31 May 93
STRUCTURAL DESIGN USING THE ROLLER-COMPACTED
CONCRETE (RCC) CONSTRUCTION PROCESS
therefore necessary to conduct temperature studies
to identify potential cracking zones and thus control
Roller-compacted concrete (RCC) construction was
cracking. In addition to strength requirements,
first considered as a low-cost, rapid construction
hydraulic structures must be designed to minimize
alternative to earth and rockfill dams and is now
seepage, to control uplift pressures, and to assure
considered a viable alternative to any conventional
long-term durability. Figure 1-1 shows a gravity
mass concrete that can be placed at sites providing
dam constructed of roller-compacted concrete.
sufficient space to accommodate spreading and
Features include an unformed RCC downstream
face and spillway. The spillway is inset and the
spillway training walls are constructed using precast
This Engineer Technical Letter (ETL) discusses the
concrete panels. The spillway crest was constructed
special problem areas and concerns related to RCC
using conventionally placed reinforced concrete.
construction in order to assure that the concrete
properties required are ultimately realized in the
completed structure. A quality RCC product
requires a coordinated effort between the structural
designer, the materials engineer, the materials
laboratory, and those responsible for field quality
control and quality assurance.
Additional detailed RCC materials information can
be found in the American Concrete Institute (ACI)
Committee 207 report 207.5R, "Roller Compacted
Concrete" (Reference 12a), and in Engineer Manual
(EM) 1110-2-2006, "Roller Compacted Concrete"
Figure 1-1. RCC gravity dam
2. Elements of RCC Mixture Design and
Construction Important to Structural Safety
b. RCC strength. The RCC construction
process results in horizontal lift joints at 6- to 24-in.
intervals. The strength at lift joint surfaces is
a. General design considerations. RCC struc-
generally lower than that of the parent concrete.
tures are generally unreinforced and must rely on
Therefore, mixture designs, placement procedures,
the concrete strength in compression, shear and
and quality control measures to assure maximum
bond and strength at the lift joint surfaces are
tension to resist applied loads as well as internal
important. Test data from constructed projects
stresses caused by non-uniform temperatures (gradi-
indicate that RCC joint strengths are sensitive to:
ents). The compressive strength of concrete is high,
and seldom a limiting factor in structural design.
(1) The time interval between the placement
Unreinforced RCC, as is the case with unreinforced
of successive lifts.
conventional concrete, has limited capacity to resist
shear and tensile stresses. Therefore, RCC struc-
(2) The water and cementitious material con-
tures are generally designed so that tensile stresses
tent (cement plus pozzolan) of the mixture, and
do not develop under normal operating conditions
total paste volume.
during the life of the structure. However, under
certain unusual and extreme load conditions (e.g.,
(3) The joint surface condition and treatment
earthquake conditions) some tensile stress is per-
used. In general, the application of joint treatment
mitted. Tensile stresses can also develop due to
(bedding mortar) and rapid placement of successive
short-term temperature gradients as the RCC
lifts will produce higher joint strengths. The design
hydrates and long-term temperature changes. It is