ASSESSMENT OF ADHESION BETWEEN MINERAL AGGREGATE AND BITUMINOUS BINDER USING DIGITAL IMAGE ANALYSIS

This work presents how to assess a rate of adhesion between bituminous binder and mineral aggregate. Asphalt mixtures composed from grade bitumen 50/70, reference or modified with adhesion promoters based on amines, and aggregate (Brant, Zbraslav, Skuteč – 8-16mm) were made and then photographed. Three adhesion assessment approaches were applied: (i) standardized adhesion visual assessment, (ii) gray level thresholding, and (iii) entropy-based image segmentation, both evaluated from digital images. It was shown that adhesion between both Brant and Skuteč and reference binder, expressed as a rate of binder-coated area onto aggregate particles, was equal to ca. 50-70 %, while mixture composed from Zbraslav exhibited ca. 70-80 %. If adhesion promoters were used, these areas increased in all three cases up to 80-90 %. It was shown that results obtained using visual and entropy segmentation analysis were very similar, while these differed in comparison with gray-level thresholding

Thermal properties of mineral wool insulation recovered from construction and demolition waste

Mineral wool is one of the most commonly used types of thermal insulation in the European Union at the present, however, it generates massive amounts of waste. From an environmental standpoint, recycling or reuse of insulation materials seems to be a wise solution. This paper aims to study the thermal and structural properties of recycled mineral wool insulation recovered from construction and demolition waste. The thermal conductivity, the basic parameter characterizing thermal insulation materials, was measured using a heat flow meter. Test specimens with various bulk density (in the range 50–120 kg/m3) were made from micro-milled and chopped waste material (cladding of 30 years old building). The obtained results were compared with reference samples (non-contaminated blown mineral wool insulation Supafil Loft 045)

New possibilities for recycling of mineral wool separated from thermal insulation waste

It has become increasingly clear, that the recent consumption of mineral resources is unsustainable. The Czech Republic produces more than 217,000 tones of mineral wool annually, while its recycling stays unacceptably limited. This paper presents new possibilities how to recycle mineral wool from building insulation systems. Cladding of 30 years old building composed of FOS 125 facade was disassembled and its mineral wool boards were subjected to micro-milling in order to get filler and shortly chopped fibers to be the multifunction micro-aggregate in new design of plaster mortars. It was shown that mortars containing up to 1.2 wt. % of such waste exhibited decrease in pressure strength in the order of tens of percent than those made from reference mixture. On the other side, their bending strength was decreased slightly or oven improved. Other improvement was detected in thermal conductivity

RECYCLING AND ITS USE IN CONCRETE WASTE PROCESSING BY HIGH-SPEED MILLING

This article discusses the possibility of recycling of concrete waste using the high-speed milling method. The resulting of milling is micronize old concrete. Used old concrete was created by crushing of old concrete, which served as a structural concrete for the construction of a supporting column. Two level of milling process was used to recycle old concrete. The main use of waste is the possibility of partial replacement of commonly used binder and microfillers in concrete. For this reason, properties as particle size distribution, dynamic modulus of elasticity, flexural strength and compressive strength were observed. The aim is to replace as much cement as possible while maintaining mechanical properties

PULLOUT BEHAVIOR OF OXYGEN PLASMA TREATED POLYMER FIBERS FROM CEMENT MATRIX

The aim of this work is to describe bonding properties between surface treated polymer fibers and a cement matrix. In order to increase an interaction between the matrix and fiber surfaces, two fiber types having approx. 0.5 mm in diameter were modified by mean of oxygen plasma treatment. Surface physical changes of treated fibers were examined using SEM morphology observation and interfacial adhesion mechanical tests. The principle of mechanical tests rested on a single fiber pulling out from the matrix (cement paste, CEM I 42.5 R, w/c 0.4). The embedded length was equal to 50 % of original fiber length (50 mm), where the fiber free-end displacement and force resisting to the displacement were monitored. It was pointed out that interfacial shear stress needed to break the bond between the modified fibers and the matrix increased almost by 15–65 % if compared to reference fibers. When the fiber free-end displacement reached to 3.5 mm, the shear strength increased almost twice

PERFORMANCE OF CEMENT COMPOSITES REINFORCED WITH SURFACE-MODIFIED POLYPROPYLENE MICRO- AND MACRO-FIBERS

This paper focuses on the mechanical properties investigation of cement pastes reinforced with surface treated polymer fibers. The cement matrix was composed of Portland cement (CEM I 42.5 R, w/c ratio equal to 0.4). Two polypropylene fiber types (micro- and macro-fibers) were used as randomly distributed and oriented reinforcement in volume amount of 2 %. The fibers were modified in the low-pressure inductively coupled cold oxygen plasma in order to enhance their surface interaction with the cement matrix. The investigated composite mechanical properties (load bearing capacity and response during loading) were examined indirectly by means of four-point bending mechanical destructive tests. A response of loaded samples containing treated fibers were compared to samples with reference fibers. Moreover, cracking behavior development was monitored using digital image correlation (DIC). This method enabled to record the micro-cracks system evaluation of both fiber reinforced samples

RECYCLING OF CONSTRUCTION WASTE USING HIGH-SPEED MILLING PROCESS: DETERMINATION OF WASTE CONCRETE

This paper deals with the use of high-speed milling process for recycling old concrete and direct determination of the potential of input waste. For this purpose, three different types of waste concrete were used: prefabricated railway sleeper, structural concrete of monolithic pillar and prefabricated drainage gutter. The paper directly examines the chemical and phase composition by XRF, X-Ray Diffraction (XRD), Energy Dispersive X-ray Spectrometry (EDS) and microscopic analysis, particle size distribution and pH of the recycled material. Results of those analysis are used to select suitable recycled material. The suitability of choice is supported by mechanical tests of 28-day old cement pastes, where the compressive strength and dynamic modulus of elasticity are observed properties. Specimens measuring 40 × 40 × 160mm are composed of 70 wt.% Portland cement and rest is micronized concrete. In all cases, the results are compared with the reference material

USE OF FINELY GROUND RECYCLED CONCRETE FOR IMPROVEMENT OF INTERFACIAL ADHESION IN FIBER-REINFORCED CEMENTITIOUS COMPOSITES

This paper deals with an improvement and an assessment of a polymeric macro-fibers adhesion to the cement matrix. For this purpose, two approaches were employed – (i) roughening of fibers using a plasma treatment and (ii) an addition of finely ground recycled concrete (amount 30 wt. %) to the matrix ensuring the roughness of interfacial zones. Polyethylene terephthalate (PET) and polypropylene (PP) fibers, both ca. 0.3mm in a diameter, were used. These were surface roughened using a cold oxygen plasma treatment and then observed by means of the scanning electron microscopy. Consequently, pull-out tests of an individual fiber embedded 25mm in the matrix were performed, while the force needed for fiber pullout was recorded. Results have shown that plasma treated fibers reached on a better adhesion with the matrix by up to ca. 5% (PET) and 20% (PP), if compared to reference fibers. When recycled concrete was used, the adhesion increased further by about 5–10% for both fiber types

PLASMA MODIFICATION OF POLYVINYL ALCOHOL MICROFIBERS TO IMPROVE COHESION WITH CEMENT MATRIX

The article describes plasma modifications of the surface of polyvinyl alcohol (PVA) microfibers using oxygen and hydrogen plasma in order to improve the properties of the composite material containing modified microfibers, cement and recyclate. Five different modification times 30, 60, 120, 240 and 480 seconds were applied. Changes on fiber surface were detected by SEM analysis, packed cell wettability measurement, and weight loss during modification. The selected durations of plasma treatment were chosen to produce test samples on which the modulus of elasticity was continuously measured and then bending and compression tests were performed. The measured values were compared with the reference samples. Oxygen modified fibers behavior is more hydrophilic compare with reference fibers, but hydrogen modified fibres behave more hydrophobic than reference fibers

MECHANICAL AND IMAGE ANALYSIS OF ADHESION BETWEEN MINERAL AGGREGATE AND BITUMINOUS BINDER

Asphalt mixtures often fail due to poor interaction between mineral aggregate and bituminous binder. Therefore, many efforts are being made on adhesion improvement between the two materials. In this work, paving grade bitumen 50/70 was doped with two types of adhesion promoters. Asphalt mixtures composed of crushed aggregate Brant coated by binder were made and exposed to stripping water. Then, they were subjected to visual and digital image analysis aiming to quantify aggregate residual bitumen-coated areas. Besides, two cylindrical samples of aggregate were bonded together by a thin film of bitumen doped with adhesion promoters. After solidification of binder, force needed for separation of the two parts was measured. It was shown that residual bitumen-coated areas were increased by 20-30% by adding adhesion promoters into binder. Mechanical adhesion of thus modified binder to aggregate was increased by up to twice