6.2 Bullet Perforation Test
167
slump and spread of UHP-BASFRC were respectively 250 mm and 630 mm, which
guarantees the workability requirements of on-site constructions.
Nineteen square UHP-BASFRC panels with dimensions of 400 mm × 400 mm
and nominal thicknesses of 40–130 mm as well as the control specimens were cast
simultaneously. Nominal thickness is the height of the mould and the actual thicknesses of panels T t are listed in Table 6.2. For such a small caliber bullet, only local
impact responses occurred and low steel bar reinforcing ratio had no obvious effect
on enhancing the impact resistance when the inner rebar mesh was not hit (Dancygier 1997). Therefore, the steel meshes were not considered from the viewpoint of
conservation. The specimens were demoulded after 24 h and cured in a standard
climate with temperature of 17.7–21.7 °C and 98.4% relative humidity. Concrete
cylinders with length of 150 mm and diameter of 75 mm as well as the specimens
with the dimension of 100 mm × 100 mm × 500 mm (loading procedure given in
Wu et al. (2015a)) were cast for uniaxial compressive and direct tensile strength. The
typical compressive and tensile curves of the present UHP-BASFRC specimen were
shown in Fig. 6.2. The average 28d unconfined cylindrical compressive strength and
the density of UHP-BASFRC were 106.2 MPa and 2530 kg/m
3 , respectively.
6.2.3 Fabric Strengthening
Attributed to low density and high tensile strength, carbon fiber reinforced polymer
(CFRP) and ultra-high molecular weight polyethylene fiber (UHMWPE) fabrics have
been widely used to strengthen/retrofit the structural members under/after blast and
impact loads (Wu et al. 2009; Rodriguez-Nikl et al. 2012; Azrul 2012; Jena et al.
2009; Ong et al. 2003). Currently, in order to reduce the ejected fragments from the
rear face of the concrete panels, as shown in Fig. 6.3, an integral piece of squared
CFRP or UHMWPE fabric (single-layered and bidirectional) with the dimensions
of 400 mm × 400 mm was adhered onto the rear face of the 10 of the total 19
UHP-BASFRC panels (Table 6.2).
Thickness of the CRFP and UHMWPE fabrics were 0.35 mm and 0.12 mm,
respectively. Provided by the manufacturer, the density, tensile strength, Young’s
modulus and elongation at break were 1850 kg/m
3 , 2.3 GPa, 390 GPa, 1.5% and
970 kg/m
3 , 3.1 GPa, 100 GPa, 3.7% for CRFP and UHMWPE fabrics respectively.
Before adhering the fabric, the surface of the panel was polished and then a primer
layer was evenly brushed on the rear side. After the primer layer was dried, the fabric
was then adhered and solidified with epoxy resins. The basic mechanic properties of
the epoxy resins were given by the National Research Center of Testing Techniques
for Building Materials, Beijing, as tensile strength of 42 MPa, Young’s modulus of
2672 MPa and elongation of 1.6%.
167
slump and spread of UHP-BASFRC were respectively 250 mm and 630 mm, which
guarantees the workability requirements of on-site constructions.
Nineteen square UHP-BASFRC panels with dimensions of 400 mm × 400 mm
and nominal thicknesses of 40–130 mm as well as the control specimens were cast
simultaneously. Nominal thickness is the height of the mould and the actual thicknesses of panels T t are listed in Table 6.2. For such a small caliber bullet, only local
impact responses occurred and low steel bar reinforcing ratio had no obvious effect
on enhancing the impact resistance when the inner rebar mesh was not hit (Dancygier 1997). Therefore, the steel meshes were not considered from the viewpoint of
conservation. The specimens were demoulded after 24 h and cured in a standard
climate with temperature of 17.7–21.7 °C and 98.4% relative humidity. Concrete
cylinders with length of 150 mm and diameter of 75 mm as well as the specimens
with the dimension of 100 mm × 100 mm × 500 mm (loading procedure given in
Wu et al. (2015a)) were cast for uniaxial compressive and direct tensile strength. The
typical compressive and tensile curves of the present UHP-BASFRC specimen were
shown in Fig. 6.2. The average 28d unconfined cylindrical compressive strength and
the density of UHP-BASFRC were 106.2 MPa and 2530 kg/m
3 , respectively.
6.2.3 Fabric Strengthening
Attributed to low density and high tensile strength, carbon fiber reinforced polymer
(CFRP) and ultra-high molecular weight polyethylene fiber (UHMWPE) fabrics have
been widely used to strengthen/retrofit the structural members under/after blast and
impact loads (Wu et al. 2009; Rodriguez-Nikl et al. 2012; Azrul 2012; Jena et al.
2009; Ong et al. 2003). Currently, in order to reduce the ejected fragments from the
rear face of the concrete panels, as shown in Fig. 6.3, an integral piece of squared
CFRP or UHMWPE fabric (single-layered and bidirectional) with the dimensions
of 400 mm × 400 mm was adhered onto the rear face of the 10 of the total 19
UHP-BASFRC panels (Table 6.2).
Thickness of the CRFP and UHMWPE fabrics were 0.35 mm and 0.12 mm,
respectively. Provided by the manufacturer, the density, tensile strength, Young’s
modulus and elongation at break were 1850 kg/m
3 , 2.3 GPa, 390 GPa, 1.5% and
970 kg/m
3 , 3.1 GPa, 100 GPa, 3.7% for CRFP and UHMWPE fabrics respectively.
Before adhering the fabric, the surface of the panel was polished and then a primer
layer was evenly brushed on the rear side. After the primer layer was dried, the fabric
was then adhered and solidified with epoxy resins. The basic mechanic properties of
the epoxy resins were given by the National Research Center of Testing Techniques
for Building Materials, Beijing, as tensile strength of 42 MPa, Young’s modulus of
2672 MPa and elongation of 1.6%.