Abstract
A great deal of information exists on the retraction occurring in pastes, mortars and concrete, twenty-four hours after being mixed; we have very little information, however, concerning the volumetric changes which take place in a shorter period of time, this being mainly due to the difficulties which arise in measuring these volumetric variations. The authors of this experimental work have been concerned with measuring the short-term changes in volume which take place in cement pastes, that is to say, in periods of less than twenty-four hours, although they have taken measurements for periods of up to three days. Experiments have been carried out on microsamples of 10 X 10 X 40 mm manufactured using the pressing method and kept throughout the measuring period in an isothermic non-aggressive atmosphere. Research has been carried out on four types of cement made up of clinkers of different composition and admixtures of pozzolana or scoria for blast furnaces.
Highlights
SUMMARYA great deal of information exists on the retraction occurring in pastes, mortars and concrete, twenty-four hours after being mixed; we have very little information, concerning the volumetric changes which take place in a shorter period of time, this being mainly due to the difficulties which arise in measuring these volumetric variations
Experiments have been carried out on microsamples of 10 X 10 X 40 mm manufactured using the pressing method and kept throughout the measuring period in an isothermic non-aggressive atmosphere
A great deal of information exists on the retraction occurring in pastes
Summary
A great deal of information exists on the retraction occurring in pastes, mortars and concrete, twenty-four hours after being mixed; we have very little information, concerning the volumetric changes which take place in a shorter period of time, this being mainly due to the difficulties which arise in measuring these volumetric variations. Fig. 1.—Efecto de la razón agua/cemento sobre las retracciones vertical y horizontal del hormigón. Análogamente ocurre con la pasta de cemento; sus partículas forman con el agua una suspensión inestable, las que tienden a depositarse por acción de la gravedad. Se produce un descenso de la fase sólida y por ende, un acortamiento vertical, que en el caso del hormigón fresco, perjudica la homogeneidad en el interior. En obras de hormigón armado, las armaduras pueden impedir la sedimentación, originando fisuras entre el hormigón que queda suspendido y el que puede sedimentar libremente [12], produciendo un despegue del hormigón bajo las armaduras
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