CE 3103 Construction Materials and Testing PDF

CE 3103 – Construction Potential sources are evaluated: Materials and Testing quality of the larger pieces, the nature and amount of fine...

CE 3103 – Construction Potential sources are evaluated: Materials and Testing quality of the larger pieces, the nature and amount of fine material, and gradation of the Module 2 – Aggregates aggregate. Aggregate - A mass of crushed stone, Drilling cores and performing trial gravel, sand, etc, predominantly composed blasts (or shots) – to evaluate how of individual particles, but in some cases the rock breaks and by crushing including clays and silts. some materials in the laboratory to Types of Aggregate evaluate grading, particle shape, Coarse Aggregate: particles that soundness, durability, and amount of are retained on a 4.75mm sieve fine material. Fine Aggregate: particles that pass Cores are examined for general a 4.75mm sieve quality, suitability of various uses, Maximum aggregate size: one and amount of deleterious materials. sieve size larger than the nominal NOTE: Price and availability are maximum aggregate size universal criteria that apply to all uses of Nominal maximum aggregate aggregates. However, the required size: one sieve larger than the first aggregate characteristics depend on sieve to retain more than 10% of the how they will be used in the structure. aggregates Aggregate Sources Aggregate Uses Natural sources – gravel pits, river As underlying material for run deposits and rock quarries foundations and pavements Manufactured aggregates – slag Aggregate underlying materials, waste from iron and steel mills and expanded shale and clays to or base courses, can add produce lightweight aggregates stability to a structure, Heavyweight aggregates can providing a drainage layer, and use steel slag and bearings frost protection damage. for the aggregate, used for radiation shields. Aggregate Uses in Portland Cement Styrofoam beads can be Concrete used as an aggregate in 60% to 75% of volume and 79% lightweight concrete used for to 85% of the weights insulation. Acts as a filler to reduce the Evaluation of Aggregate Sources amount of cement paste needed The physical and chemical in the mix and have greater properties of the rocks determine the acceptability of an aggregate source volume stability than cement for a construction project. paste These characteristics vary within a Maximising the amount of quarry or gravel pit, making it aggregate, improves the quality necessary to sample and test the and economy of the mix materials continually as the Aggregate Uses in Portland Cement aggregates are being produced. Concrete Cost and availability of the 75% to 85% of volume and 92% aggregates are important when to 96% of the weights selecting an aggregate source. One of the primary challenges facing Asphalt cement acts as a binder the Materials Engineer on a project to hold the aggregates together, is how to use the locally available but does not have enough material in the most cost-effective strength to lock the aggregate manner. particles into position © Nikolai  𝑆𝑆𝐷 𝑊𝑒𝑖𝑔ℎ𝑡 𝑊𝑠 +𝑊𝑝 = (𝑇𝑜𝑡𝑎𝑙 𝑃𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑉𝑜𝑙𝑢𝑚𝑒)𝛾𝑤 (𝑉𝑠 +𝑉𝑖 +𝑉𝑝 )𝛾𝑤 Aggregate Properties 𝑊𝑠𝑠𝑑 Physical: = (𝑊𝑠𝑠𝑑 −𝑊𝑠𝑢𝑏 ) Particle shape and size - Shape Apparent Sp. Gr = and surface texture of an 𝐷𝑟𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 𝑊𝑠 = aggregate particles determine (𝑉𝑜𝑙𝑢𝑚𝑒 𝑁𝑜𝑡 𝐴𝑐𝑐𝑒𝑠𝑠𝑖𝑏𝑙𝑒 𝑡𝑜 𝑊𝑎𝑡𝑒𝑟)𝛾𝑤 (𝑉𝑠 +𝑉𝑖 )𝛾𝑤 how the material will pack into a 𝑊𝑑 = dense configuration and also (𝑊𝑑 −𝑊𝑠𝑢𝑏 ) determines the mobility of the stones within a mix. 2 considerations in the shape: Where: angularity and flakiness 𝑊𝑠 = weight of solids NOTE: Angular and rough-textured 𝑉𝑠 = volume of solids aggregates produce bulk materials with 𝑉𝑖 = volume of water higher stability than rounded, smooth- impermeable voids textured aggregates. However, angular 𝑉𝑝 = volume of water permeable aggregates will be more difficult to work voids into place than rounded aggregates. 𝑊𝑝 = weight of water in the permeable voids when the aggregate is Particle surface texture – in the SSD condition Angular, Rounded, flaky, 𝛾𝑤 = unit weight of water Elongated, Flaky and elongated. Flakiness – describes the Effective Sp. Gr = relationship between the dimensions 𝐷𝑟𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 𝑊𝑠 of the aggregate = (𝑉𝑜𝑙𝑢𝑚𝑒 𝑁𝑜𝑡 𝐴𝑐𝑐𝑒𝑠𝑠𝑖𝑏𝑙𝑒 𝑡𝑜 𝐴𝑠𝑝ℎ𝑎𝑙𝑡)𝛾𝑤 (𝑉𝑠 +𝑉𝑐 )𝛾𝑤 Porosity Specific gravity - Weight-volume Where 𝑉𝑐 = volume of permeable voids characteristics of aggregates are not filled with asphalt cement not important indicator of aggregate quality, but are ASTM C127 – specific gravity and important for concrete mix design absorption of coarse aggregates are Specific gravity – mass of a determined in this test material divided by the mass of ASTM C128 – procedure for an equal volume of distilled water determining the specific gravity and absorption of fine aggregates Four types of specific gravity are based on how voids in the aggregate particles are Soundness - The ability of considered: aggregate to withstand o Bulk-dry weathering o Bulk-saturated surface dry ASTM C88 – soundness test o Apparent specific gravity Simulates weathering by soaking o Effective specific gravity the aggregates in either a sodium Bulk Dry Sp. Gr = sulphate or a magnesium 𝐷𝑟𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 𝑊𝑠 = sulphate solution (𝑇𝑜𝑡𝑎𝑙 𝑃𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑉𝑜𝑙𝑢𝑚𝑒)𝛾𝑤 (𝑉𝑠 +𝑉𝑖 +𝑉𝑝 )𝛾𝑤 Alternative screening tests for 𝑊𝑑 = evaluating soundness: (𝑊𝑠𝑠𝑑 −𝑊𝑠𝑢𝑏 ) AASHTO T103 – soundness test Bulk SSD Sp. Gr = by freeze thaw © Nikolai  ASTM D4792 – test for potential Four moisture condition for an expansion from hydrated aggregate particle: reactions a) Bone dry Unit weight - Bulk unit weight is b) Air dry condition needed for the proportioning of c) Saturated surface-dry (SSD) Portland cement concrete mixtures. condition ASTM C29 – procedure to d) Free moisture determine the bulk unit weight of aggregate Percent moisture content (MC) in the Bulk unit weight of aggregate aggregate can be calculated as: (𝛾𝑏 ): 𝑾𝒔 𝑾𝒎𝒐𝒊𝒔𝒕 − 𝑾𝒅𝒓𝒚 𝜸𝒃 = 𝑴𝑪 = 𝒙𝟏𝟎𝟎 𝑽 𝑾𝒅𝒓𝒚 Where, where: 𝑊𝑠 = weight of aggregate 𝑊𝑚𝑜𝑖𝑠𝑡 = weight of moist aggregate V = volume of container 𝑊𝑑𝑟𝑦 = weight of dry aggregate If bulk dry specific gravity of the aggregate (𝐺𝑠𝑏 ) is known, Gradation - Describes the particle size distribution of the percentage of voids between particles can be determined: aggregate. 𝑊⁄ Large aggregates are 𝑉𝑠 𝛾𝑠 economically advantageous in %𝑽𝒔 = 𝑥100 = 𝑥100 𝑉 𝑊⁄ 𝛾𝑏 Portland cement and asphalt 𝛾𝑏 concrete. However, large = 𝑥100 𝛾𝑠 aggregate mixes are harsher and 𝜸𝒃 more difficult to work into place. = 𝒙𝟏𝟎𝟎 𝑮𝒔𝒃 ∙ 𝜸𝒘 % Voids = 100 - %𝑽𝒔 ASTM C136, E11 – process to Where, evaluate the aggregates passing 𝑉𝑠 = volume of aggregate through a series of sieves 𝛾𝑠 = unit weight of Maximum Density Gradation aggregate Density of an aggregate mix is a 𝛾𝑤 = unit weight of water function of the size distribution of the aggregates Absorption - The amount of Determining the distribution of water the aggregates absorb is aggregates that provides the important in the design of maximum density or minimum Portland cement concrete. amount of voids as No specific level of aggregate 𝒅𝒊 𝒏 absorption that is desirable for 𝑷𝒊 = 𝟏𝟎𝟎 ( ) 𝑫 aggregates used in Portland Where, cement concrete, but aggregate 𝑃𝑖 = percent passing of a sieve of absorption must be evaluated to size 𝑑𝑖 determine the appropriate 𝑑𝑖 = sieve size in question amount of water to mix into the D = maximum size of the concrete. Low-absorption aggregate aggregates are desirable for n = 0.45 (Federal Highway asphalt concrete Administration) or 0.5 (Fuller) © Nikolai Percent passing is computed to a whole contaminated by clay, shale, percent, except for the 0.075mm organic matter, and other material, which is computed to 0.1% deleterious materials, such as coal. Dense gradation is desired in many Deleterious substance – any construction applications because of its material that adversely affects the high stability quality of Portland cement or asphalt concrete made with the Aggregates for asphalt concrete must aggregate be dense but must also have sufficient Substance Harmful voids in the mineral aggregate to Effect provide room for the binder, plus room for voids in the mixture. Organic Delay settling impurities and hardening; Other Types of Gradation May reduce a) Dense strength gain; b) One-sized – good permeability, May cause deterioration poor stability Minus Weaken bond; c) Gap-graded 0.075mm May increase d) Open-graded – highly permeable, water material may not have good stability requirements Gradation Specifications Gradation specifications define Coal, lignite or Reduce maximum and minimum other low- durability; cumulative percentages of density May cause pop- material passing each sieve materials outs or stains Portland cement concrete requires separate specifications Clay lumps Pop-outs; for coarse and fine aggregates and friable Reduce particles durability and wear resistance Fineness Modulus Measure of the aggregates’ Soft particles Pop-outs; gradation Reduce Used primarily for PCC mix durability and design wear resistance 100th of the sum of the cumulative percentage weight retained on the 0.15-, 0.3-, 0.6-, In asphalt concrete, deleterious 1.18-, 2.36-, 4.75-, 9.5-, 19.0-, substances are clay lumps, soft or 37.5-, 75- and 150-mm sieves friable particles, and coatings. Sieves larger than 9.5mm are not To limit the clay content of fine used for fine aggregates aggregates used in asphalt concrete, Fineness modulus for fine AASHTO T176 or Sand Equivalency aggregates – 2.3 to 3.1 Test is required. Cleanness and Deleterious Sand Equivalent value: Materials - Since aggregates are 100ℎ𝑠𝑎𝑛𝑑 𝑆𝐸 = natural product, there is a ℎ𝑐𝑙𝑎𝑦 potential they can be © Nikolai The value is an indication of aggregates Chemical Properties cleanness. Alkali-Aggregate Reactivity - Most common reaction, particularly in humid and warm Mechanical: climates, is between the active silica constituents of an Toughness, Hardness & aggregate and the alkalis in Abrasion Resistance - ability of cement (sodium oxide and aggregates to resist the potassium oxide) damaging effect of loads which is related to the hardness of the Alkali-silica reaction results in aggregate particle excessive expansion, cracking or popouts in concrete The aggregate must resist crushing, degradation, and Less harmful reaction – alkali- disintegration when stockpiled, carbonate reactivity mixed as either Portland cement or asphalt concrete, placed and The best way to evaluate the compacted, and exposed to potential for alkali-aggregate loads. reactivity is by reviewing the field service history ASTM C131, C535 – Los Angeles abrasion test, which ASTM C227 – test to determine evaluates the aggregates’ the potential alkali-aggregate toughness and abrasion reactivity resistance ASTM C289 – quick chemical Strength and Modulus - test, identify potentially reactive Strength of PCC and asphalt siliceous aggregates concrete cannot exceed that of the aggregates. ASTM C586 – test to determine potentially expansive carbonate Aggregate strength is generally rock aggregates important in high strength concrete and in the surface course on heavily travelled How do we reduce the reactivity if pavements. alkali-reactive aggregate must be used? Tensile strengths of aggregates: Can be minimised by limiting 0.7 to 16 MPa the alkali content of the cement Compressive strength of aggregates: 35 to 350 MPa Keeping the concrete structure as dry as possible AASHTO T292 – resilient Fly ash, GGBS, silica fume, or modulus test, currently the test is natural pozzolans mostly limited to research projects Lithium-based admixtures, such as Sika brands © Nikolai  Replace about 30% of a population of materials that is reactive sand-gravel being quantified with the test. aggregate with crushed The best location for sampling limestone the aggregate is on the conveyor belt that feeds the mixing plant. Affinity for Asphalt Sampling from stockpiles must be Stripping, or moisture-induced performed carefully to minimise damage, is a separation of the segregation. asphalt film from the aggregate At least five samples should be through the action of water. collected from random locations in the stockpile. These samples Hydrophilic (water-loving) are then combined before aggregates – silicates, greater laboratory testing. affinity for water than asphalt Larger-sized aggregates require larger samples to minimise Hydrophobic (water-repelling) segregation errors. Field samples aggregates – limestones, greater are typically larger than the affinity for asphalt than for water samples needed for testing. Field samples must be reduced Hydrophilic aggregates are more using sample splitters or by susceptible to stripping than quartering (ASTM C702). hydrophobic aggregates Aggregates Sustainability Early compatibility tests submerged the sample of asphalt LEED Considerations concrete in either room- Potential LEED (Leadership in temperature (ASTM D1664) or Energy and Environmental boiling water (ASTM D3625) Design) credits can be earned through the reclamation of Handling Aggregates aggregate bearing products. Aggregates must be handled and How? For example, concrete, stockpiled in such a way as to during the demolition phase of minimise segregation, the project. degradation and contamination LEED credits may be earned by Drop height should be limited to specifying the use of either avoid breakage, especially for primary or secondary recycled large aggregates materials. Segregation can be minimised by Primary recycled materials: moving the material on the belt crushed products that were frequently or by installing a baffle primarily aggregate based, such plate, rubber sleeve, or paddle as crushed concrete wheel at the end of the belt to Secondary products: waste remix coarse and fine particles products from other industries, Different sizes should be such as slag from iron and steel stockpiled and batched production separately Other Sustainability Considerations Sampling Aggregates NSSGA (National Stone Sand Sample of material being tested and Gravel Association) must represent the whole published a guideline principles © Nikolai  for sustainable aggregate Fineness of cement particles operations. must be carefully controlled The finer the cement particles, Module 3 - CEMENT the larger the surface area and the faster the hydration Portland Cement Finer material results in faster A fine powder made by heating strength development and limestone and other materials greater initial heat of hydration such as clay or shale in a kiln to form clinker, which is Maximum size of cement then ground into a fine powder particles: 0.09mm Key ingredient in concrete, 85% to 95% of the particles are mortar, and grout smaller than 0.045mm Its strength, durability, and Average diameter is 0.01mm versatility make it suitable for Particle size specifications are wide range of construction defined in terms of the surface applications, such as buildings, area per unit weight bridges, tunnels, dams, factories, pavements and Both the Blaine and Wagner tests roads are indirect measurements of Main Purpose of Portland Cement: surface area and use somewhat different measurement principles 1. To make Portland Cement Tests on a single sample of Concrete (PCC) cement will produce different 2. Stabilizing Soils results 3. Stabilizing aggregate bases for Fineness can also be measured highway construction by determining the percent passing the 0.045mm sieve Portland Cement Production (ASTM C430) Two basic raw ingredients:\ Calcareous material – calcium Specific Gravity of Portland Cement oxide (limestone, chalk, or oyster Needed for mixture-proportioning shells) calculations Argillaceous material – Specific gravity of Portland combination of silica and alumina cement (without voids between (clay, shale, blast particles): 3.15 furnace slag) Can be determined according to ASTM C188 Chemical Composition of Portland Density of bulk cement (including Cement voids between particles) varies C3S and C2S provide the desired depending on handling and characteristics of concrete when storage hydrated Cement quantities are specified Alumina and iron, C3A and and measured by weight rather C4AF, are included with the other than volume raw materials to reduce the temperature required to produce Voids in Hydrated Cement C3S from 2000ºC to 1350ºC Concrete strength, durability, and volume stability are greatly Fineness of Portland Cement influenced by voids. © Nikolai  Two types of voids formed during does not penetrate visibly into the hydration: paste Interlayer hydration space – Gillmore Needle Test contributes 28% to the porosity of Initial Set Time – until the pat the cement paste bears the force of the needle Capillary voids – result of the without appreciable indentation hydrated cement paste having a Final Set Time – when final lower bulk specific gravity than Gillmore needle is applied the cement particles Air can be trapped in the cement Initial set time must allow for paste during mixing handling and placing the concrete Trapped air reduces strength and before stiffening increases permeability Maximum final set time should be Properties of Hydrated Cement specified and measured to Specifications do not guarantee ensure normal hydration the quality of the concrete made with the cement Gypsum is added to regulate the Mix design, quality control, and setting time the characteristics of the mixing Other factors affecting set time: water and aggregates also fineness of cement, water cement influence the quality of concrete. ratio, and the use of admixtures Properties of the hydrated False set might occur in which cement are evaluated either the cement stiffens within a few cement paste (water and cement) minutes of being mixed, without or mortar (paste and sand) the evolution of much heat; Three properties of hydrated False set can be remedied by cement: setting, soundness, and remixing whereas quick set and compressive strength of mortar flash set cannot be remedied Properties of Hydrated Cement Soundness Setting Soundness – ability to retain its volume after setting Setting - stiffening of the cement paste or the change from a Expansion after setting, caused plastic state to a solid by delayed or slow hydration or state other reactions, could result if Hardening – strength gain in a the cement is unsound set cement paste Autoclave expansion test (ASTM Two levels of setting: C151) – used to check the soundness of the cement paste Initial set Final set ASTM C150 limits autoclave Measured either by: expansion to 0.8% Vicat apparatus (ASTM C191) Gillmore needles (ASTM C266) Compressive Strength Mortar Measured by preparing 50mm Vicat Test: cubes and subjected to compression according to Initial Set Time – time when a ASTM C109 penetration of 25mm occurs Mortar is prepared with cement, Final Set Time – when the needle © Nikolai  water and standard sand (ASTM Types and Applications of Standard C778) Portland Cement Compressive strength of mortar Type Name Application cubes is proportional to the I Normal General concrete work; compressive strength of concrete Suitable for floors, reinforced concrete cylinders structures, pavements Compressive strength of the II Moderate Protection against moderate concrete cannot be predicted sulphate sulphate exposure, 0.1- accurately from mortar cube resistance 0.2% weight water-soluble strength sulphate in soil or 150-1500 ppm sulphate in water (sea water); Suitable for large Water-Cement Ratio piers, heavy abutments, Ratio of the weight of water to the retaining walls weight of cement III High early Used for fast-track strength construction when forms Strength and other desirable need to be removed asap; properties are improved by Reduces time required for reducing the weight of controlled curing in cold water used per unit weight of weather cement IV Low heat Used when mass of of structure requires careful Term water-cement ratio has hydration control of the heat of been expanded to water- hydration cementitious materials ratio V High Protection from sever to include the cementitious sulphate sulphate exposure, 0.2- materials resistance 2.0% weight water-soluble sulphate in soils or 1500- Amount of water added to 10,800 ppm sulphate in concrete must be sufficient for water hydration, water absorbed by the aggregate, water lost Air entrainers can be added to through evaporation and Type I, II, and III cements during absorption into forms, and manufacturing, producing Types additional water needed for the IA, IIA, and IIIA, which provide workability of the plastic concrete better resistance to freeze and Hydration – chemical reaction thaw than non-air entrained between cement and water cements 2 components: chemical and Type I – most common and physical widely used type of cement in the Chemical bonding requires Philippines approximately 0.22 to 0.25 kg of Type II is the second most water per 1 kg of cement available type Cement cannot fully hydrate Strength gain of Type I cement without gel-water – 0.19 kg of can be accelerated by increasing gel-water per 1 kg of cement the cement content per unit PCA recommends a minimum of volume of concrete 0.40 Other Cement Types in the Philippines Type Name Application PPC Blended Made by combining PSC Cement Portland cement with © Nikolai  supplementary cementitious apparatus (ASTM C191), not be materials; 1 hour less than or 1.5 hours More environmentally more than the set time of paste friendly and offer improved workability and durability; made with potable or distilled Suitable for general water construction, particularly in Disposal and Reuse of Concrete structures exposed to harsh Wash Water conditions Waste-water usually generated Masonry Improved workability and Cement lower strength compared to from truck wash systems, standard Portland cement; washing of central mixing For masonry work plant, storm water runoff from the White Made with raw materials ready-mix plant yard, waste water Cement that produce white colour; generated from Used for architectural and decorative applications water sprayed dust control and Specialty Oil Well Cement – for conveyor washdown Cement drilling operations to seal Hazardous substance (contains the space between well caustic soda and potash) casings and boreholes Expansive Cement – used High pH level in situations where Conventional practice: dumping controlled expansion of at the job site, dumping at land concrete is required; repair fill, or dumping into a concrete works wash water pit at the ready-mix plant Alternatives: settling ponds, Mixing Water storm water detention/retention Any potable water is suitable for facilities, water reuse systems making concrete Chemical stabilising admixture Some non-potable water may systems also be suitable Admixtures for Concrete Impurities in the mixing water can ingredients may be added to affect concrete set time, strength concrete to impart a specific and long-term durability quality to either the plastic mix or Chloride ions can accelerate the hardened concrete (ASTM corrosion of reinforcing steel C494) Some admixtures are charged Acceptance Criteria into the mix as solutions Acceptance criteria for Admixtures are classified: questionable water are specified Air entrainers in ASTM C94 Water reducers After 7 days, the average compressive strength of mortar Retarders cubes made with questionable Hydration controller admixtures water should not be less than Accelerators 90% of the average strength of Specialty admixtures cubes made with potable or Reasons for Using Admixtures distilled water (ASTM C109). To reduce the cost of concrete Set time of cement paste made construction with the questionable water To achieve certain properties in should, as measured using Vicat concrete more effectively than by © Nikolai  other means Pozzolith AEA: suitable for To ensure quality of concrete general concrete applications during the stages of mixing, where enhanced durability transporting, placing, and is required curing in adverse weather Darex AEA: highways, bridges conditions and other infrastructure in harsh To overcome certain environments emergencies during concrete Water Reducers operations Workability of fresh or plastic concrete requires more water Types of Admixtures than is needed for hydration Air Entrainers Water-reducing admixtures – to Air entrainers produce tiny air gain workability and maintain bubbles in the hardened concrete quality to provide space for water to Increase the mobility of the expand upon freezing cement particles in the plastic Internal stresses reduce the mix, allowing workability to durability of concrete achieved at lower water contents Air entrainment is recommended Produced with different levels of for all concrete exposed to effectiveness: conventional, mid- freezing range and high- range Improves concrete’s resistance to Effects of Water Reducer several destructive factors: Adding water reducer without freeze-thaw cycles, deicers and altering the other quantities in the salts, sulphates and alkali-silica mix increases the slump reactivity Strength of the mix can be Increases workability of fresh increased by using the water concrete reducer by lowering the quantity High strength is difficult to attain of water and keeping the cement with air-entrained concrete content constant Usually liquid and should meet Cost of the mix can be reduced; the specifications of ASTM C260 water reducer allows a decrease in the amount of water Common Air-Entraining Admixture A water reducer allows the use of Brands and Suppliers in the a lower amount of mixing water Philippines whilst maintaining the same Sika Aer: Concrete exposed to workability level. freeze-thaw conditions, pavements Superplasticizers (plasticizers) MasterAir series: improve freeze- Either greatly increase the flow of thaw durability, workability and the fresh concrete or reduce the reduced permeability amount of water required for a CHRYSO Air: roads and bridges, given consistency especially in areas prone to Reducing the amount of mixing freeze-thaw cycles water reduces the water-cement Mapeair: ideal for concrete ratio, which increases the exposed to wet and cold strength of hardened concrete conditions Can be used when: A low-water cement ratio is © Nikolai  beneficial same as that of normal Placing thin sections concrete Placing concrete around tightly Used to: spaced reinforcing steel Increase rate of strength gain Placing cement underwater Reduce the amount of time Placing concrete by pumping before finishing operations begin Consoli Reduce curing time Fresh concrete stays workable Plug leaks under hydraulic for a short time, 30-60 minutes, pressure efficiently and is followed by rapid loss Calcium chloride, CaCl2, is the in workability most widely used accelerator (ASTM D98) Retarders Concrete with CaCl2 develops Retarders can be used to delay higher early strength compared the initial set of concrete with plain concrete cured at the Used for several reasons: same temperature o Offsetting the effect of hot PCA recommends against using weather CaCl2 o Allowing for unusual Concrete is prestressed placement of long-haul Concrete contains embedded distances aluminium such as conduits, o Providing time for special especially if the aluminium is in finishes (e.g., exposed contact with steel aggregate) Concrete is subjected to alkali- Reduce the strength of concrete aggregate reaction at early ages (1 to 3 days) Concrete is in contact with Some retarders entrain air and water or soils containing improve workability sulphates Increase the time required for the Concrete is placed during hot initial set but reduce the time weather between the initial and final set Mass applications of concrete Several alternatives to the use of Hydration-Control Admixtures calcium chloride: Able to stop and reactivate the Using high early strength (Type hydration process of concrete III) cement Consists of 2 parts: stabiliser and Increasing cement content activator Curing at higher temperatures Stabiliser: completely stops the Using non-calcium chloride hydration of the cementing accelerators such as calcium materials for up to 72 hours nitrate, sodium thiocyanate, Activator: re-establishes normal calcium formate, triethanolamine hydration and setting Special Admixtures Accelerators Workability retaining Used to develop early strength of Corrosion inhibitors concrete at a faster rate than that Damp-proofing agents developed in normal concrete Permeability-reducing agents Ultimate strength of high early Fungicidal, germicidal, and strength concrete is about the insecticidal admixtures © Nikolai  Pumping aids Natural occurring pozzolans: Bonding and grouting agents fine volcanic ash Gas-forming and colouring agents Module 4 – CONCRETE Shrinkage reducing Properties of Hardened Concrete Supplementary Cementitious important to the Materials Engineer: Materials (SCM) 1. Strength Fly ash - Classified according to 2. Modulus of Elasticity ASTM C618: 3. Durability Class N – raw or calcined 4. Porosity natural pozzoland Class F – fly ash with pozzolan Three Qualities Required Of Properly properties Proportioned Concrete Mixtures Class C – fly ash with pozzolan (Kosmatka Et Al. 2008) and cementitious properties 1. acceptable workability of freshly Increases the workability of the mixed concrete fresh concrete and extends the 2. durability, strength, and uniform hydration process appearance of Ground granulated blast furnace hardened concrete slag (GGBS) - Made from iron 3. economy blast furnace slag Non-metallic hydraulic cement Basic Steps for Weight and consisting basically of silicates Absolute Volume Methods and aluminosilicates of calcium Specific gravity of slag cement: Strength Requirements 2.85 - 2.95 In order to compute the strength Silica fume - By-product of the requirements for concrete mix design, production of silicon metal or three quantities must be known: ferrosilicon alloys 1. the specified compressive As a mineral admixture in strength , f’c concrete 2. the variability or standard Very reactive pozzolan deviation s of the concrete Concrete containing silica fume 3. the allowable risk of making can have very high strength and concrete with an unacceptable can be very durable strength Can reduce concrete corrosion The standard deviation in the strength is induced by deicing or marine determined for a plant by making salts batches of concrete, testing the strength Natural pozzolans for many samples, and computing the Pozzolan is a siliceous and standard deviation aluminous material that possesses little or no cementitious value but will react chemically with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties (ASTM C595) © Nikolai For mixes with a large standard deviation in strength, the ACI has another risk criterion that requires If the standard deviation is computed from 15 to 30 samples, then the standard deviation is multiplied by the following factor, F, to determine the modified standard deviation s’. Coarse Aggregate Requirements If fewer than 15 tests are available, the Large dense graded aggregates provide following adjustments are made to the the most economical mix. Large specified strength. aggregates minimize the amount of water required and, therefore, reduce the amount of cement required per cubic meter of mix. Round aggregates require less water than angular aggregates for an equal workability. Water Cement Ratio Requirements Used for estimating the water– cement The gradation of the fine aggregates is ratios for the trial mixes when no other defined by the fineness modulus. The data are available. The required desirable fineness modulus depends on average compressive strength is used the coarse aggregate size and the with the strength versus water–cement quantity of cement paste. A low fineness relationship to determine the water– modulus is desired for mixes with low cement ratio required for the strength cement content to promote workability. requirements of the project. Air Entrainment Requirements Air entrainment is required whenever concrete is exposed to freeze–thaw © Nikolai conditions and deicing salts. Water Content Requirements The water content required for a given The exposure levels are defined as slump depends on the nominal follows: maximum size and shape of the Mild exposure—Indoor or outdoor aggregates and whether an air entrainer service in which concrete is not exposed is used. to freezing and deicing salts. Air entrainment may be used to improve workability. Moderate exposure—Some freezing exposure occurs, but concrete is not Cementing Materials Content exposed to moisture or free water for Requirements long periods prior to freezing. With the water-cement ratio (water Severe exposure—Concrete is exposed cementitious materials) ratio and the to deicing salts, saturation, or free required amount of water estimated, the water. Examples include pavements, amount of cementing materials required bridge decks, curbs, gutters, canal for the mix is determined by dividing the linings, etc. weight of the water by the water–cement ratio. Workability Requirements Workability is defined as the ease of placing, consolidating, and finishing Admixture Requirements freshly mixed concrete. Concrete should Admixture manufacturers provide be workable but should not segregate or specific information on the quantity of excessively bleed (migration of water to admixture required to achieve the the top surface of concrete). desired results. Fine Aggregate Requirements The weight of the fine aggregates is determined by subtracting the weight of the other ingredients from the total weight. In the absolute volume method of mix design, the component weight and the specific gravity are used to determine the volumes of the water, coarse aggregate, and cement. These volumes, along with the volume of the air, are subtracted from a unit volume of concrete to determine the volume of the fine aggregate required. The volume of © Nikolai the fine aggregate is then converted to a Mixing Placing, and Handling Fresh weight using the unit weight. Generally, Concrete the bulk SSD specific gravity of The proper batching, mixing, and aggregates is used for the weight– handling of fresh concrete are important volume conversions of both fine and prerequisites for strong and durable coarse aggregates. concrete structures. There are several steps and precautions that must be followed in mixing and handling fresh concrete in order to ensure a quality material with the desired characteristics Ready-Mixed Concrete Ready-mixed concrete is mixed in a central plant, and delivered to the job Moisture Corrections site in mixing trucks ready for placing. Mix designs assume that water used to Three mixing methods can be used for hydrate the cement is the free water in ready-mixed concrete: excess of the moisture content of the aggregates at the SSD condition 1. Central-mixed concrete is mixed (absorption). completely in a stationary mixer and delivered in an agitator truck (2 rpm to 6 Therefore, the final step in the mix rpm). design process is to adjust the weight of water and aggregates to account for 2. Shrink-mixed concrete is partially the existing moisture content of the mixed in a stationary mixer and aggregates. If the moisture content of completed in a mixer truck (4 rpm to 16 the aggregates is more than the SSD rpm). moisture content, the weight of mixing 3. Truck-mixed concrete is mixed water is reduced by an amount equal to completely in a mixer truck (4 rpm to 16 the free weight of the moisture on the rpm). aggregates. Similarly, if the moisture content is below the SSD moisture Mobile Batcher Mixed Concrete content, the mixing water must be Concrete can be mixed in a mobile increased. batcher mixer at the job site. Aggregate, cement, water, and admixtures are fed Trial Mixes continuously by volume, and the After computing the required concrete is usually pumped into the amount of each ingredient, a trial forms. batch is mixed to check the mix design. Depositing Concrete Three 0.15 m * 0.30 m 16 in. * 12 Concrete should be deposited in.2 cylinders are made, cured for continuously as close as possible to its 28 days, and tested for final position. Advance planning and compressive strength. good workmanship are essential to The air content and slump of reduce delay, early stiffening and drying fresh concrete are measured out, and segregation Pumped Concrete Pumped concrete is frequently used for © Nikolai large construction projects. Special Spreading and Finishing of Concrete pumps deliver the concrete directly into the forms. Vibration of Concrete Quality concrete requires thorough consolidation to reduce the entrapped air in the mix. On small jobs, consolidation can be accomplished manually by ramming and tamping the concrete. For large jobs, vibrators are used to consolidate the concrete. Curing Concrete Several types of vibrators are available, Curing is the process of maintaining depending on the application. Internal satisfactory moisture content and vibrators are the most common type temperature in the concrete for a used on construction projects. definite period of time. Hydration of cement is a long-term process and Pitfalls and Precautions for Mixing requires water and proper temperature. Concrete Therefore, curing allows continued Water should not be added to the hydration and, consequently, continued concrete during transportation. Crews gains in concrete strength. frequently want to increase the amount of water in order to improve workability. If water is added, the hardened concrete will suffer serious loss in quality and strength. The engineer in the field must prevent any attempt to increase the amount of mixing water in the concrete beyond that which is specified in the mix design. Measuring Air Content in Fresh Cement Types of Curing 1. Ponding or Immersion 2. Spraying or Fogging 3. Wet Coverings 4. Impervious Papers or Plastic Sheets 5. Membrane-Forming Compounds 6. Forms Left in place 7. Steam Curing 8. Insulating Blankets or Covers 9. Electrical, Hot Oil, and Infrared Curing The curing period should be as long as is practical. The minimum lime depends on overall factors, such as type of cement, mixture proportions, required © Nikolai strength, ambient weather, size and 1. Producers of structural steel shape of the structure, future exposure including hot-rolled structural conditions, and method of curing. For shapes and hollow sections. most concrete structures the curing 2. Service centres that function as period at temperatures above 5°C (40°/) warehouses and provide limited should be a minimum of seven days or preprocessing of structural until 70% of specific compressive air material. flexure strength is attained. The curing 3. Structural steel fabricators that period can be reduced to three days if prepare the steel for the building high early strength concrete is used and process. the temperature is above 10°C (50°H). 4. Erectors that construct steel frames on the project site. Properties of Hardened Concrete 1. Early Volume Change Steel Products Used in Construction 2. Creep Properties Structural steel 3. Permeability Cold-formed steel 4. Stress-Strain Relationship Fastening products Reinforcing steel (rebars) Miscellaneous products Testing of Hardened Concrete Steel Production 1. Compressive Strength Three phases: 2. Split-Tension Test Reducing iron ore to pig iron 3. Flexure Strength Test Refining pig iron (and scrap steel 4. Round-Hammer Test from recycling) to steel 5. Penetration Resistance Test Forming the steel into products 6. Ultrasonic Pulse Velocity Test 7. Maturity Test During the steel production process, oxygen may become dissolved in the Module 5 – Steel liquid metal. Steel Alloy made primarily of iron and Deoxidising agents, such as aluminium, carbon, with small amounts of ferrosilicon and manganese, can other elements such as eliminate the formation of the carbon manganese, chromium, nickel, or monoxide bubbles. vanadium, depending on its specific properties Completely deoxidised steels are known One of the most widely used as killed steels. materials in the world due to its strength, durability and versatility Killed steels generally included: Key characteristics of steel: Those with carbon content High strength greater than 0.25% Ductility and malleability All forging grades of steels Corrosion resistance Structural steels with carbon Hardness content between 0.15 and 0.25% Four Components of Steel (AISC, Some special steel in the lower 2015) carbon ranges © Nikolai  holding the temperature until all steel transforms into either austenite or austenite-cementite, depending on carbon content Process annealing – used to treat work-hardened parts made with low carbon steel (less than 0.25% carbon) Stress relief annealing – used to reduce residual Heat Treatment of Steel stresses in cast, welded Properties of steel can be altered and cold-worked parts and by applying a variety of heat cold-formed parts treatments Spheroidisation – used to The response of steel to heat improve the ability of high treatment depends upon its alloy carbon (more than 0.6% composition carbon) steel to be Common heat treatments for machined or cold worked steel: Annealing Normalising Normalising Steel is normalised by heating to Hardening about 60ºC above the austenite Tempering line and then colling under natural convection Normalising produces a uniform, fine-grained microstructure Since the rate of cooling is faster than that used for full annealing, shapes with varying thicknesses results in the normalised parts having less uniformity than could be achieved with annealing Structural plate Hardening Annealing Hardened by heating to a To refine the grain, soften the temperature above the steel, remove internal stresses, transformation range and holding remove gases, increase ductility it until austenite is formed and toughness, and change Quenched by plunging it into, or electrical and magnetic properties spraying it with water, brine, or oil Four types of annealing: Rapid cooling changes the grain Full annealing - requires structure forming martensite heating the steel to about Hardening puts the steel in a 50ºC above the austenitic state of strain due to rapid temperature line and cooling © Nikolai  Must be followed by tempering The materials and products used in building design and Tempering construction in the PH are Tempering is performed to designated by ASTM improved ductility and toughness specifications. Process of tempering: ASTM specification names Heating – steel is heated consist of a letter, followed by an to a temperature below its arbitrary, serially assigned critical point number Holding – steel is held at ASTM A36 this temperature for a set amount of time, allowing Designation Properties and internal structure to adjust Composition of ASTM Structural Cooling – steel is slowly Steel cooled, usually in air Why is tempering important? Ensures the steel has enough toughness to withstand impact and stress whilst maintaining adequate hardness for wear resistance Structural Steel Used in hot-rolled structural shapes, plates and bars Used for various types of AISC (American Institute of Steel structural members, such as Construction) Manual for Steel columns, beams, bracings, Construction is an excellent reference frames, trusses, bridge girders, on the types of steel used for structural and other structural applications applications Structural Steel Grades Wide variety of systems for Sectional Shapes identifying or designated steel, a) Wide-flange (W, HP and M based on grade, type and class shapes) Several associations that write b) I-beam (S shape) specifications for steel: c) Channel (C and MC shapes) US – AISI (American Iron d) Equal-legs angle (L shape) and Steel Institute) and e) Unequal-legs angle (L shape) ASTM (American Society f) Tee for Testing Materials) g) Sheet piling UK – NSSS (National h) Rail Structural Steelwork Specifications) and SCI (Steel Construction Institute) PH – PNS (Philippine National Standard for Steel Structures) © Nikolai  The W, M, S, HP, C and MC Prestressed reinforcement shapes are designated by a – steel is under continuous letter, followed by two numbers tension separated by an ‘x’ Letter indicated the shape, while the two numbers indicate the Conventional Reinforcing nominal depth and the weight per Reinforcing steel (rebar) is linear unit length manufactured in three forms: W 1100 x 548 and L 102 x Plain bars – round, without 102 x 12.7 surface deformations UB 203 x 102 x 23 – UK Deformed bars – sections protrusions exist at the W shapes are commonly used as surface beams and columns Plain and deformed wire HP shapes are used as bearing fabrics – flat sheets in piles which wires pass each S shapes are used as beams or other at right angles girders Deformed bars – used in Composite sections can be concrete beams, slabs, columns, formed by welding different walls, footings, pavements shapes to use in various Welded wire fabrics – used in structural applications some concrete slabs and Sheet piling sections are pavements connected to each other and are used as retaining walls Reinforcing Steel Standard Sizes Specialty Steels in Structural Applications HPS – high performance steels HPS 50W HPS 70W – stronger tensile properties 480 MPa yield strength Reinforcing Steel Grades 580 to 750 MPa tensile strength These are weathering steels that form a corrosion barrier on the surface of the steel when first exposed to the environment Reinforcing Steel Structural concrete members must be reinforced either: conventional or prestressed Reinforcing Stel Identification Codes reinforcing Conventional reinforcing – stresses fluctuate with loads on the structure © Nikolai Steel for Prestressed Concrete Typical Stress-Strain Behaviour of Prestressed concrete requires Mild Steel special wires, strands, cables and bars Steel must have high strength and low relaxation properties High-carbon steels and high- strength alloys are used ASTM A416/A416M and AASHTO M203 requires a seven- wire uncoated steel strand Stress-relieved (normal relaxation) steel Tensile Stress-Strain Diagrams of Low relaxation steel Hot-Rolled Steel Bars w/ Different Both can be Grade Carbon Contents 250 (1725 MPa) or Grade 270 (1860 MPa) Required Properties for Seven-Wire Strand Torsion Test (ASTM E143) To determine the shear modulus of structural materials Amount of applied torque and the corresponding angle of twist are MECHANICAL TESTING OF STEEL measured Shear modulus – ratio of Tension Test (ASTM E8/E8M) maximum shear stress to the To determine the yield strength, corresponding shear strain below yield point, ultimate (tensile) the proportional limit of the strength, elongation and material reduction of area For a circular cross-section, 𝑇𝑟 Performed at temperatures 𝜏𝑚𝑎𝑥 (maximum shear stress) = ; 𝐽 between 10ºC and 35ºC 𝜏𝑚𝑎𝑥 G (shear modulus) = Desirable to use a small cross- 𝛾 𝜃𝑟 sectional area at the centre 𝛾 (shear strain) = 𝐿 portion of the specimen to ensure Where: fracture within the gauge length T = torque; r = radius; θ = angle A 12.5mm diameter round of twist (radians); specimen is used in many cases 4 J = polar moment of inertia, 𝜋𝑟 ⁄2 LVDT extensometer – used to measure the deformation of the for solid circular cross section entire gauge length Charpy V Notch Impact Test (ASTM E23) © Nikolai  To measure the toughness of the hardness of steel and other material or the energy required to materials fracture a V-notched simply Rockwell superficial hardness supported specimen test – to test very thin steel or thin Used for structural steels in surface layers tension members Hardness tests are simple, Lateral expansion of the inexpensive, non-destructive, and specimen is measured after the do not require special specimens test using a dial gauge device Lateral expansion – measure of Ultrasonic Testing the plastic deformation during the Non-destructive method for test detecting flaws in materials Useful for evaluation of welds Sensor captures the energy of Bend Test (ASTM E290) the reflected wave and the results Semi-guided bend test (ASTM are displayed on an oscilloscope E290) used to check the ductility Highly sensitive in detecting to accommodate bending planar defects Test evaluates the ability of steel, or a weld, to resist cracking during bending Steel Corrosion Bend test is made by applying a Corrosion – defined as the transverse force to the specimen destruction of a material by in the portion that is bent, usually electrochemical reaction to the at mid-length environment Three Arrangements for Semi-guided Corrosion of steel bridges, if left Bend Test unchecked, may result in lowering weight limits, costly steel replacement, or collapse of the structure Corrosion of steel pipes, trusses, frames and other structures Corrosion requires four elements: anode, cathode, conductor, electrolyte Salt, from deicing or a marine environment, is a common contaminant that accelerates corrosion of steel bridges and reinforcing steel in concrete Hardness Test (ASTM E18) How to prevent corrosion? Apply Hardness – measure of a protective coatings. material’s resistance to localised plastic deformation Hard materials result in small impressions, corresponding to Steel Sustainability high hardness numbers LEED Considerations Rockwell Hardness Test (ASTM Building reuse E18) – method used to measure Construction Waste and © Nikolai  Recycling Resource Reuse Recycled Content Use of exposed steel as the finish rather than using conventional products such as tiles and dry wall Minimising weight of steel Design the structure for recyclability Deconstruction and reuse MODULE 6 – ASPHALT Classification of Asphalt- Asphalt Cutback and Emulsion Cutback Rapid Curing Medium Curing Slow Curing Emulsion Rapid Setting Medium Setting Classification of Asphalt Slow Setting Asphalt binders (Asphalt cement) Asphalt Cutbacks Asphalt Mix Design Asphalt Emulsions Asphalt Concrete-Specimen Classification of Asphalt Binder Preparation Compacted Bulk Specific Gravity, Gmb: Loose or uncompacted Theoretical maximum Specific Gravity, Gmm © Nikolai  board To used wood efficiently, it is important to understand its basic properties and limitations In the design of a wood structure, joints and connections often limit the design elements Asphalt Concrete- Density & Void Trees are classified either: Analysis Endogenous – palm trees, Voids in Total Mix (VTM) not generally used for Voids in Mineral Aggregate (VMA) engineering applications Voids Filled with Asphalt (VFA) Exogenous – hardwood or softwood Hardwood – harder, denser and harder to cut Softwood – softer, less dense and easier to cut STRUCTURE OF WOOD Growth rings or annual rings – concentric layers in the stem of exogenous trees Physical Features of Tree Stem Anisotropic Nature of Wood Wood is an anisotropic material – has different and unique properties in each direction MODULE 7 WOOD 3 axes orientations in wood: Longitudinal or parallel to the grain, radial or cross the Wood growth rings, and tangential Natural, renewable product from Affects physical and mechanical trees properties such as shrinkage, Used extensively for buildings, stiffness and strength bridges, utility poles, floors, roofs, Result of the tubular geometry of trusses, and piles the wood cells Civil engineering applications Centres of tunes are hollow, include both natural wood and whereas the ends of the tubes engineered wood products, such are tapered as laminates, plywood and strand © Nikolai  Hollow tube structure is efficient 20% at temperatures less than in resisting compressive and 27ºC and 90% humidity tensile stresses parallel to its Relationship between shrinkage length but deforms when loaded and moisture content on its side Fluctuations in moisture contents expand or contract the tube walls Moisture Content in Wood Weight of water in the specimen expressed as a percentage of the oven-dry weight of the wood Oven-dried sample – 100 to 105ºC Physical properties such as Wood Production weight, shrinkage and strength – Dimensional lumber (50x100, depends on the moisture content 50x150, 50x200, 50x250, of wood 50x300, 100x100, 100x150) Moisture exists in wood as either: Rough-sawn dimensions Bound – held within cell of the lumber in inches wall by adsorption forces To produce smooth Free water – either surfaces, 6.5mm per side condensed or water is removed vapour in the cell cavities For dimensions 200mm FSP – fibre saturation point – and larger, 9.5mm per side level of saturation at which the is removed cell walls are completely Heavy timber saturated, but no free water Round stock exists in the cell cavities Engineered wood (structural FSP is of great practical panels, glulam, composite significance because the addition lumber) or removal of moisture below the Specialty items (handrails) FSP has a large effect on all Cutting Techniques physical and mechanical Sawing into desired shape properties of wood Seasoning FSP assumed to be 30% Surfacing (planning) of wood Tangential shrinkage assumed to surface be 8% Grading Radial shrinkage assumed to be Preservative treatment (optional) 4% Common Log Sawing Patterns Moisture content varies depending on air temperature and humidity Equilibrium moisture content (EMC) – moisture content for the a) Live (plain) sawing average atmospheric conditions b) Quarter sawing EMC ranges from less than 1%, c) Combination sawing at temperatures greater than 55ºC and 5% humidity, to over © Nikolai Types of Board Cut a) Flat sawn b) Rift sawn c) Quarter-sawn (vertical- or edge- sawn) Seasoning Green wood contains from 30% to 200% moisture by the oven-dry PHYSICAL PROPERTIES OF weight WOOD Seasoning – removes the excess moisture from wood Specific Gravity and Density Structural wood – 7% to 14% Depends on cell size, cell wall moisture content thickness and number and types Framing lumber – 15% average of cells moisture content Regardless of species, the Seasoned by air and kiln drying substance composing the cell Lumber Grading walls has a specific gravity of 1.5 Lumber is graded according to Dry density of wood: 160 kg/cu.m the characteristics that affect (balsa) to 1335 kg/cu.m (black strength, durability and ironwood) workability Majority of wood types: 300 to Common grade-reducing 700 kg/cu.m qualities of lumber: knots, checks, pitch pockets, shakes Thermal Properties and stains Thermal Conductivity – measure Due to the high degree of natural of the rate at which heat flows variability within lumber, it is through a material nearly impossible to develop an Wood has thermal exact, uniform set of grading conductivity that is a standards fraction of that of the most Hardwood grades – amount of metals and 3-4x greater usable lumber in each piece of than common insulating standard length lumber materials Softwood grades – grades by Depends on: grain visual inspection and is machine orientation, moisture stress graded content, specific gravity Common Defects in Lumber extractive content and a) Knots structural irregularities b) Shakes such as knots c) Wanes Specific Heat – ratio of the d) Checks and splits quantity of heat required to raise e) Bowing the temperature of the material f) Crooking one degree to that required to g) Cupping raise the temperature of an equal h) Twisting mass of water one degree © Nikolai  Thermal Diffusivity – measure of material decreases with time the rate at which a material Reduction in amplitude is due to absorbs heat from its internal friction within the material surroundings and resistance of the support Low thermal diffusivity of system wood does not feel hot or Under normal conditions of cold to the touch temperatures and moisture Coefficient of Thermal Expansion content, the internal friction in – measure of dimensional wood (parallel to grain) is 10x changes caused by a that of structural metals temperature variance TESTING TO DETERMINE Electrical Properties MECHANICAL PROPERTIES Air-dry wood is a good electrical insulator Flexure Test of Structural Members Resistivity decreases by a factor (ASTM D198) of three for each 1% change in moisture content ASTM D198 presents testing standards MECHANICAL PROPERTIES OF for full-size tests: WOOD Flexure (bending) Compression (short Strength Properties column) Strength properties of wood vary Compression (long to a large extent, depending on column) the orientation of grain relative to Tension the direction of force Tensile strength in the Flexural Test of Small, Clear longitudinal direction (parallel to Specimen (ASTM D143) grain) is more than 20x the Tests for small-clear wood tensile strength in the radial specimens (ASTM D143): direction (perpendicular to grain) Static bending (flexure) Common strength properties: Impact bending modulus of rupture in bending, Compression parallel to compressive strength parallel and the grain perpendicular to the grain, tensile Compression strength parallel to the grain and perpendicular to the grain shear strength parallel to the Tension parallel to the grain grain Less common strength Tension perpendicular to properties: torsion, toughness the grain and fatigue strength For large specimens, a span of Load Duration 710mm is used and the load is Wood can support higher loads of applied at a rate of 2.5 mm/min short duration than sustained For small specimens, a span of loads 360mm is used and the load is Generally, a load duration of 10 applied at a rate of 1.3mm/min years is used for design Reading taken to the nearest Damping Capacity 0.02mm Damping – phenomenon in which the amplitude of vibration in a © Nikolai Test Specimens of Wood supplier who is certified by the a) Tension parallel to grain FSC (Forest Stewardship b) Tension perpendicular to grain Council), then one credit is c) Compression parallel to grain earned. d) Compression perpendicular to If 95% of wood is from an FSC grain supplier, an additional credit can e) Hardness perpendicular to grain be earned for exceeding the f) Hardness parallel to grain minimum g) bending Wood is a renewable resource when the forests are properly managed Globally only 8% of the natural forest areas and 13% of the managed forests produce certified products. Methods of Loading a Wood Beam a) two-point loading b) Third-point loading c) Centre-point loading ORGANISMS THAT DEGRADE WOOD Fungi Insects Marine Organisms Bacteria WOOD SUSTAINABILITY LEED Considerations If 50% of wood is sourced from a © Nikolai