The present study addresses the effective utilization of tannery sludge as a partial replacement of fly ash in brick manufacturing. The main objective of this research is to determine the optimal sludge content that can be incorporated in flyash bricks and thereby to assess the key engineering properties while mitigating potential radiological emissions. Sludge incorporated bricks were cast with the tannery sludge varying from 5% to 30 %. The bricks were tested for its compressive strength, water absorption, efflorescence and radiological tests. Samples were prepared for radiation test with varying percentage of tannery sludge. Various parameters, including internal and external hazard indices, radium equivalent activity (Req), annual effective dose rates, and absorbed dose rates, were thoroughly examined in this research. The results of various tests revealed that the newly formulated fly ash tannery bricks showed significant compressive strength upto 20% replacement. The water absorption and efflorescence were found to be within permissible limit as per BIS IS 3495. The gamma-ray spectrometry measurements of Primordial radionuclide activity concentrations, including Uranium-238, Thorium-232, and Potassium-K, in sludge bricks were found well within the permissible limits as per UNSCEAR 2000. The radium equivalent activity was found below the permissible limit of 370 Bq/kg. The absorbed gamma dose, radioactivity level index, external hazard index, indoor effective dose rate and outdoor effective dose rate, were all determined to be below the threshold of one (1.0), indicating that they were comfortably within the safety standards recommended. The results claimed the tannery sludge did not pose any serious radiation effect and it can be utilized as an eco-friendly as well as user- friendly construction material.

This paper presents an investigation of the bond performance of corrosion-free sand-coated glass fiber reinforced polymer bars (GFRP) implanted in two types of fly ash-based eco-friendly concrete. Steel reinforcement is prone to corrosion and is expensive to fix, therefore finding an effective alternative has become a must. One of these alternatives is GFRP bar. On the other hand, conventional concrete (CC) is not issueless, as it significantly affects the environment through its high-intensity CO₂ emissions. Thus, other alternatives have been looked into to mitigate the CO₂ problems. One of these alternatives is partially substituting Portland cement with another CO₂ emission-free material such as fly ash. In this study, two levels (50% and 70%) of high-volume fly ash concrete (HVFAC) were used to investigate their bond performance with GFRP bars. Cylindrical specimens were tested under the effect of pullout load. Furthermore, the bars were investigated chemically and microstructurally to see if the fly ash had some influence on the GFRP bar. For concrete, performance rank analysis was carried out to identify the best concrete mixture in terms of slump, unit weight, cost, and bond strength. In addition, to verify the experimental work, two-dimensional finite element models were built using translator elements to present the bond action between the concrete and its reinforcement. The results of the investigation showed that the bond strength of GFRP bars was less than that of mild steel owing to GFRP bar deformation. In addition, CC resulted in a higher bond strength than HVFAC. The bar analyses did not yield any obvious signs of microstructural deterioration or chemical attack.

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

The present paper preliminarily illustrates the mechanism of damages caused by the alkali-silica reaction (ASR) between the high alkali content of the dry shake-hardener due to the high cement content on the top of the concrete industrial floors and the alkali-reactive coarse aggregate in the concrete substrate. To mitigate or prevent these damages a special dry shake-hardener, based on the partial replacement of the Portland cement by siliceous fly ash, is used. The beneficial influence of the fly ash, as well as that of other fine pozzolanic materials, is due to the distribution of a very large number of amorphous silica-based fine particles which can potentially react with the alkali in the same way as the amorphous or badly crystallized silica of the alkali-reactive coarse aggregates. The introduction of a very high number of pozzolanic particles significantly reduces the alkali availability for the reaction with the few alkali-reactive coarse aggregates. In other words, the alkalis instead of concentrating their aggression on a few grains of the alkali-reactive coarse aggregates, usually 5 to 15 mm (2 to 6 in.) in size, spread their action on a large number of very fine pozzolanic particles so that their expansive and destructive power is lost. However, another problem can arise when the Portland cement is partially replaced by fly ash due to the longer setting time, particularly in cold weather, of the dry shake-hardener, so that the workers must wait a very long time before the mechanical troweling and the opening of the finished surface to the pedestrian traffic. To avoid this drawback a combined use of the siliceous fly ash and a setting accelerator, based on tetra-hydrate calcium nitrate in powder form [4H₂O∙Ca(NO₃)₂ > 4H₂O∙CaO∙N₂O₅ > H₄CN₂] has been studied at three different temperatures: 35°C (95°F), 20°C (68°F) and 5°C (41°F). In warm weather, at temperatures as high as 35°C (95°F), there is no need for H₄CN₂ since the Portland cement hydration occurs at a very great rate and only the dry shake-hardener containing fly ash without H₄CN₂ can be applied within few hours and incorporated into the concrete substrate. At 20°C (68°F) the delay in the setting times caused by the partial replacement of Portland cement by fly ash can be compensated by the use of H₄CN₂ at 1% by weight of the cementitious materials. In cold weather, such as that caused by a temperature as low as 5°C (41°F), a much higher percentage of H₄CN₂, up to 5% by weight of the cementitious materials, must be used to reduce the setting times at approximately the same values as those recorded at 20°C (68°F) when the dry shake-hardener without fly ash is used.

Pavement subgrade is an in-situ material upon which the pavement structure is constructed. A soil with a high plasticity index will experience high shrinkage and swell depending upon its moisture content with detrimental impacts on its supported pavement structure. Removing and replacing the weak soil with better-quality soil is an alternative to stabilization of poor subgrade soil and may be a very expensive solution, typically for large road networks. Secondly, stabilization of weak soil -subgrade using conventional cement may not be sustainable due to its high CO₂ footprint. The feasibility of this non-conventional method using blended geopolymer binder for stabilization of weak subgrade soil was investigated compared to the conventional cement stabilization method. Laboratory testing of design mixes included unconfined compression test, maximum dry density, CBR and shrink & swell testing determining its feasibility and optimum extent. This research paper will present the findings on the effectiveness of blended geopolymer (fly ash and slag) as an alternative to conventional cement-based soil stabilizers for weak subgrade and its sustainability potential.