Why hot weather causes plastic shrinkage cracks in concrete and how landscape contractors prevent them

Hot days, fresh concrete, and a desert breeze—sounds like Nevada, right? It’s a combo that can turn a smooth, glossy pour into a spiderweb of tiny cracks if you’re not careful. The phenomenon you’ll see is called plastic shrinkage cracking, and in hot weather it’s mostly about one simple idea: water evaporates too quickly.

Let me explain what’s going on and how you, as a landscape contractor working in Nevada’s climate, can head off trouble before it shows up on the surface.

What plastic shrinkage cracks really are (and why heat makes them worse)

When you place concrete, the paste around the aggregates is still soft and plastic. If water on the surface evaporates faster than the concrete underneath can compensate, the surface layer dries and shrinks while the deeper portions stay a bit wetter. That mismatch creates tensile stresses right at the surface. If the surface can’t accommodate those stresses by deforming, tiny cracks appear—often in a fine, spiderweb pattern or small, shallow lines near the surface.

A few things to keep in mind:

• This isn’t the same as cracks that form after the concrete hardens. Plastic shrinkage cracks happen during placement, while the mix is still workable and the moisture exchange with the environment is happening in real time.

• Heat accelerates this process. The hotter it is, the faster water evaporates from the surface. In Nevada, where July afternoons can feel like you’re standing in an oven, that evaporation rate can spike quickly.

• Other factors can contribute to cracking, but they don’t directly cause the plastic shrinkage phenomenon. Improper mixing or curing, or an unstable ground, can degrade overall concrete quality, yet the immediate culprit for plastic shrinkage cracks is rapid surface evaporation.

In plain terms: heat plus wind equals fast surface drying, and fast surface drying equals a higher chance of plastic shrinkage cracks.

Why Nevada’s climate puts you in a tricky spot

Nevada isn’t just hot—it’s dry and windy, often at the same time. Those conditions are a perfect setup for rapid evaporation. Think: midday sun beating down on a light-colored concrete surface, with a sweeping gust off the desert that robs moisture away in minutes. Even a light breeze can yank away water that’s trying to keep the surface hydrated.

Here are the key climate-related culprits you’ll face on most projects:

• High surface temperatures. Dark finishes or blacktop surfaces absorb more heat, accelerating evaporation from the surface.

• Low humidity. The atmosphere isn’t holding much moisture, so the concrete surface dries out faster.

• Wind. Even a moderate breeze can intensify evaporation, especially on elevated or exposed pours.

• Rapid cooling rates at night aren’t always a relief in Nevada. If a pour sits in heat during the day and then cools quickly, the surface still has to catch up, which can compound the problem if moisture loss isn’t controlled.

What you’ll notice on site

You’ll see fine cracks or light surface cracks, often aligned with the direction of drying. They show up before the concrete has a chance to set fully. If you’ve got a hot, windy day on your schedule, you’ll want to be on the lookout for these telling signs:

• Hairline cracks near the surface, sometimes forming a mosaic pattern.

• A surface that feels dry and dusty when you touch it, even though the interior is still plastic enough to shape.

• Uneven sheen across the slab—the surface dries faster in some areas than others, creating stress differentials.

If you catch cracks early, you can still manage them. The goal isn’t to pretend they don’t exist but to minimize their spread and impact with smart prevention and timely care.

Prevention first: a practical playbook you can actually use

The best defense against plastic shrinkage cracks is simple in concept: slow down surface water loss and keep the surface moist long enough for the mix to gain strength. Here’s a practical set of steps you can apply, especially when you’re working in Nevada’s hot seasons.

Plan the pour with the climate in mind

• Schedule pours for cooler parts of the day. Early morning or late afternoon rather than the peak heat window can dramatically reduce evaporation.

• If timing allows, monitor the forecast for wind speed and humidity. A light wind day is preferable to a gusty one when you’re trying to hold moisture at the surface.

Control the mix and its workability

• Aim for a workable slump that allows you to place and finish without dragging water to the surface. The goal isn’t a “too flowy” mix but a stable, placeable mix that won’t sag too much and then dry on the surface.

• Consider admixtures that help manage early set and workability. Set-retarding admixtures can slow surface drying just enough to give you time to finish without creating cold joints or honeycombing. If you use admixtures, follow the manufacturer’s guidance for dosage and compatibility with your cement type.

• Use proper air-entraining agents to improve resistance to early cracking and shrinkage, especially in drier climates. Air entrainment helps develop a microstructure that can tolerate some shrinkage without cracking.

Protect the surface as you place and finish

• Use shading and wind protection during placement. A portable shade sail, paired with temporary windbreaks, can dramatically cut evaporation rates on a hot Nevada afternoon.

• Keep the surface moist as you place and finish. This doesn’t mean flooding it with water; it means applying moisture-control measures that prevent rapid surface drying.

• If you’re pouring in extremely hot conditions, you might place a surface barrier after the finishing pass. Film-forming curing compounds or moisture-retaining coverings help lock water in without extending cure times dangerously.

Curing properly is more than a single step

• Immediate curing is critical. Moist curing (fogging, misting, or covering with burlap that’s kept damp) is a reliable method. In Nevada’s dry heat, moist curing is often the simplest and most effective approach.

• Film-forming curing compounds are a strong alternative when you can’t easily maintain surface moisture. They create a barrier that reduces water loss while the concrete gains strength.

• Don’t assume curing is optional after you finish finishing. The longer the surface stays adequately moist during the early hours and days, the better the final surface looks—and the lower the crack risk.

Finish timing and technique

• Don’t rush the finishing step. Finishing too soon can trap moisture and create surface irregularities; finishing too late can cause a rough surface and microcracking from rapid surface drying.

• Use gentle troweling and avoid overworking the surface. Aggressive finishing can draw water upward, increasing the risk of surface cracking.

• If you see the surface beginning to dry, pause and re-wet or re-apply curing compound as appropriate, depending on your chosen method.

Joint design and crack control

• Plan for control joints to manage where cracks tend to form. Even with perfect curing, minor plastic shrinkage cracks may occur; joints guide where they appear and help minimize their visual impact.

• Place joints at the right intervals and depths for the slab size and exposure. In hot climates, deeper or more frequent joints can be beneficial if you’re working with larger areas.

On-site tips you can actually use tomorrow

• Bring a simple evaporative-rate checklist to the job site: air temp, surface temp, relative humidity, wind speed, and surface moisture level. If the evaporation rate is high, shift tactics toward more aggressive curing and moisture retention.

• Use shade, water misting, or fogging for the surface during critical steps—especially the initial finishing pass.

• Keep burlap or curing blankets handy for quick, practical moisture retention on large pours.

• Have a plan for wind. If gusts pick up mid-pour, pause and adjust, perhaps by adding temporary windbreaks to protect the surface while it gains initial set.

• Consider a small, controlled test section on larger projects. A quick sample area gives you a feel for how the surface reacts to your chosen curing method under current weather.

A quick Nevada-focused reference you can print and put in your truck

• Pour timing: Coolest parts of the day, or break the pour into smaller sections to manage exposure.

• Surface moisture: Choose one method (misting, burlap, or curing compound) and apply consistently.

• Joints: Plan early—don’t wait until the slab is nearly done to decide where joints go.

• Materials: Use a concrete mix with appropriate set characteristics for warm weather; consider additives that improve workability and reduce early water loss.

• Protection: Have shade, windbreaks, and curing supplies ready on site.

Common sense and professional judgment matter most

Plastic shrinkage cracks aren’t a sign of a failed project by themselves, but they’re a telltale signal that surface moisture loss was too rapid for the ongoing hydration process. In Nevada’s climate, the temptation to hurry a pour—because the afternoon heat is beating down—can be strong. But with the right planning, materials, and curing strategy, you can keep those cracks at bay and deliver a durable, smooth surface that stands up to foot traffic, wheelbarrows, and the occasional stony Nevada breeze.

If you’re new to this line of work, here’s a simple mental model to keep in your head: heat accelerates evaporation; evaporation causes shrinkage at the surface; shrinkage cracks appear if the surface dries too fast before the paste hydrates enough to resist stress. Your job is to slow the evaporation enough to let the concrete set evenly and gracefully.

A closing thought

Concrete is a stubborn partner—not a bad partner, just particular. In a place like Nevada, where the sun is relentless and the air can be bone-dry, you learn to listen to the weather and respond with a disciplined approach. The tricks aren’t glamorous: schedule smart, manage the surface moisture, cure properly, and plan joints with intention. When you do, you’ll notice fewer surface cracks and a more resilient finish that keeps its beauty long after the dust has settled.

If you want to keep exploring this topic, you’ll find plenty of practical references in standard concrete handbooks and local guidelines that discuss curing and jointing in hot climates. The key is applying those principles on the job site every single day, in that Nevada heat, with a calm plan and a willing pair of gloves. And yes—when the wind kicks up on a hot afternoon, it might test your resolve, but it also reminds you why thoughtful curing matters so much. You’ve got this.