Cast a job site mock-up before the installation for approval of color and finish. Utilize all materials, tools, and techniques from the actual job in the mock-up. Consistent batching, pouring, finishing, curing, sealing, and preparation techniques will ensure the uniformity of architectural concrete. Verify adequate wet and dry slip resistance. Maintenance requirements shall also be discussed.
BATCHING
The maximum loading of SikaColor®-40 L CB shall not exceed 10% by weight of the total cement and cement substitutes in the mix. Higher loadings may reduce the strength of the finished product. A loading below 1% may appear muted and or mottled. The ideal loading is between 2% and 6%.
The mixer drum shall be in good condition with little or no buildup on the fins. One-quarter (1/4) of the mixer volume is the minimum amount of concrete that shall be batched to develop a consistent mix.
- When introducing color at the Ready Mix plant, introduce SikaColor®-40 L CB into the mixer, then batch the concrete.
- When introducing color on the job site into a pre-mixed Ready Mix truck, spin the drum in reverse until the concrete load backs up to the top, and then add SikaColor®-40 L CB directly onto the concrete.
Once SikaColor®-40 L CB is added, ensure that any colorant retained on the fins is thoroughly mixed into the load by slowly reversing the drum so that the concrete contacts and removes the colorant from the fins. Rotate the drum at optimal mixing speed as the mixer manufacturer recommends for a minimum of 100 revolutions.
INSTALLING COLORED CONCRETE FLATWORK
Subgrade
When placing and finishing, the subgrade shall be leveled and compacted to ensure a uniform concrete thickness. The subgrade must be free of frost with no standing water. Before placing concrete in hot conditions, dampen the sub-base uniformly with water without pooling.
Placing and Finishing
Once placing has begun, do not randomly add water to the mixer drum or the surface of the colored concrete. This will create color variations and a strength loss. Water may be added to the drum before initial discharge to attain but not exceed the specified slump. Once discharged, the specified slump must be maintained throughout the installation, particularly for adjacent concrete pours. Never retemper concrete that has started to set. Water-reducing and plasticizing admixtures may be used with SikaColor®-40 L CB. The use of such admixtures may affect the finishing characteristics of the concrete. The use of SikaCem®-190 Concrete Control shall be considered in hot or adverse conditions.
After placing and initial bull floating, no further finishing shall be performed until the bleed water has dissipated, after which final finishing can occur. Texture all exterior surfaces adequately and uniformly for slip resistance. Apply a broom finish or swirl finish for exterior installations using a float. When broom finishing concrete, shake off any water left on the broom after rinsing, as it may cause discoloration. Finishing techniques must be consistent. Differing finishing methods will change the appearance of the color.
Control Joints
The timely and correct placement of control joints minimizes random cracking of a concrete slab. Control joints may be introduced during concrete placement with a groover or after the concrete has reached the initial set by power sawing. Each method shall be evaluated before installation and incorporated into the pre-job mock-up. Refer to American Concrete Institute publications for additional information: Guide to Concrete Floor and Slab Construction (ACI 302.1R-15), Joints in Concrete Construction (ACI 224.3-95).
INSTALLING VERTICAL-COLORED CONCRETE
Unless a specific form liner has been specified, use a clean epoxy-coated or urethane-coated plywood form. Use non-leaking snap-tie cones. Clean and then tape or seal all joints to prevent leakage. Any bleed water leaking along joints may discolor the wall. Choose a release agent that does not discolor concrete. Do not use metal form ties or chairs within 1.5 in. (38.1 mm) from the surface.
Keep the slump consistent from load to load. Do not add water after a portion of the load has been discharged. Never retemper concrete that has started to set. Cast all walls in a continuous pour to their full height between engineered horizontal joints. When possible, use both external and internal vibrators. Vibrate the concrete in lifts up to 2 ft. (61 cm) or less. Do not touch the interior face of the form with the vibrator. Perform vibration long enough to consolidate concrete and dislodge entrapped air. Do not over-vibrate the concrete, as this can cause mix segregation.
Strip all forms when the concrete is the same age. Lightly sandblast all surfaces sufficiently to remove form marks and form release residue.
Note: Excessive sandblasting may expose sand and aggregates, substantially changing the color of the finished wall.
CURING AND SEALING
Never use plastic sheeting or water spray to cure colored concrete; it will mottle and streak the surface. Use liquid, membrane-forming compounds. Use SikaCem®-100 Clear Guard®, SikaCem®-100 PRO 350®, or SikaCem® water-based sealers for exterior applications. Use SikaCem® water-based sealers for interior applications. Consult the most current SikaCem® sealer local Product Data Sheets for complete Application Instructions.
