N. García

The influence of different additions on portland cement hydration heat

Abstract This paper presents the results obtained using the Langavant Calorimeter method on portland cements with different addition materials that are commonly used in the manufacture of commercial cements. The effects of these materials on the hydration heat with respect to a control cement were studied. The first hours show that most of the additions, which present highet activity at early stages, increase the hydration heat of their mixed cements in relation to the control cement. The use of pozzolans reduces the heat given off by the cements during hydration. However, the reactions of the pozzolanic materials with the lime also produce heat and the decrease should not be proportional to the level of clinker substitution in the mixed cements.

Determination of specific surface area by the laser diffraction technique. Comparison with the blaine permeability method

Abstract The present paper highlights the applicability of the laser diffraction technique in the determination of the specific surface area of materials. The results obtained show that this technique may offer an alternative to other conventional methods such as the Blaine permeability. A comparative study is made, comparing the results obtained with both techniques.

Contribution of toxic elements: Hexavalent chromium in materials used in the manufacture of cement

Abstract One of the problems currently affecting certain industries, and more specifically cement companies, is the need to determine and control the content of water soluble hexavalent chromium because, due to its toxic effects, it may soon be regulated. The study covers the determination of hexavalent chromium in materials related to the construction sector, namely raw materials, clinker and additions. Spectrophotometric and inductively coupled plasma emission spectrometry (ICP) techniques are compared. Also included is the setting up of the most favourable test conditions for chromate extraction and a study of possible interferences in the colorimetric quantification.

THE COLOUR OF THE SANDSTONE FROM THE WHOLE CATHEDRAL OF SALAMANCA

The aim of the present paper is to study to the variations in colour of the sandstone comprising the set of monuments of the Cathedrals of Salamanca as a starting point for the application of conservation and restoration treatments of the stone. Using VIS spectrophotometry, the reflectance values, as expressions of colour, were determined in samples of sandstone (undeteriorated and deteriorated stone) from a broad sampling carried out on several areas of the buildings and following different criteria. The surface colour was also compared with that of the interior of the samples.