Hot and Windy Weather Concrete in Casper, Wyoming

Casper sits at 5,150 feet, the airport is higher at 5,344 feet, and the ground north and east of town is open. Wind blows across fresh slabs here with nothing to slow it. A slab that looks wet at 9 a.m. can develop plastic shrinkage cracks by 10, because the surface loses water faster than bleed water arrives. Finishers call it a crust, and it is a sign the slab is drying too fast.

We place concrete in hot, dry and windy conditions by controlling three things: the temperature of the mix, the rate of surface evaporation and the cure. None of those requires special tools. They require attention, a plan and a willingness to stop a pour that is going badly.

Summer here is not tropical, but the sun, wind and low humidity combine to make flatwork harder than in many wetter places. The cure often decides whether a slab lasts.

Three levers: mix, shade and moisture

The mix is the first lever. We ask the plant to chill batch water or add ice when hot weather arrives, and we keep aggregate stockpiles shaded and damp. Retarding admixtures extend working time. A mix that arrives at 70 degrees is easier to finish than one at 90. Trucks wait in the shade, not in the sun, and we do not allow long waits at the site.

The second lever is moisture on the surface. Fog misters, evaporation retarders sprayed between passes and windbreaks all cut surface drying. The third is the cure. Curing compound goes on as soon as the surface is ready, or wet burlap and plastic are placed. A slab that is cured poorly in its first day has a weaker, dustier surface for life.

Open ground and the haul

The Casper Logistics Hub, listed at 984 acres, and the NCIA Business Park next to the airport sit on open ground where wind passes unhindered. Large floor pours there face exposure on all sides before the building is enclosed. The airport itself covers 5,150 acres at 5,344 feet, with runways of 10,165 and 8,679 feet, which gives a sense of how exposed the area is.

Midwest, Wyoming, has recorded a high of 106 F, and summer afternoons can run hot even with a breeze. Warehouse floors, aprons and parking areas are large, flat and sunlit, which is the worst case for evaporation. Pouring in the morning, finishing before the heat builds and starting the cure at once is the pattern we follow. Aprons and dock approaches that front onto a distribution center get the same treatment, because they are large, flat and exposed.

Reading the evaporation rate

Air temperature, concrete temperature, relative humidity and wind speed combine into an evaporation rate. When the rate nears one-tenth of a pound per square foot per hour, plastic cracking is likely, and we take action. A handheld weather meter on site tells us the numbers in minutes, and we check them before and during the pour.

Wind is the variable most often ignored. A strong gust can double the rate of drying. We build temporary windbreaks from plywood, snow fence with fabric or parked equipment on the windward side. Sometimes the best move is to start a pour earlier, around dawn, when the wind is calmer. If gusts exceed safe limits for a pump boom or form bracing, we stop, and we do not restart until the gusts settle. Casper's engineering criteria list a 115 mph 3-second gust for design, which tells you how seriously the wind is taken here.

What the specification asks for

Most specifications set a maximum concrete temperature at placement, commonly around 90 or 95 F, and require hot-weather measures when conditions call for them. They also set curing duration and method. Special inspectors check temperatures at delivery and record them. A load above the limit can be rejected.

Concrete tests include slump, air, unit weight and temperature at the truck, and cylinders for strength. Our testing and quality control plan covers the sampling frequency. The City of Casper lists the 2024 International Codes and requires engineered drawings for commercial permits. We follow the project specification, which is typically stricter than the code minimum.

Pour at dawn, cure by noon

The schedule that works in summer starts early. Subgrade is dampened ahead of time, forms are wet, and the first truck arrives at first light. Finishers work the slab while it is cool, and the cure goes on before the sun is high. If the slab is large, we break it into placements that crews can finish before the heat builds.

On long hauls from the plant, delays cost workability. We confirm trucking capacity the day before and, for big placements, schedule a plant check. Pumps are positioned in the shade where possible. Chilled water, ice and retarders are ordered ahead, because they cost money and the plant needs notice. If the weather turns on the morning of the pour, the call to postpone is made by the foreman, with the owner informed right away, and the trucks are cancelled before they load.

Work this affects

The same techniques protect sidewalks and flatwork, concrete paving and industrial floors. For logistics and warehouse developers, they often decide whether a floor meets its flatness and wear numbers.

In cold months, the issue reverses. See our page on cold-weather concrete for how we protect slabs when the problem is freezing, not drying.

Pour on our schedule

Tell us the area, the finish and the target date. We will propose a start time, a protection plan and a testing schedule that fits the season.

Questions Owners Ask

What is plastic shrinkage cracking?

It is a pattern of short, random cracks that form in the first hours when the surface dries faster than bleed water rises. High wind, low humidity and heat all increase it. Fog, windbreaks, evaporation retarders and quick curing prevent it.

Do you use fogging or misting?

Yes, fog misters can add moisture to the air above the slab without wetting the surface. We use them in dry, windy conditions. They do not replace curing, but they buy time during finishing.

What is the maximum concrete temperature?

Specifications often set limits between about 90 and 95 F, but the project documents control. We measure at the truck and reject loads that exceed the limit, or adjust the plan with the engineer.

Can you add water to a stiff load?

Only within the amount allowed on the mix ticket and by the specification. Adding water at the site raises the water-cement ratio and weakens the concrete. Admixtures are the better way to restore workability.

When should curing compound go on?

As soon as the surface is ready, meaning bleed water is gone and finishing is complete, and before it dries out. In hot, windy weather that might be minutes after the last trowel pass. Early curing matters more here than almost anywhere.

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