International Concrete Abstracts Portal

Lightweight and high-performance materials have become necessary for infrastructure with advanced construction and performance requirements. One of the major challenges with structures made of these materials is their performance under natural and man-made hazards, such as wind, fire, and blast. Therefore, in this study, the performance of ultra-high-performance concrete (UHPC) and UHPC coated with foamed concrete (UHPC-Foamed) and polyurea (UHPC-Polyurea) is investigated under blast load. A finite element model is developed to assess the behavior of UHPC and coated UHPC panels under far-field and near-field blast scenarios. The constitutive behaviors of UHPC and foamed concrete are considered using the concrete damage plasticity model with respective parameters. The polyurea is modeled as a hyperelastic material with the Mooney-Rivlin model. Moreover, the effectiveness of the additional coatings, i.e., foamed concrete and polyurea, on the blast resistance of each panel is presented. The finding of the study shows that both foamed concrete and polyurea enhance the blast resistance of the UHPC concrete panels. Moreover, a comparison between the blast resistance of UHPC-Foamed and UHPC-Polyurea is conducted under far-field and near-field blast scenarios. Also, the effectiveness of foamed concrete and polyurea coatings with different thicknesses to UHPC panels is assessed under both blast scenarios.

Foamed geopolymers possess excellent fire resistance similar to ordinary geopolymers and can also provide good thermal insulation when using lightweight aggregates, making them ideal for fire-resistant coatings. However, foamed geopolymers are susceptible to significant and uneven shrinkage, which can result in cracks and breakage when heated due to the dehydration of the weakly bound water in the C-A-S-H or N-ASH gels. To address this issue, this study incorporated the expanded perlite particles (EPP) and replaced a portion of fly ash with crushed stone powder (CSP) in a ground granulated blast furnace slag/fly ash-based geopolymer that was foamed using fine metallic silicon powder. The EPP and CSP acted as inactive precursors to form a stable particle skeleton with a continuous gradation in the foamed geopolymers. Experimental results indicate that the suitable inclusion of CSP and EPP effectively mitigated geometrical deterioration and cracking under elevated temperatures. The foamed geopolymers with these additives showed no warping or cracking, even as they decreased in dimension and bulk density when heated on a one-side surface. It is considered that continuous gradation of CSP and EPP particles formed a stable particle skeleton within the foamed geopolymer to effectively diminish the shrinkage caused by the thermal decomposition of gels.

Although radiation is used for many useful purposes today, it has properties that can cause serious harm to human health. Especially, the harmful effects of radiation come from radioactive sources used for diagnosis and treatment in hospitals. Armoring the environment that is used and preventing its effect from being transferred to the external environment is one of the most frequently used methods. For this purpose, lead plates (0.1-3 mm) and concrete (6-26 cm) are used in hospitals. The new building material to be produced is healthy compared to lead since it will have a thin section compared to concrete, and it will have the characteristics of lightness and workability. Precautions to be taken in concrete against radiation are available in the literature, but the concretes in the proposed solutions are both heavy, prone to cracking, and have low fire resistance. In this study different fine minerals are optimized to minimize pores and X-Ray, gamma, and neutron shielding effectiveness were measured. Different thicknesses 1-5 cm were molded after the preparation of glass fiber-reinforced concrete (GRC) to get an equivalent value of 2 mm lead.

William L. Gamble is Prof. Emeritus of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign. He was on the faculty for 40 years, where he was engaged in teaching and research in the fields of reinforced and prestressed concrete. He is a member of ACI/TMS Comm. 216, Fire Resistance; ACI/ASCE Committees 421, Concrete Slabs and 423, Prestressed Concrete; and an Assoc. Member of ACI Comm. 543, Concrete Piles.

Fireproofing deterioration is widespread in industrial facilities throughout the country. Spalling concrete has potential to damage equipment and harm personnel. Replacing concrete fireproofing like-in-kind, without consideration for proper anchorage or material durability, does not eliminate the hazard as spalls may potentially occur again over time. However, when properly designed and installed, concrete is a durable option for replacing deficient fireproofing in aggressive environments typically present in industrial processing units. This paper presents the results of a case study on a structure in a Midwest industrial complex. Extensive concrete fireproofing repairs were performed on the structure 12 years ago. Design requirements included normal weight concrete with polypropylene fibers which enhance durability by improving cracking resistance. During a fire, the fibers melt forming relief channels for moisture to escape, thus eliminating explosive spalling. Installation methods included welded wire reinforcement (WWR) with positive anchorage to structural steel. WWR was attached to post-installed adhesive anchors between column flanges where existing fireproofing was sound and difficult to remove. After 12 years in service, repairs exhibit no significant defects. This level of durability is attributed to the design and installation methods utilized. Concrete fireproofing is a durable option for fire protection, provided structures are designed to support its weight, its mixture design is properly proportioned, and it is adequately anchored and reinforced.