Tag: Clint Chapman

ANSWER: Internal curing is fairly straightforward. Lightweight aggregates are highly absorptive, holding significant water. Once concrete takes its initial set, this water gradually releases from the aggregate, hydrating the cement and curing the concrete from within.

Lightweight fines are preferred over coarse aggregates for internal curing as they disperse more evenly within the matrix, allowing water to reach the paste more effectively.

The capillary voids in the paste structure are slightly larger than those in the aggregate particles holding the curing water. This size difference creates a vacuum that draws water out of the lightweight fines, filling capillary voids on demand when the concrete needs curing water.

ANSWER: The main benefit of internal curing is reduced shrinkage, as it addresses chemical, drying, and plastic shrinkage. Reducing these forces significantly decreases the likelihood of cracking in the concrete.

Additionally, internal curing enhances strength and durability by creating a denser paste structure, which decreases permeability. Lower permeability reduces the risk of harmful substances infiltrating and damaging the reinforcing steel, improving long-term durability.

ANSWER: Internal curing has been widely adopted in bridge decks, with the New York DOT requiring it for all bridge decks.

Denver Water has also utilized internal curing extensively in water tanks, significantly reducing leaks. In many cases, they’ve observed a complete elimination of leaks.

ANSWER: Beyond bridge decks, mainline paving is an ideal application for internal curing, as it reduces cracking and minimizes curling and warping.

Water-tight structures, including sewage treatment facilities, hazardous waste containments, and water tanks, benefit greatly from internal curing. It’s also effective for high-strength concretes with low water-cement ratios, which are more prone to cracking, and in severe environments or mixes with supplementary cementitious materials.

In short, any application where concrete longevity is critical is a good candidate for internal curing.

ANSWER: It’s a little bit different. The biggest requirement is order lead time. You want to ensure the material arrives with enough time for saturation before it’s pump placed.

Saturation can be achieved in several ways, like submersion in water or setting up sprinkler systems on your stockpile. You can submerge stockpiles in a water pond, or perform an ambient soak with sprinklers. The material is free-draining, allowing water to penetrate through. Avoid over-handling or turning the stockpile, as this can degrade the material. Just stack it, apply sprinklers, and allow time for saturation.

ANSWER: No, that is not true. Lightweight concrete has been pumped over substantial distances. For example, the Salesforce Tower in San Francisco and the Wilshire Grand in Los Angeles both used pumped lightweight concrete for over 70 stories.

When proportioned and pumped correctly, lightweight concrete can be transported over great distances effectively.

ANSWER: We recommend adhering to ACI guidelines, including using a minimum five-inch line throughout the system. Reduce rubber line usage as much as possible.

Opt for steel slick line whenever possible, and maintain a flat boom angle to avoid pumping vertically and allowing concrete to fall straight down. Using a pump primer at the start of pumping is also recommended for best results.

Keep pump pressures low and control stroke limits, aiming for pumping rates of about 60-70 yards per hour.

ANSWER: Yes, generally finishing lightweight concrete is similar to finishing normal weight concrete. The primary difference is that most lightweight concrete is air-entrained, resulting in a reduced bleed rate.

Patience is key when finishing lightweight concrete. Starting too early can trap moisture, leading to blistering. Allow adequate time to ensure the concrete is ready for finishing.

ANSWER: Internal curing is fairly straightforward. Lightweight aggregates are highly absorptive, holding significant water. Once concrete takes its initial set, this water gradually releases from the aggregate, hydrating the cement and curing the concrete from within.

Lightweight fines are preferred over coarse aggregates for internal curing as they disperse more evenly within the matrix, allowing water to reach the paste more effectively.

The capillary voids in the paste structure are slightly larger than those in the aggregate particles holding the curing water. This size difference creates a vacuum that draws water out of the lightweight fines, filling capillary voids on demand when the concrete needs curing water.

ANSWER: The main benefit of internal curing is reduced shrinkage, as it addresses chemical, drying, and plastic shrinkage. Reducing these forces significantly decreases the likelihood of cracking in the concrete.

Additionally, internal curing enhances strength and durability by creating a denser paste structure, which decreases permeability. Lower permeability reduces the risk of harmful substances infiltrating and damaging the reinforcing steel, improving long-term durability.

ANSWER: Internal curing has been widely adopted in bridge decks, with the New York DOT requiring it for all bridge decks.

Denver Water has also utilized internal curing extensively in water tanks, significantly reducing leaks. In many cases, they’ve observed a complete elimination of leaks.

ANSWER: Beyond bridge decks, mainline paving is an ideal application for internal curing, as it reduces cracking and minimizes curling and warping.

Water-tight structures, including sewage treatment facilities, hazardous waste containments, and water tanks, benefit greatly from internal curing. It’s also effective for high-strength concretes with low water-cement ratios, which are more prone to cracking, and in severe environments or mixes with supplementary cementitious materials.

In short, any application where concrete longevity is critical is a good candidate for internal curing.