Strength and Chloride Content of Nanoclayed Ultra-High Performance Concrete

The major cause for degradation of reinforced concrete due to chloride penetration has been the great research effort. A large number of published literatures on chloride penetration for ultra-high performance concrete have been reported. In this paper, the strength and the chloride resistance characteristic of the nanoclayed ultra-high performance concrete ( UHPC-NC ) were investigated. Series of ultra-high performance concrete specimens comprise of 0%, 1%, 3% and 5% of nanoclay replacing the total weight of cement were produced. Four ( 4) series of UHPC-NC specimens were designated as UHPC, UHPC-NC1, UHPC-NC3 and UHPC-NC5 respectively. The workability of fresh UHPC and UHPC-NCs, strength performance and chloride content of UHPC and UHPC-NCs measured using Mercuric Thiocyanate method were investigated. It is reported that all the UHPC mixes have high workability however; UHPC-NC5 recorded the lowest slump reading. It also clearly emerges that replacing 1% of cement with nanoclay enhance significantly the compressive and splitting tensile strength as compared to that without nanoclay. The optimum nanoclay replacement level was found to be 1% from the total weight of OPC for strength, but not for chloride diffusion. In term of total chloride content, it is revealed that the incorporation of nanoclay into UHPC mix leads to the reduction of chloride diffusion of the resulted UHPC. It shows that 5% replacement level of nanoclay effectively decreases the chloride diffusivity in UHPC

Chloride Permeability of Nanoclayed Ultra-High Performance Concrete

It is widely recognized that the ingress of chlorides into concrete can initiate reinforcement corrosion and ultimately result in deterioration of the concrete structure. Chloride permeability of concrete has been recognized as a critical intrinsic property affecting the durability of reinforced concrete. From the previous research, the use of nano clay (NC) in cement mortar due to chloride permeability has been well-documented. In this paper, the ability of ultra-high performance concrete (UHPC) to withstand the action of chloride penetration were investigated. An experimental research was carried out in order to investigate the influence of incorporating NC material as cement replacement into ultra-high performance concrete (UHPC-NC) on chloride-related transport characteristic. The workability, compressive strength and charge passed in rapid chloride permeability test (RCPT) of UHPC-NC were reported. Those parameters were also determined for normal strength concrete (NPC) and plain without nano clay ultra-high performance concrete (UHPC) as comparison. Three (3) series of UHPC-NC mixes were produced incorporating 1 % (UHPC-NC1), 3 % (UHPC-NC3) and 5 % (UHPC-NC5) of NC replacing cement (OPC). The results showed that incorporating NC in concrete mixes causes a reduction in the workability. It was also found that replacing of OPC with NC improved the strength of UHPC-NC as compared to those mixes without NC material. The optimum NC replacement level recorded at 3 % (UHPC-NC3) from the total weight of OPC. For the chloride permeability, it is clearly shown that the presence of NC has important benefit in terms of chloride resistance