ABRASION RESISTANCE OF CONCRETE TERRAZZO FLOORING TILES
Building Research Station, Technzon, Israel Institute of Technology, Haifa (Israel)
(Received February z6th, 1964; accepted July Sth, 1964)
The present note summarises a series of tests undertaken with a view to investigate the effect of the cement content, and the grading and type of aggregate, on the abrasion resistance of concrete terrazzo flooring tiles. The cement content (ordinary Portland) varied between 260 and goo kg/ma, the aggregate grading (fineness modulus) between 3.23 and 5.43, and its hardness (crushing value-BBS 812 : 1951) between 7.6 and 19.1%. Three types of aggregate were involved, namely, crushed soft limestone aggregate (white aggregate), crushed limestone aggregate of medium hardness (yellow aggregate) and crushed hard basalt aggregate (black aggregate). Three different gradings were studied for each type of aggregate, coarse (fineness modulus 5.25~5.43), medium (4.70-4.76) and fine (3.23-3.64).
The abrasion resistance was evaluated from the results of tests carried out at 28 and 90 days on a Bohme machine, in accordance with DIN 52108. In this test two pieces of tile, 7 cm square, are subjected to abrasion by rotation against a steel plate with emery sand as the abrasive agent. The number of revolutions, the radius and speed of rotation, the type and amount of emery, sand etc. are standardised and the resistance is measured as the reduction in specimen thickness (in mm).
BLACK AGGREGATE YELLOW AGGREGATE WHITE AGGREGATE I
CEMENT CONTENT (kg/m3)
Fig. I. Abrasion us. cement content for the different types of aggregate and gradings. -, 28 days abrasion; ----, go days abrasion.
Wear, 8 (1965) zzo--221
ABRASION RESISTANCE OF CONCRETE TERRAZZO FLOORING TILES 221
It is often argued that such a test is unrepresentative of the wear properties of the tile under service conditions, the abrasive effect in the flooring being completely different from that produced in the B&me machine. As far as concrete terrazzo tiles are concerned, deterioration through wear may be of a local nature, namely, crumbling of soft aggregate particles, formation of pits and holes in the mortar etc. or alternati- vely of a general character, namely, over-all reduction in tile thickness. In the former case, the Bijhme machine fails to provide the required indication of quality; in the latter case, however, the author is of the opinion that the above procedure is fairly satisfactory.
For the sake of brevity, presentation of data is limited to the diagrams given in Fig. I. From this, as well as from other data not presented here, the following conclusions may be drawn within the limited scope of the present study.
(a) The abrasion resistance of concrete terrazzo tiles is improved by the use of coarse aggregate in the fineness modulus range of 3.23-5.43. This effect iS related to the type of aggregate and the cement content. For the basalt aggregate it is more pronounced in the finer range (fineness modulus 3.64-4.75) as against the coarser range (4.70-5.29) for the limestone aggregate. In addition, for all the aggre- gates involved, this effect is more pronounced in leaner mixes than in rich ones.
(b) Resistance to abrasion is improved by the use of harder aggregate in the crushing value range of 7.6-19.1%, irrespective of mix proportions (cement content) and aggregate grading.
(c) Resistance to abrasion is improved by a higher cement content in the range of 260-900 kg/ms. However, depending on type and grading of the aggregate, there exists an optimum content from both the technological and economic view- points, i.e. a limiting value for which any further increase in the cement content would only lead to slight improvement in the resistance to abrasion. For the condi- tions in hand, the following values were found.
Grading Optimum cement content (kglcms)
Black Yellow White
Fine 550-600 600-650 600-650 Medium 450-500 550~-600 600-650 Coarse 450-500 500-550 550-600
(d) Longer curing, between 28 and 90 days, improves abrasion properties irrespective of cement content, type of aggregate and its grading.
The author wishes to express his sincere gratitude to the Israel Ministry of Housing for providing grants which made this study possible.
Wear, 8 (1965) z-z-o--221