Effect of Granular Silica Aerogel as Filler on Tensile and Flexural Strengths and Moduli of Stone-Wool-Fibre-Reinforced Composite as Rigid Board Roof Insulation Material

Installation of stone wool as thermal insulation in the roof assembly can be adopted to store heat in the living space, if the building is exposed to cold weather, and, inversely, to retard heat from entering the living space, if it is exposed to hot weather. In spite of the effectiveness of stone wool as a roof insulation material, during installation, it can cause irritation to the skin and can be hazardous to the lungs. Therefore, incorporation of stone wool with other materials to form a rigid board, without compromising its effectiveness as a roof insulation material, is imperative. Strength properties of a stone-wool-fibre-reinforced high-density polyethylene (HDPE) composite roof insulation material were studied. Granular silica aerogel, which possesses an ultra-low thermal conductivity, was added as filler to reduce the thermal conductivity of the composite. Hot compression moulding was performed to prepare samples of the composite with varying silica aerogel content of 0, 1, 2, 3, 4, and 5 wt. %. Findings suggest that 2 wt.% is the optimum silica aerogel content as it resulted in the highest flexural strength and modulus, which is 24.4 MPa and 845.85 MPa, respectively, even though it reduced the tensile strength and modulus by 10% and 4.45% respectively, relative to 0 wt. %, which can be considered as inconsequential. Higher silica aerogel content above 2 wt. % may result in poor interfacial adhesion and low compatibility to the stone wool fibre and HDPE, which further reduces the tensile and flexural strengths and moduli of the composite.

Antibacterial Properties and Cytotoxicity of 100% Waste Derived Alkali Activated Materials: Slags and Stone Wool-Based Binders

In this study we compare the leaching behavior and the antibacterial and cytotoxic properties of 100% slag or stone wool derived alkali activated materials. The antibacterial activity was measured as the inhibiting capacity against two Gram-negative bacterial strains, Escherichia coli and Pseudomonas aeruginosa and one Gram-positive bacterial strain: Enterococcus faecalis. The cytotoxicity properties were tested on mouse embryonic fibroblast NIH-3T3 cell-line. It was proved that the high quality of the 3D aluminosilicate network of the consolidated materials obtained from powders of CaO or MgO-rich slags or stone wool, opportunely activated with NaO and/or Na-silicate, was capable of stabilizing heavy metal cations. The concentrations of leachate heavy cations were lower than the European law limit when tested in water. The effect of additives in the composites, basal fibers or nanocellulose, did not reduce the chemical stability and slightly influenced the compressive strength. Weight loss in water increased by 20% with basalt fibers addition, while it remained almost constant when nanocellulose was added. All the consolidated materials, cement-like in appearance, exhibited limited antibacterial properties (viability from 50 to 80% depending on the bacterial colony and the amount of sample) and absence of cytotoxicity, envisaging good acceptance from part of the final consumer and zero ecological impact. CaO-rich formulations can replace ordinary Portland cement (showing bacterial viability at 100%) with a certain capability for preventing the reproduction of the E. coli and S. aureus bacteria with health and environmental protection results.

Life Cycle Energy and Environmental Assessment of the Thermal Insulation Improvement in Residential Buildings

The refurbishment of the building stock is a key strategy towards the achievement of the climate and energy goals of the European Union. This study aims at evaluating the energy and environmental impacts associated with retrofitting a residential apartment to improve its vertical envelope thermal insulation. Two insulation materials, stone wool and cellulose fibers, are compared. The life cycle assessment methodology is applied assuming 1 m2 of retrofitted vertical envelope as functional unit. Moreover, to estimate the net energy and environmental benefits achievable in the retrofitted scenario compared with the non-retrofitted one, a second analysis is performed in which the system boundaries are expanded to include the building operational phase, and 1 m2 of walkable floor per year is assumed as reference. The results show that the use of cellulose fibers involve lower impacts in most of the assessed categories compared to stone wool, except for abiotic resource depletion. In detail, the use of cellulose fibers allows to reduce the impact on climate change up to 20% and the consumption of primary energy up to 10%. The evaluation of the net energy and environmental benefits shows the effectiveness of the retrofit energy policies.