Q: Why should I use internal curing in my project?
A: Extensive research studies have demonstrated that internal curing improves hydration, reduces early age cracking, reduces chloride ingress, reduces curling and warping, eliminates autogenous shrinkage and improves durability, all of which extend the concrete’s service life.
Q: In what projects can I use internal curing?
A: Internal curing can be used in all concrete, however, it’s most beneficial in bridge decks, concrete pavement, curb and gutter, sidewalks, driveways and other applications that are exposed to the elements. If curling and warping of concrete slabs are a concern, internal curing helps to reduce it.
Q: Our state DOT is rehabbing several area bridges and is interested in using internal curing. How do we incorporate internal curing into the specification?
A: Incorporating internal curing into the specification is easy and straightforward. The National Concrete Pavement Technology Center developed the Guide Specification for Internally Curing Concrete as part of FHWA’s Pooled Fund TPF-5(286) in November 2017. It is also recommended that the ESCS lightweight aggregate suppliers be contacted as they work closely with DOT’s and engineers who have developed concrete specifications that incorporate internal curing.
Q: How do I adjust my concrete mixture to incorporate internal curing?
A: ESCSI’s internal curing calculator will adjust your existing concrete mixture design and calculate the amount of prewetted ESCS lightweight aggregate needed to provide the proper amount of internal curing water. Contact the ESCS supplier for ESCS aggregate density, absorption, desorption and relative density (specific gravity).
Q: What is the cost per cubic yard of internally cured concrete?
A: Contact your ESCS aggregate supplier as they work with ready-mix suppliers who can give you the cost per cubic yard of IC concrete.
Q: Why should I consider using structural lightweight concrete in my next project design?
Using structural lightweight concrete in a design reduces the dead load of the concrete which has many advantages in economics, performance and durability. This weight reduction allows the structural designer to reduce the size of columns, footings and other load bearing elements. Structural lightweight concrete mixtures can be designed to achieve similar and, in many cases, superior strength, mechanical and durability performance requirements. The more efficient strength-to-weight ratio in structural elements allows for project savings in less reinforcing steel and reduced volumes of concrete. Structural lightweight concrete provides a higher fire-rated concrete, greater r-values and thus greater energy efficiencies to structures. Structural lightweight concrete has been used for bridge decks, piers and beams, slabs and wall elements in steel and concrete frame buildings, parking structures, tilt-up walls, topping slabs and composite slabs on metal decks.
Q: Why is lightweight concrete able to resist fire better than normalweight concrete?
The superior fire resistance of lightweight concrete is a function of the thermal stability and the insulative properties of lightweight aggregate that are the result of its exposure to temperatures greater than 2,000° F while being expanded in a rotary kiln. These properties allow lightweight concrete to have lower thermal conductivity (slower temperature rise on the unexposed surface) and a lower coefficient of thermal expansion (lower forces developed under restraint).
Q: What is a realistic value for in-place compacted density for a lightweight fill using your products?
A good maximum value for in-place compacted density for an expanded shale, clay or slate fill is 65 pounds per cubic foot.
Q: I notice that the density of your product is less than 62.4 pounds per cubic foot. Will it float?
The density of lightweight aggregate includes the voids between the particles. Typical dry specific gravities of expanded shale, clay or slate particles range from 1.25 – 1.65 which is heavier than water.
Q: What is the best way to determine in-place compacted density when using expanded shale fills?
The best way to determine what the approximate in-place compacted density is to test material with the delivered moisture content and gradation utilizing a one point proctor test conducted in accordance with a modified version of ASTM D 698 “Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort.” Because of the cohesionless nature of coarse lightweight aggregate, the standard shall be modified as follows: The aggregate sample shall be placed in a 0.5 cubic foot bucket at the moisture content that the aggregate will be delivered to the jobsite. The sample shall be placed in three equal layers and compacted by dropping a 5.5 pounds rammer from a distance of 12 inches 25 times on each layer.
Q: Do you have recommendations for installation of lightweight fill?
Lightweight fill can be placed in approximately uniform layers not to exceed 12 inches loose thickness. Each layer should be compacted using vibratory compaction equipment weighing not more than 12 tons static weight. The actual lift thickness, exact number of passes, and need for vibrating the roller will be determined by the engineer, depending on the project requirements (i.e., strength, compressibility, density) and equipment used. In confined areas, vibratory plate compaction equipment should be used (5 hp to 20 hp) with a minimum of two passes in 6″ lifts for a 5 hp plate and 12″ lifts for a 20 hp plate. The contractor should take all necessary precautions during construction activities in operations on or adjacent to the lightweight fill to ensure that the material is not over-compacted. Construction equipment, other than for compaction, should not operate on the exposed lightweight fill.
Q: Why should I use SmartWall Systems in my building project?
SmartWall units are made with expanded shale, clay and slate (ESCS) and are able to provide thermal stability and strength other wall systems simply can not.
Q: How does expanded shale, clay and slate (ESCS) aggregate make dollars go farther in my chip seal project?
Roadway service life is extended because of ESCS’s unique and superior capabilities to bond with asphalt. ESCS aggregate does not polish as it wears. The pavement maintains its high skid resistance because as it wears, fresh interior cells with rough ceramic edges are continually exposed.
Q: Why is expanded shale, clay and slate (ESCS) the best choice for water filtration?
ESCS filtration media has up to 100 times the specific surface area than ordinary filtration sand and gravel. This advantage combined with ESCS’s lower density and excellent durability offer superior performance, increased volume flows and reductions in clogging and blinding over standard silica, granite or quartz granular media.
Q: I notice that the pH of expanded shale, clay and slate (ESCS) is over 8.0, so how does that affect the media after it is blended with ESCS?
It depends on the test method. ESCS is chemically inert and does not act like lime and buffer soil. Most testing labs crush the material and test the pH of the dust which gives a result not indicative of the actual outer surface of the aggregate. Another reason for a higher pH is residue on the aggregate from firing the raw material. These are oxidized minerals that will wash out eventually. The pH of rain water and most soils on the East Coast are more acidic. The percentage of ESCS in the mixture when tested in a mixture will not dramatically affect the pH of the media.
Q: Does ESCS breakdown over time?
ESCS is a vitrified material after firing and most of these products are very strong. With an LA Abrasion Test report showing denigration of under 30% chance of decomposition from water, temperature or microbial action over a very long period of time are unheard of. Unless constant wear and tear from heavy vehicular traffic over a hard surface is the norm, the ESCS should remain intact through the life of the project.
Q: How does ESCS affect the weight of green roof media?
ASTM E2399 Standard Test Method for Maximum Density for Dead Load Analysis of Green Roof Systems provides the weight of a green roof growing media at maximum water holding capacity. The actual percentage of ESCS in the media will vary with the mix design. In most cases, with extensive green roofs, 70-80% is ESCS and in intensive green roof media, the ESCS is 45-65%. When ESCS is dry, the weight can be between 38 and 55 pounds per cubic foot for coarse aggregate and 50 – 62 PCF for fines. When saturated, the coarse aggregate can jump up to 68 pcf at full water holding capacity and the fines up to 78 pcf. ESCS is still the lightest material in the media blend. Sand and organics when saturated will weigh more, so the more ESCS in the blend, the lighter the media, but it also means the more irrigation will be needed to sustain the plant life. See ASTM E2788 Standard Specification for Use of Expanded Shale, Clay and Slate (ESCS) as a Mineral Component in the Growing Media and the Drainage Layer for Vegetative (Green) Roof Systems.
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