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The current mantra for our industry is “low carbon concrete,” but the question is – what do you actually mean by that? What is the benchmark you are using to say what is ‘low’– and how does that actually compare with what is being produced today? We’ve been making low-carbon concretes for decades – what we haven’t been doing is counting that carbon. Looking back at some history and at some recent projects, we can see that Low Carbon Concrete is certainly not rocket science and does in fact give us the durability and performance that we need for sustainability. The other side of the coin that we must be very wary of, in light of failures from the past, is that we produce concrete that is fit for purpose – making something that is ultra-green in the lab, but ultimately unusable in the real world serves no purpose and may even endanger lives. This paper shows a very small snapshot of the millions of cubic meters of binary, ternary, and quaternary cementitious blend concretes that have been used over the last 50 years, concentrating on more current examples showing that low carbon concrete is nothing new – it is already in major use.

The Canada Centre for Mineral and Energy Technology (CANMET) of Natural Resources of Canada, Ottawa, ON, Canada, has played a significant role for more than 40 years in the broad area of concrete technology in Canada. In recent years, CANMET has become increasingly involved in research and development dealing with supplementary cemen¬titious materials, high-performance normalweight and lightweight concretes, and alkali-aggregate reactions. As part of CANMET’s technology transfer program, an international symposium on Advances in Concrete Technology was sponsored jointly with the American Concrete Institute (ACI) and other organizations in Athens, Greece, in May 1992. In June 1995, CANMET, in association with ACI and other organizations in Canada and the United Staes, sponsored the Second CANMET/ACI Symposium on Advances in Concrete Technology in Las Vegas, NV, USA. For the Athens symposium, the CANMET publication “Advances in Concrete Technology,” constituted the proceedings of the symposium. The proceedings from the Las Vegas symposium were published by ACI as SP-154. In August 1997, CANMET, in association with ACI and other organizations in Canada and New Zealand, sponsored the Third CANMET/ACI Symposium on Advances in Concrete Technology in Auckland, New Zealand. The main purpose of the symposium was to bring together representatives from industry, universities, and government agencies to present the latest information on concrete technology, and to explore new areas of research and development. Thirty-three refereed papers from 15 countries were presented and distributed at the symposium. The proceedings were published as ACI SP-171. In June 1998, CANMET, in association with ACI, Japan Concrete Institute (JCI), and several other organizations in Canada and Japan, sponsored the Fourth CANMET/ACI Conference on Recent Advances in Concrete Technology in Tokushima, Japan. More than 80 papers from 20 countries were received and reviewed in accordance with the policies of ACI. Sixty-one refereed papers were accepted for presentation at the conference and for publication as ACI SP-179. In addition to the refereed papers, more than 30 papers were presented and distributed at the conference. In July-August 2001, CANMET, in association with ACI and several organizations in Singapore, sponsored the Fifth CANMET/ACI Conference on Recent Advances in Concrete Technology in Singapore. More than 100 papers from 25 countries were received and reviewed in accordance with the policies of ACI. Forty-six refereed and more than 25 additional papers were accepted for presentation at the conference. The proceedings of the conference were published as ACI SP-200. In June 2003, CANMET, in association with ACI and several organizations in Romania, sponsored the Sixth CANMET/ACI Conference on Recent Advances in Concrete Technology in Bucharest, Romania. More than 40 papers presented at the conference were distributed “as received,” and no formal ACI special publication was published. In May 2004, CANMET, in association with ACI and several other organizations in the United States, sponsored the Seventh CANMET/ACI Conference on Recent Advances in Concrete Technology in Las Vegas, NV. Seventeen refereed papers from more than 10 countries were presented and distributed at the conference. The proceedings of the conference, consisting of the refereed papers, were published as ACI SP-222. In addition to the refereed papers, 20 additional papers were presented and distributed at the conference. In May 2006, CANMET, in association with ACI and several other organizations in Canada and the United States, sponsored the Eighth CANMET/ACI Conference on Recent Advances in Concrete Technology in Montreal, QC, Canada. The proceedings of the conference, consisting of 17 refereed papers, were published as ACI SP-235. In addition to the refereed papers, more than 30 additional papers were presented and distributed at the conference. In May 2007, CANMET, in association with ACI and several other organizations in Canada, Europe, and the United States, sponsored the Ninth CANMET/ACI Conference on Recent Advances in Concrete Technology in Warsaw, Poland. The proceedings of the conference, consisting of 10 refereed papers, were published as ACI SP-243. More than 20 additional papers were presented and distributed at the conference. In October 2009, ACI, in association with several organizations in Canada, Europe and the United States, sponsored the Tenth ACI Conference on Advances in Concrete Technology in Seville, Spain. The proceedings of the conference, consisting of 20 refereed papers, were published as ACI SP-261. In addition to the refereed papers, more than 20 additional papers were presented at the conference and published in a supplementary papers volume. In May 2010, the Committee for the Organization of International Conferences (COIC) (formerly CANMET/ACI Conferences), in association with the Chinese Ceramics Society (CCS) and several other organizations in China, sponsored the Eleventh International Conference on Advances in Concrete Technology and Sustainability Issues in Jinan, China. More than 40 papers were presented at the conference. The proceedings of the conference were published by the CCS, Beijing, China. In October 2012, the COIC, in association with ACI, sponsored the Twelfth International Conference on Advances in Concrete Technology and Sustainability Issues in Prague, Czech Republic. The proceedings of the conference, consisting of more than 30 refereed papers, were published as ACI SP-288. In addition to the refereed papers, more than 40 other papers were presented at the conference and published in a supple¬mentary papers volume. In July 2015, the COIC, in association with ACI, sponsored the Thirteenth International Conference on Advances in Concrete Technology and Sustainability Issues in Ottawa, ON, Canada. The proceedings of the conference, consisting of 28 refereed papers, were published by ACI as SP-303. In addition to the refereed papers, more than 40 other papers were presented at the conference and published in a supplementary papers volume. In October 2018, the CCS and the China Academy of Building Research (CABR), Beijing China, in association with the COIC sponsored the Fourteenth International Conference on Recent Advances in Concrete Technology and Sustainable Issues in Beijing, China. The proceedings of the conference, consisting of 19 refereed papers, were published by ACI as SP-330. In addition to the refereed papers, more than 52 other papers were presented at the conference and published in a supplementary papers volume. In July 2022, after a postponement for the Covid-19 pandemic, the ACI Italy Chapter and the University of Bergamo, Italy, sponsored the Fifteenth International Conference on Recent Advances in Concrete Technology and Sustainable Issues in Milan, Italy. The proceedings of the conference, consisting of 44 refereed papers, were published by ACI as SP-355. In addition to the refereed papers, about 20 other papers were presented at the conference and published in a supplementary papers volume. The main topics of the papers presented at the conference include: the deterioration of concrete structures; the corrosion of metallic reinforcement; the repair techniques of damaged concrete structures by using shrinkage-compensating cement-based mixtures; the protection of concrete structures by special materials to obtain watertight concrete; the reduction of the damage caused by alkali-silica reaction; the use of mineral additions such as fly ash, silica fume, and ground-granulated blast-furnace slag to improve the durability of concrete structures; and the production of concrete by reducing gas emissions and energy consumption such as the use of binders alternative to portland cement (alkali activated materials, geopolymers, sulphoaluminate cement) and recycling of wastes coming from different sources. Thanks are extended to the reviewers for the valuable efforts in reviewing all the manuscripts published in the conference proceedings and in the supplementary volume. The guidance from Dr. V. M. Malhotra and Prof. M. Collepardi, the Honorary Chairpersons of the conference, is sincerely appreciated. Also, acknowledged is the support the American Concrete Institute for the publication of the proceedings (ACI SP-355). The Editors Dr. Denny Coffetti Prof. Luigi Coppola Dr. Terence Holland

Major bridges are requiring extended service lives of 100 years or more. This requires the use of high performance concretes and often enhanced corrosion protection provided by improved corrosion resistance of the reinforcing bars by using alloying, coatings, and/or corrosion inhibitors. Producing the entire bridge deck out of high performance concrete can lead to excessive cracking due to autogenous and drying shrinkage. Though this can be reduced by using shrinkage reducing admixtures or lightweight fines, the cost to implement these techniques for a full deck is high. However, a high performance concrete overlay uses considerably less high performance concrete, and as such can reduce the overall cost of the bridge deck and potentially allow for use of a more user friendly, less costly base concrete. This paper models the service life of a bridge deck using a high performance overlay. A probabilistic approach is used and the effect of cracking is included.

Supplementary cementing materials (SCM) have a great importance for preventing ASR in concrete structures worldwide. Different materials were used, e.g. fly ashes, silica fume or metakaolin. However, the results are often contradictory. What works with one aggregate does not necessarily work with another, or in other cases, the efficiency is not the same. Not all effects can be explained by fluctuations in the SCM composition.

Long-term investigations were carried out using three different aggregates. Concrete prisms were produced, and parallel aggregates were stored together with different SCM`s (different types and concentrations) in highly alkaline solutions with and without calcium hydroxide in the system. The reaction products, which precipitated as a result of the interactions between aggregate and SCM`s at different storage times, could be investigated by NMR and even XRD. The results were surprising because different aggregates formed different reaction products when using the same SCM. Such effects can only be explained by the release of different soluble minerals that are part of aggregates.

The conclusion is that obviously aggregates control the formation process of reaction products which are formed as a result of the interactions between SCM`s and aggregates. And these products are responsible for preventing ASR when using the SCM`s.

Composite materials that employ modified cement-based mortars are usually named Fabric-Reinforced Cementitious Matrix (FRCM). The two main components are the cementitious matrix and the reinforcement fabric. The matrix can contain silica fume, blast furnace slag, fly ash and in some cases chemical property that can act as corrosion inhibitor. Some types of fabrics commonly used for the strengthening of existing Reinforced Concrete (RC) structures include nets with carbon or polyparaphenylene benzobisoxazole fibers disposed along one or two orthogonal directions, and unidirectional steel ropes (S-FRCM).

The S-FRCM system can be applied according to the traditional Externally Bonded (EB) or the innovative Inhibiting-Repairing-Strengthening (IRS) technique. The latter is a sustainable strengthening method and it is a useful solution for existing RC structures with deteriorated or damaged cover concrete.

Experimental tests show that for S-FRCM systems, applied with EB or IRS technique, the debonding occurs at fiber-matrix interface without significant damage at concrete substrate. Consequently, the debonding strain depends mainly by geometric and mechanical properties of external reinforcement and elastic/fracture properties of fiber-matrix interface. Considering experimental data available in literature, related to RC beams strengthened in flexure using S-FRCM systems, a predictive strain debonding relationship is defined and its reliability is evaluated through comparison between experimental and theoretical ultimate load.