International Concrete Abstracts Portal

This study aimed to investigate the effect of different curing conditions/temperatures on the compressive strength, flexural strength (FS), modulus of elasticity (ME), and abrasion resistance of concrete developed with different mixture compositions. The studied parameters included different water-binder ratios (w/b) (0.4 and 0.55), different coarse-to-fine aggregate ratios (C/F) (0.7 and 1.2), addition of steel fibers (SFs), and different supplementary cementitious materials (SCMs) (metakaolin [MK] and silica fume [SLF]). The developed mixtures were cured at four different curing conditions: moist curing (C1); air curing (C2); and cold curing, including +5°C curing (C3) and –10°C curing conditions (C4). The results indicated that the effect of curing concrete samples at cold curing conditions was more pronounced on FS results compared to all other mechanical properties results, in which the FS reduced by 23% and 41% at +5°C and –10°C curing conditions, respectively, compared to at the moist-curing condition. Despite the considerable enhancement in the mechanical properties and abrasion resistance when SFs or SCMs were used in the mixtures, cold curing of mixtures with SCMs or SFs significantly reduced this enhancement. The results also revealed that the rotating-cutter test results of the mixture with SFs were more affected by cold curing conditions than the sandblasting test results.

Recently, alkali-activated cement (AAC) has been studied to partially replace portland cement (PC) to reduce the environmental impact caused by civil construction and the cement industry. However, with regard to durability, few studies have addressed the behavior of AAC. This study aimed to evaluate the performance of AAC made from blast-furnace slag with contents of 4 and 5% sodium hydroxide as an activator (Na2Oeq of 3.72% and 4.42%, respectively) when subjected to alkali-aggregate reaction (AAR). Length variation tests were carried out on mortar bars immersed in NaOH solution (1 N of NaOH, T = 80°C [176°F]) and on concrete bars (T = 60°C [140°F], RH = 95%); compressive strengths tests and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analyses were also made. Two types of PC were used as a comparison. The results showed good behavior of the AAC in relation to the AAR, with expansions lower than those established by the norm (34% of the limit) and without the finding of losses of mechanical resistance or structural integrity. The alkaline activator content had a small influence on the behavior of the AACs, in which the lowest amount of NaOH (4%) showed fewer expansions (only 15% of the limit established by the norm). Even for the highest activator content (5%), the results were good and comparable to those of PC with pozzolans, which is recommended for the inhibition of AAR.

This study evaluated the abrasion resistance for a number of lightweight self-consolidating concrete (LWSCC) incorporating coarse and fine lightweight expanded slate aggregates (LC or LF, respectively). The study also investigated the abrasion resistance before and after exposure to freezing-and-thawing cycles in the presence of deicing salt. The investigated parameters included different volumes of LC and LF aggregates, three binder contents (500, 550, and 600 kg/m3 [31.2, 34.3, and 37.5 lb/ft3]), and different types of concrete (LWSCC, lightweight vibrated concrete, and normal-weight self-consolidating concrete). Increasing the percentage of expanded slate aggregate decreased the abrasion resistance. Mixtures with LF showed higher strength-per-weight ratio and higher abrasion and salt-scaling resistance compared to mixtures with LC. Samples exposed to abrasion before salt scaling had higher mass losses due to salt scaling with an average of 26.8% compared to non-abraded ones. Higher mass loss was also observed in mixtures exposed to abrasion after the exposure to salt scaling with an average of 26% and 43.3% in the rotating-cutter and sandblasting abrasion tests, respectively.

The main objective of this paper is the investigation of the corrosion resistance of reinforced concrete containing various proportions of recycled aggregates (RA) combined with 25% ground-granulated blast-furnace slag (GGBS) as a partial cement replacement. An accelerated corrosion system was designed to test the steel corrosion in reinforced concrete by subjecting the samples to 150 and 300 wetting-and-drying cycles. The results, in general, showed that the use of RA in concrete mixtures was found to reduce the compressive strength, increase chloride penetration, decrease the corrosion potential of reinforcing bars, reduce the electrical resistance of concrete, and hence increase the corrosion risk. However, better results were achieved by the addition of 25% GGBS, which increased the core compressive strength and electrical resistance. Moreover, better results were achieved for normal and slag mixtures that have 0.788 in. (20 mm) concrete cover than those having 0.394 in. (10 mm) cover.

Development of geopolymer concrete (GPC) with industrial by-products is a solution to the disposal of the industrial wastes, thus making the concreting process sustainable. This paper focuses on the development of GPC using ground-granulated blast-furnace slag (GGBS) and dolomite (by-product from rock crushing plant) as source materials. Strength properties of slag-based GPC are studied with different proportions of dolomite. It is observed that the addition of dolomite into slag-based GPC reduces the setting time, enhances workability, and rapidly improves the early-age strength. Addition of dolomite into slag GPC also improves the durability properties, such as high resistance towards water absorption, sorptivity, marine attack, and chemical attack.