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CURSO PARA LA DIRECCIN DE OBRAS PORTUARIAS
DICTADO POR DIVISIN HORMIGONES INGENIERA
CENTRO DE INVESTIGACIN, DESARROLLO E INNOVACIN EN ESTRUCTURAS Y
MATERIALES IDIEM DE LA UNIVERSIDAD DE CHILE
Santiago de Chile, 31 de julio, 1 y 2 de agosto de 2013.
TECNOLOGA DEL HORMIGN PARA
OBRAS PORTUARIAS
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MDULO 1
TECNOLOGA DEL HORMIGN
Hormign Convencional y
Hormign Marino
Relator: Guillermo Cavieres Pizarro
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a. Introduccin Aspectos generales sobre durabilidad del hormign
Condiciones de exposicin de estructuras en ambiente
marino Especificaciones tcnicas por comportamiento y por
descripcin. Caractersticas propias de las obras portuarias
b. Estado del arte de estructuras martimas de hormign Anlisis de
normativa chilena e internacionales Terminologa y tipologa de
estructuras marinas Consideraciones para la construccin segn su
tipo
Temario
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a. Introduccin
Aspectos Generales sobre Durabilidad
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a. Introduccin
Hormign Mezcla artificial constituida por un aglomerante, agua,
ridos y aditivos, que bajo condiciones adecuadas fragua y endurece
para dar forma a diversos elementos. La principal propiedad del
hormign se define normalmente por su resistencia mecnica.
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Sin embargo, los aspectos de durabilidad, que son de mayor
relevancia y a mayor plazo, muchas veces se olvidan, se obvian o no
se consideran. Si bien a mayor resistencia a compresin la
durabilidad aumenta, existen otros factores de mayor importancia.
La impermeabilidad es la propiedad que mejor puede asociarse a la
durabilidad del hormign. La impermeabilidad del hormign se puede
estimar a travs de ensayos, como es el caso de la penetracin de
agua, permeabilidad al oxgeno y otros.
a. Introduccin
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Una estructura de hormign poco durable sufrir daos antes de lo
previsto, y los problemas pueden estar asociados a muchos factores,
entre ellos: Inadecuado diseo de la mezcla Materiales no apropiados
Condiciones ambientes y de exposicin Defectuosa fabricacin del
hormign Defectos constructivos Cambios de uso durante su vida til.
Poco o nulo mantenimiento
a. Introduccin
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Es aquel hormign que una vez endurecido es capaz de mantener sus
propiedades bajo las condiciones de exposicin previstas para su
vida til. Un hormign durable es obtenido a partir de componentes de
buena calidad, diseado mediante una dosificacin de la mezcla
cuidadosamente estudiado, tomando en cuenta las condiciones a que
estar expuesto y fabricado a travs de un proceso productivo
debidamente controlado, desde la compra y recepcin de los
materiales en terreno hasta su correcta colocacin, compactacin y
curado en obra.
Hormign Romano
Dolos Caleta Higuerillas 1993
Hormign Resistente y Durable
a. Introduccin
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Diseo de la Mezcla y
Condiciones de Exposicin
Colocacin Compactacin
Curado Recubrimiento
Fabricacin y Control de
Calidad en Obra
Calidad de Materiales
componentes
HORMIGON DURABLE
Y RESISTENTE
a. Introduccin
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FACTORES INTERNOS 1. Cambios volumtricos debido a efectos
qumicos:
- Cal libre - Magnesio libre - Sulfatos - Reaccin
lcali-agregado
2. Cambios volumtricos debido a efectos fsicos:
- Retraccin por secado - Hinchamiento
3. Cambios volumtricos debido a efectos trmicos:
- Calor de Hidratacin
a. Introduccin
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FACTORES EXTERNOS 1. Actan sobre toda la estructura:
- Cargas estticas o dinmicas - Fuego - Terremotos - Temperaturas
y vientos extremos
2. Actan sobre la superficie: - Desgaste mecnico
3. Actan principalmente sobre el recubrimiento del hormign:
- Carbonatacin - Sales descongelantes, deshielo - Ataque de
sulfatos - Ciclos hielo/deshielo - Lquidos o gases agresivos
a. Introduccin
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a. Introduccin
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Distintas Condiciones de Exposicin del Hormign
Diseo de Mezclas y Materiales
La condicin de uso a la que estar expuesto el hormign determina
el diseo de la mezcla, los componentes (tipo cemento, tipos de
aditivos, ridos), la forma de colocacin y las posibles
protecciones.
a. Introduccin
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Exposicin de estructuras en ambiente marino
a. Introduccin
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Las estructuras martimas se ven expuestas a una serie de
condiciones, especialmente agresivas, que afectan su durabilidad
durante su vida til. El mayor problema lo constituyen las sales
solubles presentes en el agua de mar. Cloruros Sulfatos Tambin se
ven afectados por procesos abrasivos, impacto y avance de la
carbonatacin. En algunas zonas tambin existen efectos por los
ciclos hielo-deshielo.
a. Introduccin
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Exposicin de estructuras en ambiente marino a. Introduccin
22 Informes de la Construccin, Vol. 38 n. 388, marzo/abril,
1987
en el aspecto micro-climtico. Habra, pues, que con-siderar que
se trata de ambientes donde puede haber elevadas HR pero donde no
hay niveles de cloruros apreciables.
Ambiente marino
La durabilidad del hormign en ambiente marino es de especial
inters; por un lado, porque mares y ocanos ocupan el 80% del globo
y buena parte de las activi-dades humanas se han ubicado en zonas
costeras, siendo sta una dinmica creciente, y por otro porque el
hormign es el material ms durable y econmico en el ambiente que nos
ocupa (18).
La agresividad del ambiente marino se debe en parte al
incremento de humedad que puede generar y, en par-ticular, a las
sales que lleva disueltas el agua de mar, cuyas concentraciones
inicas medias correspondien-tes a las sales ms frecuentes, se
muestran en la figu-ra 9 (10). De entre estas sales, destaca el ion
cloruro, responsable del mayor nmero de casos que se cono-cen de
corrosin de las armaduras (18).
Nombre del ion
Cloruro Sodio Sufato Magnesio Calcio Potasio otros TOTAL
Abreviatura quinnica
C1" Na* So Mg** Ca** K"
Concentracin / en peso
19.35 10.76 2.71 1.29 0.41 0.39 0.23
35.U
Fig. 9.Concentraciones inicas habituales en el agua de mar.
La experiencia ha demostrado que los procesos indi-vidualizados
de deterioro tienden a especializarse en las diferentes partes de
la estructura, tal y como mues-tra la figura 10 (18), pudiendo
establecerse diferentes tipos de exposicin (2):
a) Zona atmosfrica, en la que la estructura recibe, an a pesar
de no estar en contacto con el agua, las sa-les. El nivel de
cloruros depende de la distancia al mar y de la altura, sin olvidar
la velocidad y direc-cin de los vientos y otros condicionantes
geogr-ficos.
b) Zona de salpicaduras, en la que se produce una ac-cin directa
del agua de mar, a causa del oleaje y de las salpicaduras que se
derivan de su impacto sobre determinados obstculos o las propias
cons-trucciones.
c) Zona de oscilacin de las mareas, que es la limita-da por los
niveles mximo y mnimo alcanzados por las mareas y en la que el
hormign puede verse per-manentemente saturado y con una acumulacin
cre-ciente de sales.
d) Zonas sumergidas, o parte de la construccin situa-da por
debajo del nivel de la marea baja y, por tanto, en rgimen de
inmersin permanente.
e) Zona de lecho marino, o parte de la estructura ente-rrada en
el lecho marino.
Hormign Armodura
Fisuracipn debida a ia corrosin del acero Fsuracin debido o los
procesos de hielo - deshielo
PYoceso fsico de abrasin debido a la occin del oleaje, de la
arena _ de IG grava y del hielo flotante
Descomposicin qumica de! cemento hidratado
Modelo de descomposicin qumica 1. Ataque del CO2 2. Ataque del
ION Mg 3. Ataque de los sulfates
G^A ^ rF^i^s^TK^
Fig. 10.Procesos de deterioro del hormign en ambiente
marino.
RIESGO DE CORROSIN' Fig. 11.Tipos de exposicin marina y variacin
del riesgo de corrosin de las armaduras.
Consejo Superior de Investigaciones Cientficas Licencia Creative
Commons 3.0 Espaa (by-nc)
http://informesdelaconstruccion.revistas.csic.es16
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Exposicin de estructuras en ambiente marino a. Introduccin
22 Informes de la Construccin, Vol. 38 n. 388, marzo/abril,
1987
en el aspecto micro-climtico. Habra, pues, que con-siderar que
se trata de ambientes donde puede haber elevadas HR pero donde no
hay niveles de cloruros apreciables.
Ambiente marino
La durabilidad del hormign en ambiente marino es de especial
inters; por un lado, porque mares y ocanos ocupan el 80% del globo
y buena parte de las activi-dades humanas se han ubicado en zonas
costeras, siendo sta una dinmica creciente, y por otro porque el
hormign es el material ms durable y econmico en el ambiente que nos
ocupa (18).
La agresividad del ambiente marino se debe en parte al
incremento de humedad que puede generar y, en par-ticular, a las
sales que lleva disueltas el agua de mar, cuyas concentraciones
inicas medias correspondien-tes a las sales ms frecuentes, se
muestran en la figu-ra 9 (10). De entre estas sales, destaca el ion
cloruro, responsable del mayor nmero de casos que se cono-cen de
corrosin de las armaduras (18).
Nombre del ion
Cloruro Sodio Sufato Magnesio Calcio Potasio otros TOTAL
Abreviatura quinnica
C1" Na* So Mg** Ca** K"
Concentracin / en peso
19.35 10.76 2.71 1.29 0.41 0.39 0.23
35.U
Fig. 9.Concentraciones inicas habituales en el agua de mar.
La experiencia ha demostrado que los procesos indi-vidualizados
de deterioro tienden a especializarse en las diferentes partes de
la estructura, tal y como mues-tra la figura 10 (18), pudiendo
establecerse diferentes tipos de exposicin (2):
a) Zona atmosfrica, en la que la estructura recibe, an a pesar
de no estar en contacto con el agua, las sa-les. El nivel de
cloruros depende de la distancia al mar y de la altura, sin olvidar
la velocidad y direc-cin de los vientos y otros condicionantes
geogr-ficos.
b) Zona de salpicaduras, en la que se produce una ac-cin directa
del agua de mar, a causa del oleaje y de las salpicaduras que se
derivan de su impacto sobre determinados obstculos o las propias
cons-trucciones.
c) Zona de oscilacin de las mareas, que es la limita-da por los
niveles mximo y mnimo alcanzados por las mareas y en la que el
hormign puede verse per-manentemente saturado y con una acumulacin
cre-ciente de sales.
d) Zonas sumergidas, o parte de la construccin situa-da por
debajo del nivel de la marea baja y, por tanto, en rgimen de
inmersin permanente.
e) Zona de lecho marino, o parte de la estructura ente-rrada en
el lecho marino.
Hormign Armodura
Fisuracipn debida a ia corrosin del acero Fsuracin debido o los
procesos de hielo - deshielo
PYoceso fsico de abrasin debido a la occin del oleaje, de la
arena _ de IG grava y del hielo flotante
Descomposicin qumica de! cemento hidratado
Modelo de descomposicin qumica 1. Ataque del CO2 2. Ataque del
ION Mg 3. Ataque de los sulfates
G^A ^ rF^i^s^TK^
Fig. 10.Procesos de deterioro del hormign en ambiente
marino.
RIESGO DE CORROSIN' Fig. 11.Tipos de exposicin marina y variacin
del riesgo de corrosin de las armaduras.
Consejo Superior de Investigaciones Cientficas Licencia Creative
Commons 3.0 Espaa (by-nc)
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Zona atmosfrica: la estructura recibe sales a travs del aire
salino y de la niebla. El nivel de cloruros es variable segn su
distancia al mar, altura y direccin de vientos.
Zona de salpicaduras (splash): recibe la accin directa del agua
de mar por oleaje e impacto sobre las estructuras.
Zona de oscilacin de mareas: limitada por los niveles mnimos y
mximos de las mareas en que el hormign est permanentemente saturado
y con acumulacin creciente de sales.
Zona sumergida: se encuentra por debajo de la marea baja y est
permanentemente saturada.
a. Introduccin Zonas de exposicin
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a. Introduccin Zonas de exposicin
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PROCESOS DE DEGRADACIN: Agua de mar
EFECTOS DEL ATAQUE POR AGUA DE MAR
PROCESOS DE DEGRADACIN: Agua de mar
EFECTOS DEL ATAQUE POR AGUA DE MAR
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Especificaciones por prescripcin. En stas se tiende a
definir,
acotar y detallar todos y cada uno de los componentes del
hormign proponiendo dosificaciones con las cuales se espera tener
ciertos resultados. No siempre se obtiene lo que se quiere.
Especificaciones por comportamiento. En stas se definen los
resultados finales que se esperan y se deja en libertad de
lograrlos de manera que sea ms eficiente, respaldando stos mediante
estudios previos serios y acabados y por controles al producto
final.
a. Introduccin Tipos de Especificaciones Tcnicas
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Caractersticas propias de las obras portuarias
a. Introduccin Las obras portuarias se construyen y desarrollan
su vida til en
un ambiente especialmente agresivo debido a la presencia de
sales solubles existentes en el agua de mar que penetran en las
estructuras, en un ambiente de humedad propio de la costa, saturado
en sales.
El factor ms determinante es la presencia de cloruros, los
cuales en presencia de humedad y oxgeno despasivan el acero el cual
entra en proceso de corrosin, generando productos expansivos de
rompen el hormign. Una vez iniciada la corrosin, las barras pierden
espesor y disminuyen la capacidad estructural de los elementos.
Es tambin importante el efecto de la carbonatacin, ya que cambia
el PH del hormign y despasiva tambin el acero.
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b. Estado del arte
Anlisis de Normativa chilena e internacional
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b. Estado del arte Norma chilena NCh170.Of1985.
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b. Estado del arte Norma chilena NCh170 Anexo G
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b. Estado del arte Norma chilena NCh170 Anexo G
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b. Estado del arte
Cdigo ACI 318 (NCh430) Sulfatos Cloruros
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b. Estado del arte
Cdigo ACI 318 (NCh430) Sulfatos
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b. Estado del arte
Cdigo ACI 318 (NCh430) Cloruros
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b. Estado del arte Cdigo ACI 357
357R-4 ACI COMMITTEE REPORT
2.7.2- Marine aggregates may be used when conformingto ASTM C 33
provided that they have been washed by freshwater so that the total
chloride and sulfate content of the con-crete mix does not exceed
the limits defined in Section 2.8.6.
2.8-Concrete2.8.1- Recommended water-cement ratios and
minimum
28-day compressive strengths of concrete for the three ex-posure
zones are given in Table 2.1.
2.8.2- Measures to minimize cracking in thin sectionsand to
prevent excessive thermal stresses in mass concrete arenecessary if
more than 700 pounds of cement per cubic yardof concrete are used
(415 kg per cubic meter). A minimumcement content of 600 pounds per
cubic yard (356 kg percubic meter) is recommended to obtain high
quality paste ad-jacent to the reinforcement for corrosion
protection.
2.8.3- The rise of temperature in concrete because of ce-ment
heat of hydration requires strict control to prevent
steeptemperature stress gradients and possible thermal cracking
ofthe concrete on subsequent cooling. Reducing the tem-perature
rise may be difficult in the rich mixes and thick sec-tions
required in concrete sea structures.
The control of concrete temperatures includes selection
ofcements which have low heat of hydration, reduced rates
ofplacement, precooling of aggregates, the use of ice to
replacesome or all of the mixing water and liquid nitrogen
cooling,as described in ACI 207.4R. Pozzolans may be used to
re-place a portion of the cement to lower the heat of
hydration.
2.8.4- When freeze-thaw durability is required, the con-crete
should contain entrained air as recommended by Table1.4.3 of ACI
201.2R. Air entrainment is the most effectivemeans of providing
freeze-thaw resistance to the cementpaste. Conventional guidelines,
such as those contained inTable 1.4.3 generally apply to
unsaturated concrete. Whereconcrete is exposed to frost action in a
marine environment,care must be taken to insure that critical water
absorptiondoes not occur. Using a rich, air-entrained mix of low
water-cement ratio, a pozzolan and an extended curing period arethe
most effective means of producing a concrete of low per-meability,
which is essential in such an environment. Light-weight aggregates
behave differently from normal weight ag-gregates. The pores in
lightweight aggregate particles arelarge and less likely to fill by
capillary action than normalweight aggregates. However, care must
be taken to preventexcessive moisture absorption in lightweight
aggregates priorto mixing. Such absorption can result in critical
saturationlevels if sufficient curing and drying do not take place
beforethe structure is subjected to severe exposures. High
strengthlightweight aggregates with sealed surfaces are effective
inlimiting water absorption.
2.8.5- Where severe surface degradation of the concreteis
expected to occur, the minimum specified concretestrength should be
6000 psi (42 MPa). Additional protectioncan be achieved by using
concrete aggregates having equal orhigher hardness than the
abrading material or by the provi-sion of suitable coatings or
surface treatments.
2.8.6- No chlorides should intentionally be added. Totalwater
soluble chloride ion (Cl-) content of the concrete priorto exposure
should not exceed 0.10 percent by weight of thecement for normal
reinforced concrete and 0.06 percent by
weight of cement for prestressed concrete. A chloride ion(Cl-)
content of up to 0.15 percent may be acceptable in rein-forced
concrete but should only be used after evaluation ofthe potential
for corrosion of the specific structure under thegiven
environmental conditions.
2.8.7- Structural lightweight concrete should conform toACI
213R. Where it will be exposed to a freeze-thaw en-vironment, it
should be air entrained, and additional meas-ures contained in
Section 2.8.4 should be followed.
TABLE 2.1--WATER-CEMENT RATIOSAND COMPRESSIVE STRENGTHS FOR
THREE EXPOSURE ZONES
2.9-Admixtures2.9.1- Admixtures should conform to Section 3.6 of
ACI
318. Limits given in this section for calcium chloride shouldnot
increase the total limits recommended for concrete asoutlined in
Section 2.8.6 of this report. When two ormore admixtures are used,
their compatibility should bedocumented.2.10-Reinforcing and
prestressing steel
2.10.1- Reinforcing and prestressing steel should con-form to
Section 3.5 of ACI 318. Low temperature or cold cli-mate
applications may require the use of special reinforcingand
prestressing steel and assemblages to achieve adequateductility. To
facilitate future repairs that might be necessary,only weldable
reinforcement should be used in the splashzone and other areas
susceptible to physical damage. Welda-ble reinforcement should
conform to the chemical composi-tion of ASTM
A706.2.11-Post-tensioning ducts
2.11.1- Post-tensioning ducts should conform to Section18.15 of
ACI 318.
2.11.2- Post-tensioning ducts should be semi-rigid andwatertight
and have at least 1 mm of wall thickness. Ferrousmetal ducts or
galvanized metal ducts passivated by a chro-mate wash may be used.
Plastic ducts are not recommended.
2.11.3- Bends in ducts should be preformed as necessary.Joints
in ducts should be bell and spigot with the ends cut bysawing so as
to be free from burrs and dents.
Joint sleeves should fit snugly and be taped with water-proofing
tape. Splices should preferably be staggered butwhere this is
impracticable, adequate space should be pro-vided to insure that
the concrete can be consolidated aroundeach splice.
2.11.4- If flexible metal ducts must be used in specialareas of
congestion, etc., they should have a mandrel insertedduring
concrete placement. Bars for supporting and holdingdown such ducts
should have a curved bearing plate againstthe duct to prevent local
crushing.
FIXED OFFSHORE CONCRETE STRUCTURES 357R-5
2.12-Grout2.12.l- Grout for bonded tendons should conform to
Sec-
tion 18.16 of ACI 318 and to applicable sections of this
report.Suitable procedures and/or admixtures should be used to
pre-vent pockets caused by bleeding when grouting of
verticaltendons or tendons with substantial vertical
components.
2.12.2- Recommendations for mixing water outlined inSection 2.6
also apply to grout mixes.
2.12.3- Admixtures may be used only after sufficienttesting to
indicate their use would be beneficial and that theyare essentially
free of chlorides, or any other material whichhas been shown to be
detrimental to the steel or grout.2.13-Concrete cover of
reinforcement
2.13.l- Recommended nominal concrete covers for rein-forcement
in heavy concrete walls, 20 in. (50 cm) thick orgreater are shown
in Table 2.2.
Concrete covers of reinforcement should not be signifi-cantly
greater than prescribed minimums to restrict the widthof possible
cracks. This would be more critical for thosemembers in
flexure.
Table 2.2-RECOMMENDED NOMINALCONCRETE COVER OVER
REINFORCEMENT
Zone
Cover over Cover overreinforcing post-tensioning
steel ducts
Atmospheric zone not 2 in. (50 mm) 3 in. (75 mm)subject to salt
spray
Splash and atmospheric 2.5 in. (65 mm) 3.5 in. (90 mm)zone
subject to saltspray
Submerged 2 in. (50 mm) 3 in. (75 mm)
Cover of stirrups M in. (13 mm)less than those listed above
2.13.2- If possible, structures with sections less than 20in.
(50 cm) thick should have covers as recommended in Sec-tion 2.13.1,
but when clearances are restricted the followingmay be used with
caution. Cover shall he determined by themaximum requirement listed
below:
(a) 1.5 times the nominal maximum size of aggregate, or(b) 1.5
times the maximum diameter of reinforcement, or(c) 3/ in. (20 mm)
cover to all steel including stirrups.Note: Tendons and
post-tensioning ducts should have 0.5
in. (13 mm) added to the above.2.14-Details of reinforcement
2.14.1- Reinforcement details should conform to Chap-ters 7 and
12 of ACI 318.
2.14.2- Special consideration should be given to the de-tailing
of splices used in areas subjected to significant cyclicloading.
Staggered mechanical and welded splices shouldpreferably be used in
these instances. Lap splices, if used,should conform to the
provisions of ACI 318. In general,noncontact lap splices should be
avoided unless adequate jus-tification can be developed for their
use. Mechanical devices
for positive connections should comply with the section ofACI
318 dealing with mechanical connections. Weldedsplices may be used
where reinforcing steel meets the chem-ical requirements of ASTM
A706.
2.14.3- Mechanical or welded connections should beused for
load-carrying reinforcing bar splices located in re-gions of
multiaxial tension, or uniaxial tension that is normalto the bar
splices.
2.15-Physical and chemical damage2.15.1- In those areas of the
structure exposed to possible
collision with ships, flotsam, or ice, additional steel
rein-forcement should be used for cracking control and
concreteconfinement. Particular consideration should be given to
theuse of additional tension reinforcement on both faces and
ad-ditional shear reinforcement (transverse to walls) to
reinforcefor punching shear. Unstressed tendons and unbonded
ten-dons are two techniques which can be used to increase theenergy
absorption of the section in the post-elastic stage.
2.15.2- The possibility of materials and equipment beingdropped
during handling on and off the platform should beconsidered. Impact
resisting capacity may be provided asmentioned in Section 2.15.1.
In addition, protective cover-ings may be installed such as steel
or concrete grids and en-ergy-absorbing materials such as
lightweight concrete.
2.15.3- A polymer or other special coating may be usedto control
ice abrasion or adfreeze between an ice feature anda structure.
Compatibility between a coating and the underly-ing concrete should
be assessed to preclude problems withbond development, coating
delamination caused by air ormoisture migration, and freeze-thaw
effects.
2.15.4- Exposed steel work and its anchor systemsshould be
electrically isolated from the primary steel rein-forcement by at
least 2 in. (50 mm) of concrete. The use ofcathodic protection
systems is generally not required for rein-forcing steel and
prestressing steel embedded in concrete.
2.15.5- Exposed steel work should normally be paintedor coated
to reduce corrosion. Particular care should be takento insure
against corrosion on the edges and horizontal sur-faces. Epoxy
coatings are normally used for protection of car-bon steel plates
and fittings. Cathodic protection systems forexternally exposed
steel should be of the sacrificial anodetype. Impressed current
should not be used unless positivecontrols are instituted to
prevent embrittlement of the rein-forcing and prestressing
steel.2.16-Protection of prestressed anchorages
2.16.1- The anchorages of prestressed tendons should beprotected
from direct contact with seawater, which could leadto corrosion. A
desirable method is to use recessed pocketsso that the steel
anchorage and tendon ends may be protectedby concrete or grout fill
in the pocket. The pocket surfaceshould be thoroughly cleaned and
the exposed steel shouldbe coated with bonding epoxy just prior to
placing the con-crete or grout fill. Particular care should be
taken to preventshrinkage and the formation of bleed lenses.
Alternative de-tails are acceptable provided they are designed to
limit thepenetration of seawater and oxygen to the same degree as
thatprovided to the tendon proper.
357R-4 ACI COMMITTEE REPORT
2.7.2- Marine aggregates may be used when conformingto ASTM C 33
provided that they have been washed by freshwater so that the total
chloride and sulfate content of the con-crete mix does not exceed
the limits defined in Section 2.8.6.
2.8-Concrete2.8.1- Recommended water-cement ratios and
minimum
28-day compressive strengths of concrete for the three ex-posure
zones are given in Table 2.1.
2.8.2- Measures to minimize cracking in thin sectionsand to
prevent excessive thermal stresses in mass concrete arenecessary if
more than 700 pounds of cement per cubic yardof concrete are used
(415 kg per cubic meter). A minimumcement content of 600 pounds per
cubic yard (356 kg percubic meter) is recommended to obtain high
quality paste ad-jacent to the reinforcement for corrosion
protection.
2.8.3- The rise of temperature in concrete because of ce-ment
heat of hydration requires strict control to prevent
steeptemperature stress gradients and possible thermal cracking
ofthe concrete on subsequent cooling. Reducing the tem-perature
rise may be difficult in the rich mixes and thick sec-tions
required in concrete sea structures.
The control of concrete temperatures includes selection
ofcements which have low heat of hydration, reduced rates
ofplacement, precooling of aggregates, the use of ice to
replacesome or all of the mixing water and liquid nitrogen
cooling,as described in ACI 207.4R. Pozzolans may be used to
re-place a portion of the cement to lower the heat of
hydration.
2.8.4- When freeze-thaw durability is required, the con-crete
should contain entrained air as recommended by Table1.4.3 of ACI
201.2R. Air entrainment is the most effectivemeans of providing
freeze-thaw resistance to the cementpaste. Conventional guidelines,
such as those contained inTable 1.4.3 generally apply to
unsaturated concrete. Whereconcrete is exposed to frost action in a
marine environment,care must be taken to insure that critical water
absorptiondoes not occur. Using a rich, air-entrained mix of low
water-cement ratio, a pozzolan and an extended curing period arethe
most effective means of producing a concrete of low per-meability,
which is essential in such an environment. Light-weight aggregates
behave differently from normal weight ag-gregates. The pores in
lightweight aggregate particles arelarge and less likely to fill by
capillary action than normalweight aggregates. However, care must
be taken to preventexcessive moisture absorption in lightweight
aggregates priorto mixing. Such absorption can result in critical
saturationlevels if sufficient curing and drying do not take place
beforethe structure is subjected to severe exposures. High
strengthlightweight aggregates with sealed surfaces are effective
inlimiting water absorption.
2.8.5- Where severe surface degradation of the concreteis
expected to occur, the minimum specified concretestrength should be
6000 psi (42 MPa). Additional protectioncan be achieved by using
concrete aggregates having equal orhigher hardness than the
abrading material or by the provi-sion of suitable coatings or
surface treatments.
2.8.6- No chlorides should intentionally be added. Totalwater
soluble chloride ion (Cl-) content of the concrete priorto exposure
should not exceed 0.10 percent by weight of thecement for normal
reinforced concrete and 0.06 percent by
weight of cement for prestressed concrete. A chloride ion(Cl-)
content of up to 0.15 percent may be acceptable in rein-forced
concrete but should only be used after evaluation ofthe potential
for corrosion of the specific structure under thegiven
environmental conditions.
2.8.7- Structural lightweight concrete should conform toACI
213R. Where it will be exposed to a freeze-thaw en-vironment, it
should be air entrained, and additional meas-ures contained in
Section 2.8.4 should be followed.
TABLE 2.1--WATER-CEMENT RATIOSAND COMPRESSIVE STRENGTHS FOR
THREE EXPOSURE ZONES
2.9-Admixtures2.9.1- Admixtures should conform to Section 3.6 of
ACI
318. Limits given in this section for calcium chloride shouldnot
increase the total limits recommended for concrete asoutlined in
Section 2.8.6 of this report. When two ormore admixtures are used,
their compatibility should bedocumented.2.10-Reinforcing and
prestressing steel
2.10.1- Reinforcing and prestressing steel should con-form to
Section 3.5 of ACI 318. Low temperature or cold cli-mate
applications may require the use of special reinforcingand
prestressing steel and assemblages to achieve adequateductility. To
facilitate future repairs that might be necessary,only weldable
reinforcement should be used in the splashzone and other areas
susceptible to physical damage. Welda-ble reinforcement should
conform to the chemical composi-tion of ASTM
A706.2.11-Post-tensioning ducts
2.11.1- Post-tensioning ducts should conform to Section18.15 of
ACI 318.
2.11.2- Post-tensioning ducts should be semi-rigid andwatertight
and have at least 1 mm of wall thickness. Ferrousmetal ducts or
galvanized metal ducts passivated by a chro-mate wash may be used.
Plastic ducts are not recommended.
2.11.3- Bends in ducts should be preformed as necessary.Joints
in ducts should be bell and spigot with the ends cut bysawing so as
to be free from burrs and dents.
Joint sleeves should fit snugly and be taped with water-proofing
tape. Splices should preferably be staggered butwhere this is
impracticable, adequate space should be pro-vided to insure that
the concrete can be consolidated aroundeach splice.
2.11.4- If flexible metal ducts must be used in specialareas of
congestion, etc., they should have a mandrel insertedduring
concrete placement. Bars for supporting and holdingdown such ducts
should have a curved bearing plate againstthe duct to prevent local
crushing.
357R-4 ACI COMMITTEE REPORT
2.7.2- Marine aggregates may be used when conformingto ASTM C 33
provided that they have been washed by freshwater so that the total
chloride and sulfate content of the con-crete mix does not exceed
the limits defined in Section 2.8.6.
2.8-Concrete2.8.1- Recommended water-cement ratios and
minimum
28-day compressive strengths of concrete for the three ex-posure
zones are given in Table 2.1.
2.8.2- Measures to minimize cracking in thin sectionsand to
prevent excessive thermal stresses in mass concrete arenecessary if
more than 700 pounds of cement per cubic yardof concrete are used
(415 kg per cubic meter). A minimumcement content of 600 pounds per
cubic yard (356 kg percubic meter) is recommended to obtain high
quality paste ad-jacent to the reinforcement for corrosion
protection.
2.8.3- The rise of temperature in concrete because of ce-ment
heat of hydration requires strict control to prevent
steeptemperature stress gradients and possible thermal cracking
ofthe concrete on subsequent cooling. Reducing the tem-perature
rise may be difficult in the rich mixes and thick sec-tions
required in concrete sea structures.
The control of concrete temperatures includes selection
ofcements which have low heat of hydration, reduced rates
ofplacement, precooling of aggregates, the use of ice to
replacesome or all of the mixing water and liquid nitrogen
cooling,as described in ACI 207.4R. Pozzolans may be used to
re-place a portion of the cement to lower the heat of
hydration.
2.8.4- When freeze-thaw durability is required, the con-crete
should contain entrained air as recommended by Table1.4.3 of ACI
201.2R. Air entrainment is the most effectivemeans of providing
freeze-thaw resistance to the cementpaste. Conventional guidelines,
such as those contained inTable 1.4.3 generally apply to
unsaturated concrete. Whereconcrete is exposed to frost action in a
marine environment,care must be taken to insure that critical water
absorptiondoes not occur. Using a rich, air-entrained mix of low
water-cement ratio, a pozzolan and an extended curing period arethe
most effective means of producing a concrete of low per-meability,
which is essential in such an environment. Light-weight aggregates
behave differently from normal weight ag-gregates. The pores in
lightweight aggregate particles arelarge and less likely to fill by
capillary action than normalweight aggregates. However, care must
be taken to preventexcessive moisture absorption in lightweight
aggregates priorto mixing. Such absorption can result in critical
saturationlevels if sufficient curing and drying do not take place
beforethe structure is subjected to severe exposures. High
strengthlightweight aggregates with sealed surfaces are effective
inlimiting water absorption.
2.8.5- Where severe surface degradation of the concreteis
expected to occur, the minimum specified concretestrength should be
6000 psi (42 MPa). Additional protectioncan be achieved by using
concrete aggregates having equal orhigher hardness than the
abrading material or by the provi-sion of suitable coatings or
surface treatments.
2.8.6- No chlorides should intentionally be added. Totalwater
soluble chloride ion (Cl-) content of the concrete priorto exposure
should not exceed 0.10 percent by weight of thecement for normal
reinforced concrete and 0.06 percent by
weight of cement for prestressed concrete. A chloride ion(Cl-)
content of up to 0.15 percent may be acceptable in rein-forced
concrete but should only be used after evaluation ofthe potential
for corrosion of the specific structure under thegiven
environmental conditions.
2.8.7- Structural lightweight concrete should conform toACI
213R. Where it will be exposed to a freeze-thaw en-vironment, it
should be air entrained, and additional meas-ures contained in
Section 2.8.4 should be followed.
TABLE 2.1--WATER-CEMENT RATIOSAND COMPRESSIVE STRENGTHS FOR
THREE EXPOSURE ZONES
2.9-Admixtures2.9.1- Admixtures should conform to Section 3.6 of
ACI
318. Limits given in this section for calcium chloride shouldnot
increase the total limits recommended for concrete asoutlined in
Section 2.8.6 of this report. When two ormore admixtures are used,
their compatibility should bedocumented.2.10-Reinforcing and
prestressing steel
2.10.1- Reinforcing and prestressing steel should con-form to
Section 3.5 of ACI 318. Low temperature or cold cli-mate
applications may require the use of special reinforcingand
prestressing steel and assemblages to achieve adequateductility. To
facilitate future repairs that might be necessary,only weldable
reinforcement should be used in the splashzone and other areas
susceptible to physical damage. Welda-ble reinforcement should
conform to the chemical composi-tion of ASTM
A706.2.11-Post-tensioning ducts
2.11.1- Post-tensioning ducts should conform to Section18.15 of
ACI 318.
2.11.2- Post-tensioning ducts should be semi-rigid andwatertight
and have at least 1 mm of wall thickness. Ferrousmetal ducts or
galvanized metal ducts passivated by a chro-mate wash may be used.
Plastic ducts are not recommended.
2.11.3- Bends in ducts should be preformed as necessary.Joints
in ducts should be bell and spigot with the ends cut bysawing so as
to be free from burrs and dents.
Joint sleeves should fit snugly and be taped with water-proofing
tape. Splices should preferably be staggered butwhere this is
impracticable, adequate space should be pro-vided to insure that
the concrete can be consolidated aroundeach splice.
2.11.4- If flexible metal ducts must be used in specialareas of
congestion, etc., they should have a mandrel insertedduring
concrete placement. Bars for supporting and holdingdown such ducts
should have a curved bearing plate againstthe duct to prevent local
crushing.
FIXED OFFSHORE CONCRETE STRUCTURES 357R-3
sary to actively control conditions to insure an adequate
mar-gin of safety for the structure, instrumentation should
beprovided to monitor the conditions. Such conditions mightbe fluid
level, temperature, soil pore water pressure, etc.
Adequate instrumentation should be provided to insureproper
installation of the structure.
When new concepts and procedures that extend the fron-tier of
engineering knowledge are used, instrumentationshould be provided
to enable measured behavior to be com-pared with predicted
behavior.
1.3-Auxiliary systems and interfacesSpecial consideration should
be given to planning and de-
signing auxiliary nonstructural systems and their interfaceswith
a concrete structure.
Auxiliary mechanical, electrical, hydraulic, and controlsystems
have functional requirements that may have a signifi-cant impact on
structural design. Special auxiliary systemsmay be required for
different design phases of an installation,including construction,
transportation, installation, opera-tion, and relocation.
Unique operating characteristics of auxiliary systemsshould be
considered in assessing structural load conditions.Suitable
provisions should be made for embedments andpenetrations to
accommodate auxiliary equipment.
CHAPTER 2-MATERIALS AND DURABILITY2.1-General
All materials to be used in the construction of offshoreconcrete
structures should have documentation demonstrat-ing previous
satisfactory performance under similar site con-ditions or have
sufficient backup test data.
2.2-Testing2.2.1- Tests of concrete and other materials should
be per-
formed in accordance with applicable standards of ASTMlisted in
the section of ACI 318 on standards cited. Completerecords of these
tests should be available for inspection dur-ing construction and
should be preserved by the owner duringthe life of the
structure.
2.2.2- Testing in addition to that normally carried out
forconcrete Structures, such as splitting or flexural tensile
tests,may be necessary to determine compliance with specified
du-rability and quality specifications.
2.3-Quality control2.3.1- Quality control during construction of
the con-
crete structure is normally the responsibility of the
contrac-tor. Supervision of quality control should be the
responsibil-ity of an experienced engineer who should report
directly totop management of the construction firm. The owner
mayprovide quality assurance verification independent of
theconstruction firm.
2.4-Durability2.4.1- Proper ingredients, mix proportioning,
construc-
tion procedures, and quality control should produce dur-able
concrete. Hard, dense aggregates combined with a lowwater-cement
ratio and moist curing have produced concretestructures which have
remained in satisfactory condition for40 years or more in a marine
environment.
2.4.2- The three zones of exposure to be considered onan
offshore structure are:
(a) The submerged zone, which can be assumed to be con-tinuously
covered by the sea water.
(b) The splash zone, the area subject to continuous wettingand
drying.
(c) The atmospheric zone, the portion of the structureabove the
splash zone.
2.4.3- Items to be considered in the three zones are:(a)
Submerged zone-Chemical deterioration of the con-
crete, corrosion of the reinforcement and hardware, andabrasion
of the concrete.
(b) Splash zone-Freeze-thaw durability, corrosion of
thereinforcement and hardware and the chemical deteriorationof the
concrete, and abrasion due to ice.
(c) Atmospheric zone-Freeze-thaw durability, corrosionof
reinforcement and hardware, and fire hazards.
2.5-Cement2.5.1- Cement should conform to Type I, II, or III
port-
land cements in accordance with ASTM C 150 and blendedhydraulic
cements which meet the requirements of ASTM C595.
2.5.2- The tricalcium aluminate content (C3A) shouldnot be less
than 4 percent to provide protection for the rein-forcement. Based
on past experience, the maximum tri-calcium aluminate content
should generally be 10 percent toobtain concrete that is resistant
to sulfate attack. The abovelimits apply to all exposure zones.
2.5.3- Where oil storage is expected, a reduction in theamount
of tricalcium aluminate (C3A) in the cement may benecessary if the
oil contains soluble sulfates. If soluble sul-fides are present in
the oil, coatings or high cement contentsshould be considered.
2.5.4- Pozzolans conforming to ASTM C 618 may beused provided
that tests are made using actual job materials toascertain the
relative advantages and disadvantages of theproposed mix with
special consideration given to sulfate re-sistance, workability of
the mix, and corrosion protectionprovided to the reinforcement.
2.6-Mixing water2.6.1- Water used in mixing concrete should be
clean
and free from oils, acids, alkalis, salts, organic materials,
orother substances that may be deleterious to concrete or
rein-forcement. Mixing water should not contain excessiveamounts of
chloride ion. (See Section 2.8.6).
2.7-Aggregates2.7.1- Aggregates should conform to the
requirements of
ASTM C 33 or ASTM C 330 wherever applicable.
29
-
b. Estado del arte BS-6349-2010
BS
6349-1:2000
B
SI 24 Ju
ly 2003205
Section 7
Table 22 Limiting values for composition and properties of
concrete classes with normal weight aggregates of 20 mm maximumsize
exposed to risk of corrosion of reinforcement induced by UK
seawater conditions for a required design
workinglifeof 50 years
Exposure class and exposure conditions in
the UK
Airborne salt Frequently wetted Infequently wetted. Upper tidal,
splash/spray, dry internal faces of submerged structures
Submerged Lower tidal, back-filled
XS1 XS2 XS2/XS3 XS3a
Min. strength cylinder/cube (Mpa)b,c C35/45 C30/37 C25/30
In accordance with Table 24 except as below
In accordance with Table 24 except as below
C40/50 C30/37 C25/30 Permitted cements BS 12d
BS 4027
BS 146
Portland slag cement
BS 6588
Portland fly ash cement A
BS 146
Blastfurnace cement
BS 6588
Portland fly ash cement B
BS 4246
BS 6610
BS 12d
BS 4027
BS 146
Portland slag cement
BS 6588
Portland fly ash cement A
BS 146
Blastfurnace cement
BS 6588
Portland fly ash cement B
BS 4246
BS 6610
Permitted proportions for combinations (% by mass)
ggbs X35 35
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b. Estado del arte BS-6349-2010
BS
6349-1:2000
206
BS
I 24 July 2003
Section 7
Table 23 Limiting values for composition and properties of
concrete classes with normal weight aggregates of 20 mm maximum
size exposed to risk of corrosion of reinforcement induced by UK
seawater conditions for a required design working
lifeof 100 years
Exposure class and exposure conditions in
the UK
Airborne salt Frequently wetted Infrequently wetted. Upper
tidal, splash/spray, dry internal faces of submerged structures
Submerged Lower tidal, back filled
XS1 XS2 XS2/XS3 XS3a
Min. strength class cylinder/cube(Mpa)b,c
C40/50 C35/45 C30/37
In accordance with Table 24 except as below
In accordance with Table 24 except as below
C55/65 C40/50 C 30/37
Permitted cements BS 12d
BS 4027
BS 146
Portland slag cement
BS 6588
Portland fly ash cement A
BS 146
Blastfurnace cement
BS 6588
Portland fly ash cement B
BS 4246
BS 6610
BS 12d
BS 4027
BS 146
Portland slag cement
BS 6588
Portland fly ash cement A
BS 146
Blastfurnace cement
BS 6588
Portland fly ash cement B
BS 4246
BS 6610
Permitted proportions for combinations % by mass
ggbs X35 35
-
b. Estado del arte Technical standars and commentaries for port
and harbour facilities en Japan
32
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b. Estado del arte 54
EH
E/0
8 Instruccin de H
ormign Estructural
Tabla 8.2.2Clases generales de exposicin relativas a la corrosin
de las armaduras
CLASE GENERAL DE EXPOSICINDESCRIPCIN EJEMPLOS
Clase Subclase Designacin Tipo de proceso
No agresiva I Ninguno Interiores de edifi cios, no sometidos a
condensaciones. Elementos de hormign en masa.
Elementos estructurales de edifi cios, incluido los forja-dos,
que estn protegidos de la intemperie.
Normal Humedad alta IIa Corrosin de origen diferente de los
cloruros
Interiores sometidos a humedades relativas medias altas (>
65%) o a condensaciones.
Exteriores en ausencia de cloruros, y expuestos a llu-via en
zonas con precipitacin media anual superior a 600 mm.
Elementos enterrados o sumergidos.
Elementos estructurales en stanos no ventilados. Cimentaciones.
Estribos, pilas y tableros de puentes en zonas, sin im-
permeabilizar con precipitacin media anual superior a 600
mm.
Tableros de puentes impermeabilizados, en zonas con sales de
deshielo y precipitacin media anual superior a 600 mm.
Elementos de hormign, que se encuentren a la intem-perie o en
las cubiertas de edifi cios en zonas con pre-cipitacin media anual
superior a 600 mm.
Forjados en cmara sanitaria, o en interiores en cocinas y baos,
o en cubierta no protegida.
Humedad media IIb Corrosin de origen diferente de los
cloruros
Exteriores en ausencia de cloruros, sometidos a la ac-cin del
agua de lluvia, en zonas con precipitacin media anual inferior a
600 mm.
Elementos estructurales en construcciones exteriores protegidas
de la lluvia.
Tableros y pilas de puentes, en zonas de precipitacin media
anual inferior a 600 mm.
Marina Area IIIa Corrosin por cloruros
Elementos de estructuras marinas, por encima del ni-vel de
pleamar.
Elementos exteriores de estructuras situadas en las proximidades
de la lnea costera (a menos de 5 km).
Elementos estructurales de edifi caciones en las proxi-midades
de la costa.
Puentes en las proximidades de la costa. Zonas areas de diques,
pantalanes y otras obras de
defensa litoral. Instalaciones portuarias.
Sumergida IIIb Corrosin por cloruros
Elementos de estructuras marinas sumergidas perma-nentemente,
por debajo del nivel mnimo de bajamar.
Zonas sumergidas de diques, pantalanes y otras obras de defensa
litoral.
Cimentaciones y zonas sumergidas de pilas de puen-tes en el
mar.
En zona de ca-rrera de mareas y en zonas de salpicaduras
IIIc Corrosin por cloruros
Elementos de estructuras marinas situadas en la zona de
salpicaduras o en zona de carrera de mareas.
Zonas situadas en el recorrido de marea de diques, pantalanes y
otras obras de defensa litoral.
Zonas de pilas de puentes sobre el mar, situadas en el recorrido
de marea.
Con cloruros de origen diferente del medio marino
IV Corrosin por cloruros
Instalaciones no impermeabilizadas en contacto con agua que
presente un contenido elevado de cloruros, no relacionados con el
ambiente marino.
Superfi cies expuestas a sales de deshielo no
imper-meabilizadas.
Piscinas e interiores de los edifi cios que las albergan. Pilas
de pasos superiores o pasarelas en zonas de
nieve. Estaciones de tratamiento de agua.
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EHE-08
33
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b. Estado del arte EHE-08
55
Cap
tulo
2 C
riterios de seguridad y bases de clculo
Tabla 8.2.3.aClases especfi cas de exposicin relativas a otros
procesos de deterioro distintos de la corrosin
CLASE ESPECFICA DE EXPOSICINDESCRIPCIN EJEMPLOS
Clase Subclase Designacin Tipo de proceso
QumicaAgresiva
Dbil Qa Ataque qumico Elementos situados en ambientes con
contenidos de sustancias qumicas capaces de provocar la alteracin
del hormign con velocidad lenta (ver tabla 8.2.3.b).
Instalaciones industriales, con sustancias dbilmente agresivas
segn tabla 8.2.3.b.
Construcciones en proximidades de reas industria-les, con
agresividad dbil segn tabla 8.2.3.b.
Media Qb Ataque qumico Elementos en contacto con agua de mar.
Elementos situados en ambientes con contenidos de
sustancias qumicas capaces de provocar la alteracin del hormign
con velocidad media (ver tabla 8.2.3.b).
Dolos, bloques y otros elementos para diques. Estructuras
marinas, en general. Instalaciones industriales con sustancias de
agresivi-
dad media segn tabla 8.2.3.b. Construcciones en proximidades de
reas industria-
les, con agresividad media segn tabla 8.2.3.b. Instalaciones de
conduccin y tratamiento de aguas
residuales con sustancias de agresividad media se-gn tabla
8.2.3.b.
Fuerte Qc Ataque qumico Elementos situados en ambientes con
contenidos de sustancias qumicas capaces de provocar la alteracin
del hormign con velocidad rpida (ver tabla 8.2.3.b).
Instalaciones industriales, con sustancias de agresi-vidad alta
de acuerdo con tabla 8.2.3.b.
Instalaciones de conduccin y tratamiento de aguas residuales,
con sustancias de agresividad alta de acuerdo con tabla
8.2.3.b.
Construcciones en proximidades de reas industria-les, con
agresividad fuerte segn tabla 8.2.3.b.
Con heladas
Sin sales fundentes
H Ataque hielo-deshielo
Elementos situados en contacto frecuente con agua, o zonas con
humedad relativa media ambiental en in-vierno superior al 75%, y
que tengan una probabilidad anual superior al 50% de alcanzar al
menos una vez temperaturas por debajo de 5 C.
Construcciones en zonas de alta montaa. Estaciones
invernales.
Con sales fundentes
F Ataque por sales fundentes
elementos destinados al trfi co de vehculos o peato-nes en zonas
con ms de 5 nevadas anuales o con valor medio de la temperatura
mnima en los meses de invierno inferior a 0 C.
Tableros de puentes o pasarelas en zonas de alta montaa, en las
que se utilizan sales fundentes.
Erosin E Abrasincavitacin
Elementos sometidos a desgaste superfi cial. Elementos de
estructuras hidrulicas en los que la
cota piezomtrica pueda descender por debajo de la presin de
vapor del agua.
Pilas de puente en cauces muy torrenciales. Elementos de diques,
pantalanes y otras obras de de-
fensa litoral que se encuentren sometidos a fuertes oleajes.
Pavimentos de hormign. Tuberas de alta presin.
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34
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b. Estado del arte EHE-08
Un hormign se considera impermeable si cumple:
35
-
b. Estado del arte Comparacin de normativas - En todas se exige
relacin A/C (0,50; 0,40 ; 0,45) - Las recomendaciones japonesas son
las menos exigentes en
resistencias, relaciones A/C y dosis mnimas de cemento. - Dosis
mnimas de cemento (350 a 400 kg/m3) - En algunas dosis mxima para
limitar fisuracin (400 kg/m3) - Las resistencias normalmente entre
30 MPa y 35 MPa. - Recubrimientos sobre 50 mm, hasta 90 mm - Los
cementos deben estar limitados en el C3A (sulfatos) - Deben ser
moderadamente resistente a los sulfatos (MS) - Se recomienda uso de
adiciones o cementos con stas.
LA IMPERMEABILIDAD ES EL PRINCIPAL FACTOR QUE SE DEBE ASEGURAR
PARA EVITAR LA CORROSIN DEL ACERO
36
-
b. Estado del arte Comparacin Hormign Convencional v/s Hormign
Marino
Propiedad Hormign convencional Hormign Marino
Resistencia Segn clculo estructural Resistencias mnimas
Tipo de cemento Sin exigencias Resistente a los sulfatos. Uso de
adiciones
Relacin A/C Para cumplir resistencia Por durabilidad (0,50 a
0,40)
Dosis mnimas Dosis mximas
Sin restriccin, cumplir resistencias
Por durabilidad Control de fisuramiento
Aditivos Slo plastificante Plastificantes, reductores de alto
rango, incorporador de aire, inhibidores de corrosin, otros
Adiciones Sin exigencias Escoria, cenizas volantes, microslice,
fibras
EL HORMIGN MARINO ES UN HORMIGN ESPECIAL Y DEBE SER CONSIDERADO
COMO TAL DESDE EL DISEO HASTA EL CURADO
37
-
b. Estado del arte Terminologa y tipologa de estructuras marinas
(Gua DOP)
Tipo de estructura Objetivo Funcin
Rompeolas Proteger y abrigar reas de inters Disipar energa del
oleaje y/o reflejarla hacia el mar
Muros costeros Retener el suelo, evitar deslizamientos, proteger
reas terrestres de erosin por olas
Reforzar sectores de borde costeros. Retener suelos ganados al
mar.
Obras de atraque, Amarre y fondeo
Proveer estructura de atraque, amarre y/o ayuda a las maniobras
de atraque de embarcaciones. Adems, proveen facilidades para el
trfico de carga
Transferir las cargas aplicadas desde la estructura principal al
fondo marino.
Ductos Transportar fluidos desde y/o hacia el mar.
Estabilidad en base a la gravedad o bombas.
Pavimentos portuarios
Proveer estructura para el trfico de vehculos, equipos,
materiales y/o pasajeros
Transferir las cargas al suelo de fundacin o subestructura.
Nota: Slo estructuras en que el material es hormign
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-
b. Estado del arte Consideraciones para la construccin segn su
tipo - El diseo y tipo de hormign a usar debe ser definido en
base al tipo de estructura y zona en que es afectado por el agua
de mar.
- Las propiedades y caractersticas de los hormigones pueden
variar si son elementos hormigonados in situ o prefabricados.
- Asimismo, las propiedades de los hormigones colocados por
distintas metodologas varan de acuerdo a dichos requerimientos: Por
ejemplo, hormigones para ser colocados bajo agua son distintos de
los hormigones colocados por procedimientos normales.
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