Effect of pore water in the powered sample extracted from cement from the site

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Author : Kriti Agnihotri

Abstract : The analysis of cement powder extracted from cement mortar is reviewed. The pH of the pore solution is the main parameter of the durability of reinforced concrete structures. A higher pH in the concrete prevents reinforcement from corroding. A pH of 12.5 is obtained if the solution is saturated with calcium hydroxide Ca(OH)₂ one of the principal products of cement hydration. When pH reaches ~10 or below, then steel reinforcement is no longer protected against corrosion. This might be possible during exposure to freshwater and, alkalis can leach and the pH of the pore solution will decrease. Here we have done a chemical analysis of powder sample extracted from cement from the site using the ex-situ leaching (ESL) method. It basically involves four steps i.e. (1) grinding the concrete to powder (here in this report we have taken a powdered sample from the site). (2) Leaching the powdered sample by putting some known amount of water for some time. (3) Separating the liquid from that solid powder sample with the use of filter paper (4) Analyzing the extracted solution. The main principle of ex-situ leaching is to extract the elements present in powder solution. Here we are using the cold-wa t er extraction method and taken L/S (liquid to solid) ratio to vary, one can take particle size or leaching time as a variable quantity. We have taken eight site samples for testing shown in fig. (1). Each sample has been tested three times to minimize the errors. The main aim of the present investigation is to analyze the powder sample. Results from the study indicated that the powder sample we are using contains some basic elements which is the main reason for corrosion in the reinforced bars containing cement mortars and when reacts with water, even after drying some molecules of water are leftover inside the pore structure which reacts with the cement and causes corrosion.

Keywords : Cement analysis, ex-situ, chemical analysis, cement extract, powdered cement.

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