CONCRETE TECH-TIP

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Hot Weather Concreting

1. WHAT is Hot Weather? 2. WHY Consider Hot Weather?

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Follow These Rules for Hot Weather Concrete

3. HOW To Concrete in Hot Weather

a. Concrete mixture designs may include: setretarders and water reducers, the lowestpractical cement factor. Modify mixturesas appropriate - retarders, pozzolanicadmixtures or other proven local solutions.

b. Adequate manpower to quickly place, finishand cure the concrete.

c. Limit the addition of water at the job site -add water only on arrival at the job site toadjust the slump. Later additions should beavoided; in no instance should they exceed10 - 15 l/m3. Never add water to concretethat is more than 1 hour old.

d. Slabs on grade should not be placed onpolyethylene sheeting - if a vapor barrier isrequired, then a bed of damp sand shouldbe placed over it.

e. Finish as soon as the sheen has left thesurface; start curing as soon as finishing iscompleted. Continue curing for at least 3days; cover to prevent evaporation or usea liquid membrane curing compound, orcure slabs with water. (See CTT-11) Theaddition of white pigment to membranecuring compounds will help by reflectingheat away from the concrete surface.

f. Moisten the subgrade, forms andreinforcement prior to placement. However,avoid standing water.

g. Protect field test cylinders by shading andpreventing evaporation. Field curing boxeswith ice or refrigeration may be used toensure required 15 - 25°C for cylinders.(See CTT-9).

h. Do not use accelerators!