydration was characterized through XRD and microstructure was characterized with SEM. The mucilage solution/cement and water/cement ratios tested were 0.30, 0.45, and 0.60. The results in cement pastes indicate that the addition of mucilage increases setting times, reduces flow, slows cement hydration, and inhibits the formation of calcium hydroxide crystals in comparison with the control. Capillary absorption was significantly reduced in concrete containing mucilage, and chloride diffusion coefficients dropped up to 20% in the mixture with a mucilage/cement ratio = 0.30. The mixture with a mucilage/cement ratio = 0.45 displayed marginal reduction, and the mixture with mucilage/cement ratio = 0.60 exhibited a diffusion coefficient that was greater than the control for the specimens without moist curing.
Highlights
Durability problems in concrete structures have significant economic impact
The present study evaluated the addition of a 3% nopal cactus mucilage solution to cement pastes, in its effects on setting times, flow, hydration, and microstructure, as well as on capillary water absorption and chloride diffusion in concrete
The results in cement pastes indicate that the addition of mucilage increases setting times, reduces flow, slows cement hydration, and inhibits the formation of calcium hydroxide crystals in comparison with the control
Summary
Durability problems in concrete structures have significant economic impact. In the six years leading up to 1997, the United States spent 20 million dollars on a fraction of the repairs needed for concrete bridges, with a significant number of bridges remaining in need of repair (1). Additives have been important and integral components of concrete; the introduction of new additives and supplementary materials (whether natural or industrially produced) has led to the development of highly workable concretes, with better mechanical properties and improved durability. These concretes are known as high performance concretes (3). Their properties include improved workability and consolidation without segregation, improved long-term mechanical properties, high compressive strength at early ages, volume stability, and extended service life under aggressive environmental conditions
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