International Concrete Abstracts Portal

Different proportions of fluidized catalytic cracking residue (FOR) and Fly Ash were mixed with cement and their pozzolanic activities were monitored by Thermogravimetric Analysis, as a function of time. Fixed lime contents were calculated to determine the relative pozzolani activities. While FOR reacts with lime at very early ages of hydration, Fly Ash reacts only at longer times. Thermal peaks due to the presence of calcium aluminate hydrate (CAH) and calcium aluminosilicate hydrate (CASH) occurred in many samples.

Over the last few years environmental problems have caught the particular attention of the public, and this has led to various investigations that attempt to study and solve the focal point that cause environmental contamination. The main aim of this study is to determine the presence of polluting elements incorporated into the manufacture of cements and concretes, which might have a noxious effect on health. One way to incorporate this kind of element is by the incorporation of industrial by-products into cement. This paper studies the leaching of trace elements from copper slag, when this by-product is incorporated into cement mortars. A dynamic leaching test has been applied, in which the specimen is studied fully immersed in drinking water. To develop this test has been designed three tanks (reference drinking water, reference mortar and blended mortar), where the samples are continuously flowing. The quantification of leaching elements from the copper slag blended mortar is carried out to different contact time.

The development of self-compacting concrete is considered as a milestone achievement in concrete technology due to several advantages. In order to be self-compactable the fresh concrete must show high fluidity besides good cohesiveness. For the purpose of evaluating these properties, several concrete mixtures were prepared with a water to cement ratio of 0.45 in the presence of an acrylic based superplasticizer at a dosage ranging from 1% to 2% by weight of very fine material fraction (passing the sieve ASTM n° 100 of 150 µm). Either limestone powder or fly ash or recycled aggregate powder (that is a powder obtained from the rubble recycling process) were used as mineral addition, in order to assure adequate rheological properties, in terms of cohesiveness, in the self-compacting concretes. Preliminary rheological tests were carried out on cement pastes containing these mineral additions. In some cases, recycled instead of natural aggregate was used by subtituting either the coarse or the fine aggregate fraction. The fresh concrete properties were evaluated through the slump flow, the L-box test and segregation resistance. Compressive strength was measured on hardened concretes at 1, 3, 7 and 28 days of wet curing.

In 2004, the Canadian Centre for Mineral and Energy Technology (CANMET), in association with the American Concrete Institute, the Electric Power Research Institute, Palo Alto, CA, UWM Center for By-Products Utilization, Milwaukee, WI, and several other organizations in Canada, sponsored the Eighth CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete. The conference was held in Las Vegas, Nevada, U.S.A., May 23-29, 2004. The proceedings of the conference containing 56 refereed papers from more than 20 countries were published as ACI Symposiuml Publication SP-221. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP221

The aim of this paper is to introduce a method for determining the coefficient of efficiency, the k-value, with respect to chloride migration in concrete. Some results for ground granulated blast furnace slag are presented and compared with traditional k-values for compressive strength. Finally, some recommendations on how to use the k-values and how to improve standards and regulations are given. Standards normally give a single k-value for each type of addition, regardless of what environment the concrete will be exposed to. The results in the investigation, how-ever, clearly indicate that this is too great a simplification. For chloride migration, for example, the k-value is three times higher for slag than is the corresponding k-value for compressive strength. For a reliable service life prediction of concrete structures produced with concrete containing additions, it is, therefore, necessary to find relevant k-values for different types of degradation mechanisms. The most important mechanisms are corrosion induced by carbonation, by chlorides from the sea or by other chlorides, freeze/thaw attack with or without chlorides and perhaps also chemical attack.