The HessPozz Scorecard
How does Hess Pumice Pozz, a natural pozzolan, stack up against the other pozzolans on the market?
| 1 • Proven durability and endurance for over 2000 years. (The Pantheon, Coliseum, Roman Aqueducts, and other pumice pozz-enhanced concrete structures still stand today.) » NOTES | |
|---|---|
| HessPozz |  |
| Fly Ash (Type F) | — |
| Metakaolin | — |
| Silica Fume | — |
| Blast Furnace Slag | — |
| 2 • Green. Naturally processed by Mother Nature. Requires no energy-intensive calcination (heating), thus reducing the carbon footprint. » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | — |
| Metakaolin | — |
| Silica Fume | — |
| Blast Furnace Slag | — |
| 3 • Clean. A non-hazardous material containing no crystalline silica, lead, mercury, arsenic or carbon; will not leach toxins into the soil. » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | — |
| Metakaolin | . . . (variable) |
| Silica Fume | . . . |
| Blast Furnace Slag | — |
| 4 • Consistent make-up and performance, pour after pour. (Predictable, repeatable performance results per concrete mix design; consistent particle size distribution, density, and chemical properties.) » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | — |
| Metakaolin | . . . |
| Silica Fume | . . . |
| Blast Furnace Slag | . . . |
| 5 • Naturally white in color. (Especially desirable for GFRC products, decorative precast, stone veneer, or light-colored concrete applications.) » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | — |
| Metakaolin | |
| Silica Fume | . . . |
| Blast Furnace Slag | . . . |
| 6 • Significantly reduces concrete porosity, and thus susceptibility to chemical attack, by reacting with free lime to form a denser Calcium Silicate Hydrate (CSH) concrete matrix. » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | |
| Metakaolin | |
| Silica Fume | |
| Blast Furnace Slag | |
| 7 • Mitigates or eliminates alkali-silica reaction (ASR), sulfate & chloride attack, and efflorescence. » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | |
| Metakaolin | |
| Silica Fume | |
| Blast Furnace Slag | |
| 8 • Enhances concrete durability, abrasion resistance and long-term strength. » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | |
| Metakaolin | |
| Silica Fume | |
| Blast Furnace Slag | |
| 9 • Reduces the heat of the hydration reaction between the water and cement, mitigating against expansion/contraction and thus reducing the threat of thermal cracking. » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | |
| Metakaolin | |
| Silica Fume | |
| Blast Furnace Slag | |
| 10 • Cost Value. (Priced near the cost of Portland cement; percent of replacement and concrete enhancement economically feasible for large-quantity use; lowers the overall carbon footprint of concrete.) » NOTES | |
| HessPozz | |
| Fly Ash (Type F) | |
| Metakaolin | — |
| Silica Fume | . . . |
| Blast Furnace Slag | |
| TOTALS | |
| HessPozz | 10 |
| Fly Ash (Type F) | 5 |
| Metakaolin | 4 |
| Silica Fume | 4 |
| Blast Furnace Slag | 5 |
Notes on SCMs
HessPozz
COLOR: Scores an 84 on GE Brightness scale. PURITY: HessPozz is also used in personal hygiene products, such as toothpastes, exfoliating cosmetics, soaps. COST VALUE: priced at or below the cost of Portland cement; effective against ASR at 15% of cement replacement, no matter the reactivity level of aggregate; sustainable source. EASE OF USE/PLACEMENT: use of pumice as SCM increases water requirements; easily brought back into desired W/C ranges with water reducer admixture; aggressive, toothy shape of pumice pozz can make some kinds of flatwork finishes more effort intensive. CONSISTENT MAKE-UP & PERFORMANCE: quantifiable chemical make-up bag after bag; predictable performance in concrete mix design load after load; makes additional and significant contributions to concrete durability; compatible with most concrete admixtures. CLEAN AND GREEN: white pumice from a naturally pure deposit; contains no hazardous compounds, safe to use, no leachate concerns; naturally calcined; requires minimal processing to grade; consistent spec.
Fly Ash (Type F)
COLOR: can be anywhere from light grey to dark brown to ocher yellow. COST VALUE: waste product, historically inexpensive or free, but declining availability of Type F causing price fluctuations and sourcing problems. EASE OF USE/PLACEMENT: been in wide use for decades so well understood; some fly ash decreases water need, some increases it; generally improves workability of concrete. CONSISTENT MAKE-UP & PERFORMANCE: different coal sources produce different ash chemistry and contaminant concentrations, as do evolving ash filtration requirements; particle sizes vary greatly; on-going testing necessary to ensure desired performance; makes additional and significant contributions to concrete durability. CLEAN AND GREEN: as a waste product (scrubbed from coal-burning furnace smoke) fly ash is loaded with hazardous chemistry and other junk particulates; heavy metal leachate concerns; use in concrete reduces amount of fly ash that must be landfilled or stored in ash ponds. PROVEN TO MITIGATE ASR: not as effective as some other pozzolans—fly ash mix designs often require an additional SCM to achieve acceptable ASR mitigation levels.
Metakaolin
COLOR: consistent white color. COST VALUE: made from heating (calcining) high-purity kaolin clay to create amorphous aluminosilicate—production costs dictate limited/specialized project usage; effective against ASR at 10 to 15% of replacement, depending on reactivity level of aggregate. EASE OF USE/PLACEMENT: variable effect on water demand depending on grade; smooth, creamy finishability; generally improves workability of concrete. CONSISTENT MAKE-UP & PERFORMANCE: The quality and reactivity of metakaolin is strongly dependent of the characteristics of the raw material used; carefully controlled selection and firing processes equal predictable chemical make-up; compatible with most concrete admixtures. CLEAN AND GREEN: modern flash-heating processes avoid introducing impurities; manufacture requires calcining (heat-induced transformation).
Silica Fume
COLOR: Varies from black to grey to off-white. COST VALUE: waste furnace product, price can vary from one-and-a-half to four times the cost of Portland cement. EASE OF USE/PLACEMENT: extreme fineness of particles (approximately 0.1 to 1.0 μm) increases water demand, use of water reducer admixture necessary; extreme fineness creates handling problems and is typically densified or slurried for transport; can contribute to stickiness and reduce concrete workability. CONSISTENT MAKE-UP & PERFORMANCE: Chemical composition varies according to the type of alloy or metal being produced; prone to clumping, which causes it to act more like a fine reactive aggregate and contribute to ASR formation and so extensive mixing necessary to facilitate proper dispersion; can be used with superplasticizers to design ultra-high-strength concrete. CLEAN AND GREEN: waste byproduct filtered from quartz+coal furnace exhaust gases; use in concrete reduces amount of fume that must be landfilled.
Blast Furnace Slag
COLOR: Can be all over the charts—from near white to grey to yellow/green. COST: Variable cost, depending on grade and color. EASE OF USE/PLACEMENT: can decrease concrete water demand; generally improves workability of concrete. CONSISTENT MAKE-UP & PERFORMANCE: uniform composition from source to source; generally improves concrete finishability; can lighten concrete color; makes additional and significant contributions to concrete durability. CLEAN AND GREEN: made from rapidly chilled iron blast-furnace slag; contains metal impurities; use in concrete reduces amount of fume that must be landfilled.
