International Concrete Abstracts Portal

ACI 347.3R-13 provides guidance on the measurement and classification of surface voids (i.e., bug holes) in as-cast formed concrete surfaces. This paper will provide perspective from a testing laboratory on the challenges encountered when asked to perform surface void ratio measurements. Measurements were performed by field technicians and an engineer using the method as described in ACI 347.3R-13, in addition to a modified approach. Based on measurements performed on test areas of a cast-in-place shear wall for a high-rise condominium, it was determined that the between-operator variation and the selected test area significantly impact the classification of the surface. Because the test method does not specify methods for test area location selection or the number of test areas to sample, test results can vary greatly. Specifically, two 24 in. x 24 in. (610 mm x 610 mm) areas that are within 12 in. (300 mm) of each other may possess the highest and lowest classification. Based on field test results, an alternative method is proposed that provides better repeatability between operators and is more time efficient. In addition, based on measuring several different test areas on the same concrete surface, the number of test areas needed to accurately represent the void area of a surface was estimated.

Bugholes on as-cast surfaces are an aesthetic issue, not a performance issue related to strength, durability, or serviceability. Because they are an aesthetic issue, attempts to evaluate bugholes objectively, with measurements, are not useful. Measuring bugholes using an evenly divided scale or other instrument can reveal their number, individual area, and total area as a percentage of a sample area. But there is no scale or instrument for aesthetic judgments. Thus, matching a mock-up surface with the as-cast surface, although subjective, is a better method for acceptance of surface appearance.

The 43.5-metre span truss footbridge over the Ovejas ravine in Alicante, made only of UHPFRC, has replaced a previous design in steel with a similar production cost, and also with improved durability and fewer maintenance costs. Thorough work was carried out in terms of material dosage, structural design and manufacturing process to minimise the total cost of the footbridge and to also make it safe, functional and pleasant. The footbridge design confers on fibres a very important role in structural behaviour. They are responsible for cracking control, ductility, confinement and, in some elements, they allow to dispense with any passive reinforcement. The most important aspects related to the structural analysis, structural design criteria, manufacturing process, cost distribution and final footbridge appearance are presented.

Today, a number of engineering structures and building are being constructed to match environment and urban landscape. From an aesthetics point of view, occurrences of efflorescence on colored concrete, unfinished concrete and concrete products of these structures are critical problems. This research aimed to study and compare the efflorescence of concrete products that substituted cement with industrial by-products namely, fly ash, blast furnace slag and gypsum and normal concrete. Both concrete products and normal concrete were manufacture for paving application in form of interlocking blocks. In this paper, we use the term "non-cement" concrete to refer to the concrete not using industrial cement. A methodology is presented that enables a quantitative evaluation of the total, soluble and insoluble efflorescence and this methodology was used to analyze both non-cement concrete and normal concrete specimens. The results show that the insoluble efflorescence of non-cement concrete is less than that of normal concrete.

Thin, fiber reinforced cementitious products offer a useful balance of properties such as strength, toughness, environmental durability, moisture resistance, dimensional stability, fire resistance, aesthetics and ease of handling and installation. For more than 30 years, AR glass fibers have been at the forefront in the development of new applications of such products throughout the World. Glass Fiber Reinforced Concrete [GFRC] is a thin, cement composite based on AR glass fibers with an excellent strength to weight ratio. Extensive early laboratory work produced a test method for determining long term strength. The validity of this work has been proven by the large number of buildings clad with GFRC, as well as a vast range of other GFRC products, used over a this 30 year period. This paper explains the fundamental principles behind GFRC and gives examples of some of its uses. These applications range from high quality, architectural wall panels and decorative elements through to modular buildings down to low cost channel sections and utility components. New developments and techniques will also be discussed.