A: A geopolymer is a material made from a binder and an alkali hydroxide-alkali silicate aqueous solution. The binder is a pozzolanic material, i.e., any alumino-silicate material. The “geo” is because the raw materials used in geopolymers usually come from rock-forming minerals.
A: Portland cement (PC) is cement made from limestone and clay that is quarried and crushed. The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln. It’s then heated to 2700°F, producing off-gases, primarily CO2. The resulting material, called “clinker”, is cooled and then cement plants grind it and mix it with small amounts of gypsum and limestone. Portland cement can contain some hazardous components such as silica and hexavalent chromium.
Portland cement-based concrete is a mixture of PC, water, and aggregate (sand, gravel). The PC mixed with water acts as a binder for the aggregate.
A: The different terms refer to the compressive strength of the material, here measured in pounds per square inch (psi). For reference, 145 psi = 1 MPa = 1N/mm2.
Normal strength concrete ranges from 3,000 – 6,000 psi.
High performance concrete ranges from 10,000 – 20,000 psi.
Ultra high performance has a compressive strength higher than 20,000 psi.
HPC and UHPC exhibit much higher durability than regular strength materials.
- Normal strength fly ash-C concrete
- Normal strength geopolymer concrete
- Patented high/ultra-high performance geopolymer concrete – the only geopolymer UHPC on the market today.
- Lightweight, high-strength geopolymer concrete in both cellular and non-cellular forms.
A: Depending on the formulation (i.e., high, ultra high, lightweight) UHM concrete is made from:
- A composite binder that consists of 2 or more materials such as ground granulated blast furnace slag, fly ash, fumed silica, and metakaolin,
- Aggregate, which may be fine sand and/or small gravel, and
- A stoichiometrically optimized activator solution that consists of alkali-hydroxide (sodium and/or potassium hydroxide), silica, and water.
- Proprietary retarders
- Lightweight cellular concrete incorporates air bubble forming agents in place of aggregate.
- Non-cellular lightweight concrete uses lightweight aggregates such as perlite.
- Ground granulated blast furnace slag is a by-product of the iron making process. The molten slag that is quenched by immersion in water produces a granulated material, which is then ground fine.
- Fumed silica is a by-product of silicon fabrication.
- Fly ash is a by-product of coal combustion.
A: As with PC concrete, UHM concrete is made by mixing a binder and aggregate with an activator at room temperature. The activator for Portland cement is water while the activator for UHM concrete is an alkaline silicate solution. See the FAQ on ingredients above.
- At room temperature, normal strength PC concrete reaches 70% of its 28-day compressive strength (e.g., 4,000 psi) in 7 days. UHM’s high/ultra-high concrete at room temperature reaches the same compressive strength in 6-12 hours depending on the specific composition of the mix.
UHM’s HPC and UHPC reach about 70% of their 28-day compressive strength (e.g., 10,000 – 28,000 psi) in 7 days and full strength in 28 days.
Curing UHM concrete at about 75°C for up to 24 hours results in the material reaching up to 80% of its 28-day compressive strength.
A: Yes, the bond strength with Portland cement concrete is fast and high (at least 5700 psi).
A: Depending on the formulation, the price of the materials in UHM concrete is comparable or less than the materials in Portland cement concrete that is on the market today.
UHM fly ash-C normal strength concrete:… compared with normal strength PC concrete.
UHM geopolymer normal strength concrete: … compared with normal strength PC concrete.
UHM geopolymer ultra high performance concrete: up to 75% less expensive compared with Portland cement UHPC.
UHM lightweight cellular concrete:…compared with Portland cement lightweight cellular concrete.
Production costs are roughly comparable to Portland cement concrete with no significant capital investment required.