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...

  Concrete 101: Coloring, Staining & Decorative Finishes Concrete doesn’t have to be plain gray. With the right techniques, it can be colorful, stylish, and even look like stone, brick, or wood. That’s where coloring, staining, and decorative finishes come into play. Ways to Add Color & Style Integral Color: Pigment is mixed directly into the concrete before it’s poured, giving it consistent color throughout. Stains: Acid- or water-based stains are applied to hardened concrete to create rich tones and natural-looking variations. Stamped Concrete: Fresh concrete is imprinted with patterns to mimic stone, tile, brick, or even wood grain. Exposed Aggregate: Surface paste is removed to reveal the natural stone or gravel inside the mix. Overlays & Sealers: Thin layers and protective coatings can refresh old surfaces and add sheen or texture. Why It’s Popular Decorative finishes give homeowners and businesses a way to personalize their space. From p...

  Sunday Slab Talk: Concrete Across America Concrete might look the same everywhere, but how it’s used and appreciated can change depending on where you are in the country. From highways to patios, every region has its own concrete story. The Northeast Cold winters mean freeze-thaw durability is king. Driveways and sidewalks need air-entrained mixes and sealers to survive snow, salt, and ice. Basements are common, so strong, watertight foundations are a must. The South Heat and humidity shape the work here. Crews often pour in the early morning to beat the sun, and decorative stamped patios and pool decks are especially popular. The Midwest Known as “America’s Heartland,” the Midwest loves concrete for both its practicality and resilience. Agricultural slabs, barns, and silo bases are everyday work, along with long stretches of concrete highway. The West Out west, you’ll find concrete in massive infrastructure projects like dams, bridges, and tunnels. Decorative concrete...

  Concrete 101: Shrinkage & How to Mitigate It Concrete may look solid, but as it cures and dries, it actually changes shape slightly. This process is called shrinkage — and if not managed correctly, it can lead to cracking. Types of Shrinkage Drying Shrinkage: Happens as moisture leaves the concrete over time. Autogenous Shrinkage: Occurs in low water-to-cement mixes as the cement particles consume water during hydration. Plastic Shrinkage: Early cracking that can occur while the concrete is still fresh, especially in hot or windy weather. Ways to Reduce Shrinkage Proper Curing: Keeping the concrete moist (with curing compounds, water spray, or coverings) helps reduce early shrinkage. Control Joints: Planned cuts in the slab that allow cracks to form in controlled, less noticeable spots. Balanced Mix Design: Using the right water-to-cement ratio and sometimes adding shrinkage-reducing admixtures. Fibers: Tiny reinforcements that help hold the ...