Valorisation of GRP Dust Waste in Fired Clay Bricks

In Europe, the total amount of Glass Reinforced Plastic (GRP) waste is increasing. In order to valorise GRP dust (GRPd) waste and to reduce the consumption of nonrenewable resources in building materials, GRPd has been already investigated in cementitious materials where it gives even an improvement in some performances of the final products. Valorisation of GRPd waste in the production of bricks can be considered as a further alternative. In this paper, GRPd waste was substituted to the clay volume at 5% and 10% for the manufacturing of fired clay bricks. All specimens were subjected to a firing temperature of 850°C for 6 hours, then tested and compared in terms of porosity, compressive and flexural strengths, density, and water absorption. Despite a decrease in compressive strength up to 46% with 10% of GRPd substitution and an increase of water absorption from 14% to 29% with 5% and 10% of GRPd substitution, respectively, an increase in terms of lightness (about 10%), maximum flexural strength (up to 31%), and deflections at the maximum load (up to 130%) has been registered by specimens with 10% of GRPd substitution

Recycled Glass as Aggregate for Architectural Mortars

Abstract The possibility of recycling mixed colour waste glass as it is for manufacturing decorative architectural mortars, has been investigated. In mortars, the 0–33–66–100% of calcareous gravel volume has been replaced with recycled glass cullets, with no other inorganic addition. To mitigate the possible alkali–silica reaction, mixes with a hydrophobic admixture were also compared. The obtained results show that the replacement of calcareous gravel with glass cullets of similar grain size distribution permits to reduce the dosage of the superplasticizer admixture to obtain the same workability of fresh mortar; it does not affect significantly the mechanical performances, the water vapour permeability and the capillary water absorption but it reduces significantly the drying shrinkage deformation. The used recycled glass is classified as no reactive in terms of alkali–silica reaction neither in water nor in NaOH solution following the parameters of the current normative, even in the absence of the hydrophobic admixture. The hydrophobic admixture further delays the expansion trigger but not the speed of its propagation

Stainless and Galvanized Steel, Hydrophobic Admixture and Flexible Polymer-Cement Coating Compared in Increasing Durability of Reinforced Concrete Structures

The use of stainless or galvanized steel reinforcements, a hydrophobic admixture or a flexible polymer-cement coating were compared as methods to improve the corrosion resistance of sound or cracked reinforced concrete specimens exposed to chloride rich solutions. The results show that in full immersion condition, negligible corrosion rates were detected in all cracked specimens, except those treated with the flexible polymer-cement mortar as preventive method against corrosion and the hydrophobic concrete specimens. High corrosion rates were measured in all cracked specimens exposed to wet-dry cycles, except for those reinforced with stainless steel, those treated with the flexible polymer-cement coating as restorative method against reinforcement corrosion and for hydrophobic concrete specimens reinforced with galvanized steel reinforcements

effect of the type of surface treatment and cement on the chloride induced corrosion of galvanized reinforcements

The effect of a new passivation treatment, obtained by immersion of the galvanized reinforcements in a trivalent chromium salts based solution, on the chlorides induced corrosion has been investigated. To investigate also the effect of cement alkalinity on corrosion behaviour of reinforcements, concretes manufactured with three different European cements were compared. The obtained results show that the alternative treatment based on hexavalent chromium-free baths forms effective protection layers on the galvanized rebar surfaces. The higher corrosion rates of zinc coating in concrete manufactured with Portland cement compared to those recorded for bars in concrete manufactured with pozzolanic cement depends strongly on the higher chloride content at the steel concrete interface

Innovative hydraulic lime-based finishes with unconventional aggregates and TiO2 for the improvement of indoor air quality

This paper reports a study on 8 unconventional hydraulic lime-based mortars able to improve indoor air quality by acting as passive systems. Mortars have been prepared with commercial sand or highly adsorbent materials as aggregates with/without TiO2 as photocatalytic agent, to test also the decomposition of airborne pollutants. Mechanical properties, hygrometric behavior, inhibition of growth of molds and depollution properties have been tested. Despite using porous materials (zeolite and activated carbon), in mortars with unconventional aggregates, compressive strength is higher than in sand-based ones, with a more than double higher water vapor permeability. Zeolite-based mortars have the highest moisture buffering capacity followed by silica gel- and activated carbon-based mortars (1.5–2 times higher than reference, respectively, because of the high porosity of unconventional aggregates). Sand-based mortars show optimum inhibitory capacity against fungal growth. Concerning unconventional aggregates, silica gel mortars have good inhibitory capacity, whereas zeolite and activated carbon give to mortars an optimum substrate for molds. Mortars with unconventional aggregates as silica gel remove more than 80% of tracer pollutant after 2 h of test, whereas zeolite-based mortars remove the 65% of it after 120 min. TiO2 enhances depollution properties as photocatalytic oxidation agent when the mortar is close to saturation

One-Part Alkali-Activated Pastes and Mortars Prepared with Metakaolin and Biomass Ash

Common alkali-activated materials (AAMs) are usually manufactured with highly alkaline solutions. However, alkaline solutions are dangerous for workers who must wear gloves, masks, and glasses when handling them. This issue makes common (or two-part) AAMs not user-friendly and problematic for bulk production if no safety procedures are followed. In this paper, the possibility of manufacturing alkali-activated pastes and mortars without alkaline solution is investigated. These innovative one-part AAMs have been prepared with metakaolin as the aluminosilicate precursor, potassium-rich biomass ash as the alkaline activator, and water. AAMs have been prepared by varying the K/Al molar ratio: pastes have been studied in terms of reaction kinetics, through isothermal calorimetry, and mortars have been tested in terms of mechanical compressive strength. Results show that the K/Al molar ratio governs both the reaction kinetics and the mechanical strength of these innovative materials. The highest compressive strength is obtained when the K/Al ratio is equal to 2.5 and the water/solid ratio is equal to 0.49. If biomass ash is heated at 700 °C to decompose the calcium carbonate, its reactivity and the final compressive strength increase

Geopolymeric and cementitious mortars for buildings: comparison at the same strength class

La tesi ha riguardato lo studio di malte geopolimeriche e cementizie a parità di classe di resistenza meccanica (R1, R2, R3 e R4 secondo la UNI EN 1504-3:2006) per applicazioni edili. Nella prima parte sono state testate malte cementizie contenenti fibre o tessuti come rinforzo di pannelli murari assemblati con malta di allettamento in calce aerea o cementizia. I rinforzi migliori sono risultate le malte di classe R2 contenenti fibre in polipropilene, poiché hanno impedito il collasso sotto compressione assiale e incrementato del 47% la resistenza diagonale dei pannelli murari assemblati con malta cementizia. Nella seconda parte, malte cementizie e geopolimeriche appartenenti alle classi R1, R2, R3 e R4 sono state confrontate in termini di densità, lavorabilità, modulo elastico dinamico, tensione di aderenza, porosità, permeabilità al vapore acqueo, assorbimento d’acqua per capillarità, ritiro igrometrico libero e contrastato, resistenza ai solfati e comportamento a corrosione di eventuali barre immerse in acciaio nero e zincato indotta da cloruri o carbonatazione. Nei geopolimeri il ritiro libero è maggiore rispetto alle malte cementizie, ma quello contrastato è minore per via del basso modulo elastico. Le dimensioni dei pori influenzano la permeabilità al vapore, maggiore nei geopolimeri, e l’assorbimento d’acqua, minore nei geopolimeri con cenere volante. L’alta alcalinità dei geopolimeri ritarda il raggiungimento dello stato passivo delle armature, soprattutto se zincate, ma dopo un mese di stagionatura si ottengono velocità di corrosione simili a quelle riscontrate nelle malte cementizie. Durante l’esposizione ai cloruri e dopo carbonatazione, i geopolimeri in cenere volante proteggono maggiormente le armature in acciaio nero; mentre le malte cementizie proteggono maggiormente gli acciai zincati. Infine, è stata studiata la possibilità di ottenere geopolimeri “one-part” aggiungendo solo acqua agli ingredienti solidi per renderne più facile l’utilizzo pratico.The work deals with the study of geopolymeric and cementitious mortars with the same mechanical strength class (R1, R2, R3 and R4 according to UNI EN 1504-3:2006) for building applications. In the first part, cementitious mortars strengthened with fibres or textiles applied to masonry panels assembled with hydrated lime- or cement-based joining mortar were compared. R2 mortar with polypropylene fibres is the best reinforcement, since it hinders the collapse under axial compression and enhances of 47% the diagonal strength of masonry panels assembled with cement-based joining mortar. In the second part, cementitious and geopolymeric mortars belonging to R1, R2, R3 and R4 strength classes were tested and compared in terms of density, workability, dynamic modulus of elasticity, adhesive strength, porosimetry and water vapour permeability. Capillary water absorption, drying and restrained shrinkage, resistance to sulphate attack, corrosion behaviour of embedded black and galvanized reinforcements in chloride-rich solution and after carbonation were also investigated. In geopolymers, drying shrinkage is higher than that of cementitious mortars, but restrained shrinkage is lower due to lower modulus of elasticity. Pore dimensions affect water vapour permeability, more pronounced in geopolymers, and capillary water absorption, much lower in fly ash ones. The high alkalinity of geopolymers delays the achievement of the passive state in particular for galvanized steels, but after one month of curing they reach the same corrosion rates of those embedded in cementitious mortars. During chlorides exposure and after carbonation, fly ash geopolymers offer the highest protection to embedded black bars. On the other hand, cementitious mortars maintain the lowest corrosion rates of galvanized steels. To permit easier practical use, the manufacture of one-part “just add water” geopolymers by substituting the alkaline activators with biomass ash was also investigated

Effect of Gasification Char and Recycled Carbon Fibres on the Electrical Impedance of Concrete Exposed to Accelerated Degradation

This paper aims to evaluate the effect of carbon-based conductive recycled additions, i.e., recycled carbon fibres (RCF) and gasification char (GCH), on the mechanical, electrical, and durability properties of concretes. The obtained results show that the compressive strength of concrete is not affected by conductive additions, whereas electrical impedance, measured according to Wenner’s method, is significantly reduced (6%, 30% and 74% with RCF, GCH, and their combination, respectively) to the advantage of self-sensing properties. As durability is concerned, conductive additions slightly increase capillary water absorption, whereas they decrease chloride ingress through diffusion and do not significantly modify carbonation resistance

Geopolymeric and cementitious mortars for buildings: comparison at the same strength class

La tesi ha riguardato lo studio di malte geopolimeriche e cementizie a parità di classe di resistenza meccanica (R1, R2, R3 e R4 secondo la UNI EN 1504-3:2006) per applicazioni edili. Nella prima parte sono state testate malte cementizie contenenti fibre o tessuti come rinforzo di pannelli murari assemblati con malta di allettamento in calce aerea o cementizia. I rinforzi migliori sono risultate le malte di classe R2 contenenti fibre in polipropilene, poiché hanno impedito il collasso sotto compressione assiale e incrementato del 47% la resistenza diagonale dei pannelli murari assemblati con malta cementizia. Nella seconda parte, malte cementizie e geopolimeriche appartenenti alle classi R1, R2, R3 e R4 sono state confrontate in termini di densità, lavorabilità, modulo elastico dinamico, tensione di aderenza, porosità, permeabilità al vapore acqueo, assorbimento d’acqua per capillarità, ritiro igrometrico libero e contrastato, resistenza ai solfati e comportamento a corrosione di eventuali barre immerse in acciaio nero e zincato indotta da cloruri o carbonatazione. Nei geopolimeri il ritiro libero è maggiore rispetto alle malte cementizie, ma quello contrastato è minore per via del basso modulo elastico. Le dimensioni dei pori influenzano la permeabilità al vapore, maggiore nei geopolimeri, e l’assorbimento d’acqua, minore nei geopolimeri con cenere volante. L’alta alcalinità dei geopolimeri ritarda il raggiungimento dello stato passivo delle armature, soprattutto se zincate, ma dopo un mese di stagionatura si ottengono velocità di corrosione simili a quelle riscontrate nelle malte cementizie. Durante l’esposizione ai cloruri e dopo carbonatazione, i geopolimeri in cenere volante proteggono maggiormente le armature in acciaio nero; mentre le malte cementizie proteggono maggiormente gli acciai zincati. Infine, è stata studiata la possibilità di ottenere geopolimeri “one-part” aggiungendo solo acqua agli ingredienti solidi per renderne più facile l’utilizzo pratico.The work deals with the study of geopolymeric and cementitious mortars with the same mechanical strength class (R1, R2, R3 and R4 according to UNI EN 1504-3:2006) for building applications. In the first part, cementitious mortars strengthened with fibres or textiles applied to masonry panels assembled with hydrated lime- or cement-based joining mortar were compared. R2 mortar with polypropylene fibres is the best reinforcement, since it hinders the collapse under axial compression and enhances of 47% the diagonal strength of masonry panels assembled with cement-based joining mortar. In the second part, cementitious and geopolymeric mortars belonging to R1, R2, R3 and R4 strength classes were tested and compared in terms of density, workability, dynamic modulus of elasticity, adhesive strength, porosimetry and water vapour permeability. Capillary water absorption, drying and restrained shrinkage, resistance to sulphate attack, corrosion behaviour of embedded black and galvanized reinforcements in chloride-rich solution and after carbonation were also investigated. In geopolymers, drying shrinkage is higher than that of cementitious mortars, but restrained shrinkage is lower due to lower modulus of elasticity. Pore dimensions affect water vapour permeability, more pronounced in geopolymers, and capillary water absorption, much lower in fly ash ones. The high alkalinity of geopolymers delays the achievement of the passive state in particular for galvanized steels, but after one month of curing they reach the same corrosion rates of those embedded in cementitious mortars. During chlorides exposure and after carbonation, fly ash geopolymers offer the highest protection to embedded black bars. On the other hand, cementitious mortars maintain the lowest corrosion rates of galvanized steels. To permit easier practical use, the manufacture of one-part “just add water” geopolymers by substituting the alkaline activators with biomass ash was also investigated

One part geopolymers activated with potassium-rich biomass ashes

Geopolymers are obtained by the chemical reaction between an aluminosilicate powder and an alkaline solution. Even if geopolymers do not contain Portland cement, they are similar to cementitious materials. Recently, many authors have tried to prepare geopolymers without alkaline activators, since they are user-hostile. These new materials are called one-part geopolymers and appear as a cementitious powder that can polymerize with water. The aim of this work is to investigate the possibility of using a potassium-rich biomass ash for the activation of one-part geopolymers