Développement des bétons autoplaçants à faible teneur en poudre, Éco-BAP: formulation et performance

Abstract : Although concrete is a relatively green material, the astronomical volume of concrete produced worldwide annually places the concrete construction sector among the noticeable contributors to the global warming. The most polluting constituent of concrete is cement due to its production process which releases, on average, 0.83 kg CO[subscript 2] per kg of cement. Self-consolidating concrete (SCC), a type of concrete that can fill in the formwork without external vibration, is a technology that can offer a solution to the sustainability issues of concrete industry. However, all of the workability requirements of SCC originate from a higher powder content (compared to conventional concrete) which can increase both the cost of construction and the environmental impact of SCC for some applications. Ecological SCC, Eco-SCC, is a recent development combing the advantages of SCC and a significantly lower powder content. The maximum powder content of this concrete, intended for building and commercial construction, is limited to 315 kg/m[superscript 3]. Nevertheless, designing Eco-SCC can be challenging since a delicate balance between different ingredients of this concrete is required to secure a satisfactory mixture. In this Ph.D. program, the principal objective is to develop a systematic design method to produce Eco-SCC. Since the particle lattice effect (PLE) is a key parameter to design stable Eco-SCC mixtures and is not well understood, in the first phase of this research, this phenomenon is studied. The focus in this phase is on the effect of particle-size distribution (PSD) on the PLE and stability of model mixtures as well as SCC. In the second phase, the design protocol is developed, and the properties of obtained Eco-SCC mixtures in both fresh and hardened states are evaluated. Since the assessment of robustness is crucial for successful production of concrete on large-scale, in the final phase of this work, the robustness of one the best-performing mixtures of Phase II is examined. It was found that increasing the volume fraction of a stable size-class results in an increase in the stability of that class, which in turn contributes to a higher PLE of the granular skeleton and better stability of the system. It was shown that a continuous PSD in which the volume fraction of each size class is larger than the consecutive coarser class can increase the PLE. Using such PSD was shown to allow for a substantial increase in the fluidity of SCC mixture without compromising the segregation resistance. An index to predict the segregation potential of a suspension of particles in a yield stress fluid was proposed. In the second phase of the dissertation, a five-step design method for Eco-SCC was established. The design protocol started with the determination of powder and water contents followed by the optimization of sand and coarse aggregate volume fractions according to an ideal PSD model (Funk and Dinger). The powder composition was optimized in the third step to minimize the water demand while securing adequate performance in the hardened state. The superplasticizer (SP) content of the mixtures was determined in next step. The last step dealt with the assessment of the global warming potential of the formulated Eco-SCC mixtures. The optimized Eco-SCC mixtures met all the requirements of self-consolidation in the fresh state. The 28-day compressive strength of such mixtures complied with the target range of 25 to 35 MPa. In addition, the mixtures showed sufficient performance in terms of drying shrinkage, electrical resistivity, and frost durability for the intended applications. The eco-performance of the developed mixtures was satisfactory as well. It was demonstrated in the last phase that the robustness of Eco-SCC is generally good with regards to water content variations and coarse aggregate characteristics alterations. Special attention must be paid to the dosage of SP during batching.

Best practice principles for management of children with developmental coordination disorder (DCD) : results of a scoping review

Background. Developmental coordination disorder (DCD) is a prevalent health condition that is frequently unrecognized despite the substantial evidence that has accumulated regarding how it affects children’s health, education and skills.Most literature focuses on measurement of impairment and description of intervention approaches for individual children; little is known about the principles that should guide best practice and service delivery for children with DCD as a population. The purpose of this study was to identify these principles. Methods. A scoping review was used to ‘map’ the information available to inform intervention and service delivery. Scholarly and grey literature written in English was identified in six databases, using a combination of keywords (e.g. guidelines, management, models and DCD); a ‘snow-balling’ technique was also used in Canada and the UK to access clinical protocols used in publicly funded health care systems. Over 500 documents were screened: 31 met inclusion criteria as they outlined practice principles for children with DCD as a population. Data regarding best practices were independently extracted by two reviewers and then compared with achieve consistency and consensus. Results. Two over-arching themes emerged, with five principles: (1) Organizing services to efficiently meet the comprehensive needs of children (e.g. Increasing awareness of DCD and coordination; Implementing clearly defined pathways; Using a graduated/staged approach); (2) Working collaboratively to offer evidence-based services (e.g. Integration of child and family views; Evidence-based interventions fostering function, participation and prevention). Conclusion Numerous documents support each of the principles, reflecting agreement across studies about recommended organization of services.While these principles may apply to many populations of children with disabilities, this review highlights how essential these principles are in DCD. Researchers, managers, clinicians, community partners and families are encouraged to work together in designing, implementing and evaluating interventions that reflect these principles.