The effect of water-to-cement ratio on the fracture behaviors and ductility of Roller Compacted Concrete Pavement (RCCP)

Abstract

Roller compacted concrete ($\mathrm{RCC}$) is a zero-slump concrete that has been extensively used in road pavements. This concrete has been considered, due to its economic and environmental potentials, including reduced construction and maintenance costs and greater environmental compatibility. A unique feature of the Roller Compacted Concrete Pavement ($\mathrm{RCCP}$) is its low water-to-concrete ($\frac{W}{C}$) ratio. Hence, $\mathrm{RCCP}$ is sensitive to the water content, compared to conventional concrete. This paper conducts an experimental studies on the effect of different ratios of $\frac{W}{C}$ on the fracture parameters of $\mathrm{RCCP}$. For this purpose, three-point bending tests were performed on $162$ notched beams and mechanical properties tests (compressive strength ($f_c$), tensile strength ($f_t$) and modulus of elasticity ($E$)) were performed on $54$ specimens with different $\frac{W}{C}$ ratios ($0.3to0.55$). For all mixtures, the fracture parameters were determined using three methods: work of fracture method ($\mathrm{WFM}$), size effect method ($\mathrm{SEM}$), and boundary effect method ($\mathrm{BEM}$). The results indicate a significant effect of $\frac{W}{C}$ ratio on $\mathrm{RCCP}$ fracture parameters, specifically, by decreasing w/c ratio from $0.55to0.3$ it was observed that; (A) The initial fracture energy ($G_f$) and the total fracture energy ($G_F$) increase in all three methods as a power function on $f_c$; (B) The fracture toughness ($K_{\mathrm{IC}}$) increases linearly in $\mathrm{SEM}$ and $\mathrm{BEM}$ methods; (C) The characteristic length ($L_{\mathrm{ch}}$) in $\mathrm{WFM}$, the effective length of the fracture process zone ($C_f$) in $\mathrm{SEM}$, and the reference crack length (ductility index) ($a_{\infty }^{\ast }$) in $\mathrm{BEM}$ are decreased. The results also show that there is a relationship between $G_F$ measured by $\mathrm{WFM}$ method, and the $G_f$ measured by $\mathrm{SEM}$ and $\mathrm{BEM}$ methods ($G_F\cong 2.43G_f$($\mathrm{SEM}$), $G_F\cong 2.61G_f$($\mathrm{BEM}$)).