International Concrete Abstracts Portal

In relation to reinforced concrete high-rise buildings built in the Fifties and Sixties of the 20th Century, it has acquired importance, in the last few years, the analysis of the capabilities to withstand various kinds of environmental risks, defined according to actual parameters. The provisions prescribed by new structural design codes practiced today, indeed, have substantially changed both design actions and verification procedures as well, if compared to the building criteria in use in the past. This kind of analysis gives evidence to specific design performances which are seen as prevalent nowadays but were not considered in older versions of the codes, as the earthquake loads. In the present work this problem is discussed with reference to the case study offered by the Milan Municipality 25 story r.c. building erected in Milano in the ‘60s. Typically, this kind of buildings were designed for the effect of vertical loads and wind lateral loads only. At present, after being recognized of strategic importance for the society, they have to be verified also for the seismic resistance. Although the seismic hazard is classified as low in the area of Milano, design seismic forces are a little more severe than wind actions for this building, due to the limited ductility resources available in the structural elements, mainly in the shear walls. Consequently, the value which can be assigned to the load reduction factor is extremely low.

The paper deals with the study of rheological and mechanical properties of concretes manufactured by using wash waters as partial replacement of drinking water. Concretes were manufactured by using only water utilized to wash concrete mixing transport trucks. Three different wash waters, with solid residue amount in the range 0.13% - 5.5% by mass were used. The waters were directly sampled in an innovative beton wash system. 30 and 35 concrete grades were manufactured. The superplasticizer dosage was adjusted in order to attain a slump value of 210 mm (8.3 in.) at the end of the mixing procedure. The workability and workability loss up to 60 minutes were also evaluated. The compressive strength at 1, 7 and 28 days was measured on cubic specimens. At 60 minutes, fresh water was added to compensate slump loss (retempering procedure) and a second series of cubic specimens was taken to evaluate compressive strength penalization. Suspended solids in wash water strongly influences the workability retention: the higher the solid content, the lower the workability loss over time and, hence, the water demand to compensate the slump decrease. At the same w/c ratio, the presence of solid particles in wash water causes an increase in the early compressive strength. A modification of the aggregate grading curve, consisting in reducing the sand fine fractions, should be considered, to manufacture concretes comparable to traditional ones.

In this work, fiber reinforced SCLWAC (self-compacting lightweight aggregate concrete) mixtures were studied, in which synthetic fibers were used. Eight different SCLWAC mixtures were prepared, by employing either fly ash or silica fume as mineral addition. In particular, as aggregates, different combinations of fine and coarse expanded clay were tried, also partially replaced by either quartz sand or recycled aggregate coming from a recycling plant, in which rubble from concrete demolition are suitably treated. The SCLWACs were characterized at the fresh state by means of slump flow, V-funnel and L-box tests, and after hardening by means of compression, splitting tension and bending tests, as well as drying shrinkage measurements. Strength class of LC 45/50 was obtained by using synthetic macrofibres when the oven dry density of SCLWAC was about 1600 kg/m³ [2700 lb/yd³], while if the oven dry density of SCLWAC was lower than 1250 kg/m3 [2100 lb/yd³] a strength class of LC 25/28 was reached as well. Splitting tensile and flexural strength measured values were consistent with concrete strength class, while the elastic modulus was quite low with respect to normal weight self-compacting concrete (SCC). The post-cracking behaviour of SCLWAC resulted strongly improved by the addition of synthetic macrofibers, which proved to guarantee a softening behaviour in flexure. In conclusion, the addition of synthetic fibers allowed to design special concretes with excellent combination of mechanical and functional properties.

Editors: Mario Alberto Chiorino, Luigi Coppola, Claudio Mazzotti, Roberto Realfonzo, Paolo Riva

With the dawn of twenty-first century, the world has entered into an era of sustainable development. The main challenge for concrete industry is to serve the two major needs of human society, the protection of the environment, on one hand, and - on the other hand - meeting the infrastructural requirements of the world growing population as a consequence of increase in both industrialization and urbanization. In the past, concrete industry has satisfied these needs well. Concrete is an environmentally friendly material useful for the construction of vast infrastructures. Skyscrapers, highway bridges, roads, water retaining structures and residential buildings are all testimonials to concrete’s use and versatility. However, for a variety of reasons the situation has changed dramatically in the last years. First of all, the concrete industry is the largest consumer of natural resources. Secondly, portland cement, the binder of modern concrete mixtures, is not as environmentally friendly. The world’s portland cement production, in fact, contributes to the earth’s atmosphere about 7% of the total CO2 emissions, CO2 being one of the primary greenhouse gases responsible for global warming and climate change. As a consequence, concrete industry in the future has to face two antithetically needs. In other words how the concrete industry can feed the growing population needs being – at the same time - sustainable?

ACI Italy Chapter has been playing a significant role in the last years in the broad area of concrete technology in Italy and, in particular, in the field of concrete durability and sustainability. ACI Italy Chapter has become increasingly involved in research and development dealing with durability and sustainability issues such as reduction in CO2 emissions, use of recycled materials and innovative products, design of durable structures and maintenance, repair and refurbishment of concrete infrastructures.

In October 2015, the American Concrete Institute Italy Chapter (ACI IC) and the Department of Civil, Chemical, Environmental, and Material Engineering (DICAM) of the University of Bologna sponsored the First International Workshop on “Durability & Sustainability of Concrete Structures” in Bologna (Italy). The workshop was co-sponsored by the American Concrete Institute and ACI Committee 201. The proceedings of the workshop were published by ACI IC as SP305. The proceedings consist of forty-eight refereed papers concerning reduction in green house gases in cement and concrete industry, recycled materials, innovative binders and geopolymers, Life Cycle Cost Assessment in concrete construction, reuse and functional resilience of reinforced concrete structures, repair and maintenance, testing, inspection and monitoring.

Many thanks are extended to the members of the technical paper review panel. Without their dedicated efforts it would not have been possible to publish the proceedings. The cooperation of the authors in accepting reviewers’ comments and suggestions and in revising the manuscripts accordingly is greatly appreciated.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-305

As residential and commercial buildings are responsible of a large energy consumption, especially for heating, Standards introduce limits to guarantee energy saving in new buildings; however, existing buildings need to be retrofitted for energy saving, given the large impact they have on the phenomenon. Under this perspective, in the framework of a European project, a multilayer prefabricated façade panel is proposed. It is characterized by an internal EPS layer, 100 mm [3.94 in.] thick, and by two external layers made of textile reinforced concrete (TRC), 12 mm [0.47 in.] thick. The insulating material is used to transfer the shear between the external TRC layers. The maximum size of the panel is 1.50 x 3.30 m² [60 x 130 in.²]; the panel height is properly chosen in order to fasten it to the frame concrete beams through four connectors placed near to the corners. In this paper the design of the panel and the results of tests performed on full scale panels are shown. The panels were fastened to the corners through suitable anchors and were loaded by means of a distributed load (considering wind pressure and suction as the main load acting on the panel).