HighPerformance Concrete Design and Control of Concrete Mixtures

High-Performance Concrete Design and Control of Concrete Mixtures – Chapter 19

Overview n Introduction to high-performance concrete n High-durability concrete n High-early-strength concrete n High-performance concrete construction n Self-consolidating concrete n Ultra-high-performance concrete

High-Performance Concrete

High-Durability Concrete n Abrasion resistance n Permeability n Diffusion n Freeze-thaw resistance n Alkali-aggregate reactivity

Abrasion Resistance n High strength HPC ideal n Incorporates silica fume n Steel fibers can be used n Useful for spillways, stilling basins, pavements subjected to studs and chains n Concrete strengths of 100 -120 MPa (14, 50017, 000 psi) correlate to abrasion resistance of granite

Permeability n Low permeability is oft specified using coulombs n ASTM C 1202 – RCPT n Example – maximum 1000 coulombs n Achieved using: n Low w/cm n Ternary mixtures n Latex-modified concrete

Diffusion n Diffusion coefficient tested according to ASTM C 1556 n SCMs are helpful, especially silica fume n Low diffusion slows ingress of ions, such as chloride

Freeze-Thaw Resistance n High resistance due to low w/cm n True for systems with and without SCMs n Studies suggest air entrainment is not needed, yet still recommended n No-slump dry-pack mortar used in Chicago sidewalks shows little damage after 90 years

Alkali-Silica Reactivity n Two characteristics aid against ASR: n Very low w/cm § Self-desiccation § ASR requires moisture n Typically high SCM contents § SCMs tend to mitigate ASR § Must be verified

High-Early-Strength Concrete

High-Early-Strength Concrete

High-Early-Strength Concrete

High-Strength Concrete

High-Performance Concrete Construction n Proportioning n Watch out for workability n Mixing n Sticky mixtures can build-up in mixers n Adjust charging sequence

High-Performance Concrete Construction n Placing n Batch adjustments supervised by producer – no retempering n Delays eliminated – smaller batches if necessary n Consolidating n More concern with under-vibration than over-vibration n Finishing n Sticky mixtures difficult to finish n Use fresno instead of bullfloat n Curing n Very important step – more so than with conventional mixtures n Low w/cm – requires evaporation control

High-Performance Concrete Construction n Temperature Control n Temperature history figures into strength and durability n Mass concrete concerns n Quality Control n More rigorous – leads to low variance

Self-Consolidating Concrete

Self-Consolidating Concrete

Self. Consolidatin g Concrete

Ultra-High Performance Concrete

Ultra-High Performance Concrete

Ultra-High Performance Concrete

Summary n Introduction to high-performance concrete n High-durability concrete n High-early-strength concrete n High-performance concrete construction n Self-consolidating concrete n Ultra-high-performance concrete

Question s ?