6.1 Introduction
165
proposed that the straight steel fibers with volumetric ratio of 1.5–2% is the optimum
choice by comprehensively considering the mechanical properties, workability, crack
prohibiting ability as well as the costs.
In this chapter, based on the above suggestions of existing works (Wu et al. 2015a,
b; Bludau et al. 2006; Sovják et al. 2013, 2015; Zhang et al. 2005), by mixing the
high strength basalt aggregates with the size range of 5–10 mm and the straight
steel fibers with the volumetric ratio of 2% into matrix of UHPC, the optimal basalt
aggregated UHP-SFRC (UHP-BASFRC) with the designed uniaxial compressive
strength of about 100 MPa was prepared under common curing temperature and
pressure procedures. Furthermore, the API bullet impact test on above bare or rear
fabric strengthened UHP-BASFRC panels with the thickness of 40–130 mm were
conducted. The impact resistances of the bare and composite UHP-BASFRC panels,
as well as the effect of externally protected fabric (CFRP or UHMWPE fabrics) were
evaluated. Finally, a practical approach to predict the terminal ballistic parameters
of bullet impacting on both traditional no coarse aggregated UHP-SFRC and present
UHP-BASFRC slabs was suggested. The experimental conclusions as well as the
suggested practical approach could provide references for the design and retrofit of
ground structures threatened by high speed small caliber arms or fragments.
6.2 Bullet Perforation Test
6.2.1 Bullet
As shown in Fig. 6.1, the in-service armor-piercing incendiary (API) bullet was used
in the present test, which was supposed to cover the most loads caused by small
caliber arms (Bludau et al. 2006). The weight of the API bullet with 7.62 mm in
diameter and 37.88 mm in length was 10.4 g. It consists of a brass jacket, a lead
spacer, incendiary agent filler and a 5.15 g, ogive-nosed hard steel core. The hard
steel core (6.12 mm in diameter and 27.5 mm in length) was machined by T12A
steel with a hardness of HRC 62–67 and the yield strength of 980 MPa, respectively.
Muzzle velocity of the in-service 7.62 mm API bullet fired from Chinese sniper rifle
85 was usually in the range of 800–815 m/s, while the actual impact velocity would
be measured during test.
6.2.2 UHP-BASFRC Panels
The optimal UHP-BASFRC was prepared by State Key Laboratory of High Performance Civil Engineering Materials, Jiangsu Research Institute of Building Science
in China. The mix proportion of UHP-BASFRC in the present impact test is listed
in Table 6.1, in which all the ingredients are commercially available in China. Based
165
proposed that the straight steel fibers with volumetric ratio of 1.5–2% is the optimum
choice by comprehensively considering the mechanical properties, workability, crack
prohibiting ability as well as the costs.
In this chapter, based on the above suggestions of existing works (Wu et al. 2015a,
b; Bludau et al. 2006; Sovják et al. 2013, 2015; Zhang et al. 2005), by mixing the
high strength basalt aggregates with the size range of 5–10 mm and the straight
steel fibers with the volumetric ratio of 2% into matrix of UHPC, the optimal basalt
aggregated UHP-SFRC (UHP-BASFRC) with the designed uniaxial compressive
strength of about 100 MPa was prepared under common curing temperature and
pressure procedures. Furthermore, the API bullet impact test on above bare or rear
fabric strengthened UHP-BASFRC panels with the thickness of 40–130 mm were
conducted. The impact resistances of the bare and composite UHP-BASFRC panels,
as well as the effect of externally protected fabric (CFRP or UHMWPE fabrics) were
evaluated. Finally, a practical approach to predict the terminal ballistic parameters
of bullet impacting on both traditional no coarse aggregated UHP-SFRC and present
UHP-BASFRC slabs was suggested. The experimental conclusions as well as the
suggested practical approach could provide references for the design and retrofit of
ground structures threatened by high speed small caliber arms or fragments.
6.2 Bullet Perforation Test
6.2.1 Bullet
As shown in Fig. 6.1, the in-service armor-piercing incendiary (API) bullet was used
in the present test, which was supposed to cover the most loads caused by small
caliber arms (Bludau et al. 2006). The weight of the API bullet with 7.62 mm in
diameter and 37.88 mm in length was 10.4 g. It consists of a brass jacket, a lead
spacer, incendiary agent filler and a 5.15 g, ogive-nosed hard steel core. The hard
steel core (6.12 mm in diameter and 27.5 mm in length) was machined by T12A
steel with a hardness of HRC 62–67 and the yield strength of 980 MPa, respectively.
Muzzle velocity of the in-service 7.62 mm API bullet fired from Chinese sniper rifle
85 was usually in the range of 800–815 m/s, while the actual impact velocity would
be measured during test.
6.2.2 UHP-BASFRC Panels
The optimal UHP-BASFRC was prepared by State Key Laboratory of High Performance Civil Engineering Materials, Jiangsu Research Institute of Building Science
in China. The mix proportion of UHP-BASFRC in the present impact test is listed
in Table 6.1, in which all the ingredients are commercially available in China. Based