Concrete Materials and Construction
Concrete Materials and Construction CIV ENG 165
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This 44 page Class Notes was uploaded by Keyshawn Nader on Thursday October 22, 2015. The Class Notes belongs to CIV ENG 165 at University of California - Berkeley taught by P. Monteiro in Fall. Since its upload, it has received 45 views. For similar materials see /class/226750/civ-eng-165-university-of-california-berkeley in Civil and Environmental Engineering at University of California - Berkeley.
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Date Created: 10/22/15
IllghWorknbillty Concrete High workability relates to both high consistency and high cohesiveness Pioneering work by Japanese and German researchers during the 1980s has led to the development of highworkability concrete mixtures that are commercially known as selfcompacting concrete Flowingconcrete that can be cast into place and can achieve deaeration without the application of a vibrator with no segregation and honeycombing Ans A BE The constructability of heavily congested reinforced concrete structures requires that the fresh concrete mixture should possess high uidity With the advent of superplasticizers it is possible now to achieve values of the order of 200 to 250 mm without an increase in the watercement ratio Flowing concrete mixtures run the risk of bleeding settlement and segregation Weak interfacial transition zone between cement paste and aggregate as well as between cement paste and reinforcing steel This risk becomes especially great with high placement heights high shear rates in pumping and excessive vibration during the consolidation of concrete Reasons for the increasing demand of SCC in Japan a complex shape of concrete structures and densely arranged bars make it more difficult to use a vibrator b vibration compaction is noisy and deleterious to the health of construction worker as well as an annoyance to people in the neighborhood d in remote areas it is difficult to find skilled workers to carry out the compacting work at construction sites n4 volume and maximum size of coarse aggregate must be controlled Compared to conventional superplasticized concrete which typically contains about 45 coarse aggregate and 25 ne aggregate by absolute volume SCC concrete mixtures are composed of approximately 25 to 30 coarse aggregate 3035 fine aggregate and about 10 extrafine particles exclusive of cement A A BE In highstrength concrete the aggregate plays an important role on the strength of concrete The lowwater to cement ratio used in high strength concrete causes densi cation in both the matrix and interfacial transition zone and the aggregate may become the weak link in the development of the mechanical strength Extreme care is necessary therefore in the selection of aggregate to be used in very highstrength concrete BE SCC the total volume of coarse and ne aggregate remains below 60 so that 40 or more of the volume consists of suspension cement extrafine material water air The maximum size of coarse aggregate is generally limited to a maximum of 20 mm A A BE According to Nagataki and Fujiwara in an experimental study when the volume of coarse aggregate was 245 most concrete was able to pass through the reinforcing bars When the volume of coarse aggregate was 345 concrete was unable to pass through the bars under all conditions High uidity with relatively low water content is achieved by the use of a superplasticing admixture Fly ash ground blastfurnace slag and limestone powder are normally used to provide the extra ne particles other than cement using cements alone would increase the cost and heat of hydration Commonly used viscositymodifying agents in concrete include acrylic or cellulose based watersoluble polymers or polysacchrides of microbial sources such as welan gum Watersoluble polymers can imbibe some of the free water in the system thus increasing the viscosity of the cement paste which in turn enables the paste to hold aggregate particles in a stable suspension Incorporation of extrafine materials in the SCC mixtures is not necessary if a viscositymodifying agent is used Enhance the cohesion of the concrete Minimize the accumulation of bleed water Formulation Watersoluble synthetic or natural organic polymers with high molecular weight Emulsions of several organic materials gem m k ESEM images of welan gum particles scalebar is 100mm a Dry particles at 70 I b After 5 minutes at RH 100 RH c After 12 minutes at l 100 RH Applications of Viscosity Modifying Agents Underwater concrete 0 Facilitates sufficient mobility of the concrete under water with little loss of cement Selfcompacting concrete 0 Leads to high flowability with no segregation Grouting o Eliminates the migration of water from the grout due to the differential pressure 0 Helps maintain the cement particles in suspension once injection ceases The anchorage for a long bridge connecting the island of Honshi and Awajishima bridge piers and highrise buildings with dense steel reinforcement stadiums with are complex in shape and where vibratory compaction is dif cult Applications in 1994 a ship ran aground at the Looe Key damaging over 1000 square meters and destroying 75 percent of the corai coionies Underwater concrete was piaced to stahiiize the boulders and the surrounding reefs Due to the sensitive environmentai conditions at the site the underwater concrete had to he fiowahie but yet without causing turbidity and poliution in water an n on 8239 4539 Florida Keys National Marine Summary cueswmmmae Cara Reef mm F arida Keys Courtesy from Sam Yao Fla da Keys Nanoml Marlnesancmziy nvnmx m quot45 133 Mumm mwa ma m H mm w mm mm m mm am am vmmuu m N w m sum mmzL Ad V c an at MN 11 m We mm m wwm Wm WM mu munSm mm w M mm m m mums ms 3 m 5 Ms 5m 7m am m cm mmr swt REEF MODULE WIHGURATION mama 1W m m ELEVAW mm m MOVE y mm m mm mm M Emma REEF WENXHINS Emu Mi WWva w m vmwwm am rm 01wa mm M 2 an n nun mme E m M E V unummmm Wm m mm 5M mm mm 5 WM 11 mm mama nu Courtesy from Sam Yao a p a I d u An 1111 wwnv Courtesy from Sam Yao par orra Fjigrjqakeys Courtesy from Sam Yao wMII h 39 k 4D 391 u OM I ml luffk L l mmv Fvauoa FLA rs DIAMETER mm LESS THAN wsxns 0141145755 1 OF THEME MW 0H LIGHT r15 WIRE mw RUEEER GASKET sump umw rsn Hm GREA rm THAN OUTSDE DIAMETER DF TNEMIE sdW FL vwouo FLA r5 puma5 2w GREA r5 WAN oursDE amme a raw5 A nhumk wuu w n o A Ilwo HTHE HE GHT 0F CONCRETE INSDE rREMIE hTHE IREMIE EMEEDMENT DEPTH IN CONCREIE DWATER DEPTH ABOVE THE CONCRETE HYDROSTATIC BALANCE POINT 125172 nn A Wu u Tremie Tremie P39 P9 Concrete CETIGSMMSQMW6 Spacing Wu u e linkkak a A E165 I r SECW39J gtusvu 39 1 iv 12 T L IIIVLII l CE1WWSMWW m v Landmark Series PLACEMENT 0F TllEMIE CONCRETE Iy aquot c mm k 139 minusquot Inlnmalrlnnl JANUARY 2004 COFFERDAM AND CAISSON SEALS provide rigid lateral support or strurtin at the base and 4 act as a distribution block to ram fer load in the piles With mode techniques available for placing of structural reinforced remit concrete ll is desirable to consider constructing fooling blocks as part of the Lremie placement This would 11 cessary39 thickness of Lhe seal for re i and reduce the dead weight on the foundation The place ment would be complelcd rapidly and economically Much chipping of high spell and laiiancc which consumes a great deal of time in the average col fcrdam could be avoided T0 at complish ihis rhc reinforcing steel must be made up as a rigid welded accu e set bars and spacings should be employed rdams and ca msnns can genep ally be pumped in 3 In 6 days depend r on stresses involvrd Tn39mir can crew will generally develop 2500 to 39 i in 7 day7 Andreiago lo mist uplift can be pro vided by piling or by drilling and grnulcd anchors The piling must clran of mud and algae In a m I m 1 mu MAI a m u g mo gem u u g n ma 1 Vaporbarriers epoxy asphalt 2 Latex permeable provides good adhesion as A u BE