Advanced Construction Techniques CM 510. Advanced Construction Techniques. CM 510- Course Description

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1 Fall Quarter 2016 Advanced Construction Techniques 1 - Course Description The course will introduce unique construction methods involved with several types of complex construction projects. The construction process will be discussed as a system to provide a background for examining various types of projects including modern concretes and infrastructure, high-rise construction, deep foundations, dams and bridges, tunneling and shotcrete, and other complex construction issues. 2 Fall Quarter

2 Lecture 1 - Text P.K. Mehta and P.J.M. Monteiro Concrete : Microstructure, Properties, and Materials, Fourth Edition, MacGraw Hill, 2014 (reserved at both Engineering and Architecture Libraries). Handouts and other reference materials will be distributed in class. Class presentations and notes will be available through the course web site at: Course Description Faculty Office Hours: Thursdays 5-6 PM or by appointment, 130J Architecture Hall. Voic , nemati@uw.edu Assignments: There will be three homework assignments in this class. All assignments are due at the beginning of the class on the date due. 20% will be deducted for each day late. Exams: One midterm test will be given on Thursday, November 17th. 4 Fall Quarter

3 Lecture 1 - Course Description Term Project: Each student will work on a term project that is pre-approved by the instructor. The term project should involve an analysis of an innovative technique or the use of an innovative building material in a construction project. Students are required to submit a one-page description of the project to the instructor by October 13th. The project is due on Thursday, December 8th at the beginning of the class. Students are expected to work individually. 5 Sample Projects in the Past Floating bridge construction processes and techniques Construction process in Experience Music Project Micro-tunneling Mast climbing construction system The use of robots in the construction industry Mechanically stabilized earth retaining wall Precast Seismic Structural Systems (PRESSS) Mobile Bridges 6 Fall Quarter

4 - Course Description Grading: Homework 20% Midterm 25% Term Project 25% Term Project Presentation 20% Class Participation 10% Participation: Students are expected to maintain an active role in class discussions. By completing assignments on time and being prepared for class you demonstrate your interest in the class. 7 - Lecture Topics Sept. 29 Introduction to Concrete as a Construction Material October 6 Alaskan Way Viaduct Replacement project; Progress in Concrete Technology October 13 Field Trip to Spokane Street Swing Bridge October 20 Site Improvement and Deep Foundations; Ground Freezing; Bridge Construction October 27 Dams; Cofferdams; Construction Dewatering; Shotcrete November 3 High-rise Construction November 10 IDX Tower Tunnels November 17 Pavement Construction, Presentations, Midterm November 24 Thanksgiving Holiday December 1 Presentations December 8 Presentations 8 Fall Quarter

5 HYDRAULIC CEMENTS AND THEIR PROPERTIES 9 Definitions Cement Powder Cement + Water Cement Paste Cement Paste + Fine Aggregate (FA) Mortar Mortar + Coarse Aggregate (CA) Concrete 10 Fall Quarter

6 Definitions Concrete is initially plastic, allows one to mold into desired shape. Chemical reaction (hydration) and paste set of concrete - producing strength and stiffness. 11 Cement Cement is a pulverized material that develops binding forces due to a reaction with water Hydraulic Cement Stable under water Nonhydraulic Cement Products of hydration are not resistant to water (i.e. limestone) 12 Fall Quarter

7 Lecture 1 Hydraulic Cements Cements that harden by reaction with water and form a water-resistant product. Portland Cement (P.C.) Portland cement is a hydraulic cement capable of setting, hardening and remains stable under water. It is composed of calcium silicates and some amount of gypsum. 13 Cement Chemistry In cement chemistry, the individual oxides and clinker compounds are expressed by their abbreviations Short Hand Notation C (CaO, calcium oxide) A (Al 2 O 3, alumina) S (SiO 2, silica) S (SO 3, sulfate) H (H 2 0, water) Reactive Compounds C 3 S (tricalcium silicate) C 2 S (dicalcium silicate) C 3 A (tricalcium aluminate) CSH 2 (gypsm) C 4 AF (tetra-calcium alumino ferrite) 14 Fall Quarter

8 Compounds of Portland Cement C 3 S 3CaO. SiO 2 C 2 S 2CaO. SiO 2 C 3 A 3CaO. Al 2 O 3 C 4 AF 4CaO.Al 2 O 3.Fe 2 O 3 C 4 A 3 S 4CaO.3Al 2 O 3.SO 3 C3S Tricalcium Silicate C2S Dicalcium Silicate C3A Tricalcium aluminate C4AF Tetracacium aluminate ferrite 15 Cement Chemistry Hydration Reactions 2C 3 S + 6H C-S-H + 3CH (120 cal/g) 2C 2 S + 4H C-S-H + CH (62 cal/g) C 3 A + 3CSH 2 +26H C 6 AS 3 H 32 (300 cal/g) 2C 3 A + C 6 AS 3 H H 3C 4 ASH 12 C 4 AF + 10H + 2CH C 6 AFH 12 C 3 S 2 H 3 (C-S-H gel) CH (calcium hydroxide) C 6 AS 3 H 32 (ettringite) C 4 ASH 12 (monosulfate) 16 Fall Quarter

9 Hydration of Portland Cement Hydration: Reaction with water 2C 3 S 6H CS H 3CH 120 Cal/g 2C 2 S 4H CS H CH 62 Cal/g A,C AF,CSH C A S H (Ettringite) C3 4 Compound Composition Morphology Amount (% Vol.) C-S-H Variable C/S 1.5 to 2 Poorly crystalline High surface area: higher bonding energy CH Ca(OH) 2 Large hexagonal crystals, low surface area, and poor bonding energy C-A-S-H C 6 AS 3 H 32 Ettringite C 4 ASH Monosulfate Long, well crystallized needles Hexagonal small crystals 50 60% 20 25% 15 20% Manufacturing Process Calcium silicates are the primary constituents of portland cement. Raw material for P.C. Calcium Silica Calcium: Limestone, chalk, etc (CaO+CO 2 ) Silica: Clays and shales (SiO 2 +Al 2 O 3 +Fe 2 O 3 +H 2 O) 2/3 Calcium 1/3 Clay Raw mix should be well homogenized before the heat treatment 18 Fall Quarter

10 Manufacturing Process Aerial Photo of a Cement Manufacturing Plant (Colorado) 19 Manufacturing Process Raw Mill Feed 20 Fall Quarter

11 Manufacturing Process Kiln Line Overview 21 Raw (Limestone +Clay) Grind Manufacturing Process Mill Rotary Kiln T = 1400C Clinker+Gypsum Grind Portland Cement 3CaO.SiO 2 Limestone CaO CO 2 2CaO.SiO 2 Clay SiO 2 Al2O3 Fe2O3 H2O 3CaO.Al2O 3 4CaO.Al2O 3.Fe2O3 C S C S C A C AF Fall Quarter

12 Lecture 1 Fineness Reactivity of cement with water is a function of its fineness. Generally, the finer a cement, the more rapidly it will react, and the strength development will be enhanced (expensive). 23 Types of Portland Cement ASTM C 150, Standard Specifications for Portland Cement Type I: General purpose. For use when the special properties specified for any other types are not required. Type II: For general use, more specially when moderate sulfate resistance or moderate heat of hydration is desired. Type III: For use when high early strength is desired. (limit the C 3 A content of the cement to maximum 15%) Type IV: For use when low heat of hydration is desired. Type V: For use when high sulfate resistance is desired. (Maximum limit of 5% on C 3 A) 24 Fall Quarter

13 Effects of Chemical Composition of Portland Cements of Strength In classic research from over fifty years ago Bouge and Lerch* found that of the four portland cement phases only C 3 S and C 2 S developed appreciable compressive strength when pure samples of each were hydrated. The compressive strength found by Bogue and Lerch** are plotted in the next Fig. as a function of age. Compressive strengths of C 3 A and C 4 AF, hydrated alone A and have not been plotted explicitly. * T.C. Powers, The Non-Evaporable Water Content of Portland Cement Paste: Its Significance for Concrete Research and Its Method of Determination, ASTM Bul., No. 158, (May 1949) pp ** R H Bouge and W Lerch Industrial Engineering, Chem (1934) 25 Effects of Chemical Composition of Portland Cements of Strength The compressive strength found by Bouge and Lerch** for hydrated samples of the pure cement phases C 3 S and C 2 S are plotted as a function of age. The compressive strengths of C 3 A and C 4 AF, hydrated along and with gypsum, fall within the crosshatched region labeled A and have not been plotted explicitly. The time scale is linear. The time scale is logarithmic, which has the effect of expanding the early ages, and this shows the differences between strength gain of C 3 S and C 2 S pastes. Fall Quarter

14 Lecture 1 The Structure of Concrete The type, amount, size, shape & distribution of phases present in a solid material constitute its structure. Concrete Consists of aggregates, paste and voids. The macrostructure of concrete is shown below: A polished section of concrete 27 The Microstructure of Portland Cement Concrete The structure of the aggregates in concrete is important but it can be characterized as a macrostructure which is visible to the human eye. The limit of resolution of the unaided human eye is approximately 1/5 millimeter which is 200 microns. 28 Fall Quarter

15 Lecture 1 The Microstructure of Portland Cement Concrete The use of both light and electron microscopes allows the study of the microstructure of concrete at the submicron level. The microstructure of concrete can be divided into regions: Cement Paste Transition Zone between Aggregate and Cement paste 29 Structure of un-damaged Concrete Macrostructure Aggregates (CA, FA) Hydrated cement paste (hcp) Entrapped air voids Microstructure Hydrated cement paste (Hydration products:c-s-h, ettriginite; monosulfate; porosity: gel, capillary pores entrained/ entrapped air voids) Transition zone (TZ) 30 Fall Quarter

16 Lecture 1 Microstructure of Concrete (Hydration products) CH C-S-H 31 Microstructure of Concrete Ettringite (Hydration products) 32 Fall Quarter

17 Lecture 1 Microstructure of Concrete (Transition Zone) Characteristics of the TZ Large crystals of Ettringite and CH with preferred orientation Porous Structure 33 The Microstructure of Portland Cement Concrete One way to view cement paste is to consider the hydration of one grain of cement. The partial hydration of one grain of cement is schematically represented in the next slide. There are many details in this process that are not yet understood, but there is sufficient information available to allow a consistent mental picture to be considered. 34 Fall Quarter

18 Lecture 1 The Microstructure of Portland Cement Concrete The hydration products formed inside and outside the cement grain are schematically represented. The multiple nature of the cement grain is neglected and assumed to be a single phase that shows two types of products. P1 refers to the primary portlandite which appears early in the originally waterfilled space. 35 The Microstructure of Portland Cement Paste The hydration of a number of cement grains is schematically represented in the next slide at different degrees of hydration. The fresh paste (i.e., the initial combination of water and cement grains) is drawn to approximately represent the 0.4 water/cement ratio, and thus there are not enough hydration products to fill the originally-water-filled space and a capillary porosity remains in the final microstructure. 36 Fall Quarter

19 The Microstructure of Portland Cement Paste A schematic representation of the hydration of a number of cement grains. The multiphase nature the cement grains has been neglected as this is like the hydration of tricalcium silicate alone. (a) Fresh paste of water-to cement ration of 0.4 is shown cement grains in the originally water-filled space. (b) After 33% hydration, the cement grains now have inner hydration regions and outer products which form a columnar zone around each grain. (c) After 67% hydration, the un-hydrated cores are clearly surrounded by thick rims of inner hydration products and the columnar zone of outer products is growing on the surface of each grain. The primary portlandite, P1, is shown with the dendrite morphology. (d) At 100% hydration, the un-hydrated cement has been consumed but the shape of the original cement grains can be distinguished if the inner product differs from the columnar zone of outer products. The intergrowth of the columnar zones from two different grains is shown at several points, but this would be larger at low water/cement rations. Originally water-filled space = clear, unhydrated cement = ///, inner hydration products =, outer hydration products =, & primary portlandite = P1. 37 Capillary Porosity The originally-water-filled space within the cement paste becomes the capillary pores which act as stress concentrations and reduce the strength significantly. The strength of most engineering materials is increased with a decrease in porosity, and by controlling the water/ cement ratio the engineer is assured that the basic porosity of the paste is also controlled. That is not to say the other sources of porosity will not occur, but at least the cement paste will have a given porosity. 38 Fall Quarter

20 Capillary Porosity Figure below shows a graphical representation of the relative volumes of hydration products during hydration. Graphical representation of the relative volumes of hydration products during hydration. The initial w/c is 0.5, and one unit of cement is shown to produce two volumes of hydration products. 39 Capillary Porosity Over a Range of W/C Ratios If cement paste specimens are prepared with a range of w/c ratios it is apparent that the density of high w/c samples is much lower than low w/c samples. This is illustrated in the next slide in a presentation originally given by T.C. Powers*. *T.C. Powers, The Non-Evaporaable Water Content of Portland Cement Paste: Its Significance for Concrete Research and Its Method of Determination, ASTM Bul., No. 158, (May 1949) pp Fall Quarter

21 Capillary Porosity Over a Range of W/C Ratios Composition of Cement Paste at different stages of hydration. The percentage indicated applied only to paste with enough water-filled space to accommodate the products at the degree of hydration indicated. 41 Advance Construction Techniques Admixtures in Concrete 42 Fall Quarter

22 ADMIXTURES A material other than water, aggregates, and hydraulic cements used as an ingredient of concrete or mortar and added to the batch immediately before or during mixing. Reason: Improve or modify some or several properties of portland cement concrete. Compensate for some deficiencies. 43 A. Chemical Admixtures Type A: Water-reducing (WR) Type B: Set retarding (SR) Type C: Set accelerating (SA) Type D: WR + SR Type E: WR + SA Type F: High-range water-reducing (HRWR) Type G: HRWR + SR 44 Fall Quarter

23 B. Mineral Admixtures Class N: Raw or calcined pozzolans Class F: Fly ash produced from burning bituminous coal Class C: Fly ash normally produced from burning lignite (subbituminous) coal. (both pozzolanic and cementatious) 45 1) Admixtures for Durability Frost action: Air-entraining agents Sulfate and acidic solutions: Pozzolans, polymer emulsions Alkali-aggregate expansion: Pozzolans Thermal Strains: Pozzolans 46 Fall Quarter

24 2) Admixtures for Increasing Strength Water reducing agents Pozzolans To reduce the water content while maintaining a given consistency Consistency: Flowability, slump Workability: High cohesiveness and high consistency (Advantage of fine particle size Cohesiveness) 47 Chemical Admixtures Surfactants (Surface-Active Chemicals/ Agents) Air-entraining surfactants: At the air-water interface the polar groups are oriented towards the water phase lowering the surface tension, promoting bubble formation and counteracting the tendency for the dispersed bubbles to coalesce. At the solid-water interface where directive forces exist at the cement surface, the polar groups become bound to the solid with the non-polar groups oriented towards the water, making the cement surface hydrophilic so that air can displace water and remain attached to the solid particles as bubbles. 48 Fall Quarter

25 Chemical Admixtures Surfactants (Surface-Active Chemicals/ Agents) Air-entraining surfactants: 49 Air-Entrained Concrete 50 Fall Quarter

26 Lecture 1 Mechanism of Frost damage in concrete Only concrete that is above the critical saturation is vulnerable to frost damage. Critical saturation occurs when more than 91.7% of pores in concrete is filled with water. Water Expands 9% on freezing. 51 Mechanism of Frost damage in concrete If 91.7% of the pores in concrete are filled with water prior to freezing, then all of the pores will be completely filled upon freezing. Water is forced ahead of the advancing freezing front. Internal hydrostatic pressure can disrupt the concrete. 52 Fall Quarter

27 Lecture 1 Freeze-Thaw Deterioration 53 Mechanism of Protection by AE 54 Fall Quarter

28 Lecture 1 Mechanism of Protection by AE 55 Mechanism of Protection by AE 56 Fall Quarter

29 Air Content Specifications ACI 318 Building Code ASTM C 94 Specs for Ready-Mixed Concrete 57 Chemical Admixtures Surfactants (Surface-Active Chemicals/ Agents) Water-Reducing surfactants: When water is added to cement, a well-dispersed system is not achieved, because: The water has high surface tension. Cement particles tend to cluster together or form flocs. When a surfactant with a hydrophilic chain is added to the cementwater system, the polar chain is adsorbed alongside the cement particle, and thus lowering the surface tension of the water, and making the cement surface hydrophilic. 58 Fall Quarter

30 Chemical Admixtures Surfactants (Surface-Active Chemicals/ Agents) Water-Reducing surfactants: 59 Mineral Admixtures Definition: Mineral Admixtures are insoluble siliceous materials, used at relatively large amounts (15-20% by weight of cement). Fine particle size, siliceous material that can slowly react with CH at normal temperatures, to form cementitious products. CH+ S Aq Normal Temp. CSH 60 Fall Quarter

31 Lecture 1 Mineral Admixtures Low heat of hydration Transform large pores to fine pores Historically, mineral admixtures are volcanic ashes. Significance: Durability to thermal cracking, chemical attack, sulfate attack, workability. 61 By-Product Mineral Admixtures Fly Ash (FA) 1-40m Particle Size; Surface Area=0.5 m 2 /g Blast Furnace Slag (BFS) 1-40m; SA=0.5 m 2 /g Condensed Silica Fume (SF) 0.1m; SA=20 m 2 /g Rice Husk Ash (RHA) 10-20m; SA=60 m 2 /g Internal bleeding is reduced Reduced Microcracking Effect of Pozzolans: It will reduce the available space for formation of large crystals Pozzolans will convert CH into C-S-H 62 Fall Quarter

32 Lecture 1 The Slump Test 63 The Slump Test Consistency of concrete is generally measured by the slump test (ASTM C143). This test is performed by measuring the slump (subsidence), in inches, of concrete after removal of the truncated cone mold in which the freshly mixed concrete was placed. Details of the test procedure and the dimensions of the cone and tamping rod are given in ASTM C143, and summarized in this figure: 64 Fall Quarter