How to pour concrete through a Gulf summer: temperature limits, cooling the mix with chilled water and ice, retarding admixtures, pour timing and the midday work ban, curing and testing.
Hot-weather concreting in the UAE and Saudi Arabia means keeping the fresh concrete cool and wet: chill the mix with cold water or ice, slow the set with a retarding admixture, pour in the cooler hours, protect the surface from sun and wind, and start curing straight after finishing. Agree the temperature limit, the admixtures and the curing method with your ready-mix concrete supplier in the UAE or in Saudi Arabia before the first summer pour.
This guide is for site engineers, contractors, ready-mix producers and QA/QC teams who place concrete through a Gulf summer. It covers what heat does to concrete, how to cool the mix, admixtures, pour timing and the midday work ban, curing, and testing. Cement and binder choice is covered in our main guide to cement types, brands and rules in the UAE and Saudi Arabia; here we deal with what happens from batching to curing.
The American Concrete Institute's Guide to Hot Weather Concreting (ACI PRC-305-20) treats hot weather as a combination of conditions, not just air temperature: high ambient temperature, low humidity, high wind, or low humidity and high wind together. These affect mixing, transporting and placing. ACI lists the potential problems as:
Behind all four are two causes: faster cement hydration at high temperature and faster moisture loss from the surface. A Gulf summer brings both, so the measures below are routine there, not exceptional.
ACI's companion Specification for Hot Weather Concreting (ACI SPEC-305.1-14(20)) sets requirements for a preplacement conference, mixture proportions, the maximum temperature of fresh concrete at discharge, measurement of the surface evaporation rate, evaporation control and curing. The limit that applies to your job is whatever the project specification states; ASTM C94, the specification for ready-mixed concrete, says that where the purchaser's requirements differ from it, the purchaser's specification governs. So:
Most of the cooling happens at the batching plant. The usual methods:
| Method | What it does | Points to agree |
|---|---|---|
| Chilled mixing water | Replaces part of the mix water with cold water. ConcreteNetwork puts the reduction at up to about 10°F (about 5.5°C). | Chiller capacity at the plant for your pour rate |
| Ice | Replaces part of the mix water with ice; up to about 20°F (about 11°C) reduction, by the same source. | Ice must melt completely before mixing is finished |
| Liquid nitrogen | Injected into the mixer for larger drops in extreme conditions. | Availability and cost; usually for critical pours |
| Shaded or sprayed aggregates | Aggregates are most of the volume, so keeping them cool lowers mix temperature. | Stockpile shading and water spraying at the plant |
| Cool cement | Using several silos lets freshly delivered cement cool before use. | Silo rotation at the plant |
None of these change the water-cement ratio, which is the point: adding water to make hot concrete workable lowers strength. Ask the plant which methods it runs, and whether its batching plant has the chiller or ice capacity for your peak hourly rate.
Slag and fly ash lower heat of hydration. The FHWA says replacing cement with fly ash reduces heat rise in mass concrete without sacrificing long-term strength, EMSTEEL says its slag improves workability in warm weather, and Dubai Municipality warns that CEM I mixes may increase heat of hydration and thermal cracking risk in mass or restrained elements. Our guide to GGBS and fly ash in Gulf concrete covers the trade-off: slower early strength.
ASTM C494, the specification for chemical admixtures, defines seven types. Three matter most in summer:
Water reducers (Types A and F) also help with slump loss without raising the water-cement ratio. Dose rates depend on concrete temperature and travel time, so agree a summer and a winter dosage at trial-mix stage with the concrete admixture supplier and the ready-mix plant, not on site.
Several construction chemical makers serve the Gulf. Sika's GCC business, based in Dubai Industrial City with companies in the UAE, Saudi Arabia and other Gulf states, lists retarders, plasticisers and superplasticisers among its concrete admixtures and says it formulates products for hot climates. Fosroc, a global construction chemicals manufacturer, lists concrete admixtures and a range of curing compounds. In Saudi Arabia, compare concrete admixture suppliers for local stock.
Schedule pours for early morning or evening and night, when air temperature and solar heating are lowest. Both countries also restrict outdoor work in summer:
A large pour that runs through midday therefore needs planning: shaded rest areas, water and cooling for the crew, and a check that the activity qualifies for any exemption. Our guide to heat stress and PPE for outdoor work in the Gulf covers the worker side.
Curing keeps water in the concrete so the cement can keep hydrating. In hot, dry, windy conditions moisture loss is fast, and poorly cured concrete may not reach its strength and can suffer plastic shrinkage cracking, scaling and lower durability. Start as soon as finishing allows. The main methods:
Check that any curing compound is compatible with later finishes, coatings or waterproofing, and follow the curing period in the project specification. Mixes with slag or fly ash gain strength more slowly, so do not cut curing short on them.
To get quotes from ready-mix plants that can supply chilled concrete for summer pours, post your concrete requirement with the volume, grade, pour date and site location. If you are also buying binder, compare Portland cement suppliers in the UAE.
More in this series: Cement Companies in Saudi Arabia, Cement Factories in the UAE, OPC vs SRC vs White Cement.
The limit is set by the project specification. ACI's Specification for Hot Weather Concreting (ACI 305.1) includes a maximum temperature of fresh concrete at discharge, and ASTM C94 lets the purchaser's specification govern ready-mixed concrete. Write the limit, the test method (ASTM C1064) and the action for loads above it into the purchase order.
Replace part of the mixing water with chilled water or ice, shade and spray the aggregates, and let cement cool in the silos before use. For extreme conditions, liquid nitrogen can be injected into the mixer. On site, pour in the cooler hours, wet down the subbase and use sunshades and windbreaks.
The UAE bans outdoor work in direct sun from 12.30 pm to 3 pm between 15 June and 15 September. Gulf News reports that work which cannot be paused for technical reasons, including concrete pouring, may continue. Plan large pours to avoid midday where possible and provide shade, water and rest for workers when they cannot.
Follow the project specification. ConcreteNetwork recommends at least 7 days of wet curing in hot weather, and mixes with slag or fly ash need curing for the full period because they gain strength more slowly. Start immediately after finishing, using wet coverings, misting, sheeting or a membrane-forming compound.
Water evaporating from the surface of fresh concrete faster than it can be replaced. High air temperature, low humidity and wind all raise the evaporation rate. Prevent it with an evaporation retarder during finishing, sunshades and windbreaks, cooler concrete and prompt curing.
Retarders (ASTM C494 Type B), water-reducing retarders (Type D) and high-range water-reducing retarders (Type G) slow setting and keep workability without adding water. Dosage depends on concrete temperature and travel time, so agree it at trial-mix stage with the admixture supplier and the ready-mix plant.
Featured image: Photo: U.S. Navy photo by Mass Communication Specialist 2nd Class Demetrius Kennon, public domain, via Wikimedia Commons
When to specify OPC, sulphate resisting cement or white cement in the UAE and Saudi Arabia: the chemistry, the standard names, why SRC alone does not stop chloride corrosion, and where white cement fits.
How GGBS and fly ash work in concrete, how much cement they replace, what they do for heat and durability, the standards and Dubai and Saudi rules, and who supplies them in the Gulf.
Which UAE cement factories make OPC, SRC, white cement, GGBS and clinker, where each plant is, which producers are listed on ADX, and how to buy in bulk, bags or for export.
