Cement-based Products Research Articles

Comparative Life Cycle Assessment of Conventional, Glass Powder, and Alkali-Activated Slag Concrete and Mortar

This study compares the cradle-to-gate greenhouse gas emissions (GHGs), energy use, water use, and potential environmental toxicity of conventional (Conv), glass powder (GP), and alkali-activated slag (AAS) concrete and mortar. The comparison is based on 1 m3 of concrete/mortar with similar 28-day compressive strength, so the same concrete/mortar member with same dimensions may be manufactured from Conv, GP, or AAS materials and used for same applications. The result shows that compared to a 35-MPa Conv concrete, a 35-MPa GP concrete has, on average, 19% lower GHGs, 17% less energy, 14% less water, and 14–21% lower environmental toxicity. A 35-MPa AAS concrete has 73% lower GHGs, 43% less energy, 25% less water, and 22–94% lower effects for all environmental toxicity categories except an 72% higher ecotoxicity effect. Environmental impact reductions are also found for using GP as a cement replacement in concrete with lower strengths and replacing cement with GP or AAS in mortars with different strengths. The paper concludes that using alternative cementitious materials GP and AAS as cement replacements could significantly reduce the environmental impacts of cement-based products.

Influence of Nanosilica on Properties of Green Cementitious Composites Filled with Waste Sulfite Pulp Fiber and Aminosilane

Developments in the field of green cement-based products are characterized as an important approach to sustainable development and are being devoted much attention by the construction industry. Num ...

Leaching in concretes containing recycled ceramic aggregate from the sanitary ware industry

Abstract The re-use of construction and demolition, ceramic and similar waste in the construction industry has aroused considerable interest in recent years, as an avenue for furthering the sustainable use of resources and reducing the volume of waste dumped in landfills. Recycling materials as components in the manufacture of cement-based products, however, calls for an understanding of the leachability of the elements present in the new materials that may be harmful to human health or the respective ecosystems. The present study addresses the effect of including recycled ceramic sanitary ware waste as a partial substitute (25%) for natural coarse aggregate in the manufacture of recycled concrete in direct contact with water intended for human consumption. The findings show that the inclusion of ceramic aggregate raises the alkali concentration (Na and K) slightly and lowers the concentration of other elements (B, Si, Cl and Mg) in the water. The levels of all the leached elements were observed to be lower than the limits specified in the legislation in effect on water for human consumption. Consequently, these new concretes are apt for use in such applications, for they ensure water quality.

Investigation of autoclaved cement systems with reactive MgO and Al2O3-SiO2 rich fired clay brick

Portland cement (PC) is one of the world's most important building materials, as it is a fundamental component of concrete. However, the manufacture of PC is highly energy intensive and leads to the emission of carbon dioxide (CO2). One promising control measure is the use of industrial wastes and by-products as supplementary cementing materials (SCMs) in order to minimise PC consumption, thereby producing greener cement-based products. This study investigates mechanical properties and phase development of hydrothermally treated cement–ground quartz sand blends with the incorporation of fired clay-brick (CB) waste and reactive magnesia (MgO). The addition of CB waste in autoclaved PC–quartz mortar mixes showed that the alumina–silica rich CB waste was pozzolanic when the Al2O3 accelerated formation and increased crystallinity of Al substituted 1·1 nm tobermorite, resulting in the observed strength gain. Autoclaved mortar specimens incorporating reactive MgO showed a reduction in strength with increasing MgO addition. This was a result of dilution when the relative proportion of PC available for the formation of the strength contributing hydration products including tobermorite is decreased.

Mechanical properties of recycled PET fibers in concrete

Fiber-reinforced concrete represents the current tendency to apply more efficient crack-resistant concrete. For instance, polyethylene terephthalate (PET) is a polyester polymer obtained from recyclable bottles; it has been widely used to produce fibers to obtain cement-based products with improved properties. Therefore, this paper reports on an experimental study of recycled-bottle-PET fiber-reinforced concrete. Fibers with lengths of 10, 15 and 20 mm and volume fractions of 0.05, 0.18 and 0.30% related to the volume of the concrete were used. Physical and mechanical characterization of the concrete was performed, including the determination of compressive strength, flexural strength, Young’s modulus and fracture toughness as well as analysis using mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Flexure and impact tests were performed after 28 and 150 days. No significant effect of the fiber addition on the compressive strength and modulus of elasticity was observed. However, the Young’s modulus was observed to decrease as the fiber volume increased. At 28 days, the concrete flexural toughness and impact resistance increased with the presence of PET fibers, except for the 0.05 vol.% sample. However, at 150 days, this improvement was no longer present due to recycled-bottle-PET fiber degradation in the alkaline concrete environment, as visualized by SEM observations. An increase in porosity also has occurred at 365 days for the fiber-reinforced concrete, as determined by MIP.

Green and durable mortar produced with milled waste glass

The concept of using milled waste glass as partial replacement for cement in cement paste and mortar was investigated to reduce the adverse environmental and energy impacts of cement and cement-based products. Based on the experimental investigations it was found that waste glass, when milled to micro-scale particle size, undergoes pozzolanic reaction with cement hydrates. These reactions bring about favourable changes in the structure, including pore system characteristics of the hydrated cement paste and mortar. Use of milled waste glass, as partial replacement of cement, produced significant gains in the resistance to moisture sorption, chemical stability and improvement in microstructure of the cementitious materials. Milled waste glass was also found to suppress alkali–silica reactions. Unlike normal pozzolanic reactions, those involving glass do not reduce the alkalinity of cement paste; this is favourable to the chemical stability of cement-based materials and the protection of reinforcing steel against corrosion in concrete.alues derived using available design codes.

Building materials. VOC emissions, diffusion behaviour and implications from their use

Five cement- and five lime-based building materials were examined in an environmental chamber for their emissions of Volatile Organic Compounds (VOCs). Typical VOCs were below detection limits, whereas not routinely analysed VOCs, like neopentyl glycol (NPG), dominated the cement-based products emissions, where, after 72 h, it was found to occur, in levels as high as 1400 μg m−3, accounting for up to 93% of total VOCs. The concentrations of NPG were not considerably changed between the 24 and 72 h of sampling.The permeability of building materials was assessed through experiments with a dual environmental chamber; it was shown that building materials facilitate the diffusion of chemicals through their pores, reaching equilibrium relatively fast (6 h).

Fresh concrete and its significance for sustainability

The push for sustainability initiatives in the construction field has been spearheaded by the green building movement. However, cement-based products and concrete are used in a variety of places, and not just buildings. While much effort on the sustainability of cement and concrete industry has been focused on cement production and the hardened state concrete – the fresh state performance and its role in sustainability has often been overlooked. Similar to hardened state concrete properties, understanding the microstructure of the fresh state concrete can provide the direction for tailoring the fresh state properties to improve the quality control, and thus the sustainability of concrete. This paper seeks to provide context for users of cement-based products to understand how the fresh state properties of concrete can be leveraged so that the quality control of concrete can be improved. Concepts such as flocculation, rheology, structural buildup, and formwork pressure will be discussed. The concepts discussed in this paper can be applied to various applications, from building to pavements to bridges to dams.

Modern earth masonry – Structural properties & structural design

There has been recent increased use of earth for construction of buildings in developed countries, largely because of concerns with the environmental impact and embodied carbon from fired bricks and cement-based products. Of all forms of earth construction, the widest impact on modern construction is likely to come from commercially produced unfired earth masonry where large-scale production can significantly reduce costs. While there are benefits to using earth masonry, structural design with earth masonry raises some specific issues that are not necessarily relevant to other forms of masonry construction. This paper summarises these issues and presents results of extensive structural testing on modern earth masonry. The structural properties required for design are compared with typical values for other masonry types in Eurocode 6, showing that commercially produced earth masonry can meet or even exceed the structural capacity of other commonly used masonry systems.

Evaluation of cement-bonded strawboard against alternative cement-based siding products

Cement-bonded strawboard was developed as a new siding product with desired aesthetic attributes, workability and engineering characteristics. The high extractive and wax content of straw presents important challenges to production of cement-bonded strawboard. A broad variety of straw pretreatment techniques were evaluated for enhancement of straw compatibility with hydration of cement. Accelerated processing techniques involve applying pressure for densification and heating system were used. Use of admixtures and the specifics of strawboard production techniques were also essential to successful development of cement-bonded strawboard. The complementary use of these measures contributed towards development of cement-bonded strawboards which met the standard requirements for cement-based siding products and did not exhibit any degradation upon exposure to accelerated aging effects.

Evaluation of surface sealers for concrete hydraulic structures exposed to low temperatures

Many hydraulic structures exhibit downstream cracks and surface degradation due to porous and non air-entrained concrete cast only a few decades ago, wetting–drying and freezing–thawing cycles. These degradations could be prevented by minimizing surface saturation and water infiltration by sealing the concrete surface. Many different types of sealers, such as silanes, siloxanes, boiled linseed oil, epoxies, urethanes and cement-based products, are presently available on the market. However, despite their ready availability, very few or no laboratory or field evaluations have ever been undertaken to evaluate their effectiveness, specifically for hydraulic structures exposed to extremely low temperatures. Consequently, 60 different surface sealers were selected for laboratory evaluation, aimed at minimizing water or moisture infiltration, and to extend the service life of hydraulic structures, besides reducing the harmful effects associated with concrete surface deterioration. The tests carried out on these sealers comprised reduction of absorption and evaporation capacity, durability under freezing–thawing and wetting–drying cycles, acid rain, UV radiation, effect of various parameters, such as concrete water:cement ratio (W/C), sealers application temperature, pH variation, presence of hydrostatic pressure, etc. Preliminary data showed that silanes and siloxanes exhibited satisfactory results, however, products from the same family yielded variable results. This paper summarizes a part of a large study on concrete sealers for hydraulic structures in cold climates.

Rice Husk Ash as a Supplementary Raw Material for the Production of Cellulose–Cement Composites with Improved Performance

Rice husk is an agricultural by-product worldwide in large quantities available. This is a suitable biomass source for energy production. Compared to other agricultural by-products, the burned rice husk presents a high yield of ash (about 20%) mainly composed of silica that will be mostly amorphous when properly incinerated. Extensive research in the past three decades has allowed the introduction of rice husk ash (RHA) as a supplementary raw material in cement-based products, whereby significant improvements in strength and durability can be achieved, also contributing to ecological demands. This paper investigates the influences of two RHA admixtures on the physical and mechanical properties of bamboo-pulp–reinforced cement composites. These fibers suffer early degradation in the alkaline environment. RHA blending will reduce the ordinary Portland cement (OPC) content and can improve strength and density due to more effective particle packing, and significantly diminish alkalinity. The composites were produced in the laboratory by a method resembling the Hatschek process used by the fibrocement industry, with fixed reinforcement content and varying amounts of RHA. The results revealed that partial replacement of ordinary Portland cement by up to 30% of RHA had not impaired the mechanical behavior of the composites. Further, use of low-carbon-content RHA decreased porosity in the matrix and enhanced interfacial bonding of the composites. Since the deterioration of cellulose–cement composites is closely related to moisture movement and alkalinity, it is concluded that introduction of low-carbon content RHA can lead to improved durability performance of these composites.

Photocatalytic Properties of Cement-Based Plasters and Paints Containing Mineral Pigments

Innovative cement-based premix products for surface coating of buildings that possess photocatalytic activity arouse great interest because of the results they can achieve in reducting air pollution and maintaining aesthetics. This photoactivity is induced by a photocatalyst, titanium dioxide, that can accelerate the oxidation processes of air pollutants, particularly nitrogen oxides and volatile organic compounds, which are mainly produced by incomplete combustion of fuel and are present in urban environments through the exhaust gases of motor vehicles. Surfaces that are coated with these products acquire a self-cleaning characteristic (maintenance of original color) because the decomposition of organic compounds significantly reduces the ability of atmospheric particles to adhere to treated surfaces, thus facilitating their removal and ensuring a more durable color. These products are particularly suited for use in highly congested areas (i.e., historical centers of cities, tunnels, roads), where air pollution reaches significant levels. This study describes the photocatalytic performances of a series of premix products containing mineral pigments. The tested products are based on hydraulic binders (natural hydraulic lime and cement), and the pigments are inorganic. A wide range of colors was chosen, and the performances of base products were investigated to provide a wider choice to the designers. After a brief introduction of the principles of photocatalysis, the results of a wide experimental work are described. Some consideration of methods of curing and natural exposure is also reported.

Comparison of the Life Cycle Assessments of an Insulating Concrete Form House and a Wood Frame House

Abstract An environmental life cycle assessment (LCA) was conducted on a single-family house modeled with two types of exterior walls: wood framed and insulating concrete form (ICF). The LCA was carried out in accordance with the guidelines of the ISO 14000 family of standards. The LCA includes the inputs and outputs of energy and materials from (i) extraction and manufacturing of materials, (ii) construction, (iii) occupancy (including heating and cooling energy use), and (iv) maintenance over a 100-year life. The houses were modeled in five cities representing a range of U.S. climates: Miami, Phoenix, Seattle, Washington, and Chicago. The results show that in almost all cases, for a given climate, the environmental impact in each category is greater (worse) for the wood house than for the ICF house. The reduction in environmental impacts provided by the ICF house compared to the wood-frame house varied from 3% to 6%, depending on climate. Furthermore, the most significant environmental impacts are not from construction products but from the production and household use of electricity and natural gas. Since the ICF walls are more highly insulating and energy efficient than the wood-frame walls, the ICF house has lower impacts. Among construction products used in the house, wood products and copper tubing have the largest environmental load, followed by cement-based products.

Leaching studies on cement-based products

Considering the increasing use of alternative fuels and raw materials in clinker manufacture for construction, the environmental behaviour of the resulting cement is a matter of particular concern. As the alternative fuels used in cement manufacture may contain elements not generally found in conventional fuels, this necessitates a study of the leaching performance of cements produced in such processes to evaluate the environmental quality of the final product and guarantee its safe use in construction. The present survey was undertaken to analyse the leaching of heavy metals and other elements from cements manufactured with both conventional and alternative fuels. The results suggest that the controlled use of alternative fuels does not affect the leaching behaviour.

Use of DTA-TG in the evaluation of autoclaved cement-based systems

Fired-clay products such as bricks, tiles and pavers, are made in large volumes for use in a variety of construction applications throughout the world. A significant proportion of them ends up being a waste product either during their production process or the demolition of buildings. High pressure steam curing or autoclaving has proven extremely versatile for the manufacture of cement-based building products incorporating waste materials such as fly-ash and blast furnace slag. The nature of hydration products in an autoclaved cement based system incorporating different amounts of finely ground brick waste was investigated by means of thermal analysis and XRD, and is the subject of this paper.

Metallic aluminum in MSWI fly ash: quantification and influence on the properties of cement-based products

This article focuses on the effects of metallic aluminum contained in municipal solid waste incineration (MSWI) fly ashes on cement-based materials in which they are added. The ash under study was treated by an industrial physicochemical process of neutralization. The paper also presents a method to quantify the metallic aluminum content of ash: it consists in measuring the amount of hydrogen gas produced by the oxidation reaction of metallic aluminum. This method is simple and fast. Results show that studied ash contains an appreciable amount of metallic aluminum. Investigations were carried out to study the incorporation of the ash in concrete: in this case, the presence of metallic aluminum is worrying because it could be responsible for disorders in concrete. In fact, swellings are observed on cement pastes and mortars containing ash during the first 24 h of hydration. A test based on hydrostatic weighing permits to quantify the swelling of fresh cement paste and to study the evolution of this swelling. Causes of swelling are analyzed. Results show that ettringite formation occurs after the end of the expansion reaction. So it can be concluded that metallic aluminum is the sole responsible for the observed swelling. Consequences of swelling are also analyzed by measuring compressive strength of ash-containing mortars: this swelling leads to cracks in the mortars and significant decrease of their compressive strength.

Cement-bonded straw board subjected to accelerated processing

Agricultural residues offer great promise and new challenges as replacement for wood in engineered wood products. Wheat straw, for example, offers desirable geometric and mechanical attributes for replacement of wood in cement-bonded particleboard. The inhibitory effects of wheat straw on hydration of cement, however, represent the major obstacle against development of cement-bonded strawboard. Accelerated processing techniques involving carbonation reactions were successfully employed to produce cement-based board products incorporating wheat straw. Comprehensive mechanical, durability and physical tests confirmed the high potential of cement-bonded strawboard as a versatile building product capable of meeting the requirements in demanding applications.

03/02488 Physical and mechanical properties of cement-based products containing incineration bottom ash: Filipponi, P. et al. Waste Management, 2003, 23, (2), 145–156

03/02488 Physical and mechanical properties of cement-based products containing incineration bottom ash: Filipponi, P. et al. Waste Management, 2003, 23, (2), 145–156

Physical and mechanical properties of cement-based products containing incineration bottom ash

This paper presents the results of a wider experimental programme conducted in the framework of the NNAPICS (“Neural Network Analysis for Prediction of Interactions in Cement/Waste Systems”) project funded by the European Commission and a number of industrial partners under Brite-EuRamIII. Based on the fact that bottom ashes from waste incineration are classified as non-hazardous wastes according to the European Waste Catalogue, the aim of the present work was to investigate the feasibility of addressing the potential use of such residues in cement-based mixtures. This issue was suggested by the analysis of the properties of different bottom ashes coming from Italian municipal and hospital solid waste incinerators, which showed a chemical composition potentially suitable for such applications. Different mixes were prepared by blending bottom ash with ordinary Portland cement in different proportions and at different water dosages. The solidified products were tested for setting time and bulk density, unconfined compressive strength and evaporable water content at different curing times. The results of the experimental campaign were analysed through a statistical procedure (analysis of variance), in order to investigate the effect of mixture composition (waste replacement level and water dosage) on the product properties.