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CSM 2342 Exam 2
Terms in this set (59)
-Crushed stone,gravel, lightweight materials
-retained NO.4 Sieve
Natural or more manufactured sand
Passes the NO.4 sieve
Naturally occurring aggregates-outcroppings, river sand
& gravel, sand & gravel pits
Man made aggregates- slag from steel prod., processed shale and clay, recycled concrete
-aggregate stockpiles, sampling tube
-typically exposed to the environment
-aggregates can have moisture within their voids and on their surface
-the moisture must be counted for when making concrete mixture
a) Oven Dry - no moisture (water) at all
b) Air Dry - partially filled voids, no moisture on surface
c) Saturated Surface Dry - voids completely filled, no moisture on surface
d) Moist (Wet) - voids completely filled, surface completely covered by moisture
Absorption Capacities (AC)
-0.2 to 4% for coarse aggregate
• 0.2 to 2% for fine aggregate
Total Moisture (TM)
-0.5 to 2% for coarse aggregate
-2 to 6% for fine aggregate
-aggregates are considered an inexpensive inert filler
-Filler: occupy volume
-alkali-silicia reaction (ASR)
Water penetrates the pores.
Water in pores freezes.
Freezing water expands.
Tension force develops.
Frozen water thaws.
Water penetrates the cracks
-Saltwater penetrates the pores.
Salt particle expands.
Tension force develops.
Water penetrates the crack
Water penetrates the paste.
Chert absorbs water.
Tension force develops.
Paste pops off.
This is an aesthetic issue.
Water penetrates the paste.
Reaction occurs at surface.
New solids form on surface.
Tension force develops.
Water penetrates the cracks.
Use a different aggregate.
Dilute a suspect aggregate with a higher
oDecrease the permeability of the paste.
oUse special cements.
• for alkali-aggregate reactivity
o Use a surface sealer.
-foreign material on particle or in a stockpile
-Fine Materials can adhere to the surface
-asphalt binder or portland cement paste will not fully bond to the agg.
-may not have important properties
Cement Production & Use
-Texas produces & consumes more cement and concrete than any other state. 11 plants.
-specific gravity of cement is 3.15
-1 bag of cement=941 lbs= 1 ft^3
1) Acquisition of Raw materials
2) Preparation of raw materials
4) Addition of gypsum
Type 1- General Purpose
Type 2- Moderate Sulfate Resistant
Type 3- High early strength
Type 4- Low heat of hydration
Type 5- High Sulfate Resistant
Supplementary Cementious Materials (SCM)
1) Fly Ash-finely divided by product from the combustion of ground or powdered coal,( SG,1.9-2.8)
-spherical in shape, Tan, Classes-F,C,N 15-40%
2) Slag-by product from steel production (SG 2.85 to 2.95)
3) Silicia Fume- by product from the manufacturing of silicon (SG, 2.2 to 2.5)
-Chemical reaction that takes place between cement, powered & water
-little water needed-surface reaction- exothermic reaction
-moisture & heat required-cement grains consumed
-all 5 compounds involved simultaneously
-both moisture and heat are needed for hydration to continue. it can continue for a over a year if moisture and heat are available
-occurs when paste stiffens considerably
-occurs when the paste hardens so it sustains the load
-no heat, mix to regain flow
-rapid final set, CAN'T regain flow
-the change from plastic to solid state
-Initial set times allow for batching, transportation, placement, initial finishing
-Final set times regulate with the addition of gypsum to clinker, allow for final finishing
-influenced water, heat, and fineness of cement
-Water-more water solutes the cement paste mixture, no velcro or surface binding, lower strength
-Low Water/cement contributes to higher strength
-High Water/cement ration dilutes the paste, contributes to lower strength
Basic COMPOSITION of Concrete
-11% portland cement
-26% fine aggregate
-41% coarse Aggregate
Cement and water hydrate to form cement
paste, or the matrix.
o Water also lubricates the mixture.
oCement paste accounts for 20% to 40% of concrete's volume.
oCement paste contributes to strength and cost
o Coarse and fine aggregates.
o An inert, economical, filler.
o Aggregates account for 60% to 80% of concrete's volume.
o Aggregates contribute to mass and a resistance to deforming.
Air in Concrete
-air is needed for durability
-causes a reduction in strength
Admixtures and SCM
Additives used to modify a property or behavior of either the fresh or hardened concrete.
• air content
• strength development
o Low strength: f'c < 3,000 psi
o Normal strength: 3,000 < f'c < 6,000 psi
o High strength: 6,000 < f'c < 12,000 psi
o Very high strength: > 12,000 psi
o Light weight: < 90 pcf
o Structural light weight: 90 < UW < 120 pcf
o Normal weight: 140 < UW < 150 pcf
o Heavy weight: > 200 pcf
o Conventional concrete
o Pervious concrete
o High performance concrete (HPC)
o Self-consolidating concrete (SCC)
o Roller Compacted concrete (RCC)
Ready Mixed Concrete Production
Concrete is produced either at a batch plant or with a mobile mixer.
• referred to as ready-mixed concrete
o Concrete is generally delivered in a ready- mix concrete truck, or transit mixer.
• drum can typically mix 9 to 10 yd3 of material
o Minimize the handling of concrete.
o Keep vertical "falls" to a minimum.
o Consolidate through vibration to insure forms are completely filled and there is good bond with the reinforcement.
o Strike off.
o Bull floating.
o Waiting - bleed water.
o Floating, trowel.
o goal is to maintain moisture and a favorable temperature.
o Should cure for a minimum 3 to 7 days.
o All types of structures can benefit from proper curing.
o Spray on compound.
o Cover with plastic sheets.
o Cover with wet burlap.
o Special considerations for hot and cold weather.
Purpose of Air Voids
o Improves durability by "absorbing" internal stresses.
• alkali-silica reaction • sulfate attack
o Need a proper air void system to achieve durability.
o Also increases the flowability of concrete.
Sources of Air
• develops naturally during mixing
• large, irregular shaped voids
o Entrained air
• develops from the addition of an air-entraining
• small, spherical shaped voids
Air Void System
• there needs to be an appropriate volume of air
• voids must be evenly distributed
• distance, in any direction, between air voids should be small
o Number and size
• there must be several voids of several different sizes
Air-Entraining Admixtures (AEA)
o A chemical admixture.
o Commonly added to a mixture with the
o Acts like a foaming agent.
• kind of like liquid soap
o Stable spherical bubbles are formed during mixing.
• kind of like when washing your hands
Influences on Air Content
o AEA Dosage.
o w/c, water content
o Quality of mixing.
o Extent of consolidation by vibration.
o Use of other admixtures.
o Presence of fine particles in the mixture. oAmbient temperature.
Quality vs. Quantity
It is the quantity, and typically not the quality, of water which is most important in producing good quality concrete.
o w/c is the ratio of the mass of all water to mass of cement in a volume of concrete.
w water c cement
o Both the w/c and total water content are important to the performance of a concrete mixture.
o Only a small amount of water is needed to hydrate cement.
• w/c ~ 0.26
o Additional water (water of convenience) is necessary for lubrication of the concrete mixture.
• w/c ~ 0.4
o Several properties of concrete are impacted by the w/c.
An inorganic material or a mixture of inorganic materials that sets and develops strength by chemical reaction with water by formation of hydrates and is capable of doing so under water.
Pozzolans and hydraulic cements.
Supplementary Cementitious Material
An inorganic material that contributes to the properties of a cementitious mixture through hydraulic or pozzolanic activity, or both.
Inorganic material such as fly ash, silica fume, metakaolin, or slag cement that reacts pozzolanically or hydraulically.
Pozzolan: ACL Definition
A siliceous or silico-aluminous material that will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds having cementitious properties (there are both natural and artificial pozzolans)
Types of SCM's
• fly ash
• silica fume
• rice husk ash
• natural pozzolans
o Materials which alone will hydrate and have cementing properties.
o Examples include blast furnace slag.
• by-product of steel production
• three grades based on reactivity
• can be used at fairly high
dosage rates • white in color
o By themselves will not hydrate.
o Possess little or no cementitious value.
o A source of silica (S) that combines with the calcium hydroxide (CH) from the hydration of cement to produce more C-S-H
• S + CH → C-S-H
o Examples include fly ash and silica fume.
• Volume change due to loss of excess water.
• Volume change under sustained load.
o Both are related to moisture movement.
o Generally, they occur simultaneously.
o Aggregates and steel reinforcement restrain volume changes.
Concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional constituents and normal mixing, placing, and curing practices.
o A cementitious composite material with:
• an optimized gradation of granular constituents
• a water-to-cementitious materials (cement + SCM) ratio less than 0.25
• a high percentage of discontinuous internal fiber reinforcement
• a discontinuous pore structure that reduces liquid ingress, significantly enhancing durability
Fresh concrete that can flow around reinforcement and consolidate within formwork under its own weight without vibration.
Concrete that can flow around reinforcement and consolidate under its own weight without additional effort and without exceeding specified limits of segregation.
A highly flowable, non-segregating concrete that spreads into place, fills formwork, and encapsulates even the most congested reinforcement, all without any mechanical vibration.
Roller Compacted Concrete
Concrete compacted by roller compaction or concrete that, in its unhardened state, will support a roller while being compacted.
Concrete compacted while fresh by a roller, often a vibratory roller.
A zero slump concrete that is placed with standard or high-density paving equipment
and consolidated/compacted using steel- drum or rubber-tired rollers to achieve a durable, wear resistant surface.
Concrete containing little, if any, fine aggregate that results in sufficient voids to allow air and water to pass easily from the surface to underlying layers.
Hydraulic-cement concrete proportioned with sufficient, distributed, interconnected macroscopic voids that allow water to flow through the material under the action of gravity alone.
Nominal dimensions of Masonry
o Common load-bearding blocks (8"x8"x16")
o Nominal dimensions is greater than specified (modular) dimensions by the thickness of the mortar joint, usually by 3/8" (10mm)
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