ACI 224R-01 PDF

Control of Cracking in Concrete Structures (ACI R) [multiple authors] on *FREE* shipping on qualifying offers. ACI R Control of Cracking in Concrete Structures (R) (Control of Cracking in Concrete Structures) [ACI] on *FREE* shipping on. ACI R, “Control of Cracking in Concrete. Structures,” indicates in. as a reasonable crack width for reinforced concrete under service loads for a dry.

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ACI 224R-01 Control of Cracking in Concrete Structures

Skip to main content. Log In Sign Up. Barlow Will Hansen Royce Ac. The current state of knowledge in microcracking and Chapter 1—Introduction, p.

224r-01 control of cracking due to drying shrinkage and crack control in flexural members, overlays, and mass con- Chapter 2—Crack mechanisms in concrete, crete construction are covered in detail. Long-term effects on cracking are p. Information is presented to assist in the development of practical 2.

Chapter 3—Control of cracking due to drying shrinkage, p. The Institute shall 4. Chapter 6 on concrete 5. Chapter 7 on mass 5. Chapter 6—Control of cracking in overlays, p. The earliest studies of 6.

R Control of Cracking in Concrete Structures (Reapproved )

Chapter 8—Control of cracking by proper During early microcracking studies, concrete was considered construction practices, p. This picture began to change in the 8. Cement paste is a nonlinear softening material, as 8. The compressive non- 8. There are many specific causes of cracking. These This report presents the principal causes of cracking and a smaller microcracks have a surface density that is two to detailed discussion of crack-control procedures.

The report three orders of magnitude higher than the density of bond consists of eight chapters designed to help the engineer and and mortar microcracks in concrete at the same compres- the contractor in developing crack-control measures. ACI Bibliogra- its constituent materials in compression. The The effect of macroscopic cracks on the performance and Committee has also prepared reports on the causes, evaluation, failure characteristics of concrete has also received considerable and repair of cracking, ACI For many years, concrete has been considered a brittle rect tension, ACI Many attempts have been made to use ACI Chapter 3 on drying shrinkage has been rewritten.

The first section tural member which is a function of the crack geometry and on compressive microcracking presents the current knowledge stress.

wci K is further designated with subscripts, I, II, and III, of the response of concrete and its constituent materials under depending upon the nature of the deformation at the crack compressive loading and the role played by the various types tip.

For a crack at which the deformation is perpendicular to of microcracks in this process. The second section discusses the crack plane, K is designated as KI, and failure occurs the applicability of both linear and nonlinear fracture mechanics when KI reaches a critical value KIc, known as the critical models to 2224r-01.

A more comprehensive treatment of the stress-intensity factor.

ACI R supersedes ACI R and became effective | Yopie Suryadinata –

KIc is a measure of the fracture tough- fracture of concrete can be found in ACI Often the region around the crack 2. This region is referred to as the oped that closely linked the formation and propagation of plastic zone in metals, or more aco as the fracture process microcracks to the load-deformation behavior of concrete. To properly measure KIc for a material, the test specimen Before loading, volume changes in cement paste cause inter- should be large enough so that the fracture process zone is facial cracks to form at the mortar-coarse aggregate bound- small compared with the specimen dimensions.

Above this Initial attempts to measure KIc in concrete were unsuccessful value, additional bond cracks are initiated throughout the because K Ic depended on the size and geometry of the test matrix.

Bond cracking increases until the load reaches about specimens Wittmann Mortar crack- exhibit a significant fracture-process zone and the critical ack continues at an accelerated rate, forming continuous load is preceded by a substantial amount of slow crack growth.

The onset of by several researchers John and Shah ; Swartz and Go mortar cracking is related to the sustained, or long-term, ; Bascoul, Kharchi, zci Maso ; Maji and Shah compressive strength. Derucher obtained a somewhat ; Castro-Montero, Shah, and Miller This research different picture of the microscopic behavior of concrete has provided an improved understanding of the fracture process using the scanning electron microscope SEM.


He subjected zone and has led to the development of more rational fracture dried concrete specimens to eccentric compressive loading criteria for concrete. A cause and effect rela- one another.

Studies by SpoonerSpooner and Dougill start to join one another and aic to do so until failure. In studies of high-strength concrete, Carrasquillo, Slate, Experimental work by SpoonerSpooner and Dougill and Nilson concluded that it was more appropriate toSpooner, Pomeroy, and Dougilland Martin, classify cracks as simple bond or mortar and combined Darwin, and Terry indicates that the nonlinear compres- bond and mortar and that the formation of combined sive behavior of concrete is strongly 224r0-1 by the nonlinear cracks consisting of more than one mortar crack signaled behavior of cement paste.

As illustrated in Fig.

They observed that the higher the paste under compression is not an elastic, brittle material as concrete strength, the higher the strain relative to the strain at stated in wci past, but a nonlinear material with a relatively high peak stress at which this unstable crack growth is observed. The nonlinear behavior of cement paste can be They observed less total cracking in high-strength concrete tied to damage sustained by the paste, even at very low stresses.

Using a cyclic loading procedure, SpoonerSpoon- Work by Meyers, Slate, and WinterShah and er and Dougilland Spooner, Pomeroy, and Dougill Chandraand Ngab, Slate, and Nilson demon- demonstrated that both paste afi concrete undergo mea- strated that microcracks increase under sustained and cyclic surable damage at strains 0.

Their work indicated that the total amount of micro- and mortar microcracking cannot be detected. The level of cracking is a function of the total compressive strain in the damage can be detected at low loads by using an energy concrete and is independent of the method in which the strain method and by a change in the initial modulus of elasticity is applied.

Suaris and Fernando also showed that the for each load cycle. The process of damage is continuous up failure of concrete under constant amplitude cyclic cai to failure.

Sturman, Shah, The physical nature of damage that occurs in cement paste, and Winter found that the total degree of microcracking like that in concrete, appears to be related to cracking. This is decreased and the total strain capacity in compression is point was first made by Spooner, Pomeroy, and Dougill increased when concrete is subjected to a strain gradient.

Darwin and Slate compressive loading. The relationship between nonlinear also monitored microcracking. In every case, however, the deformation and cracking in cement paste is now firmly es- average amount of mortar cracking was slightly greater for tablished by the work of Attiogbe and Darwin This small yet Studies of the stress-strain behavior of concrete under cyclic consistent difference may explain the differences in the compressive load Karsan and Jirsa ; Shah adi Chandra stress-strain curves.

Their results also indicate that reducing the inter- sive strength of the concrete. They attributed Work by Carinousing polymer-impregnated the heat to sliding at the interfacial boundary. The work of concrete, corroborated these last two studies. Two studies seemed to indicate a very large effect, thus emphasizing the importance of interfacial The importance of mortar in controlling the stress-strain strength on concrete behavior in compression Shah and behavior of concrete is illustrated by the finite-element work Chandra ; Nepper-Christensen and Nielsen These studies used relatively thick, soft coatings on coarse Buyukozturk used a finite-element representation of aggregate to reduce the bond strength.

Because these soft a physical model of concrete. The model treated mortar in coatings isolated the aggregate from the surrounding mortar, compression and aggregate in compression and tension as the effect was more like inducing a large number of voids in linear elastic materials while allowing cracks to form in the the concrete matrix. Buyukozturk Two 224r-001 studies Darwin and Slate ; Perry and simulated the overall crack patterns under uniaxial loading.

224R-01: Control of Cracking in Concrete Structures (Reapproved 2008)

Gillott that did not isolate the coarse aggregate from His finite-element model, however, could not duplicate the the mortar indicated that interfacial strength plays only a minor full nonlinear behavior of the physical model using the for- role in controlling the compressive stress-strain behavior of mation of interfacial bond cracks and mortar cracks as the concrete.

Darwin and Slate used a thin coating of only nonlinear effects. Maher and Darwinhave polystyrene on natural coarse aggregate. They found that a shown that a very close representation of the actual stress- large reduction in interfacial bond strength causes no change strain behavior can be obtained using a nonlinear representation in the initial stiffness of concrete under short-term compressive for aco mortar constituent of the physical model.

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As the applied strain was increased, however, the crack density increased more rapidly in the mortar, eventually surpassing the value obtained in the cement paste. While sand particles can reduce crack density due to volume changes in cement paste, these results indicate that they act as stress raisers when load is applied. This increase in crack density under applied loading may explain the reduction in ultimate strain capacity exhibited in Fig.

Using analytical procedures, Attiogbe and Darwin established that a significant portion of the nonlinear strain in cement paste and mortar can be attributed to the microcracks within the cement paste.

Overall, the damage to cement paste in compression seems Fig 2. In normal- weight concrete, aggregate particles act as stress risers, Maher and Darwin also studied the behavior of the mortar increasing the initial stiffness and decreasing the strength constituent of concrete under monotonic and cyclic com- of the paste and controlling the compressive strength of the pression Degradation in mortar was shown to be a concrete.

An understanding of concrete behavior in compres- continuous process and a function of both total strain and sion, thus, requires an understanding of both the behavior of ce- load history.

The study indicated that residual strain as well ment paste in compression and the interaction of cement as the change in the initial modulus of elasticity are good paste with aggregate particles. Accumu- lations of 224r-01 strain were obtained for values of maxi- 2.

The work showed that the 2. Their work concludes as monotonically increasing load. If the load-CMOD curve is linear, 224t-01 can bond and mortar microcracking in concrete is a function of be used to calculate KIc based on the measured maximum load the compressive strain in the concrete and is independent of and the length of the crack just before failure ASTM E Because the maxi- KI c is used in the design of metal structures to prevent brittle mum strain does not appear to completely control degrada- failure where fatigue crack growth is expected to occur.

Martin, Darwin, and Terry studied the behavior of When KI c was calculated for concrete, as described previ- paste, mortar, and concrete under cyclic and short-term sus- ously, significant effects of the size and geometry of the test tained compression. They found a great similarity in the be- specimen were observed by many investigators Kaplan havior of concrete and its mortar constituent although the ; Naus and Lott ; Higgins and Bailey The bond and mortar microcracking found in concrete were not data presented in Fig.

Of the three materials stud- that KI c increases with the specimen depth. Such results led ied, 242r-01 paste has the greatest strain capacity and strength, many to question the applicability of LEFM to concrete. Results obtained from single-edge notched beams were also To understand the compressive response aic the cement analyzed by several investigators to determine if concrete dis- paste and mortar constituents of concrete, Attiogbe and plays any notch sensitivity. Notch sensitivity can be expressed Darwinused the SEM to study submicro- as the ratio of net stress at the crack tip to the modulus of rup- scopic cracking under uniaxial compression Fig.

Ma- ture of an unnotched specimen. The specimens showing in. The results acu concrete structures, such as dams, where the heteroge- indicate, however, that avi mortar and concrete display less neities and the fracture process zone are small compared notch sensitivity than hardened cement paste.

It is widely with the structure dimensions. It is also widely accepted Linsbauer et al. Laboratory-size specimens satisfy this cri- and geometry of test specimens. Precritical crack growth terion for metals. The fracture process zone in concrete is substantially dif- aggregates would 22r4-01 a beam with a depth of at least of 2 m ferent from the plastic zone in metals.