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The study presented herein investigated the effect of supplementary cementitious materials (SCMs) on the sulfate resistance of ultra-high-performance concretes (UHPCs) made with ASTM Type III and Type V cement. Three types of UHPCs were prepared for each cement type, namely, one with 100 % cement (C100) and two others with 20 % cement replaced by fly ash (FA20) and a combination of silica fume and fly ash (FA15SF5). These UHPCs were exposed to a 5 % sodium sulfate solution for 365 days to evaluate their sulfate resistance. In addition to the sulfate-induced expansion, the compressive strengths of the studied UHPCs were evaluated under two curing conditions: continuous water curing and curing under exposure to the 5 % sulfate solution. The Rapid Sulfate Permeability Test (RSPT) was also conducted at 28 and 90 days to assess rapid sulfate ions penetration into the studied UHPCs. The results revealed that the addition of supplementary cementitious materials (SCMs) significantly enhanced sulfate resistance in both Type III and Type V cement UHPCs. However, Type V cement UHPCs consistently showed reduced sulfate-induced expansion by approximately 20.4 % compared to Type III cement UHPC, primarily due to its lower C 3 A content. The Rapid Sulfate Permeability Test (RSPT) results revealed that, at both 28 and 90 days, Type V UHPCs consistently displayed lower penetrability compared to Type III UHPCs. Furthermore, Type V cement UHPCs incorporating SCMs exhibited an average surface penetration reduction of about 6 % relative to their Type III cement counterparts.

The current study aims to assess the transport and durability properties of alkali-activated concretes made with hybrid aluminosilicate precursors having different proportions of natural pozzolan as a low-calcium precursor and ground-granulated blastfurnace slag as a high-calcium precursor, which are activated with different concentrations and combinations of sodium hydroxide and sodium silicate. The studied parameters included precursor combination (natural pozzolan'slag combinations of 30/70, 50/50, and 70/30), sodium hydroxide concentration (1, 1.75, and 2.5 M), and activator combination (sodium hydroxide/sodium silicate combinations of 70/30, 75/25, and 80/20). The resulting concrete mixtures were tested for slump flow, setting time, compressive strength, absorption, rapid chloride penetration, rapid chloride migration, resistance to sulfuric acid attack, chloride-induced corrosion, and frost resistance. Mercury intrusion porosimetry and X-ray diffraction were used to justify the observed behaviors. The performance of alkali-activated natural pozzolan/slag concretes was also compared with that of a reference concrete made with solely portland cement binder. In view of overall performance, an equal proportion of natural pozzolan and slag (50/50) and a 30/70 combination of sodium silicate and sodium hydroxide proved to be the optimum precursor and activator combinations. The optimum sodium hydroxide concentration was dependent on the precursor and activator combinations as well as the expected fresh, strength, transport and durability performance. In terms of the measured transport properties (that is, absorption, chloride penetration depth, and passing charges) and resistance to acid attack and chloride-induced corrosion, all the studied alkali-activated concretes performed considerably superior to the reference portland cement concrete. In the case of frost resistance, only alkali-activated concretes with 50 and 70% slag performed superior to the reference portland cement concrete. Keywords: acid attack; activator combination; alkali activation; corrosion; frost resistance; natural pozzolan; precursor combination; slag; sodium hydroxide concentration; transport properties.

This study aimed to determine the abrasion resistance of ultra-high-performance concretes (UHPCs) for railway sleepers. Test samples were made with different cementitious material combinations and varying steel fiber contents and shapes, using conventional fine aggregate. A total of 25 UHPCs and two high-strength concretes (HSCs) were selected to evaluate their depth of wear and bulk properties. The results of the coefficient of variation (CV), relative gain in abrasion, and abrasion index of the studied UHPCs were also obtained and discussed. Furthermore, a comparison was made on the resistance to wear of the selected UHPCs with those of the HSCs typically used for prestressed concrete sleepers. The outcomes of this study revealed that UHPCs displayed excellent resistance against abrasion, well above that of HSCs. Amongst the utilized cementitious material combinations, UHPCs made with silica fume as a partial replacement of cement performed best against abrasion, whereas mixtures containing fly ash showed the highest depth of wear. The addition of steel fibers had a more positive influence on the abrasion resistance than it did on compressive strength of the studied UHPCs.

This study investigated the wear resistance of selected fast-track Type III Portland cement concrete (FTC) under early opening times (6, 8 hours) and at full maturity (28 days). The effects of varying Type III Portland cement content (386, 445, and 505 kg/m³), with and without an accelerating admixture, were analysed to assess wear depth and deterioration rate. These factors were examined across different opening-time categories and maturity duration. The coefficients of variation and abrasion index from the abrasion tests were also evaluated. Additionally, the correlation between abrasion resistance (wear depth) and bulk strength was explored at both early and maturity durations. Results indicated that the studied FTCs showed improved wear resistance and compressive strength with higher cement content, longer curing periods, and the addition of an accelerating admixture. Test results also revealed that cement content, curing time, and accelerating admixture influenced depth of wear more than compressive strength.

The aim of this study was to determine the loss in compressive strength of concrete cylinders due to alkali–silica reactivity (ASR) for which an aggregate exhibits reactive or innocuous behavior. For the stated purpose, the expansions of 14 aggregate groups, obtained from the accelerated mortar bar and modified concrete prism tests at various immersion ages, were correlated with the loss in compressive strength of the companion concrete cylinders at the immersion ages of 4 and 28 weeks. The test results concluded that the compressive strength generally was not sensitive to ASR at early age; however, it was significantly impacted at the extended immersion age when excessive expansions and cracks were experienced. The ASR classifications of the investigated aggregate groups based on the expansion limits of mortar bars and concrete prisms showed good correlations with those obtained from the proposed failure limits due to loss in compressive strength.

In this study, surface resistivity of the non-proprietary ultra-high-performance concretes (UHPCs) using traditional aggregates were evaluated. Four plain UHPCs were batched using various cementitious materials at a constant water-to-cementitious materials ratio of 0.21 with an aggregate-to-cementitious materials ratio of 1.20. The 28-day surface-resistivity was measured for a duration of 60 minutes (10 minutes intervals). The influence of testing time on surface resistivity of the studied UHPCs was also examined. The results of this study highlighted that surface resistivity of UHPC could be used with confidence to assess its chloride penetration resistance. The outcome of the study also revealed that the binary blend UHPC containing silica fume, as a partial replacement of Portland cement, displayed the highest surface resistivity, lowest chloride ion penetration, and highest compressive strength amongst the studied UHPCs. Time of testing had a minor effect on surface-resistivity of the studied UHPCs.

This paper examines the freezing and thawing resistance of high early-strength concrete (HESC) developed for rapid repair of pavements and bridge decks. The cement types chosen for this study included ASTM Type III, ASTM Type V, and Calcium Sulfoaluminate (CSA). A cement content of 386 kg/m 3 was maintained for all studied concretes. Specimens were tested after 24 hours and 28 days of curing in order to evaluate compressive and flexural strengths. In addition, the opening time was determined based on the required time to achieve the minimum compressive strength of 20.7 MPa. The freezing and thawing (F–T) resistance of the test samples were evaluated in accordance with the F–T duration of 96 hours per cycle for a total of 25 cycles. Test results revealed that at the opening time and after 24 hours curing, CSA cement concrete displayed the highest compressive and flexural strengths, but lowest resistance to freezing and thawing with de-icing salt. The 28-day cured Type V cement concrete produced the highest strength and de-icing salt resistance, while CSA cement concrete produced the contrary.

This study examines the suitability of ASTM Type V cement concrete for rapid repair applications. To this end, experimental results on transport and durability properties of high early-strength concretes using ASTM Type V cement were compared with those of a more traditional cement used for rapid repair, i.e. Type III cement. A cement content of 445 kg/m 3 (750 lb/yd 3 ) was maintained for all studied concretes. The experimental program included compressive strength, absorption, rapid chloride migration, corrosion resistance, and mass loss due to freezing and thawing regimes. The results of this study revealed that use of Type III and V cements were both effective for concrete rapid repair applications. The opening time to reach the minimum compressive strength of 21 MPa (3000 psi) was found dissimilar. Type III cement concrete showed better strength properties at early ages due to its high fineness. However, as curing age was extended to 24 hours and 28 days, Type V cement concrete produced higher strength results. Moreover, Type III cement concretes failed to display better performance in transport properties, corrosion, and frost resistance when compared to that of the studied Type V cement concretes.

This paper examines the abrasion resistance of high early-strength concrete developed for rapid repair of highways and bridge decks. The cement types chosen for this study included ASTM Type III, ASTM Type V, and Calcium Sulfoaluminate (CSA) cements. A cement content of 386 kg/m 3 (650 lb/yd 3 ) was maintained for all studied concretes. Test samples were tested after 24 hours and 28 days of curing in order to evaluate compressive strength and depth of wear. Test results revealed that the opening time to attain minimum required compressive strength for CSA cement concrete was one hour, whereas the values for Type V and Type III cement concretes were 8.5 and 6 hours, respectively. After 24 hours curing, CSA cement concrete displayed the highest strength, but lowest resistance to wear. The 28-day cured CSA cement concrete produced the highest strength and resistance to abrasion, while Type III cement concrete showed a similar strength, but lower resistance to wear, when compared to those of the Type V cement concrete.

The study presented herein evaluates effects of alkaline activator (sodium hydroxide) concentration, solution (sodium hydroxide solution)-to-binder ratio (S/B), and curing condition on properties of alkali-activated natural Pozzolan mortars (geopolymers). To this end, several mixtures were made having natural Pozzolan as their binder with different concentrations of alkaline activator solution including 2.5, 5, 7.5, 10, and 12.5 molar (M) at various S/B of 0.50, 0.54, and 0.58. The produced mortars were cured at 80 °C under three different conditions of exposed (dry), sealed (wrapped), and moist until testing at ages of 1, 3, and 7 days. Multiple tests were conducted on the alkali-activated natural Pozzolan mortars including flow spread, compressive strength, flexural strength, PH measurement, absorption, and rapid chloride migration. Test results showed the sealed curing condition to be most conducive to strength gain, whereas the exposed curing condition caused dehydration and/or carbonation within the samples and the moist curing condition did not allow for full removal of excess water resulting in reduced bond formations. The moist oven-cured mortars produced higher strength than the exposed cured mortars when alkaline activator with lower molarities was used. The opposite trend was observed for the higher molarities mortars. The compressive and flexural strengths, absorption, and depth of penetrated chloride improved when NaOH concentration increased and S/B decreased.