RLW: The Mixer Minute

  Concrete 101: Shotcrete & Gunite Applications Sometimes concrete doesn’t get poured — it gets sprayed. That’s the case with shotcrete (also called gunite in some applications), a method where concrete is pneumatically projected through a hose at high velocity. What is Shotcrete? Shotcrete is concrete or mortar conveyed through a hose and “shot” onto a surface. It’s applied using compressed air, which compacts the mix as it hits the surface. It can be either wet-mix (pre-mixed with water before spraying) or dry-mix (water added at the nozzle). Where It’s Used Swimming Pools: Creates curved, watertight shells. Retaining Walls & Slopes: Stabilizes soil and rock faces. Tunnels & Mines: Provides quick, strong linings for underground structures. Architectural Features: Allows for creative, free-form shapes that are hard to achieve with traditional formwork. Why It Matters Shotcrete is versatile, fast, and efficient. It can be applied ove...

  Concrete 101: Concrete in Cold Climates & Freeze-Thaw Resistance If you live in a region with cold winters, you’ve probably seen cracked sidewalks or spalled driveways. That damage often comes from the freeze-thaw cycle — when water gets into concrete, freezes, expands, and puts pressure on the material. Over time, this can weaken and break apart the surface. How Concrete Fights Back Air-Entrained Concrete: Tiny air bubbles are added during mixing. These bubbles act like “pressure relief valves,” giving freezing water room to expand without cracking the slab. Proper Sealing: Applying a quality sealer keeps excess water from soaking into the surface. Mix Design: Using the right water-to-cement ratio and aggregates improves durability in harsh climates. Good Drainage: Sloping surfaces so water runs off instead of pooling helps prevent freeze-thaw damage. Why It Matters Freeze-thaw resistance is critical for driveways, sidewalks, and outdoor slabs in cold-...

  Concrete 101: Moisture Vapor Emission & Vapor Barriers in Slabs Concrete might look solid, but it’s actually porous. That means water vapor can move through it — and in some cases, this leads to big problems like flooring failures, mold, or damp basements. This process is called moisture vapor emission (MVE). What is Moisture Vapor Emission? MVE is the movement of water vapor from the ground or within the concrete up to the surface. Even slabs that “look dry” may still be releasing moisture. Flooring like hardwood, tile, or vinyl can fail if the vapor pressure isn’t managed properly. Controlling Moisture in Slabs Vapor Barriers/Membranes: Placed under the slab before the pour to block vapor from the soil. Proper Curing: Ensures concrete dries evenly and reduces excess trapped moisture. Moisture Testing: Tools like RH probes or calcium chloride tests measure MVE before flooring is installed. Sealants & Coatings: Can provide extra protection on...

  Concrete 101: Self-Consolidating Concrete (SCC) Concrete usually needs to be vibrated or worked into place to eliminate air pockets and fully surround rebar. But there’s a special type of mix that does the job on its own — Self-Consolidating Concrete (SCC). What Makes SCC Different? SCC is highly flowable — it spreads easily under its own weight. It doesn’t require mechanical vibration to settle. It still delivers strength and durability equal to (or better than) conventional concrete. Where It’s Used Architectural Projects: SCC flows into detailed molds and around complex rebar designs, capturing fine details. High-Rise Buildings: Helps with congested reinforcement areas where normal concrete would be hard to place. Precast Elements: Factories often use SCC for panels, pipes, and structural members. Benefits of SCC Saves labor and time by reducing the need for vibration. Provides smoother finishes with fewer surface defects. Reduces noise on...