Kevin Paine

Hygrothermal Performance of an Experimental Hemp-Lime Building

The use of hemp-lime as a construction technique is a novel approach which combines renewable low carbon materials with exceptional hygrothermal performance. The hemp plant can grow up to 4m over a four month period, with a low fertilizer and irrigation demand, making it very efficient in the use of time and material resources. All parts of the plant can be used the seed for food stuffs, the fibre surrounding the stem for paper, clothing and resin reinforcement, and the woody core of the stem as animal bedding and aggregate in hemp-lime construction. The unique pore structure of the woody core (shiv) confers low thermal conductivity and thermal and hygric buffering to hemp-lime. The construction technique promotes good air tightness and minimal thermal bridging within the building envelope. All these factors combine to produce low carbon, hygrothermally efficient buildings which are low energy both in construction and in use, and offer opportunities for recycling at end of life. This paper reports on the hygrothermal performance of an experimental hemp-lime building, and on the development of a computerized environmental model which takes account of the phase change effects seen in hemp-lime.

Investigations on cementitious composites based on rubber particle waste additions

The amount of waste rubber has gradually increased over recent years because of over-growing use of rubber products. The disposal of waste rubber has caused serious environmental problems. The incorporation of recycled materials into cementitious composites is a feasible alternative that has gained ground in civil construction. The performance of such materials is much affected not only by the rubber addition, but also the particle size which has been controversially reported in the literature. In order to investigate the single effect of rubber particles into cement based materials, rubber cementitious composites were prepared with no silica particle additions. A full factorial design has been conducted to assess the influence of the rubber particle size (0.84/0.58 mm and 0.28/0.18 mm); mass fraction used (5, 15 and 30%); and water/cement ratio (0.35 and 0.50) on the physic-mechanical properties of the composites. The materials were characterized through apparent density, porosity, compressive strength, flexural strength, modulus of elasticity and microstructural analysis. The interactions of rubber particle size, rubber fraction and water/cement ratio affected significantly the density and compressive strength of the composites. The apparent porosity was influenced mainly by the rubber particle size. The flexural strength was affected by the main factors and the modulus of elasticity was affected by the interaction factors rubber particle size and fraction, and rubber fraction and w/c ratio.

Incinerator Bottom Ash: Engineering and Environmental Properties as a Cement Bound Paving Material

This paper reports a laboratory study investigating the use of incinerator bottom ash (IBA) as cement bound material (CBM) for use in sub-base and roadbase layers. Engineering properties associated with its use are determined and practical limits on IBA content discussed. It was found that IBA could be practically used in proportions of 40% or more by mass for all CBM categories defined in the UK Highway specification. However, the use of IBA as aggregate in CBM required higher cement contents to achieve the same compressive and tensile strength. Tests carried out to confirm that leachable constituents were bound in the mixture and raised no environmental concern were carried out by comparing the results of tank leach tests with a one-dimensional model. It was observed that despite the tests and models being designed to maximise release of species, that leachates were well within typical regulatory drinking limits.

Dispersed Inorganic or Organomodified Montmorillonite Clay Nanoparticles for Blended Portland Cement Pastes: Effects on Microstructure and Strength

Nanotechnology offers an opportunity to modify and observe cement at the nanolevel. In this research, the degree of dispersion of two aqueous suspensions of organomodified montmorillonite (OMMT) clay nanoparticles and one inorganic nanoclay (nC) dispersion was verified by TEM. The effect of the addition of each one of the three dispersions to a high limestone content (40 % by mass of binder) Portland limestone cement was investigated in terms of compressive strength, thermogravimetric (TG) analyses and morphological characteristics of the pastes. It was found that the upper limit of nC addition, in such pastes is 1 % nC solids by mass of binder and that intercalated OMMT cannot offer significant compressive strength improvement. However, there were strong indications that the pozzolanic reactions were promoted by the better dispersed OMMT and by the inorganic nC dispersion. The FESEM images captured, depicted the morphological characteristics of the nanomodified cement formulations. Furthermore, evidences suggest that the specific nanoclays can offer enhancement for flexural performance of blended cements with no degradation over time. Overall, the inorganic nC dispersion exhibited the highest pozzolanic activity, the highest flexural strength improvement and the most dense microstructure. The research reported was part of a much broader research project (FIBCEM) supported by the EU.

Alkaliphilic Bacillus species show potential application in concrete crack repair by virtue of rapid spore production and germination then extracellular calcite formation

Characterization of alkaliphilic Bacillus species for spore production and germination and calcite formation as a prelude to investigate their potential in microcrack remediation in concrete.

Inorganic and organomodified nano-montmorillonite dispersions for use as supplementary cementitious materials – a novel theory based on nanostructural studies

Abstract The compatibility of three nano-montmorillonite (NMt) dispersions in hydrating cement binders was investigated and a new theory linking the nanostructure of nanoclay dispersions to their effect on the macroscale performance of cement pastes is presented. Two aqueous organomodified NMt dispersions (one dispersed with non-ionic fatty alcohol and the other with anionic alkyl aryl sulfonate) and one aqueous inorganic NMt dispersion (dispersed with sodium tripolyphosphate) were characterized via transmission electron microscopy imaging and crystallography, X-ray diffraction, Scanning electron microscopy/X-ray energy dispersive spectroscopy, and thermogravimetric analysis/differential thermogravimetry. With this characterization protocol, the way carbon loading and surfactants interact with the nanostructure of the nanoclay dispersions in light of their addition in composite cements was clarified. The suggested methodology is suited for the characterization of nanoclay dispersions and the new theory developed will open up a new horizon for the understanding and exploitation of nano-montmorillonite as a supplementary cementitious material.

Steel Fiber Reinforcement for Extruded Prestressed Hollow Core Slabs

An experimental investigation was conducted to assess the potential of steel fibers as secondary reinforcement in prestressed hollow core slabs. Following a brief laboratory study and a feasibility trial, a series of fibre reinforced extruded slabs were made at the premises of a local manufacturer and subsequently tested in shear: one of a number of potential modes of failure which cause concern in this type of slab because of the lack of shear or secondary reinforcement. The addition of the fibres increased both the ultimate strength and toughness of the slabs leading to safer and more controlled failures. The predictive equations of other researchers were shown to accurately estimate the shear strength in the case of plain hollow core slabs, but to overestimate the shear enhancement due to adding steel fibres. Additionally, the effect of the manufacturing process, in which the concrete is compacted by rotating augers, on the fibre distribution and orientation was investigated. While fibres were found to be randomly distributed within the cross-section, a tendency to align vertically within the webs was observed. This has particular relevance to the vertical shear performance.

Bacteria-based concrete

Abstract Several strains of bacteria can induce the precipitation of calcium carbonate, if the appropriate conditions, sufficient nutrients and a calcium source are provided. The metabolic pathway that is followed by the bacterial strain will dictate the type of nutrients to be selected. This precipitation ability has been investigated during recent decades to improve the mechanical properties and durability of construction materials. Starting with applications for the consolidation of natural stones in weathered cultural heritage buildings and the consolidation of sandy soils, the research efforts have moved towards applications in concrete. When bacteria are mixed into fresh concrete, viable cell numbers rapidly decrease with time. Still, positive effects on concrete strength have been reported. To improve the survival rate of bacteria in concrete, various encapsulation and immobilization strategies have been explored and bacterial spores have been used instead of vegetative cells. Furthermore, added nutrients may impair concrete properties and may also be encapsulated for this reason. Encapsulated bacterial spores have shown the ability to self-heal cracks in concrete and first in-situ applications have been launched.

Ultra-thin topping upgrades for improved serviceability performance

Timber floors can be refurbished by connecting a concrete topping to the timber joists; stiffening the floor and reducing serviceability problems, including vibration. Research to date has focused on upgrade solutions with relatively thick toppings (40mm or greater). This paper presents a novel, ultra-thin topping solution where the topping is placed at a thickness of 20mm or less. Advantages of the solution include: reducing the mass added to the existing structure and minimising the change in floor to ceiling height whilst delivering a significant increase in floor stiffness. This paper reports the findings from the serviceability testing of an upgraded, full scale timber floor. Measurements prior to and after the upgrade are compared, including: elastic testing under static loads, vibration testing and short-term bending tests. The paper also compares the results with simple analytical approaches and design limits prescribed in Eurocode 5 Part 1-1.

Large scale application of self-healing concrete: design, construction and testing

The work reported in this paper was carried out as part of the EPSRC funded project Materials for Life (M4L), reference EP/K026631/1 and supported with PhD studentship funding from Costain Group PLC.