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Self-healing of concrete is the process in which the material regenerates itself repairing inner cracks. This process can be produced by autogenous or autonomous healing. Autogenous healing is a natural process, produced by carbonation and/or continuing hydration. Autonomous healing is based on the use of specific agents to produce self-healing, which can be added directly to the concrete matrix, embedded in capsules or introduced through vascular networks. Some examples are superabsorbent polymers, crystalline admixtures, microencapsulated sodium silicate, and bacteria. This review is structured into two parts. The first part is an overview of self-healing concrete that summarises the basic concepts and the main advances produced in the last years. The second part is a critical discussion on the feasibility of self-healing concrete, its possibilities, current weaknesses, and challenges that need to be addressed in the coming years.

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Microbial-induced calcium precipitation (MICP) has shown adequate potential to act as a healing product through Calcium Carbonate (CaCO3) precipitation inside cracks. This work studies the self-healing capability of conventional concrete incorporating two dosages of Bacillus subtilis encapsulated in diatomaceous earth and a liquid solution consisting of a combination of Bacillus, denitrifying, and photosynthetic bacteria. The two bacterial agents used are commercial or industrial products from other sectors. For these mixes, disks of size ϕ100×50 mm were pre-cracked at the age of 21 days by splitting test until reaching residual cracks of 100 to 450 µm. At the age of 28 days, self-healing was promoted during 28 days in three exposures, continuous water immersion at 20°C, a high humidity environment at 20°C and 95% of relative humidity, and 7 days immersed in water at 20°C and 21 days in the high humidity environment. Self-healing was analyzed with water permeability by comparing the results before and after healing. Afterward, chlorides’ penetration was performed to study the possible healing protection on cracked disks compared to uncracked reference disks. As a result, after 7 days of immersion in water, the mixes with bacteria presented acceptable healing results. Some healed cracks could also significantly reduce the penetration of chlorides towards the interior of the concrete matrix.

RESUMO O incremento de atividades na construção civil observado nos anos recentemente transcorridos, justifica e impulsiona estudos de novas técnicas que tem como objetivo aprimorar práticas obsoletas, que reprimem a liberdade de criatividade dos projetistas e vão contra o necessário e difundido pensamento sustentável. Nesse sentido, estudou-se características físicas do Bloco de Concreto Celular Espumoso (BCCE) quando se substitui Cimento Portland pelo resíduo industrial Cinza Volante. Desde a extração dos minerais necessários para a produção do Cimento Portland, a calcinação dos mesmos, processo de moagem e de transporte, resultam em elevados índices de emissão de dióxido de carbono, principal gás causador do efeito estufa. Sabe-se que vários setores da indústria brasileira são referência no que tange a pegada ecológica, apresentando índices de emissão de CO2 25% menores em relação à média mundial. Uma boa explicação para esse dado positivo se dá na utilização das adições como escória de alto forno, cinza volante e cinza de casca de arroz, resíduos que apresentam características físicas e químicas que possibilitam o uso em larga escala na fabricação de derivados de cimento, além de ser possível oferecer uma destinação adequada a esses materiais. Dentre os métodos de produção de blocos de concreto celular espumoso, testou-se o qual é inserida a espuma já preparada junto à argamassa. Utilizou-se dispositivo gerador de espuma produzido por Lencina, confeccionando blocos referência, sem a substituição de Cimento Portland por cinza volante e blocos com teores de 10%, 15% e 20 % de cinza volante, substituindo o cimento Portland. Analisando os resultados finais, observou-se um incremento da resistência conforme se aumentava o teor de cinza volante. No que tange a densidade, os BCCE ficaram de acordo com o que apresenta a NBR12644 (ABNT, 1992). Palavras-chave: Cinza Volante. Concreto Espumoso. Cimento Portland. ABSTRACT The activity increase in construction observed in recent years have elapsed justifies and promotes studies of new techniques that aims to improve outdated practices that repress freedom of creativity of designers and go against the necessary and widespread sustainable thinking. In this sense, were studied physical characteristics of the foamed cellular lightweight concrete block (CLC) when replacing Portland cement by the fly ash. Since the extraction of minerals required for the production of Portland cement, calcining the same, and transport the milling process results in high carbon dioxide emission rates, main cause of the greenhouse gas. Brazilian industry is known that is a reference in terms of carbon footprint, with rates of CO2 emissions 25% lower compared to the world average. A good explanation for this positive value is the use of additions like blast furnace slag, fly ash and rice husk ash, residues that have physical and chemical characteristics that enable large-scale use in the manufacture of cementitious products, as well it is possible to provide an adequate allocation to these materi...