Page 5 - November-2022

TECHNICAL PAPER

Hence, it can cause remarkable influence on mechanical
property and microstructure of UHPC. Herein, we define the
late age hydration reaction for UHPC with water curing as re-
hydration. Until now, few literature reported the re-hydration
of MK contained UHPC immersed in water for a long period.
Therefore, this study attempts to investigate the re-hydration
including strength, chemically bound water, hydration products,
pore structures and micromorphology of UHPC pastes blended
with MK as reactive powder. Additionally, LS replacing part of
cement is also incorporated in UHPC pastes. The synergism
effect for MK, and LS can further improve mechanical property
and microstructures of cementitious materials due to the
reaction of aluminium (Al) phase from MK, and LS grains in
alkaline environment [11, 23-24] . Therefore, the synergistic effect
evolution of MK and LS in UHPC paste with long term water
curing will also be noticed in this study.
Figure 1: Particle size distributions for the selected raw materials.
2. MATERIALS AND METHODS
Table 2: Mix proportions of UHPC mixtures (Weight
2.1 Raw materials fraction %)
No. PC MK LS S SP w/b w/c
Selected cement was P.I 42.5 type Portland cement (PC)
produced from Ludong Cement Company in China. MK was P00/C00 100 0 0 0/100 0.6 0.20 0.20
used as the reactive powder for UHPC paste and LS was P15/C15 85 15 0 0/100 1.0 0.20 0.24
selected as supplementary material of cement. The strength
PLS00/CLS00 70 0 30 0/100 0.45 0.20 0.29
activity index [25] of MK is 1.10. Silica sand (S) as fine aggregate
was purchased from Sinomo Factory (Xiamen, China). For PLS15/CLS15 55 15 30 0/100 1.0 0.20 0.36
improving the workability of fresh UHPC mixture, Plasticizer obvious degradation of the mechanical property [18] . Therefore,
having a water-reducing rate range of about 25-45 % was used. the levels of 15 % and 30 % by binder mass were determined for
Table 1 presents the chemical compositions as well as Figure 1 MK and LS, respectively in this study. As a contrast, pure cement
shows the particle size distributions of raw materials. The specific paste, and binary paste incorporating LS were manufactured
surface area for employed PC, MK as well as LS in this study simultaneously. Table 2 presented the detailed formulations of
were measured with Brunauer Emmett Teller (BET) method.
paste and mortar specimens.

2.2 Experiment methods
2.2.2 Mixing and curing procedures
2.2.1 Mix design for the fresh mixtures Mortar and paste mixtures were prepared by a planetary mixer in

In this study, UHPC paste and mortar specimens were laboratory. For obtaining a homogeneous matrix, the following
manufactured with the constant water to binder ratio (w/b) of 0.2. mixing procedures were obeyed. The dry ingredients were firstly
Relevant studies indicated that the MK addition level ranging mixed in a mixing pan at a speed of 62 rpm for about 120.0
from 10-20 % by binder mass in UHPC can help obtaining seconds. Then the required water and soluble superplasticizer
satisfactory mechanical and durability properties [8-9] . Similarly, (SP) were incorporated with the dry mixture. Immediately, all
when LS level used in UHPC was around 30 %, there was not raw materials were mixed at the speed of 62 rpm until behaving

Table 1: Chemical compositions for the selected raw materials (%)
OXIDE LOSS ON IGNITION SPECIFIC SURFACE
( %) SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO SO 3 Na 2 O f-CaO K 2 O TiO 2 ( %) AREA (m /g)
2
PC 21.87 4.47 3.39 64.05 2.41 2.44 0.52 0.85 - - 1.21 342
MK 52.96 43.05 0.66 0.41 - 0.49 - - 0.15 1.47 1.03 25000
LS 0.45 0.61 0.19 55.36 0.48 0.012 0.025 - 0.038 - 42.84 913

THE INDIAN CONCRETE JOURNAL | NOVEMBER 2022 19