CONCRETE STRUCTURES
CONCRETE STRUCTURES 
An intimate mixture of Cement (binder) Water Aggregates Admixtures (optional)
Drinkable Water/Cement Ratio the most important factor affecting the strength of concrete w (lbs) / c (lbs) pounds of water per pounds of cement used in mix or gallons of water for each 94-lb bag of cement 0.4 - 0.7 range the lower the w/c ratio the higher the strength lower w/c - good higher w/c - bad
A binder such as Portland cement which binds the aggregates into a hard concrete or mortar
Roman Cement 100 B.C. light, porous volcanic rock = pozzolana hydraulic cement 1796 James Parker Isles of Sheppey patented "Roman Cement" Natural Cement lime & natural rock properties vary greatly low strength not building code approved
1824 Joseph Aspdin similar to limestone in Portland Wet Process: slurry fed into kiln 30-35% water Dry Process: dry mix fed into kiln gypsum regulates setting time Partial Fusion 2700 F (1482 C) 325 mesh openings/sq.inch. 90% bulk shipments 10% in paper sacks standard cement sack 94 lb (42.6 kg) approx. 1 cubic foot (0.028M3) Setting and hardening of Cement hardens by hydration hydration = chemical reaction between water & cement Setting = process of hardening Types of Portland Cement: air-entrained portland cement white portland cement special cements OPC Ordinary Portland Cement RHPC Rapid Hardening Portland Cement SRPC Sulphate Resistant Portland Cement HAC High Alumina Cement Tpe Name I Normal II Moderate III High-Early IV Low Heat V Sulfate resisting
Mineral Aggregates Fine Aggregate Sand passing No. 4 sieve (1/4" space) retained on No. 200 sieve (74-micorn) sintered fly ash Coarse Aggregate retained on No. 4 (4.76 mm) sieve crushed stone gravel crushed gravel Manufactured Aggregates air-cooled blast furnace slag expanded slag lightweight concrete iron punchings steel punchings
Accelerators shorter setting time earlier strength 3 F lower frost point Air entraining higher workability higher durability lower water cement ratio Latex patching higher tensile & flexural strenght Plasticizing plastic placement pump applications lower w/c ratio Retarders massive concrete hot weather more slump tests Pigments color
