Thomas D. Dyer

Chloride binding in GGBS concrete

Abstract This paper reports the results of chloride binding measurements of GGBS pastes, as well as chloride diffusion and permeability measurements of GGBS concrete mixes. Chloride binding capacity was found to increase with increasing GGBS replacement levels and the chloride exposure concentration. Thermal analysis measurements suggest that much of the improvement in chloride binding is a result of high aluminate levels in GGBS leading to the production of higher quantities of Friedels salt. When concrete mixes with relatively similar permeabilities are used the chloride binding capacity of the cement matrix becomes a major determining factor in how resistant the concrete is to Chloride permeation.

Developing chloride resisting concrete using PFA

PFA concrete mixes were designed to optimise resistance to chloride ingress. Chloride binding capacity, intrinsic permeability and their concomitant influence on the coefficient of chloride diffusion have been investigated. PFA replacements up to 67% and exposure concentrations of 0.1, 0.5, 1.0 and 5.0 mole/litre were used. Chloride binding capacity was found to increase with increasing PFA replacement up to 50% and to then decline. It increased with chloride exposure concentration as well as water/binder ratio. The coefficient of chloride diffusion of concrete samples was found to be dependent on both the intrinsic permeability of the concrete and the ability of its cement matrix to bind chlorides.

An investigation of the hydration chemistry of ternary blends containing cement kiln dust

During the manufacture of Portland cement, dust is generated composed of particles of feedstock and condensed volatilised inorganic salts. Due to its highly alkaline soluble fraction, the dust can be used as an activator in blends containing pozzolanic materials or hydraulic slags, allowing them to undergo cementitious reactions. The inclusion of Portland cement in such blends enhances strength development further, although careful proportioning of materials will be required to obtain optimum performance. Ternary systems containing cement kiln dust, pulverised-fuel ash and Portland cement were characterised in this paper in terms of strength development and hydration products. For a given Portland cement content, optimum strength was achieved in blends containing approximately 10% cement kiln dust for Portland cement levels up to 80%. Beyond this level a CKD/PFA ratio of one was optimal. Isothermal conduction calorimetry results and measurements of calcium hydroxide levels indicated that this was due to an acceleration of the reactions of the blend constituents by the dust. Additionally, the chemical composition of the optimal blends promoted the production of calcium aluminate and ferrite hydrates of a type conducive to maintaining the integrity of the cementitious matrix.

Durability of 'self-cure' concrete

Abstract When cured in air, ‘self-cure’ concrete possesses improved properties in comparison to identically cured controls. This paper reports the results of several durability tests conducted on self-cure concrete specimens. It was found that initial surface absorption, chloride ingress, carbonation, corrosion potential and freeze / thaw resistance characteristics were all better in air cured self-cure concrete than in the air cured control. This improvement appears to be dependent on admixture dosage, and although the durability properties obtained in this study were not as good as the film cured concrete controls, it may be possible to achieve such properties with higher quantities of self-cure chemical.

Hydration Chemistry of Sewage Sludge Ash Used as a Cement Component

The hydration chemistry of sewage sludge ashes (SSAs) used as cement components is examined using X-ray diffraction, thermal analysis, and isothermal conduction calorimetry. The presence of SSA leads to the formation of significant quantities of Al2O3-Fe2O3-mono (AFm) phases. Large quantities of amorphous hydration products are also formed. An additional series of small-scale experiments is used to show that it is highly probable that amorphous or poorly crystalline hydroxyapatite (Ca5(PO4)3OH) is generated in addition to calcium silicate hydrate gel. Thus, the reactions of SSA in combination with portland cement cannot be viewed simply as comparable to the pozzolanic or latent hydraulic reactions of other by-product materials used in similar ways.

Bioprotection of the built environment and cultural heritage

The growth of microbial biofilms and various biomineralization phenomena can lead to the formation of stable layers and veneers on rocks known as ‘rock varnishes’ that can stabilize surfaces and protect from further weathering. This article describes the potential application of fungal systems for bioprotection of rock and mineral‐based substrates and the evidence to support this concept of utilizing natural or engineered colonization and metabolic properties of fungi, including lichens.

Characterisation of two chemical compounds formed between hydrated portland cement and benzene-1,2-diol (pyrocatechol)

Exposure to benzene-1,2-diol (pyrocatechol), a common soil contaminant, has been shown to cause loss of strength in concrete. Synthesis and characterisation of two compounds formed when Portland cement comes in contact with benzene-1,2-diol has been conducted. These compounds are (benzene-1,2-diolato(1-))hydroxidocalcium(II) (formula: [Ca(C6O2H5)OH]) and triaqua(benzene-1,2-diol)(benzene-1,2-diolato(1-))hydroxidocalcium(II) (formula: [Ca(C6O2H5)(C6O2H6)(H2O)3(OH)]). The compounds may play a role in the deterioration process. Characterisation was conducted in terms of thermal decomposition behaviour, infra-red spectra and crystal structure (using powder X-ray diffraction). The likely thermal decomposition reactions of both compounds have been determined, and features in the infra-red spectra assigned to molecular vibrations. Both structures have been solved, with the exception of the location of some hydrogen atoms, and the structures refined using Rietveld refinement methods. It is anticipated that both the thermal analysis data obtained, and crystal structures deduced, in this article can now be used to quantify these phases in cement and concrete exposed to benzene-1,2-diol.

Chapter 14 – Glass Recycling

Glass has established itself as an essential material in our lives. The composition of glass depends on what it is used for, but the majority of glass in circulation is of the soda-lime–silicate type. It is a material that is eminently recyclable, in the sense that it merely needs to be remelted and reformed to produce another glass article. However, glass must be color-sorted and processed to remove contaminants to ensure it is compatible with the product being manufactured. The key benefit of recycling via remelting is the reduced energy demand. However, because differences in color composition can arise between recovered glass and manufacturing output, alternative outlets are also often necessary. This chapter examines both the recycling of glass back into glass manufacture and these alternatives.

Chemical profiles of cement pastes exposed to a chloride solution spray

This paper reports on the findings of a study of the chemistry of chloride penetration into cement pastes. Three binder combinations were used with three types of curing. At certain exposure times, specimens were sliced at 5-mm intervals, ground, and analysed using X-ray fluorescence (XRF) and thermogravimetry (TG) techniques. Up to 6-month exposure results are reported in this paper. As a result of leaching of calcium, silicon content was used to determine binder content for the XRF measurements. It was found that the vast majority of chloride permeation had occurred by absorption, and that curing by sealing in film or the addition of self-cure admixture more than halved the depth to which chlorides penetrated. In some instances, sodium was present in proportionally higher quantities than chloride, which has been attributed to the replacement of sodium ions by potassium ions.

Biodeterioration of Concrete

S t r e s z c z e n i e Konstrukcje betonowe należą do tych, które zazwyczaj są uważane jako niezniszczalne ze względu na ich dłuższy okres użytkowania w porównaniu z większością wyrobów konstrukcyjnych. Jednak mogą one ulegać zniszczeniu z różnych przyczyn, włączając te pochodzenia biologicznego. Wiele budowli architektonicznych i innych konstrukcji budowlanych ulega biodeterioracji w przypadku narażenia na kontakt z glebą, wodą i ściekami, jak również produktami i odpadami żywnościowymi i pochodzenia rolniczego. Ten przegląd wyjaśnia działanie na beton niektórych biogennych substancji korozyjnych produkowanych przez mikroorganizmy. K e y w o r d s : Concrete; Biodeterioration; Microorganisms; Metabolic activity; Biogenic substances. 4 / 2 0 0 8 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 133 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T The Si les ian Univers i ty of Technology No. 4/2008