MODELING OF TRANSIENT HEAT TRANSFER IN FOAMED CONCRETE SLAB

This paper reports the basis of one-dimensional Finite Difference method to obtain thermal properties of foamed concrete in order to solve transient heat conduction problems in multi-layer panels. In addition, this paper also incorporates the implementation of the method and the validation of thermal properties model of foamed concrete. A one-dimensional finite difference heat conduction programme has been developed to envisage the temperature development through the thickness of the foamed concrete slab, based on an initial estimate of the thermal conductivity-temperature relationship as a function of porosity and radiation within the voids. The accuracy of the model was evaluated by comparing predicted and experimental temperature profiles obtained from small scale heat transfer test on foamed concrete slabs, so that the temperature history of the specimen calculated by the programme closely matches those recorded during the experiment. Using the thermal properties of foamed concrete, the validated heat transfer program predicts foamed concrete temperatures in close agreement with experimental results obtained from a number of high temperature tests. The proposed numerical and thermal properties are simple yet efficient and can be utilised to aid manufacturers to develop their products without having to conduct numerous large-scale fire tests

Engineering Performance Of High Strength Concrete Containing Steel Fibre Reinforcement

The development and utilization of the high strength concrete in the construction industry have been increasing rapidly. Fiber reinforced concrete is introduced to overcome the weakness of the conventional concrete because concrete normally can crack under a low tensile force and it is known to be brittle. Steel fibre is proved to be the popular and best combination in the high strength concrete to result the best in the mechanical and durability properties of high strength concrete with consideration of curing time, steel fibre geometry, concrete grade and else more. The incorporation of steel fibre in the mortar mixture is known as steel fibre reinforced concrete have the potential to produce improvement in the workability, strength, ductility and the deformation of high strength concrete. Besides that, steel fibre also increases the tensile strength of concrete and improves the mechanical properties of the steel fibre reinforced concrete. The range for any high strength concrete is between 60MPa-100MPa. Steel fibre reinforced concrete which contains straight fibres has poorer physical properties than that containing hooked end stainless steel fibre due to the length and the hooked steel fibre provide a better effective aspects ratio. Normally, steel fibre tensile strength is in the range of 1100MPa-1700MPa. Addition of less steel fibre volumes in the range of 0.5% to 1.0% can produce better increase in the flexural fatigue strength. The strength can be increased with addition of steel fibre up to certain percentage. This paper will review and present some basic properties of steel fibre reinforced concrete such as mechanical, workability and durability properties

Mechanical Properties of Lightweight Foamed Concrete Reinforced with Raw Mesocarp Fibre

Lightweight foamed concrete (LFC) is recognised for its high flowability, minimal utilization of aggregates and superior heat insulation properties. LFC is excellent under compression but poor in tensile stress, as it produces multiple microcracks. LFC cannot withstand the tensile stress induced by applied forces without additional reinforcing elements. Hence, this study was conducted to examine the potential utilisation of oil palm mesocarp fibre (OPMF) reinforced LFC in terms of its mechanical properties. Two densities, 600kg/m3 and 1200kg/m3, were cast and tested with six different percentages of OPMF, which were 0.15%, 0.30%, 0.45% and 0.60%. The parameters evaluated were compressive strength, flexural strength and tensile strength. The results revealed that the inclusion of 0.45% of OPMF in LFC helps to give the best results for the compressive strength, flexural strength and splitting tensile strength. The OPMF facilitated to evade the promulgation of cracks in the plastic state in the cement matrix when the load was applie

Potential of Using Lightweight Foamed Concrete in Composite Load-Bearing Wall Panels In Low-Rise Construction

This paper will look at the potential of using lightweight foamed concrete (LFC) in composite load-bearing wall panels in low-rise construction. From the experimental verification, as expected the mechanical properties of LFC were reasonably low when compared to normal strength concrete. Nonetheless there was a potential of using LFC as fire resistant partition or as load-bearing walls in low-rise residential construction. In order to demonstrate the feasibility of this proposal, this paper presents a preliminary feasibility study on its fire resistance and structural performance of LFC based system. The objectives of this feasibility is two-fold; to investigate the fire resistance performance of LFC panels of different densities when exposed to fire on one side for different fire resistance ratings based on insulation requirement and to examine whether the composite walling system had sufficient load carrying capacity, based on compression resistance at ambient temperature

Effective thermal conductivity of foamcrete of different densities

The main purpose of this study is to investigate the thermal conductivity of foamed concrete. Various densities of foamed concrete samples ranging from 650, 700, 800, 900, 1000, 1100 and 1200 kg/m3 with constant cement-sand ratio of 2:1 and water-cement ratio of 0.5 were produced. This study was limited to the effect of density, porosity and pore size on thermal conductivity of foamed concrete. Hot-guarded Plate method was used to obtain the thermal conductivity of foamed concrete at different densities. The porosity value of foamed concrete was determined through the Vacuum Saturation Apparatus. In turn to examine the effect of pore size on thermal conductivity of foamed concrete, pore size measurements were made under a microscope with a magnification of 60x. Lower density foamed concrete translates to lower thermal conductivity. The density of foamed concrete is controlled by the porosity where lower density foamed concrete indicates greater porosity. Therefore, thermal conductivity changes considerably with the porosity of foamed concrete because air is the poorest conductor compared to solid and liquid due to its molecular structure

Elastic Modulus of Foamcrete in Compression and Bending at Elevated Temperatures

This paper will presents the experimental results that have been performed to examine and characterize the mechanical properties of foamcrete at elevated temperatures. Foamcrete of 650 and 1000 kg/m3 density were cast and tested under compression and bending. The tests were done at room temperature, 100, 200, 300, 400, 500, and 600°C. The results of this study consistently demonstrated that the loss in stiffness for cement based material like foamcrete at elevated temperatures occurs predominantly after about 95°C, regardless of density. This indicates that the primary mechanism causing stiffness degradation is microcracking, which occurs as water expands and evaporates from the porous body. As expected, reducing the density of LFC reduces its strength and stiffness. However, for LFC of different densities, the normalised strength-temperature and stiffnesstemperature relationships are very similar

Consideration of Active Fire Protection and Coating for Commercial Buildings

For buildings and other constructions, fire protection is a must. The fear of uncontrolled fires and the desire to avoid their consequences is as ancient as human civilization. This fear has obvious enduring roots: unwanted fire is a destructive force that takes many thousands of human lives and destroys large quantities of asset. The primary objective of fire protection is to limit loss of properties and lives in the event of unexpected fires. Active fire protection is effective and efficient in most situations. However, passive fire protection, which includes the use of fire-proofing materials, provides an on-site fire resistance measure to prolong the longevity of load-bearing structures. Certainly, the nature, causes and scope of such events have changed considerably over millennia but fear and avoidance have remained as a primary human reaction and as an important human objective, respectively, for virtually every society. This paper will discuss on risk posed by fire, the passive fire protection components, conventional protection materials and thermally reactive materials. From the review, it can be concluded that active fire protection is effective and efficient in most situations passive fire protection, which includes the use of fire-proofing materials, provides an on-site fire resistance measure to prolong the longevity of load-bearing structures

Distinctive Structural and Non-Structural Building Defects and Failures in Educational Buildings

Although the maintenance-free building may be a theoretical possibility, all buildings are subject to the vagaries of defects, failures, deterioration and variation. The examples of these problems are fungus growth, peeling paint, termite attack, dampness, defective rainwater goods, roof defects, harmful growth, settlement, foundation failure, roof collapse and others. There are a great number of building defects and failures arose and being reported officially by mass media, especially problems with educational buildings. Theoretically, all buildings tend to deteriorate over period of time due to aging or other factors, regardless the types of buildings. There are several main factors can be taken into account such as design fault, poor maintenance, poor workmanship, building age and location of building. This paper will discuss on distinctive structural and non-structural building defects and failures than frequently happened in educational buildings. This paper is noteworthy to render varies of problems generally faced by Malaysian educational buildings to the public. As such, the awareness among them can be raised or improved. Furthermore, the public will concern, especially the government authorities should emphasize the laws and regulations to enforce the safety of construction work as well as the procedure in giving approval to the occupation of educational buildings

Prediction of Elevated Temperature Flexural Strength of Lightweight Foamed Concrete Strengthened with Polypropylene Fibre and Fly Ash

This paper focuses on an experimental investigation and statistical analysis of elevated temperature flexural strengths of lightweight foamed concrete (LFC) strengthened with polypropylene fiber (PF) and fly ash (FA) up to 600°C. Five mixes of LFC with 600, 800, 1000, 1200 and 1400 kg/m³ densities were made and tested in current exploration. Two mixes were casted by substituting 15% and 30% of cement content with FA and in other two series; PF was added to LFC mix, correspondingly by 0.2% and 0.4% of binder volume, one controlled mixture without additives was also fabricated. From the experimental results, it can be concluded that the lessening of LFC flexural strength exposed to elevated temperature may be mainly due to the formation of micro cracks at temperature exceeding 93°C since the flexural strength is unfavourably influenced by formation of cracks so that a rigorous strength loss was experiential at 600°C and the flexural strength was only about 40% of its original value. In order to predict the flexural strength of LFC at high temperatures, some existing models applied for normal strength concrete have been considered. The most consistent model for predicting flexural strength of LFC strengthened with PF and FA and also LFC made by ordinary Portland Cement CEM1 at elevated temperature is Li and Guo prediction model. Keywords: foamed concrete, flexural strength, bending strength, elevated temperature, polypropylene fiber, fly as