International Concrete Abstracts Portal

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

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.

The need to attain the correct assessment of industrial by-products and wastes re-quires an in-depth knowledge of their characteristics. One of the most important characteristics that affects in the aptitude of a thermally calcined product is the calcining conditions like temperature and stay in furnace. This is the aim of the current work which considers the importance of calcining conditions on the pozzolanic properties of a paper sludge as cementing material. The by-product used for this research is a Spanish paper sludge coming from a paper industry which uses 100% of recycled paper as raw materials. Due to the high content of organic material and calcium carbonate and, to the presence of different clayey minerals in sludge like kaolinite and talc, the calcining conditions play an important role on the mineralogy and pozzolanic activity of this sludge. For this reason, different intervals of temperature between 700 and 800°C and, different times of stay in furnace (2.5 and 5h) are studied in order to get the best pozzolanic properties for the paper sludge. The reaction kinetics of pozzolanic reaction cured at 40°C varied with the calcining conditions. The main crystalline phases identified by XRD were hydrocalumite (Ca4Al2O6C121OH2O) and calcium aluminium carbonate hydrate (Ca4Al2O6CO311H2O), stratlingite and hydrogamet.