To investigate the fundamental causes of utility air voids content failures in asphalt layers to achieve Specification for the Reinstatement of Openings in Highways (SROH) compliant performance

The linkage between air voids content and durability in footways reinstatements with the limits currently in SROH is non-proven and unsupported by evidential research or trial data. Compounding of errors, particularly in density measurement of core samples and subsequent variability, generate biased air void content results that make the compliance largely a matter of chance. This led to a very wide range of predicted outcomes, putting both the contractor and the client at unacceptable risk. The use of a measured in situ air voids content criteria in a specification for footway reinstatements, where the entire operation is in restricted areas with hand laying process using recipe mixed materials, cannot be sustained on technical grounds with respect to relevant British Standard and Transport Research Laboratory (TRL) guide. Taking account of the service loads, nature and scale of works in footways, an in-service guarantee by the undertaker for an agreed extended period, linked to an allowable intervention level, could be a simple, realistic and acceptable solution, ensuring a durable reinstatement that removes the financial risk of failure from the highway authority

Future of clay-based construction materials – A review

Sustainability in the manufacture of different construction materials raises many important issues. Nowadays, there is increasing demand for such materials to be produced using environmentally friendly, low energy consuming production methods. This paper presents a review of the current research relating to the use of various production techniques for clay-based construction materials. The techniques which will be reviewed are: blending and stabilising, alkali activation (geopolymerisation) and the use of microwave heating as an innovative sintering, curing and drying method. The advantages and disadvantages of each technique will be discussed. Additionally, a comparison between the environmental and economic aspects of the studied production techniques along with some suggestions to improve the sustainability of different production techniques will be discussed

Analytical investigation of hydration mechanism of a non-Portland binder with waste paper sludge ash

The development and production of new materials requires advanced analytical characterisation to explain the relation between the physico-chemical structure of the material and its properties. Highly integrated microelectronic structure analysis of surfaces with laser beams and X-ray fluorescence aided devices are found to be helpful for providing important information, including the interrelationships between physical, chemical, mechanical and durability characteristics of the new developed products. In most instances no single technique provides all the needed information and hence simultaneous application of several techniques becomes necessary. This study was aimed for hydration analysis, characterization and evaluation of a new novel non-Portland binder (NPB) with waste paper sludge ash (PSA) using FTIR and TG/DTA. The progressive formation of hydration products within the non-Portland binder was identified and their microstructural characteristics were analysed. The stable and non-expansive nature of secondary ettringite formation was also identified after a period of 365 days curing

Development of New Precursors for One-Part Alkali-Activated Geopolymer Using IndustrialWastes

Conventional two-part alkali activation has many drawbacks: the hazardous activating solution, which makes it less friendly to handle and the absence in long-term availability of its main precursors such as fly ash and ground granulated furnace slag. This research aimed to develop a one-part alkali-activated cement, which is free of chemical solutions. A blend of alumina-silicate rich materials with adequate alkaline content to minimise the limitations associated with the current (AAC) relating to source materials was utilised. At the same time, applying alternative activation methods such as thermo-mechanical activation, alkali-thermal activation or thermo-chemical activation of new (AAC) precursors were investigated. Materials were analysed in terms of their physical, chemical and metallurgical properties to understand the changes after thermal activation. Enhanced compressive strength was recorded from individual thermal activation of the materials at 450 °C and 950 °C

Investigating effective building fabric as a passive cooling technique to combat overheating in UK residential buildings

The Intergovernmental Panel on Climate Change has predicted that the earth’s temperature is increasing by 1.5°. Research indicates that 9 out of 10 homes within the United Kingdom may experience overheating. The growing concern of overheating within residential homes should be resolved before occupants turn to the use of mechanical means. Passive cooling strategies need to be implemented into residential homes as a contribution to the current aim of the United Kingdom government to reduce carbon emission by 77% by 2035 compared to 1990 levels. This research investigates the most appropriate building construction fabric as a passive cooling strategy that can be implemented into residential homes to mitigate the impact of climate change. Computational fluid dynamic simulation of different building fabric scenarios of EcoBIM construction, Passivhaus construction and Standard construction are performed using EDSL Tas thermal modelling software. The simulations incorporate Chartered Institution of Building Services Engineering (CIBSE) weather data files for Glasgow, Belfast, Manchester, and London for 2020s, 2050s and 2080s climatic projections. The results from this investigation show that the standard construction overall did present the most effective solution against the number of hours experiencing overheating. The research provides evidence to suggest that the current 2021 Building Regulations in place are not at risk of experiencing overheating in Manchester, Belfast, and Glasgow across the 2020, 2050 and 2080 simulations, as well as for the 2020 and 2050 London simulation. This proposes that within these locations the current 2021 Building Regulations regarding the U values in document Part-L shall be deemed as having an acceptable tolerance to overheating, and further adaptations are not necessary, as there is no concern regarding the encountering of overheating within these regions and weather periods. Furthermore, the utilization of the EcoBIM construction on average did cause significant increased risk of overheating. The only exception to this was the 2080 simulation for London in which the EcoBIM construction obtained 71.10% less overheating compared to the Standard construction. The outcome of this research suggests that London is at extreme risk of enduring overheating by 2080, as all the constructions during this simulation process were perceived as exceeding the CIBSE TM59 requirement

Investigating the Mechanical and Durability Performance of Cement Mortar Incorporated Modified Fly Ash and Ground Granulated Blast Furnace Slag as Cement Replacement Materials

The process of cement manufacturing produces a huge amount of carbon dioxide (CO2). The utilization of alternative waste materials from various industrial processes as a partial substitution to cement is encouraged due to environmental and specific technical requirements. This strategy will have the potential to reduce cost of cement, conserve energy, and reduce waste volumes. Therefore, the aim of this research is to investigate effect of the replacement of cement with modified fly ash (MFA) and ground granulated blast furnace slag (GGBS) to reach 80% total replacement on mechanical and durability performance of cement mortar. Normal consistency, the initial and final setting times, compressive strength and electrical resistivity of all the ternary mixtures were determined and compared with the control binder. Compressive strength and electrical resistivity were tested at various curing ages of 3, 7, 14, and 28 days. Test results revealed that the normal consistency of the ternary mixtures increased with increasing the GGBS and MFA content, while the initial and final setting time decreased compared to that of control mixture. The results also showed that the compressive strength of all the ternary blends mortars were lower at early and later ages in comparison with control mortar. The reductions in the compressive strengths of the ternary mixtures T40, T60 and T80 compared to the control mixture were approximately 16%, 29% and 37%, respectively at 28 days. The surface electrical resistivity of ternary blends mixtures was higher than the control mixture at all curing ages. The use of GGBS and MFA in the production of cement mortar and concrete can significantly help in reducing the CO2 emissions of the cement industry and reduce the overall cost of cement

Prospect and barrier of 3D concrete: a systematic review

This paper aims to explore the current state of the art and potential of 3D concrete printing and its use in large-scale applications. The study analysed 373 academic research, all of which were obtained from the Scopus database. The review conducted on some crucial issues on development of 3D concrete that included materials and their desirable properties, printer nozzle developments, reinforcement in printing, geopolymers as printing materials, and the use of coarse graded aggregates. This study provides researchers and institutions with an in-depth insight into 3D concrete printing and research trends worldwide and assesses the future of 3D concrete printing in large-scale applications. The requirement of more research on the mechanics of 3D printers, standardising a printer nozzle, the automation of reinforcing processes, and use of coarse graded aggregate for large-scale structural application were identified in this review. It also shows how 3D concrete printing has evolved and changed over time and gives an insight into the future of 3D concrete printing—making this scientometric review a framework for future studies

Long-term performance of novel high-calcium one-part alkali-activated cement developed from thermally activated lime kiln dust

The traditional activation approach for alkali-activated cement AAC has several problems resulting mainly from the hazardous and corrosiveness of the alkaline chemicals, such as (NaOH, Na2SiO3), which in turn impede the utilisation of AAC in the construction fields. In this study, A second generation of alkali activated binder was developed using Metakaolin (MK) and natural pozzolan material (NP) (as a source of alumina-silicate), these materials were activated using high-calcium lime kiln dust as solid activator to transform the alumina-silicate crystalline phases to cementitious hydrated products. This was achieved with the aid of heat treatment of materials at different temperatures. Raw materials and final AAC samples were characterised using analytical methods, such X-Ray powder diffraction (XRD), Thermogravimetric Analysis (TG-DTA), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Additionally, long-term compressive strength, chemical and microstructural performance were investigated. The transformation of raw materials from crystalline to amorphous phases happened due to the effect of the heat treatment and the formation of stratlingite products in the final AAC paste, which were evidenced using the mentioned characterisation methods. The findings of the present study proved that the compressive strength of the new binder reached 27 MPa and 51 MPa after 28 and 180 days of curing, respectively, ensuring a progressive as well as a higher degree of alkali-activation and disappearance of unreacted alkaline substances in the final AAC products

Developing One-Part Alkali-Activated metakaolin/natural pozzolan Binders using Lime Waste as activation Agent

Among the several schemes that have been reported to be a satisfactory alternative to Portland cement is Alkali Activated Cement (AAC), which has recently started to gain greater consideration in construction sectors. Conventional two-part alkali activation has many drawbacks, including the activating solution being viscous, problematic and non-user friendly to handle. Thus, this research aims to produce a one-part alkali activated metakaolin/natural pozzolan, by using an earth alkaline source (rich in CaO) from waste material (lime kiln dust), as an activating precursor to break the alumina-silicate crystalline phases. Thermal treatment of materials at two levels of treatment (450°C and 950°C), was used as an assisted activation approach. Analytical techniques including X-Ray powder diffraction XRD, Thermogravimetric Analysis TG-DTA, Fourier Transform Infrared Spectroscopy FTIR and Scanning Electron Microscope SEM, were utilised to investigate the performance of the developed materials at a molecular level. Reduction of crystalline peaks as well as the appearance of new wollastonite minerals within the calcined lime kiln dust, contributed to the development of 27 MPa compressive strength after 28 days. The dissolution made through the pozzolanic reaction as well as thermal treatment evidently contributed to transform crystalline to amorphous phases