PSI - Issue 64

Kevin Isaac Escobar et al. / Procedia Structural Integrity 64 (2024) 1476–1483 Kevin Isaac Escobar/ Structural Integrity Procedia 00 (2019) 000 – 000

1478

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2. Experimental program Twenty-seven tensile tests on TRM specimens were conducted utilizing carbon and basalt textiles in combination with conventional cement-based mortar, mortar with short glass fibres, and a mortar with synthetic fibres. Latex and epoxy resins to impregnate the carbon textile were studied, while basalt fibres were already saturated with acrylic resin and did not require additional treatment. To properly differentiate the textiles and the coating used, they are named in the present study using the notation TC, where T = textile employed (C = carbon, and B = basalt), and C = coating used (L = latex, E = epoxy, and A = acrylic). Furthermore, a total of twenty-three bond tests were performed on TRM specimens attached to a concrete substrate. A cementitious mortar preblended with short glass fibres was selected for the matrix of the carbon and basalt fibres in bond tests. Commercial bidirectional meshes Mapegrid C200 and Mapegrid B250 were selected for the carbon and basalt textiles. Basalt fabric was supplied impregnated with acrylic resin. For carbon fibres, they were coated with either latex or epoxy resin by submerging them in a container filled one third with resin for a few minutes. The textile was then removed, allowed to drain, and squeezed using gloves to eliminate excess resin, ensuring not to twist the textile to avoid damaging the fibres. Fig.1 shows different textiles and coating, along with their spacing in their orthogonal directions. The textiles were characterized under uniaxial tension using the same number of bundles as the TRM composites. Testing was performed under displacement control at a rate of 0.20 mm/min. Metallic tabs were epoxy bonded to each end of the textiles to provide a proper gripping area. The strain was computed using the displacement measured by a clip-on extensometer with base length of 50 mm and positioned in the middle of each specimen. The ultimate stress was calculated dividing the maximum load by the cross-sectional area provided by the manufacturer. Table 1 summarizes the results of tensile tests on the textiles in terms of the average values, as well as their coefficients of variation [CoV], obtained from at least three tests on nominally identical textile specimens. 2.1. Material properties

Fig. 1. Meshes utilized: (a) carbon coated with latex, (b) carbon coated with epoxy resin, (c) basalt coated with acrylic resin.

Table 1. Material properties of textiles in the warp direction

Notation Textile

Coating

Spacing (mm)

Number of bundles tested

A f (mm

2 )

ε f (%) [CoV]

σ f (N/mm

2 )

E f (N/mm

2 )

[CoV]

[CoV]

CL CE BA

Carbon Carbon Basalt

Latex resin Epoxy resin Acrylic resin

15 15

4 4

3.30 3.30 2.33

1.13 [6.9%] 1.54 [3.5%] 2.05 [5.7%]

2015 [4.6%] 2909 [4.4%] 1588 [5.1%]

181056 [3.0%] 223436 [3.0%] 77429 [1.7%]

6

10

Three types of mortars were selected as matrices for the TRM composites. The first matrix consists of a conventional cementitious mortar. The commercial mortar products Planitop HDM Maxi and Mapegrout 430 Zero were selected for the two other matrices. Planitop HDM Maxi is a bicomponent, high strength cement-based mortar with short glass fibres that forms a plastic-thixotropic mixture. Mapegrout 430 Zero is a preblended mortar that contains synthetic fibres. Mechanical properties of each mortar were obtained by flexure and compressive tests over prims of 40x40x160mm. Casting, curing conditions, and testing parameters were in accordance with the European standard EN 1015-11 (2019). Table 2 presents the results of mortar tests corresponding to the different batches used to fabricate the TRM, along with the properties of the concrete used as substrate in the single-lap shear tests. For