This paper reports on stabilised clay-hemp building material for sustainability and low carbon use. Ground Granulated Blast-furnace Slag (GGBS) was used as a partial substitute for conventional stabiliser (lime or Portland cement) to stabilise Lower Oxford Clay (LOC) incorporating industrial hemp. The development of stabilised clay-hemp building material is expected to underpin the potential of commercial production of non-fired stabilised hemp walls, hemp blocks and hemp bricks, with a potential to offer an environmentally friendly alternative to traditional concrete, fired clay bricks and cement bricks. The parameters considered in this study are: material characterisation, unconfined compressive strength, linear expansion and cost. The 50-day linear expansion results for the test specimens showed that the maximum overall expansion rate for all the stabilised mixtures was 2%. The expansion behaviour of all stabilised clay-hemp material was significantly reduced with the presence of GGBS. The cost analysis results showed that the stabilised clay-hemp material manufactured with lime – GGBS system had the lowest net present value.

Ground Granulated Blast-furnace Slag (GGBS) and Pulverised Fuel Ash (PFA) were used to replace up to 60% of Portland cement (PC) in concrete. The testing program of the concrete included the determination of the consistency of fresh concrete, the measurement of the density and compressive strength of the hardened products cured for up to 56 days and the evaluation of their durability via visual inspections and strength loss calculations after the freeze and thaw cycles. The results showed that the blend proportion and type had affected the consistency of the fresh concrete. Replacing the PC with 20% for PFA or 40% for GGBS had similar performances as the control mix. The durability of concrete subject to freeze and thaw had little effect on the concrete specimens. It was observed that the concrete without blends suffered the worst, resulting in chips along the edges of the cube and scaling of the faces compared to mixes with 20% GGBS and 20% PFA which resulted in increased durability. However, blended concrete exhibited more loss in strength compared to the concrete without cement blends.

This research work reports the potential of using Pulverised Fuel Ash (PFA) as a partial substitute for Portland Cement (PC) in the development of concrete. PFA is a by-product of the combustion of pulverized coal in electric power generating plants. Its use in concrete will alleviate the environmental concern for PFA disposal and ease the growing shortage and increasingly high cost of PC. In order to investigate the cement replacement potential of PFA, six types of mixes, at varying PFA replacement levels were designed— 5%, 10%, 15%, 20%, 25% and 30%; all with a water binding ratio of 0.6 and tested at 7, 14, and 28 days. The testing programme included material characterization; the determination of slump value and compressive strength. The results showed that the addition of PFA to the concrete mix causes the compressive strength to reduce at early age and that the slump values increased as the quantity of PFA increased in the mix. Index Terms Pulverised Fuel Ash, Slump, Concrete, Compressive Strength

This work reports the potential of using Brick Dust Waste (BDW) as a partial substitute for clay in the development of unfired clay building materials (brick, block and mortar). BDW is a waste material from the cutting of fired clay bricks. There are various reasons necessitating the cutting of bricks — corner bricks, construction of chimneys, and other uses needing bricks of various shapes and sizes. This results in the disposal of BDW as an environmental problem of concern. In order to investigate the clay replacement potential of BDW, four types of mixes were designed at varying BDW replacement levels — 5%, 10%, 15% and 20%. Ground Granulated Blastfurnace Slag, an industrial by-product from steel manufacture was activated using quick lime and the mixture was used to stabilise Mercia mudstone clay for unfired clay production. The 56 day compressive results using cylinder test specimens showed a significant strength gain (up to 2.1 N/mm2). Overall, the results suggest that it is possible to develop unfired clay building material using up to 20% BDW as partial substitutes for primary clay.

This paper presents the results of an investigation for the application of alumina filler wastes and coal ash waste for unfired brick production. Mechanical test and durability assessment were carried out on unfired brick test specimens made using marl clay soil and alumina filler waste as a target material, and 70% mix of coal ash waste were used as commercials additive (Portland cement and Lime) replacement. The laboratory results demonstrate that the compressive strength resistance of the unfired bricks reduced as the clay replacement level increased. The unfired brick test specimens made with the blended mixtures containing coal ash waste and lime tended to achieve higher strength values when compared with the coal ash waste and Portland cement blends. The unfired brick test specimens were able to withstand the repeated 48-hour freezing/thawing cycles. The results obtained suggest that there is potential to manufacture unfired bricks from alumina filler waste and coal ash waste.

This paper reports on designed non-fired clay mixes for sustainability and low carbon use. Ground Granulated Blastfurnace Slag (GGBS), an industrial by-product, was used as a partial substitute for conventional stabiliser (Lime or Portland cement) to stabilise Kaolinite Clay (KC) and Lower Oxford Clay (LOC), for sustainable and low carbon non-fired clay building material production. Although GGBS has been used extensively in concretes to reduce the carbon footprint, there is an unexplored potential for its use as a cement replacement for stabilised soil production. The benefits of using GGBS in non-fired clay building material development include lower emissions of greenhouse gases and improved durability. The parameters considered under this study are: (1) material characterisation, (2) unconfined compressive and (3) durability. For the assessment of durability, a MX 2000VJ Tech multi-channel data logger equipped with a digital displacement transducer and computer device was employed to monitor the linear expansion behaviour of the stabilised test specimens. The 90-day unconfined compressive results for the test specimens showed that there is significant strength gain (up to 5N/mm2) for all the stabilised mixtures. The lime-activated GGBS stabiliser has significantly higher influence in the strength gain compared to the equivalent PC-based system. These results suggest that there is potential in using Lime or Portland cement activated GGBS blend for the stabilisation of natural clay soil for sustainable and low carbon building materials production.

Currently there is a growing pressure on energy efficiency for new buildings in the UK and worldwide. This has arisen partly due to the increasing awareness of the public for sustainable building construction. In addition, there is pressure on building materials manufacturers, due to new government regulations and legislations that are targeting energy usage and carbon dioxide emissions in new buildings. This paper reports on unfired clay bricks for environmental and sustainable use. Lime or Portland cement was used as an activator to an industrial by-product (Ground Granulated Blastfurnace Slag) to stabilise Lower Oxford Clay for unfired clay brick production. Portland cement was used in the formulation of the unfired clay brick test specimens predominantly as a control. Industrial scale brick specimens were produced during two separate industrial trials. The first trial was at Hanson Brick Company Ltd, Bedfordshire, UK, while the second was carried out at PD Edenhall Ltd, Bridgend, South Wales, UK. From the environmental and sustainability analysis results, the unfired clay material has shown energy-efficiency and suggests a formidable economical alternative to the firing of clay building components. This study is one of the earliest attempts to compare fired and unfired clay technologies, and also to combine energy use and CO2 emission for the evaluation of unfired clay bricks relative to those bricks used in mainstream construction. This is an attempt to come up with one parameter rating. The overall results suggest that the spinoff from this technology is an invaluable resource for civil engineers and other built environment professionals who need quick access to up-to-date and accurate information about the qualities of various building and construction materials.

This paper reports on a laboratory and theoretical method for determining the design values for thermal conductivity and thermal resistance of unfired clay masonry bricks from both experimental and theoretical design point of view. The paper describes the methodology of obtaining these values using the measured lower and upper lambda limits. In order to determine the basic design thermal value and the design thermal resistance, a Laser-comp FOX 200 thermal conductivity meter equipped with WinTherm32an software package was employed for the laboratory data collection and analysis. Lime or Portland cement (PC)-activated Ground Granulated Blastfurnace Slag (GGBS) binder was used to stabilise Lower Oxford Clay (LOC) for unfired masonry brick specimen production. The major influence of the design values on the thermal conductivity and thermal resistance are illustrated in this study, using two different types of unfired clay bricks (LG and PG) at 2% moisture content prior to test. This paper covers conductivity test for each unfired clay bricks within the temperature range 2.5–17.5°C. The measured thermal properties of the unfired clay bricks were compared to the design thermal properties of fired bricks. The results were used to predict the design thermal values of unfired clay masonry bricks at varied density and moisture contents prior to testing. A comparison of the measured thermal values for the unfired bricks to the design thermal values of fired clay bricks can also be seen. The results demonstrate that the unfired clay bricks were able to comply with the design thermal requirements for clay masonry units, suggesting that the unfired clay bricks can be used for low-medium cost housing and energy efficient masonry structures.

This paper discusses the potential of using slate waste generated from roofing slate production in the UK in the manufacture of unfired clay masonry bricks. Ground granulated blast-furnace slag activated by lime and Portland cement were used to stabilise Lower Oxford Clay incorporating slate waste in the preparation of laboratory cylindrical test specimens. The specimens were moist cured at room temperature (20 +/- 2 degrees C) for between 3 and 90 days before testing for compressive strength. The drying and linear expansion behaviours of the test samples were assessed by means of moisture content measurement (at the age of testing) and linear expansion measurement after soaking the samples in deionised water. The strength of the cement-activated blended mixture was lower than that of the lime-activated mixtures. An environmental comparison of the unfired clay masonry bricks with mainstream construction (fired) bricks shows that the unfired clay bricks have good environmental characteristics over a range of important criteria. These results suggest that there is potential for using activated slag mixtures in the manufacture of bricks for low-cost environmentally friendly housing and energy-efficient masonry wall construction within the UK.

Blended mixtures of ground granulated blastfurnace slag and Portland cement were used in making sustainable masonry mortars suitable for brick joints and for plastering, with Portland cement mortar as control. The testing programme included the determination of a relationship between the mortar flow value and mortar water demand for a wide range of mix compositions. The mortar tensile strength is not a very critical property due to the fact that brickwork mortar is not usually under tension when in service; however, this parameter was determined in the laboratory using a standard briquet towing/testing machine. Chemical durability of the control and blended mortar in aggressive sulfate-bearing exposure conditions was investigated. The relationship between compressive strength of the mortar cured in water and in sodium sulfate solution at room temperature (20 ± 2°C) for from 3 to 120 days was established. The results demonstrated that after a prolonged period of exposure, significant strength and weight loss in the control mortar was observed. This phenomenon is explained, due to calcium hydroxide production as a consequence of Portland cement hydration, change in mortar morphology, inhibition of reaction species and the final disruption of the mortar matrix, resulting in loss of strength and weight at late age. The results obtained suggest that ground granulated blastfurnace slag can be incorporated into Portland cement for the development of sustainable and durable mortars in the UK.

This paper reports on the engineering properties and microstructure of concrete incorporating slate waste aggregates generated from roofing slate production in the UK. Various concrete mixtures were designed using different sizes of slate waste as aggregate replacement. Concrete produced with limestone aggregate was used as control. The results showed that concrete produced with limestone aggregate tended to fail predominantly through the interfacial zone between the aggregate surface and the cement paste and mortar, without any observed aggregate fragmentation. In contrast, the concrete made with slate waste aggregate showed signs of failure emanating from both the interfacial zone as well as from the cracking and subsequent fragmentation of the aggregates. The findings show that the concrete made with slate waste aggregates attained compressive strength of 25-30 N/mm(2), splitting strength of 2-3 N/mm(2) and elastic modulus of 25-32 kN/mm(2) thus indicating potential for using slate waste as a replacement for limestone aggregate in most low-to medium-strength engineering applications.

This paper reports on freezing and thawing of stabilised clay brick incorporating a latent hydraulic binder. The latent hydraulic binder used for the stabilised clay bricks is an industrial by-product (slag) arising as an inherent consequence of iron production. Laboratory and industrial-scale masonry bricks were produced. In order to improve on the cementitious properties of the latent hydraulic binder, between 1·4 to 2·6% of lime was used as an activator. The brick specimens were moist cured at a room temperature of about 20°C for between 3 and 90 days before testing for compressive strength. Since the major factor influencing the durability of clay masonry units is the degree to which the clay masonry unit becomes saturated with water, the durability assessment of the unfired bricks was carried out by means of 24 h repeated freezing/thawing cycles. The results showed that the compressive strength values of the industrial-scale bricks were higher than those of the laboratory bricks. The results of the freeze–thaw suggest that both the laboratory and industrial unfired clay bricks were able to withstand 100 (24 h) repeated freeze–thaw cycles. These results gave an indication of the feasibility of a durable stabilised clay brick incorporating a lime-activated latent hydraulic binder.

The potential of using slate waste generated from roofing slate production in the UK in various applications is reviewed and the environmental impact of the stockpile of slate waste is also assessed. The findings suggest that there is potential for using slate waste in many situations, including engineering applications. In order to reduce the environmental impact arising from the quarrying of conventional construction materials, the abundance of slate waste in Wales in particular and the UK in general could be exploited. With associated economic advantages despite reported transportation difficulties, utilisation of this waste stream for most practical and low-to medium-strength engineering applications is feasible and would maximise the use of surplus regional and national industrial wastes and minimise the environmental impact of their disposal.

This paper reports on the compressive strength and microstructure of unfired clay masonry bricks. Blended binders comprising of lime-activated Ground Granulated Blastfurnace Slag (GGBS) and Portland Cement (PC)-activated GGBS were used to stabilise Lower Oxford Clay (LOC) for unfired masonry brick production. The compressive strength of the stabilised bricks incorporating lime–GGBS–LOC was higher than that of PC–GGBS–LOC. Scanning Electron Microscopy (SEM) with a Solid-state Backscattered Detector (SBD) and Energy Dispersive X-ray (EDX) analysis was employed to obtain a view of the microstructure and to conduct an analysis on the morphology and composition of the dried unfired clay brick samples, after 28days of moist curing. The analytical results together with the physical observations have shown the formation of Calcium Silicate Hydrate (C-S-H) gel and additional pozzolanic (C-S-H) gel. The quantification of the compound content of the unfired bricks showed the presence of Calcite (CaCO3), Quartz (SiO2), Alumina (Al2O3) and Wollastonite (CaSiO8) crystals. Traces of other crystals were also detected.

This paper reports on the production of unfired clay masonry bricks at both laboratory and industrial scales. The laboratory-scale bricks were produced at the University of Glamorgan while industrial brick production was carried out at Hanson Brick Company in Stewartby, Bedfordshire. Lime-activated ground granulated blast-furnace slag and Portland cement activated slag was used to stabilise Lower Oxford Clay (LOC) for laboratory and industrial brick production. The engineering performance (strength) of the industrial-scale bricks (blended binder content around 7%) at the end of a 90-day moist curing period tends to be higher than that of the laboratory bricks (blended binder content of 13·1%). It was extremely difficult to make a thorough technical comparison of the overall engineering performance of the laboratory and industrial bricks owing to disparities in test methods, brick format (one solid and the other a frog brick) and mixing and compaction methods. However, a comparison of the strength and other properties required for practical application of unfired clay bricks with those of bricks currently used in mainstream construction was carried out. A comparison of the environmental profile was also conducted. The results suggest that there is potential for using unfired clay bricks for low–medium cost housing and energy efficient masonry wall construction within the UK.

The shortage of low cost and affordable housing in the UK has led to many investigations into new building masonry materials. Fired clay masonry bricks are conventionally used for mainstream masonry wall construction but suffer from the rising price of energy plus other related environmental problems such as high energy usage and carbon dioxide emission. The use of stabilised unfired clay bricks for masonry construction may solve these problems.This paper reports on the engineering properties of unfired clay bricks produced during the first industrial trial of unfired clay material development carried out at Hanson Brick Company, in Stewartby, Bedfordshire, under the Knowledge Exploitation Fund (KEF) Collaborative Industrial Research Project (CIRP) programme. The mixes were formulated using a locally available industrial by-product (Ground Granulated Blastfurnace Slag - GGBS) which is activated with an alkaline (lime or Portland cement) combined with clay soil. Portland cement was not used in the formulation of the unfired stabilised masonry bricks, except as a control, which is a significant scientific breakthrough for the building industry. Another breakthrough is the fact that only about 1.5% lime was used for GGBS activation. This level of lime is not sufficient for most road construction applications where less strength values are needed and where 3-8% lime is required for effective soil stabilisation. Hence, the final pricing of the unfired clay bricks is expected to be relatively low.The laboratory results demonstrate that the compressive strength. moisture content, rate of water absorption, percentage of void, density and durability assessment (repeated 24-hour freezing/thawing cycles) were all within the acceptable engineering standards for clay masonry units. The paper also discusses on the environmental performance of the unfired clay in comparison to the bricks, used in mainstream construction of today. The bricks produced using this technology can be used for low-medium cost housing and energy efficient masonry wall construction. (C) 2009 Elsevier B.V. All rights reserved.

This paper reports on an investigation on the use of ground granulated blast-furnace slag (GGBS) in the development of a sustainable unfired clay binder material for stabilised masonry-brick. The compressive strength of the stabilised masonry-brick, using a semi-processed industrial kaolinite clay soil and a ‘real’ clay soil (Lower Oxford Clay) commonly used in masonry clay brick manufacture were examined. In practice between 1 and 3 wt.% lime is needed for modifying the soil properties and between 2 and 8 wt.% lime for stabilisation. Due to the high strength requirement in the building industry in comparison with stabilised highway pavement layers for example, a high maximum stabiliser dosage of 20% was used. However, only a small proportion of this high stabiliser content (20%) was lime or Portland cement. Cylindrical specimens were made at moisture contents of 25, 30, 35 and 40%, and cured for 28 days, before testing for unconfined compressive strength. Preliminary results show that the strength values for the stabilised clay systems investigated were within the strength range of 65 to 2077 kN/m2 at 28 days, with the lime–Portland cement blends tending to achieve lower strength values relative to the lime–slag blends. The results suggest that there is potential for the use of GGBS in unblended binders for the development of unfired clay masonry bricks.

This paper discusses laboratory tests on Lower Oxford Clay (LOC) stabilised using different levels of lime (L) or Portland cement (PC), with and without blending with ground granulated blast-furnace slag (GGBS). LOC is used by Hanson Brick Company Ltd in the manufacture of fired ‘London’ bricks at the Stewartby brick plant in Bedfordshire. The research investigated L-PC, L-GGBS and PC-GGBS blends to assess their potential for application in sustainable unfired clay building materials (bricks, mortar, etc.). Use of unfired materials reduces not only energy costs, but also environmental damage associated with the traditional firing process used in the manufacture of clay building components. Due to the high strength requirements of the building industry compared with, for example, stabilised highway pavement layers, a high maximum stabiliser dosage of 20% was used. For road construction, typical stabiliser dosages are 3–8% for lime and 3–5% for PC. In the current investigation, cylindrical test specimens were cured for 28 days at moisture contents of 25, 30, 35 and 40% before testing for unconfined compressive strength. Preliminary results show that the strength values for all stabilised material investigated was within the strength range of 737–2077 kN/m2 at 28 days, with L-PC blends tending to achieve lower strength values than L-GGBS blends. Overall results suggest that there is potential in using GGBS-based binders for the manufacture of unfired building components.