THE INFLUENCE OF CHOPPED COPPER FIBRE (CF) ON THE IMPROVEMENT OF PURE GYPSUM BY COMPRESSIVE STRENGTH

This study investigates the efficacy, performance, and effect of chopped Copper Fibre (CF) on a Pure Gypsum (PG) mixture. The Copper Fibre (CF) is extracted from the waste of electrical wires that are considered as environmental waste. Three models of Copper Fibre (CF) with a diameter of 0.83 (mm) and lengths of 10 (mm), 20 (mm), and 30 (mm) (Aspect-Ratio L/d = 12, 24 and 36 respectively), with Volume Fraction (V.f.) for Copper Fibre (CF) by two Water/ Gypsum Ratios (W/G) worth (0.5 and 0.6) are created. The mixtures are divided into two groups of W/G ratios. Each group contains four samples, one reference without Copper Fibre (CF) and the other three with the addition of Copper Fibre (CF) individually with different lengths. The results show that adding Copper Fibre (CF) to the Pure Gypsum (PG) mixture increases the Compressive Strength. Further, the effect is to heighten the Compressive Strength of Pure Gypsum (PG) when the Aspect-Ratio is raised. In other words, when the (W/G) Ratio is reduced, the Compressive Strength increases in the presence or absence of Copper Fibre (CF). Moreover, the efficiency of the Copper Fibre (CF) develops further when the W/G ratio is decreased.


INTRODUCTION
Gypsum substance (calcium sulphated hydrate, CaSO4 2H2O) is necessary for most building applications. It is popularly available as a binder, in boards and precast parts, indoor finishing work and walls for Acoustic Isolation [1][2]. Gypsum has multiple excellent features such as a readily formed process, volumetric stability, affordable cost, fire and thermic protection, engaging design, reduced density and simply made [2][3]. Gypsum is used as a support material in medicine and dentistry [4]. Concrete admixtures use gypsum to delay timing for setting in cement and ceramic casting [5]. According to various experimental research studies [6][7][8][9][10][11][12][13][14][15][16][17], the addition of substances such as fly ash, gum tree powder, silica fume, clay, polyvinyl chloride, cork, Portland, and minerals to a mixture may support the developmental properties of the gypsum matrix. This is true in terms of the physical and chemical aspects appearing in the actual effects of its hardening and fresh characteristics. Regarding the use of strengthening substances, a good deal of research demonstrates the relevance of including various fibres in gypsum mixtures [3,[18][19][20][21][22][23]. This is because the fibres increase the gypsum tensile strength and shape stability to support the mixture to reduce degradation and breakdown.Many researchers have studied the effect of even more substances such as steel fibre or chipped carbon fibres to reinforce a concrete mix, cement mortar, and asphalt concrete admixtures [24][25][26][27][28][29][30][31][32].The current work proposes to design Pure Gypsum (PG) of unique fibres that strengthen as a composite form by use of compact and ductile copper fibres haphazardly scattered in the gypsum. Copper fibres present high ductility [33] to improve problematic brittle material fractures to become ductile fractures and also block the tendency to pull-out from the gypsum. Therefore, this work adopts copper fibres as an additive to gypsum.

RESEARCH OBJECTIVES
The objectives of this research are to: • Test and study the potential of adding for the first time copper fibres extracted from environmental waste to pure gypsum as an environmental sustainable form. • Study the effect of copper fibre on a pure gypsum mixture and discover if it has the ability to improve Compressive Strength.

Pure Gypsum (PG)
Essentially Pure-Gypsum (PG) is used in this investigation as pure calcium sulphate hemihydrate-gypsum (Ca-

Chopped Copper Fibre (CF)
Waste electrical wiring is considered an environmental waste, which is the material used in this study. After electrical work is performed for buildings, the wires are gathered from the waste materials. The standard properties that apply to copper wire are "BS. EN. 50525-2-31" and "IEC. 60227-3", with 9810 Kg/m 3 density, 70 MPa Yield Strength, 220 MPa Ultimate Strength [34]. The Single Core Stranded wires used in this work have a total diameter of 4 mm, and after stripping the rubber outer insulation, they produce seven wires with a combined diameter of 3.2 mm. To create a suitable model for the fibre-forming electrical conductors, the seven-wires were modelled as a single wire with a diameter of 0.83 mm.
Then the copper wires are divided into three groups with different lengths, so that the length of each group is one of 10 mm, 20 mm, or 30 mm individually. The Aspect-Ratio (L/D) will be (12,24, and 36 consecutively) as shown in Figure 1. The Aspect Ratio may be defined as the ratio between the length and diameter of the copper wire.

Figure 1: Copper Fibre (CF)
The mixing water The pure gypsum mixture utilises tap water to perform this work.

Figure 2: Experimental Work Plan
The experimental plan contains eight mixtures separated into two sets with the (W/G) ratio fixed at (0.5 and 0.6).
Each set comprises of four mixtures containing one reference mixture without copper fibre and three mixtures containing three individual models of copper fibres (V.f. = 0.4). The 0.83 mm diameter copper fibre model employs 10 mm, 20 mm, and 30 mm individual lengths of each model (with an Aspect ratio equal to 12, 24, and 36 consecutively), as detailed in Figure 2 and Table 1.

Mixing procedure
The mixing process starts with the weight of Copper Fibre (CF) equivalent to the Volume Fraction (V.f.) of 0.4 %, then mixed with the amount of Pure Gypsum (PG) required for mixing (dry mixing) until the Copper Fibre (CF) is homogeneous with the Pure Gypsum. After that, water is added according to the W/G ratio (0.5 or 0.6).
The mixture is mixed and placed in cubic moulds of (50 × 50 × 50) mm. After completing the hardening phase, the Pure Gypsum (PG) mixture is removed from the moulds and exposed for 30 hours to a heat source with a temperature of 45 °C. The reference mixtures use the same previous steps but without Copper Fibre (CF).

Testing programme
All tests are performed at the College of Engineering using the tools and a series of test machines of the MUS-TANSIRIYAH UNIVERSITY laboratories known as the "Structural Materials Laboratory".

Compression strength
The  Figure 3 and Table 2 Table 3 show the influence of changing the Water Gypsum ratios on the Compressive Strength of the Pure Gypsum (PG) with the variable Aspect Ratios (variable length) of the Copper Fibre (CF).

Figure 4. Effect of Water Gypsum ratio on Pure Gypsum (PG) Compressive Strength values with the variable Aspect Ratios (variable length) of the Copper Fibre (CF)
The decrease in the Water Gypsum ratio may help to increase the Compressive Strength value. This increase in behaviour applies in the presence or absence of the Copper Fibre (CF) in the mixture. This increase occurs in mixtures that contain Copper Fibre (CF), which increases when the Aspect ratio is increased by increasing the length of the copper fibre.