土木工程混凝土论文中英文资料外文翻译文献

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土木工程混凝土论文

中英文资料外文翻译文献

外文资料

STUDIES ON IMPACT STRENGTH OF CONCRETE

SUBJECTED TO SUSTAINED

ELEVATED TEMPERATURE

Concrete has a remarkable fire resisting properties. Damage in concrete due to fire depends on a great extent on the intensity and duration of fire. Spalling cracking during heating are common concrete behaviour observed in the investigation of the fire affected structures. Plenty of literature is available on the studies of concrete based on time temperature cures. In power, oil sectorsand nuclear reactors concrete is exposed to high temperature for considerable period of time. These effects can be reckoned as exposure to sustained elevated temperature. The sustained elevated temperature may be varying from a few hours to a number of years depending upon practical condition of exposures. The knowledge on properties under such conditions is also of prime importance apart from the structures subjected to high intensity fire. Impact studies of structure subjected to sustained elevated temperature becomes more important as it involves sensitive structures which is more prone to attacks and accidents. In this paper impact studies on concrete subjected to sustained elevated temperature has been discussed. Experiments have been conducted on 180 specimens along with 180 companion cube specimens. The temperatures of 100°C, 200°C and 300°C for a duration of exposure of 2 hours 4 hours and 6 hours has been considered in the experiments. The results are logically analyzed and concluded.

1. INTRODUCTION

The remarkable property of concrete to resist the fire reduces the damage in a concrete structure whenever there is an accidental fire. In most of the cases the concrete remains intact with minor damages only. The reason being low thermal conductivity of concrete at higher temperatures and hence limiting the depth of penetration of fire

damage. But when the concrete is subjected to high temperature for long duration the deterioration of concrete takes place. Hence it is essential to understand the strength and deformation characteristics of concrete subjected to temperature for long duration. In this paper an attempt has been made to study the variation in Impact Strength of concrete when subjected to a temperature range 100oC, 200oC and 300oC sustained for a period of 2 hrs, 4 hrs and 6 hrs.

The review of the literature shows that a lot of research work [1 – 3] has taken place on the effect of elevated temperature on concrete. All these studies are based on time –temperature curves. Hence an attempt has been made to study the effect of sustained elevated temperature on impact strength of concrete and the results are compared with the compressive strength. The experimental programme has been planned for unstressed residual strength test based on the available facilities. Residual strength is the strength of heated and subsequently cooled concrete specimens expressed as percentage of the strength of unheated specimens.

2. EXPERIMENTAL INVESTIGATION

2.1. TEST SPECIMEN AND MATERIALS

A total of 180 specimens were tested in the present study along with 180 companion cubes. An electric oven capable of reaching a maximum temperature of 300oC has been used for investigation. Fine and coarse aggregates conforming to IS383 has been used to prepare the specimen with mix proportions M1 = 1:2.1:3.95 w/c = 0.58, M2 = 1:1.15:3.56 w/c = 0.53, M3 = 1:0.8:2.4 w/c = 0.4.

2.2 TEST VARIABLES

The effects of the following variables were studied.

2.2.1 Size s

Size of Impact Strength Test Specimen was 150 mm dial and 64 mm thickness and size of companion cube 150 x 150 x 150 mm.

2.2.2 Maximum Temperature

In addition to room temperature, the effect of three different temperatures (100oC, 200oC and 300oC) on the compressive strength was investigated.

2.2.3 Exposure Time at Maximum Temperature

Three different exposure times were used to investigate the influence of heat on compressive strength; they are 2 hrs, 4 hrs and 6 hrs.

2.2.4 Cooling Method

Specimens were cooled in air to room temperature.

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