PSI - Issue 64

Eric Williams et al. / Procedia Structural Integrity 64 (2024) 1573–1580 Williams, Annooz, and Myers / Structural Integrity Procedia 00 (2024) 000 – 000

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1. Introduction Reinforced concrete (RC) is one of the most common materials used in building and infrastructure construction in the world. The steel reinforcement of RC compensates for the low tensile capacity of concrete, resulting in a composite material capable of withstanding tensile and compressive loading. Corrosion of reinforcing steel is a major concern when considering the lifetime of a structure. In North America, reinforcing steel most often corrodes in the presence of chloride ions, typically found in road salts or seawater, according to ACI Committee 222 (2019). According to Bloomfield (2007), c oncrete’s high alkalinity creates a “passive” layer around the reinforcing steel, which protects against corrosion. This passive layer, Bloomfield (2007) expands, can be deteriorated via carbonation of the concrete and extended exposure to chlorides. Anticipating the deterioration of the passive layer, especially in marine environments or colder climates where road salts are used, it is common to incorporate an additional layer of protection to the reinforcing steel, like with an epoxy coating or galvanizing the steel with zinc. A novel coating to resist corrosion is magnesium potassium phosphate cement (MKPC). Yang (1999) states MKPC demonstrates potential as an anti-corrosion coating for new construction and repair due to its rapid hardening, early strength, and good bond qualities. The aim of this paper is to investigate those bond qualities. 2. Test specimens and experimental work 2.1 Materials A conventional concrete mix design was used with a target strength of 34.5 MPa, shown in Table 1. The coarse aggregate used was dolomitic limestone, and the fine aggregate used was river sand. Table 2 shows the measured properties of fresh concrete. No air entraining admixture was used in this study. Concrete cylinders were prepared and cured according to ASTM C192 2019. Cylinders were tested at 7, 28, and 56 days for compression following ASTM C39 2020 and splitting tensile strength following ASTM C496 2014.

Table 1. Concrete mix proportions. Water ( kg/m 3 )

Cement ( kg/m 3 )

Coarse aggregate ( kg/m 3 ) Fine aggregate ( kg/m 3 )

176

449

993

657

Table 2. Concrete mix design fresh properties. Property Specification

Value

Slump, mm Air content (%)

ASTM C143 ASTM C231

114 0.4

Concrete and repair material properties are shown in Table 3. Concrete specimens were tested at 7, 28, and 56 days for compressive strength and tensile strength, while repair material specimens were tested at 7 and 56 days for compressive strength and tensile strength. The rebars were manufactured with mild steel grade 60 rebars (tensile strength of 420 MPa).

Table 3. Concrete and repair material properties.

[ASTM C 39, ASTM C 109] 7-, 28-, and 56-day Compressive Strength ( MPa )

[ASTM C 496] 7-, 28-, and 56-day Tensile Strength ( MPa )

[ASTM C 143] Slump ( mm )

[ASTM C 231] Air content ( % )

Material Concrete

100

4.0

48.0, 51.6, 54.7

3.27, 3.35, 3.93

Corrosion inhibitor repair material Self-consolidating repair material

-

-

48.0, na, 60.7

4.43, na, 4.63

-

-

49.1, na, 53.1

3.05, na, 4.29