Comparison of standards and requirements for porous asphalt mixtures

Porous asphalt is a bituminous material prepared in such a manner that it has a very high content of interconnected voids that allow passage of water and air in order to provide the compacted mixture with better drainage and noise reducing characteristic. The analysis of available regulations and scientific literature shows that the national standards of porous asphalt mixtures differ in type of granulometric envelopes, the type of bitumen and its content in the mixture and the limits of the air voids content in the mixture. In this paper, standards used for porous asphalt in Croatia are compared with the US, Australian and Dutch standards for this type of asphalt. In addition, samples prepared based on HRN EN 13108-7 and HRN EN 12697-17 requirements were tested and results were compared using Croatian and other available standards. This paper also investigates the effects of ambient temperature on abrasion loss of porous asphalt. The abrasion loss results are compared to the other standards.

Influence of basalt micro-fibres on the abrasion resistance of concrete in hydraulic structures

In hydraulic structures, abrasion resistance can be a significant driver in concrete specification. Basalt micro-fibres represent a potentially sustainable construction product and have been shown to provide various benefits in concrete, however the implications for hydrodynamic abrasion resistance are to date unclear. This paper is the first investigation of its kind to examine the abrasion resistance of basalt fibre-reinforced (BFR) concretes using the ASTM C1138 underwater test method. Towards this, concretes incorporating fibre dosages of 0.5, 1, 1.5 and 3 kg/m3 were tested. The relationships between concrete abrasion and its fundamental mechanical properties are evaluated. For the particular concretes examined, it is found that based on the Shapiro-Wilks tests at 95% confidence, abrasion loss in BFR concretes followed a normal distribution; the use of basalt fibre in contents of up to 3 kg/m3 did not have a significant effect on abrasion resistance, compressive and tensile splitting strengths, as well as modulus of elasticity. It can be concluded that basalt micro-fibre can be used for their other attributes such as controlling bleeding, shrinkage and plastic cracking in concrete hydraulic structures without deleterious effects on abrasion resistance. The regression models proposed to predict concrete abrasion loss from its mechanical properties were found to be only significant at 48 h for compressive strength and 24 h for both tensile splitting strength and modulus of elasticity.

Influence of Redispersible Powder on Properties of Self-Leveling Mortar of Ternary Cementitious System

The self-leveling mortar (SLM) of a ternary cementitious system with different dosages of redispersible powder (RP) with ordinary Portland cement (OPC), sulfoaluminate cement (SAC), and calcium sulfate (CS) as cementitious materials was investigated with regard to fluidity, bond strength, shrinkage rate, abrasion resistance, flexural strength, and compressive strength. The performance parameters obtained from the experimental test for SLM were weighted values calculated with an analytic hierarchy process (AHP). The comprehensive index of performance was evaluated on the basis of a weighted-sum method, and the optimal dosage of RP was determined according to the comprehensive index. The experimental results demonstrated that the fluidity of SLM decreased with the increase in RP dosage at the beginning but then increased thereafter and decreased rapidly as the dosage went beyond 3.0%. The addition of RP resulted in a significant improvement in bond strength (of SLM), reduction in the shrinkage rate, abrasion loss, early flexural strength and compressive strength, and resistance to cracking. The properties of SLM with 3.0% RP can meet the requirements of the industrial standard for cementitious self-leveling floor mortar. Compared with the SLM without RP, the bond strength of SLM with 3.0% RP was increased by 46.7%, while the shrinkage rate and abrasion loss were reduced by 50% and 71.9% respectively. The weighted values of fluidity, compressive strength, flexural strength, stability, cohesiveness, and abrasion resistance were 0.422, 0.196, 0.196, 0.089, 0.058, and 0.039, respectively. A higher value of the comprehensive index generally denotes a better performance. The comprehensive index of SLM with 3.0% RP was the highest.

Durability assessment of open-graded friction course using a sustainable polymer

Open-graded friction course (OGFC) asphalt mixture, usually used to construct porous pavements, represents one of the materials supporting low-impact development (LID) philosophy due to its use of coarse aggregate gradation. Using such mixtures brings several benefits related to safety, environment and economy. Alas, coarse, open-graded skeleton of OGFC mixtures is prone to failure, particularly raveling and stripping. Continuous traffic loading and the environmental impacts give hand in hand to further increase the potential for failure, hence higher pavement maintenance and rehabilitation costs. Application of different types of modifiers has proved effective in mitigating failure potential. The most common modifiers are polymers, fibers and anti-stripping agents. Aiming at minimizing the costs and maximizing the lifespan while considering sustainability, the study was to investigate the effect of using a recycled stabilizing material as an asphalt modifier on the performance of OGFC asphalt mixtures. Recycled Low-Density Polyethylene (R-LDP) was adopted in this investigation. Changes in mixture air void, porosity, draindown, permeability, rut depth, moisture damage and abrasion loss were observed to evaluate the effect. Compared with unmodified asphalt samples, R-LDP modification increased mixture air void, porosity and permeability by 15%, 10% and at least 40%, respectively. Also, it noticeably contributed to reducing rut depth, moisture damage and abrasion loss (both unaged and aged) by 31%, 20% and at least 40%, respectively. More significantly, it almost eliminated the draindown problem. Incorporating R-LDP proved effective in upgrading OGFC mixture properties to an acceptable level required by most specifications.

Effects of Epoxidised Natural Rubber on the Oil Resistance Property of NBR/ENR Blends used for Safety Footwear Application

Epoxidised natural rubber, ENR has emerged as a sustainable material for many applications due to its unique properties. This study sets out to investigate the effects of ENR on the oil resistance property of nitrile rubber, NBR composites used for safety footwear application. Blends of NBR/ENR i.e. 100/0, 90/10, 80/20, 70/30, 60/40 and 50/50 were prepared and tested for their oil resistance property and other physical properties such as hardness, tensile properties and abrasion loss. Results showed that varying the amount of ENR did not significantly affect the hardness and tensile properties of the composites. Nonetheless, it was found that ENR content highly influences the abrasion loss of the composites in which the abrasion resistance decreased with further addition of ENR contents. Despite the increase in oil swelling of the composites with increasing ENR content, the oil swelling values are considered low (< 5% volume change), indicating superior oil resistance property of the composites. These results confirm the possibility of ENR as a sustainable material for the production of eco-friendly composites with high oil resistance property for the footwear industry.

Performance and Durability of Porous Asphalt Mixtures Manufactured Exclusively with Electric Steel Slags

Electric arc furnace slag (EAFS) and ladle furnace slag (LFS) are by-products of the electric steelmaking sector with suitable properties for use in bituminous mixtures as both coarse and fine aggregates, respectively. In this research, the production of a porous asphalt mixture with an aggregate skeleton consisting exclusively of electric steelmaking slags (using neither natural aggregates nor fillers) is explored. The test program examines the asphalt mixtures in terms of their mechanical performance (abrasion loss and indirect tensile strength), durability (cold abrasion loss, aging, and long-term behavior), water sensitivity, skid and rutting resistance, and permeability. The results of the slag-mixes are compared with a standard mix, manufactured with siliceous aggregates and cement as filler. The porous mixes manufactured with the slags provided similar results to the conventional standard mixtures. Some issues were noted in relation to compaction difficulties and the higher void contents of the slag mixtures, which reduced their resistance to raveling. Other features linked to permeability and skid resistance were largely improved, suggesting that these mixtures are especially suitable for permeable pavements in rainy regions. In conclusion, a porous asphalt mixture was produced with 100% slag aggregates that met current standards for long-lasting and environmentally friendly mixtures.

Abrasion Behaviour of Wool-Viscose Hand Tufted Carpets using Response Surface Methodology

The effect of viscose blend in pile yarn, pile height and pile density on abrasion resistance of hand tufted carpets has been studied. The interaction between the process variables has been analyzed by using response surface methodology based on the Box-Behnken design of experiment. Overall, higher percentage (%) of viscose in the blend, lower pile height and lower pile density yield the minimum abrasion loss for the hand tufted carpets.