Baja calidad constructiva. E. NT .. terraza. Comportamiento bioclimático - Secciones tipo SECCIONES CONSTRUCTIVAS ESCALA A3. La Salle BCN - Arquitectura, Barcelona, Spain. likes · 3 talking about this · were here. La Salle BCN ha formado 15 promociones de arquitectos. This Pin was discovered by i. Discover (and save) your own Pins on Pinterest.
|Author:||Dr. Lawrence Nader|
|Published:||13 April 2014|
|PDF File Size:||21.59 Mb|
|ePub File Size:||42.46 Mb|
|Uploader:||Dr. Lawrence Nader|
Ropeways - Doppelmayr - Newsroom
Due to the great affinity between water and cement, cement particles tend to form flocs that prevent particle dispersion and retain water in their structure. Retained water contributes inefficiently to cement hydration and strength development.
In this sense, SPs secciones constructivas repulsive forces among cement particles that prevent flocculation and promote mobility.
Recent studies secciones constructivas confirmed the influence of secciones constructivas types of SPs on cement hydration and the corresponding affectation of the microstructure of the hardened material [ 3 ].
SP efficiency is defined as the capacity to increase the flow of a mix and its persistence over time. It not only depends on secciones constructivas superplasticizer and cement compositions but also on the manner in which they are mixed mixing capacity, mode of secciones constructivas, mixing time [ 4 ].
Cement characteristics, such as fineness, composition contents of C3A, secciones constructivas sulphate, and alkalisand secciones constructivas of mineral additions contained, are key factors for the interaction with SP [ 56 ].
Moreover, important characteristics of SP include molecular weight and distribution, length of the polymeric chain and, in the case of naphthalene-based admixtures, the nature of the counter-ion included in them [ 26 ].
The anhydrous phases and hydration products of cement do not adsorb the same amount of SP [ 5 ]. The C3A phase displays higher adsorption capacity of admixtures, due to its more positive zeta potential values, than C3S and C2S phases. In the presence of gypsum, admixtures and sulphates compete for adsorption on C3A, with a more favourable reaction with sulphates [ 5 ].
Therefore, more quantity of admixture remains available in the aqueous phase to secciones constructivas a flowing effect on the paste. Thus, indirect influence by the amount of secciones constructivas on the efficiency of the admixture would be revealed.
This is also helpful to explain the differences in the efficiency of admixtures with different cement secciones constructivas. Nowadays, secciones constructivas cement market is dominated by cement types other than Ordinary Portland Cement O. Some of the most common blended cements are Blended Portland Cement Be.
Adding natural pozzolan to cement does not necessarily modify water demand secciones constructivas a given consistency level [ 8 ]. The effectiveness of the different types secciones constructivas water reducers has been previously addressed for the particular case of pozzolan-admixed cement type [ 9 ].
However, in the particular case of polycarboxylic-based SP, this efficiency has been reported to be lower for pozzolanic cements than for limestone or slag blended cements [ 10 ]. In terms of the influence of slag, it has been determined that its interparticle forces are stronger than those of Portland clinker particles secciones constructivas 12 ].
However, the efficiency of SP on cement is increased with slag content, mainly due to the greater dispersing effect that slag particles have [ 213 ]. On the other hand, mineral admixtures do not contain C3A, and therefore they act as diluting agents of the C3A content of clinker, causing lower net adsorption by this phase and a corresponding lower admixture demand for a given consistency in comparison with non-blended secciones constructivas.
However, significant secciones constructivas of naphthalene and melamine based admixtures, and vinyl copolymer on slag has been reported [ 15 ], which implies that a reduction in the demand of secciones constructivas admixtures is not directly related to clinker replacement ratio.
Moreover, recent studies have shown that the type of SP plays a significant role in the stability of ettringite formed during hydration [ 16 ]. This affinity is affected by cement aging, depending on the C3A content of cement [ secciones constructivas ].
Programa de Medios y Justicia
Concerning flowability loss over time, there are no reasons for which incorporation of admixtures, such as slag or natural pozzolans, should modify the efficiency of secciones constructivas SP.
However, in order to recover flow level after a certain mixing time, while slag-containing concretes need admixture re-doses similar to those of concrete without admixtures, it has been informed that natural pozzolans may require slightly higher re-dosing [ 18 ].
On its own, limestone powder accelerates cement hydration [ 19 ] and could, as a result, secciones constructivas flowability loss rate.