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Influence of plasticizer on concrete hardening in low temperatures
Konferencja
V Konferencja Naukowa Rzeszowsko-Lwowsko-Koszycka Aktualne problemy budownictwa i inżynierii środowiska, Rzeszów, 25-26 września 2000. Cz.1. Budownictwo
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Abstrakty
Concrete work in wintertime is always connected with the risk of disturbances in the process of hydration of cement. This may later slow down the process of reaching the planned strength of concrete, or even worse, it can permanently destroy its structure. This kind of concrete may never acquire the desired strength, or it may turn out to be vulnerable to the activity of the environment. This situation can be avoided by appropriate preparation of the concrete work in conditions of lower temperature, and by using proper types of admixtures. Besides the ones, which are labelled as anti-freeze, good protection results can be achieved by using plasticizer or superplasticizer. The paper presents the results of examination of continuous footing concrete, curing in natural conditions, with long term impact of freezing temperatures. As the initial protection of this concrete, KLUTAN P plasticizer was used in the amount equal to 0,7% of the cement mass. The designed class of concrete B15, at the indicator W/C = 0,53. The concrete mixture was produced in a mixer-plant 8 kilometres away, without heating the components. Concrete works was done with the use of pump on 22 December. The temperatures in the time of concrete works and in the time of curing were shown in chart 1 and, in a graphic form, in figure 1. As a result of doubts concerning the strength of concrete obtained, destructive tests were made on samples of 50 millimetres in diameter, cut out from three chosen elements, following the scheme presented in figure 2. This way 31 results of strength of concrete were obtained - depending on their distance form the edge of the element as well as its depth. The statistical analysis confirmed the B12,5 class concrete, without visible structural defects, with small fractures in the comers. Although the desired class of concrete was not obtained, the final level was 70-80% of the designed strength. This proves that the process of hydration was considerably slowed down, but in spite of the fact that the temperature fell much below 0°Celsius, it was not stopped altogether. The results of examination, in spite of their considerable dispersion, do not show any clear tendencies suggesting the occurrence of certain sections with better or worse parameters of strength. In spite of the unfavourable conditions of preparation, building-in and curing of the concrete, it achieved quite satisfying parameters of strength and obtaining the designed class would have been possible, but in a longer period of time and in better temperature conditions. This is the result of using the plasticizer, which lowered the freezing point for water in the cement paste so much, that, it did not allow the paste to freeze. The hydration processes were slowed down, nevertheless they did proceed. Each case of raised temperature, although it never reached 0°Celsius, caused their faster action. Using the admixture resulted in more gradual curing of the concrete, than would have been the case otherwise. The conclusions of the presented research may be useful in planning protective actions for concrete work in wintertime conditions.
Rocznik
Tom
Strony
11--18
Opis fizyczny
Bibliogr. 4 poz., il.
Twórcy
autor
- Politechnika Rzeszowska, Wydział Budownictwa i Inżynierii Środowiska
Bibliografia
Typ dokumentu
Bibliografia
Identyfikator YADDA
bwmeta1.element.baztech-article-BTB2-0049-0008
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