Hot-weather concreting

Retarders and Accelerators. Materials that control hardening of cement may be either organic or inorganic. Retarders are often incorporated in oil well cementing and hot-weather concrete appHcations, whereas accelerators may be useful for cold-weather concrete appHcations in which higher rates of reactivity are desirable. In most cases, these admixtures are used in low concentrations, suggesting that they act by adsorption. 

Other applications for the stabilizer and the recycling system include hot-weather concreting, the transportation of ready-mixed concrete over long distances (particularly in the Middle East countries) or through city traffic where unexpected delays can be encoimtered. Higher dosage of the admixture can be used to obtain the desired set extension and the appropriate dosage of the activator (carried on the truck) can then be added at the destination. 

High temperatures during hot-weather concreting result in an increase of the amount of mixing water required to produce a given slump [91, 94]. This effect of temperature is attributable to its accelerating effect on the hydration rate of the cement. At temperatures in excess of 25 °C, the mix... 

When considering the use of retarding admixtures in situations where the temperature exceeds 30°C, the relevance of the ASTM C 494 compliance test data (done under laboratory conditions) to the field conditions the concrete will experience must be considered. The actual temperatures experienced in most hot-weather countries (> 40°C) go beyond the scope of many current recommended practices. For example the ACI guide to hot-weather concreting (ACI 305 R-89) does not meet the needs of, and is not practical... 

HOT-WEATHER CONCRETING (PLASTIC SHRINKAGE IN FLAT-SLABS DUE... 

Figure 14.3 Determination of rate of water evaporation during curing. (From ACI, Hot Weather Concreting.

ACI. 2000. Hot weather concreting. AC 305R-99. Farmington Hills, MI American Concrete Institute. 

ACI 318-71- Building Code Requirements for Reinforced Concrete ACI 347-68- Recommended Practiee for Concrete Formwork ACI 305-72- Recommended Practice for Hot Weather Concreting ACI 211.1-70 - Recommended Practice for Selecting Proportions for Concrete... 

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