Concrete Knowledge Center - Technical Questions


ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

ACI Documents	•	Referencing ACI documents in specifications
	•	ACI Reference Specifications

Decorative	•	Other decorative concrete information sources
	•	Minimizing color variations in decorative concrete
	•	Polished concrete floors
	•	Effects of Coloring Pigments on Setting Time and Air Content

Floors	•	ACI standards for floor finishes
	•	Floor finish tolerances — F-numbers versus the 10 ft straightedge method
	•	Fibers and welded-wire reinforcement in slabs-on-ground
	•	Expansion joints in exterior pavements
	•	What are F-numbers?
	•	What are “superflat” floors?
	•	Contraction Joints for Composite Slabs
	•	How F-Numbers are measured
	•	Levelness Requirements for Unshored Composite Decks
	•	Can floors be accepted or rejected based on FF or FL results from one sample measurement line?
	•	Emergency Construction Joint Procedures
	•	Floors for Freezer Facilities

Formwork	•	Classes A, B, C, and D — formed surfaces
	•	Stripping time for forms
	•	Veins in Aluminum-Formed Walls
	•	Determining In-Place Concrete Strength for Form Removal

Placement	•	Limits on free fall of concrete
	•	Maximum temperature limits for hot-weather concreting
	•	Adjustment of Entrained Air at the Job Site
	•	Adjustment of Slump at the Job Site
	•	Estimating Evaporation Rates to Prevent Plastic Shrinkage Cracking
	•	Wet Setting Weld Plates in Tilt-up Panels

Repair	•	Resurfacing a worn concrete floor
	•	Cement-based repair materials
	•	Durability - Carbonation
	•	Nonshrink repair materials
	•	Surface bruising
	•	Alkali-aggregate reaction in mass concrete
	•	Cracks in Repair
	•	In-place pull-off test
	•	Parking deck service life
	•	Corroded reinforcing steel
	•	Hydrodemolition for concrete removal
	•	Selecting Repair Materials

Residential	•	Slab-on-ground design
	•	Foundation wall design
	•	Other residential concrete information sources
	•	Veins in Aluminum-Formed Walls

Sustainability	•	Earning LEED™ points with concrete
	•	ACI information on sustainable development
	•	LEED™ Certification
	•	Design life of concrete structures
	•	Definitions of sustainable development and sustainable construction materials
	•	Points for Pervious

Testing	•	Standards for 7-day and 28-day strength test results
	•	Estimating in-place concrete strength
	•	Curing strength-test cylinders
	•	Low-strength cylinder test results
	•	Documenting concrete compressive strength for mixture proportions
	•	Can ASTM C 109 cube tests be used in lieu of ASTM C 39 cylinder tests?
	•	Strength test cylinder size
	•	What does type of fracture tell us about the cylinder test result?
	•	Evaluating strength test results
	•	Rapid Chloride Permeability Tests
	•	Tests for flowable fill
	•	Are air tests needed for non-air-entrained concrete?
	•	Tests for concrete resistance for bullet penetration
	•	Using core strengths to evaluate the structural capacity of an existing structure

Thermal	•	What is mass concrete?
	•	Concrete cover required for specific fire rating


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