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*This is an outline and guide for curing of decorative concrete for horizontal applications. The guide does not include any guidelines for vertical applications. Please refer to ACI 303.
This guide is different to many other guides on curing and stresses thinking outside of the box (ACI 308) with decorative concrete. One of the primary purposes of curing is to slow the moisture loss from the concrete and reduce carbonization (ACI 302 9.1 The Purpose of Curing).
This guideline recognizes that normal curing for decorative concrete is unrealistic, in some cases. When executing decorative curing practices, it is highly recommended that all materials be on the job site and ready to use when the appointed curing window becomes open. All parties involved must perform this critical operation as quickly as possible.
When making use of decorative concrete applications, with either stamping or trowel finish or colored floors, consider the weather and the effects on the concrete. Low humidity, windy and hot weather all increase the rate of bleed water evaporation and should be avoided if construction schedules allow postponement of pours. When possible, schedule decorative concrete pours at different times from than normal concrete. The final look of decorative concrete is typically much more important than the speed of placement. When postponement of a pour is not possible, the use of wind breaks, misting to increase humidity and early morning or late evening pours are within the guidelines of ACI 308 1.4.1 can be effective mitigation techniques. For pouring on windy and hot days, refer to ACI 308 Nomograph on evaporation rates.
Mix designs that optimized aggregate gradation will have lower water demands. Use of clean, sound, hard aggregates is recommended for decorative concrete applications. Aggregate sources that contain more than two-percent materials passing a number 150 µm (No. 100) sieve or that have low durability should not be used. Aggregate that is known to be reactive shall not be used. Lower water-cement ratios reduce the amount of water and result in better concrete color as well as durability for the concrete.
Air-entrained mixes properly compacted and graded subgrades and surface hardeners reduce slab surface dehydration rates. This can reduce the risk of carbonization on the surface of the concrete. Many stamped and stenciled concrete projects make use of fiber reinforcement. Fiber reinforcement helps reduce plastic shrinkage cracking and should be considered for use as many decorative applications cannot be cured as quickly thus the need for fibers in help with control of early shrinkage.
The use of chemical admixtures should be considered as they reduce the mixes water demand and increase workability, which aids the placement of decorative concrete. Please note that color suppliers of both integral and hardener, and curing manufactures should be contacted for their preferred methods of curing and compatibility of cures with coloring agents, especially dyes and stains!
Related topics
References:
¨ ACI 302 Concrete Floor and Slab Construction
¨ ACI 308 Guide to Curing
¨ ACI 310
¨ ASTM C156 Test for Moisture Retained After Cures are Applied
¨ ASTM C309 Specification for Curing
¨ ASTM C1315 Test for Cures with Special Properties
¨ ICRI Guideline 03732 Guide for Selecting Profiles for Floor Coatings and Surface Preparation Methods
