Fibre mortar composites in fire conditions

A small-scale test series was carried out using the heating system (radiant exposure) of a cone calorimeter to detect any differences in the way different fibres affect the thermal properties of a standard mortar. The fibres were different polypropylene, polyacrylonitrile, aramide, carbon or steel. Fibres affect the release of moisture from the fibre mortar material. Local pressures caused by water vaporization due to rapid heating can be decreased by incorporating fibres. Fibres have a weak insulating effect. However, use of polyacrylonitrile fibres in mortar may increase the risk to spalling under rapid thermal exposure such as fire. The moisture level in specimens is highly significant for their thermal properties and hence their fire behavior.     

Ignitability and heat-release properties of forest products

Forest products comprising sawn boards of seven timber species, plywoods of three timber species, two hardboards and one particleboard have been tested to ASTM E 906—Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products. One plywood was also tested after fire-retardant treatment by pressure impregnation. The fire-retardant treated plywood was also tested after being overlaid with untreated face and back veneers. One sawn board product was also tested after coating with an intumescent fire retardant. The ignition times of the forest products that had not been fire-retardant treated increased with density when exposed to heat fluxes of 20 and 40 kWm^?2. The maximum rate of heat release and the cumulative heat released rose with increasing impressed heat flux over the range 20–60 kWm^?2. Heat-release properties were dependent upon the impressed heat flux. Relationships were also established between the maximum rate of heat release and the cumulative heat released for heat flux exposures of 20, 40 and 60 kWm^?2. The ignition times of plywood were increased by pressure-impregnated fire retardants. Fire-retardant treatment by pressure impregnation prevented the ignition of a plywood and reduced its heat-release properties. The heat-release properties of a sawn board product were reduced by a fire-retardant surface coating.     

Flammability of GRP for use in ship superstructures

The burning characteristics of glass-reinforced panels with an isophthalic polyester resin, the same resin with an inorganic flame retardant, two differing vinylester resins or a resole phenolic as the matrix were tested at a range of incident heat flux values using a cone calorimeter. The phenolic composite was superior at all levels showing a longer ignition time, reduced heat output, less contribution to a low-level sustained fire (25 kWm^?2) and lower smoke yield.     

The fire behaviour of rendered straw bales

Experimental and theoretical investigations were conducted on the combustion behaviour of compacted, rendered straw bales exposed to two radiant heat flux regimes—(1) 30kWm^?2 for 30 min and (2) 50kWm^?2 for 40 min. The objective was to examine the fire safety of the rendered straw bales, which are used to construct houses in rural areas or on the urban fringe. The rendered bales were ～950 mm × 450 mm × 550 mm in size, comprising a ～45 mm thick render layer on all sides. Two types of render materials—earth‐based and lime‐based—were tested. The 30kWm^?2, 30‐min regime resulted in little damage to the render layer and no combustion of the straw bale. The 50kWm^?2, 40‐min regime initiated combustion of the straw 24 h after the end of the exposure regime, consuming the entire straw bale over 11 days. A two‐dimensional mathematical model describing the heat transfer through the render and the straw, and the combustion of the straw is presented. The kinetic parameters for the pyrolysis and combustion were derived from thermo‐gravimetric analysis of the straw. The physical and thermal properties of the render and the straw were obtained from measurements and literature. The model predicted transient temperature profiles within the straw bale. The trends of predicted temperatures compare favourably with the experimental measurements, although aspects of the theoretical predictions of the ignition of the straw could not be reconciled with experimental results. © Commonwealth of Australia 2008.     

Effect of short fibers on residual permeability and mechanical properties of hybrid fibre reinforced high strength concrete after heat exposition

Mechanical and permeability performance of fibre reinforced high strength concrete after heat exposition were evaluated in the experimental study. Cylindrical concrete specimens were exposed to heat with the rate of 10 °C/min of up to 400 °C. In order to study the effect of short fibres on residual performance of heated high strength concrete, polypropylene and steel fibres had been added into the concrete mix. The melting and vaporization of its fibre constituents were found to be responsible for the significant reduction in residual properties of polypropylene fibre reinforced high strength concrete. In terms of non-destructive measurement, UPV test was proposed as a promising initial inspection method for fire damaged concrete structure. Furthermore, the effect of hybrid fibre on the residual properties of heated fibre reinforced high strength concrete was also presented.     

Zum Fließverhalten von kurzglasfasergefüllten Styrol-Acrylnitril-Copolymeren

The viscosity of high polymer melts increases usually when adding fibres. Such an increase has been measured for a short fibre reinforced styrene/acrylonitrile copolymer with 25 and 35% (by weight) glasfibres on a rotational viscometer in the range of shear rates from 10^?3 to 10¹s^?1 for different temperatures and pressures. The viscosity curves show a zero shear viscosity. Its dependence on temperature, pressure and concentration of fibres can be described by straight lines. Furthermore it is possible to shift the viscosity curves in a way that they form a temperature- and pressure-independent, and even a concentration-independent master curve.     

A study on fire behaviour of combustible components of two commonly used photovoltaic panels

Photovoltaic (PV) modules are installed in some modern buildings for generating renewable energy. When a building catches fire, burning PV panels can contribute to an already very hazardous environment. Two common polycrystalline silicon PV samples A and B were selected with their chemical composition analysed by the Fourier transform infrared spectroscopy with justification by X‐ray photoelectron spectroscopy results. Sample A was confirmed to be a silicate product with polyurethane adhesive, and sample B has epoxy resin and is likely to have flame retardant as claimed. Thermal analysis by heating the samples was carried out using thermogravimetric analysis and thermogravimetric analysis coupled with infrared spectroscopy. The fire behaviour was then studied by a cone calorimeter under radiative heat fluxes from 10 to 70 kWm^?2. Three key parameters representing flashover propensity, total heat release per unit area and smoke toxicity hazard were obtained from the cone calorimeter tests for ranking the thermal and smoke hazards. The thermal hazards of both PV samples are low, at least during the early stage of a fire without flame acting directly on the sample. However, vast quantities of smoke were emitted from burning PV panels under high heat fluxes. Copyright © 2016 John Wiley & Sons, Ltd.     

Aluminophosphate bonded refractory mortars

Conclusions Chamotte mortars containing aluminophosphate bonds considerably improve the strength of the joint between firebrick refractories after heating to 400–800°C compared with mortars based on Portland cement and water glass. The highest strength for the mortar-firebrick bond is provided with a phosphoric acid density of 1.42–1.43 g/cm³ (60% phosphoric acid), and incorporating 20% bond in the mortar.It is possible to increase the strength of the chamotte mortar containing aluminophosphate bond during air setting and during heating, and also to increase the strength with time, by adding active materials to the mortar.Aluminophosphate-bonded mortar markedly increases the strength of the refractory-metal bonding, which is very important in building linings which are subject to movement during operation for example, in rotary kilns. It is desirable to test mortars containing aluminophosphate bonds in rotary kilns, and also in similar plant in the refractories, ceramic, and cement industries.Translated from Ogneupory No. 1, pp. 37–42, January, 1971.     

Characterization of stem phoenix fibres as potential reinforcement of self compacting mortar

In this work, we investigate the effect of different treatment process on stem Phoenix fibres. Underwent different surface modification methods such as alkali treatment with concentration of 10%, epoxy treatment, and combine both of procedures preceded. The treated fibres reinforcement was used in self compacting mortar (SCM) with a length of 20 ± 2 mm and different proportions (0.5, 1, 1.5, 2, 2.5 and 3%) by mortar volume. Flowability of fresh modified self compacting mortar is carried out using two main techniques, including flow table experiments and mini V-funnel flow test. Mechanical performance is derived from bending and compression testing at different curing times. Results show a positive effect of fibre treatment on the rheological and mechanical performances of self compacting mortars. Results show also that optimal formulations need to use fibres treated with (10% NaOH + epoxy resin) by an amount of 3%. These formulations reveal superior mechanical performance compared to all tested mixes after 28 curing days, by 20% in compressive strength and 40% of tensile strength.     

Mechanical and durable behaviour of alkaline cement mortars reinforced with polypropylene fibres

The development of new binders, alternative to traditional cements and concretes obtained by the alkaline activation of different industrial by-products (blast furnace slags and/or fly ashes), is an ongoing study and research topic of the scientific community.

The mechanical and durable behaviour of alkaline cement mortars reinforced with polypropylene fibres has been the object of the present investigation. Three different alkaline matrices were used: (a) granulated blast furnace slag activated with waterglass (Na₂SiO₃+NaOH) with a concentration of 4% Na₂O by mass of slag and cured at room temperature, (b) aluminosilicate fly ash activated with 8M NaOH and cured at 85 °C during the first 24 h and (c) 50% fly ash+50% slag activated with 8M NaOH solution at room temperature. In the mechanical tests (flexural and compressive strengths), two different dosages of fibres were used: 0.5% and 1% by mortar volume. Shrinkage tests according to ASTM C 806-87 standard with (1%) and without fibres were also carried out. The durability tests carried out were freeze/thaw and wet/dry cycles. In these tests, the dosage of fibre was 0.5% by mortar volume. The results obtained show that the nature of the matrix is the most important factor to strength development, more than fibre presence and content amount.     

Tensile properties of plant fibre‐polymer composites in fire

The structural performance of polymer composites reinforced with plant fibres when exposed to fire was experimentally evaluated and compared against an E‐glass fibre laminate. Fire testing under combined one‐sided radiant heating and static tensile loading revealed that flax, jute, or hemp fibre composites experience more rapid thermal softening and fail within much shorter times than the fibreglass laminate, which is indicative of vastly inferior structural performance in fire. The plant fibre composites soften and fail before the onset of thermal decomposition of the plant fibres and polymer matrix, whereas the E‐glass fibres provide the composite with superior tensile properties to higher temperatures and higher applied tensile stresses. The tensile performance of the three types of plant fibre composites in fire was not identical. When exposed to the same radiant heat flux, the flax fibre composite could withstand higher tensile stresses for longer times than the hemp and jute laminates, which showed similar performance.     

Time to ignition,heat release rate and fire endurance time of wood in cone calorimeter test

The combustibility of wood specimens was tested by cone calorimeter. A total of nine wood species (four softwood and five hardwood) were used. The thicknesses of the specimens were 10, 20 and 40 mm. The heated surfaces were radial, tangential, and cross‐sections of wood. The irradiance levels were 20, 25, 30, 40 and 50 kWm^?2. The effects of wood species, density, specimen thickness, heated surface (radial, tangential or cross‐section), and irradiance level on time to ignition, mass loss rate, heat release rate and fire endurance time were studied. Simple formulae were proposed to forecast those indices and their validity was examined. Copyright © 2002 John Wiley & Sons, Ltd.     

新旧水泥砂浆界面粘结性能试验研究

在荷载和环境因素作用下,混凝土结构产生不同程度的劣化。为了保证结构的安全性和耐久性,需要对损伤水泥基材料进行修复。基体的含水饱和度、界面粗糙度、修补砂浆的水灰比以及试件的养护条件都会影响修补砂浆与基体间的粘结强度。选取四种含水饱和度(0%、30%、70%、100%)的旧砂浆作为基体,浇筑水灰比为0.4和0.6的新砂浆,试件密封养护28 d,剪切试验结果表明:当新砂浆水灰比为0.6,旧砂浆含水饱和度按照70%、30%、100%、0%的顺序变化时,界面的剪切强度逐渐减小;当新砂浆水灰比为0.4,旧砂浆含水饱和度按照30%、0%、70%、100%的顺序变化时,界面的剪切强度逐渐减小。同时发现,新砂浆水灰比为0.4时的界面剪切强度普遍大于水灰比为0.6的数值。通过切槽法改变旧砂浆的界面粗糙度,然后浇筑水灰比为0.6的新砂浆,试件标准养护。剪切试验结果表明:当旧砂浆界面粗糙时,界面间的剪切强度是旧砂浆光滑时的1.26倍。选取两种含水饱和度(0%、100%)的旧砂浆作为基体,浇筑水灰比为0.4和0.6的新砂浆,分别进行标准养护和密封养护,剪切试验结果表明:在旧砂浆含水饱和度和新砂浆水灰比相同的情况下,标准养护下的界面剪切强度明显大于密封养护下的界面剪切强度。     

Fire risks of burning asphalt

Eyewitnesses describe burning pavement surfaces in extreme fire scenarios. However, it was believed that the pavement plays a negligible role in comparison to other items feeding such an extreme fire at the same time. The asphalt mixtures used differ widely, thus raising the question as to whether this conclusion holds for all kinds of such materials. Three different kinds of asphalt mixtures were investigated with the aim of benchmarking the fire risks. Cone calorimeter tests are performed at an irradiance of 70kWm^?2. All three investigated asphalts burn in extreme fire scenarios. The fire response (fire load, time to ignition, maximum heat release rate and smoke production) is quite different and varies by factors of up to 10 when compared to each other. The fire load per mass is always very low due to the high content of inert minerals, whereas the effective heat of combustion of the volatiles is quite typical of non‐flame retarded organics. The heat release rate and fire growth indices are strongly dependent on the fire residue and thus the kind of mineral filler used. Comparing with polymeric materials, the investigated Mastic Asphalt and Stone Mastic Asphalt may be called intrinsically flame resistant, whereas the investigated Special Asphalt showed a pronouncedly greater fire risk with respect to causing fire growth and smoke. Thus the question is raised as to whether the use of certain kinds of asphalts in tunnels must be reconsidered. Apart from the binder used, the study also indicates varying the kind of aggregate as a possible route to eliminate the problem. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of Moisture and Heat Treatment of Corn Germ on Oil Quality

The changes in the quality of crude corn oil caused by moisture and two different thermal pretreatments (oven heating and steam heating) of wet‐milled corn germ were evaluated and compared with those of untreated oil. Increasing the moisture content of the corn germ from 8 to 25% before oil extraction increased the acid value (AV) (3.02–4.01 mg KOH g^?1), peroxide value (PV) (0.52–1.05 meq kg^?1), and the red value (7.3–8.7) and decreased the content of total tocopherols by 37% and that of γ‐tocopherols by 31%. Oven heating tended to decrease the AV and PV while steam heating significantly increased the total and individual tocopherol contents (P < 0.05). The different moisture contents and thermal pretreatments of corn germ caused no significant differences in the fatty acid composition and the contents of total and individual phytosterols of the crude oils. The γ‐tocopherol contents were found to be highly correlated with the red values (the corresponding R² reached 0.9977 and 0.9089 for moisture and heat pretreatments, respectively).     

VOLUME CHANGES IN BRICK MASONRY MATERIALS1

Volume changes in brick and mortars attending variations in moisture content and temperature have been studied. There were included in the study 21 cements (both Portland and masonry), 7 limes, and 8 makes of brick received from various sections of the United States. The shrinkage of mortars during hardening and the alternate expansion on wetting and shrinkage on drying occurring subsequent to hardening have been measured. Varying the moisture content produced far smaller volume changes in well-fired brick than in most of the mortars. Underfired brick expanded appreciably on wetting. It is indicated that differential volume changes between brick and mortar caused by variations in moisture content are apt to be greater than those produced by normal temperature variations. Volume changes in hardened mortars were least in the case of straight lime-sand mortars.     

Fibre-reinforced boroaluminosilicate geopolymers: A comparative study

This paper investigates the effect of fibres on the physical and mechanical behaviour of boroaluminosilicate geopolymers (BASG) compared to conventional aluminosilicate binders. The use of various types of fibres by the means of reinforcing geopolymers against flexural loads is very common. In this work, fly ash and ground granulated blast furnace slag (GGBS) are utilised as raw materials to generate geopolymer specimens. Different alkaline solutions comprising sodium hydroxide, sodium silicate, and borax are prepared to activate precursors. The sodium silicate solution is substituted with borax by 30?wt% and 70?wt% in order to produce fly ash and slag-based BASG respectively. Steel and polymer fibres are employed in the mixtures for reinforcement. Three-point bending and mini slump tests are conducted for assessing the flexural strength, elastic modulus, toughness, and flow of geopolymer specimens. A pair plotting interpretation is also used in order to illustrate the patterns. The obtained results indicate that the fly ash-based BASG mortar shows superior flexural strength to the GGBS-based BASG mortar. The flexural strength of fly ash-made aluminosilicate geopolymer declines from 7.3?MPa to 6.4?MPa with an increase in the content of steel fibres from 1% to 2%. Inversely, raising the percentage of steel fibres in the fly ash-based BASG mortar caused a slight growth in the flexural strength of specimens. The polypropylene fibres, when added sufficiently, play a significant role in improving the toughness of fly ash-based BASG and slag-based aluminosilicate mixtures, more than 0.8 and 0.7?J surge in the toughness respectively. In addition, the polypropylene and steel fibres perform well in improving the elastic modulus of slag-based BASG and fly ash-based aluminosilicate binders. While keeping the water to binder ratio constant, introducing the steel fibre increased the flow of fly ash-based geopolymers. Nonetheless, the polymer fibres declined the flow of mortars.     

Fibre fractionation using air‐sparged hydrocyclone

Fractionation of mechanical wood pulp into two or more streams on the basis of fibre length has been investigated to recover valuable long fibres from virgin or recycled wood pulp. An air‐sparged hydrocyclone was used to fractionate the pulp at feed mass concentrations (consistencies) of 0.15% and 0.30%. The extent of fibre fractionation, as affected by feed flow rate, air flow rate, ratio of overflow to underflow rates, was studied. As well, the effects of pore size of the air sparger and cyclone length are presented. It was found that at low consistencies of the pulp feed, the overflow stream from the hydrocyclone had a significantly longer average fibre length than that of the feed pulp. The feed pulp consistency, feed flow rate, air flow rate and the ratio of overflow to underflow flow rates had a direct effect on the fractionation performance.     

Procedure for determining sodium content of carbon fibres by atomic-absorption spectrophotometry

Conclusions The process of sodium vaporization from carbon fibres has been studied. It has been shown that sodium atoms are present in carbon fibres in three different forms, vaporization of each of which on heating the yarn can be described by a first-order kinetic equation. Coefficients of the kinetic equation have been found. Possible mechanisms of vaporization of sodium from the fibre are discussed.Metrological characteristics of the procedure of atomic-absorption determination of sodium in carbon fibres using an independent vaporizer and atomizer have been determined. The procedure based on ashing the yarn has a systematic error connected with losses of sodium during ashing.Translated from Khimicheskie Volokna, No. 2, pp. 56–58, March–April, 1989.     

A study of spalling behaviour of PAN fibre-reinforced concrete by thermal analysis

Comparisons are made between polypropylene (PP) fibres and polyacrylonitrile (PAN) fibres in order to relate the thermal properties of fibres with the respective fibre mortar behaviour under thermal exposure. Thermogravimetry (TG), differential scanning calorimetry (DSC) and thermochromatography (ThGC) are utilized. When a cementitious fibre mortar is being heated, several physical phenomena occur in the temperature range between 100°C and 200°C. There is a significant difference in the thermal behaviour between PP and PAN fibres. PP fibres melt at 160–170°C. The non-melting behaviour of PAN fibre together with its rapid exothermic degradation reactions at around 300°C may add risk to the spalling of fibre mortar under rapid thermal exposure.