Distresses In CRCP Due To Horizontal Cracking: A Parameter Analysis

Continuously reinforced concrete pavements are known for their durability and longevity as well as for the driving comfort, thanks to the absence of transverse joints. The strength and weakness of CRCP is situated in the network of fine transverse shrinkage cracks whose spacing distance and opening width are determining the pavement behaviour. The most commonly known distress is the punch-out: a fragmentation of the concrete over full depth. During the last decade, a new type of distress was encountered at Belgian worksites. It is characterised by a delamination at the level of the longitudinal reinforcement, a partial fragmentation of the pavement, mostly positioned under the wheel tracks. The first case was the worksite "N49 at Zwijndrecht", where severe distresses were observed after three years of service. An examination with the technique of ultrasonic tomography detected the presence of horizontal cracks at the level of the reinforcement. The use of recycled concrete aggregates was supposed to be the cause. A significant indicator was also the presence of widely opened cracks. In the period 2011-2018 other cases were observed in Belgium, some of them leading to early degradation and others not. Also in other countries (South-Korea, U.S., Japan, ...) distresses due to horizontal cracking were reported. Based upon observations an analysis is made of the main parameters that may cause the wide initial cracks: the use of recycled aggregates, temperature and temperature changes during construction and concrete quality. Preventative measures such as active crack control will be presented.

MONITORING OF MONOLITHIC OVERLAP WITH PRESTRESSED BEAMS

A method for monitoring the stress-strain state of building structures has been developed. A technical inspection of monolithic slab structures using electronic beacons for crack control was carried out. The basis of the monitoring system of monolithic reinforced concrete structures is a fiber-optic technology based on the control of changes in the parameters of the light wave. For the experimental part, a scheme for testing fiber-optic sensors has been developed.

Continuously Reinforced Concrete Pavement Cracking Patterns and Properties with Internal Curing and Active Cracking

Transverse cracking in continuously reinforced concrete pavement (CRCP) develops over time and may exhibit irregular patterns such as cluster cracks, Y-shaped cracks, and divided cracks. These undesirable cracking patterns can increase the probability of premature spalling and punchouts. Ideally, a uniform transverse cracking pattern with small crack widths leads to favorable long-term performance in CRCP. An experimental field project was constructed with internally cured concrete and active cracking to control crack initiation timing, patterns, and properties. Prewetted fine lightweight aggregate was used for internal curing, and edge notches of 2 in. depth and 2 ft length every 4 ft along the test section were sawcut for active crack control. The three experimental CRCP sections in Illinois were monitored for crack spacing, crack width, and formation of undesirable cracks over a 4-year period. Internally cured concrete significantly reduced the undesirable crack patterns relative to the control section. Internally cured concrete coupled with active crack concrete produced superior crack patterns and properties, that is, uniform crack spacing of 3.6 ft without cluster cracks, 0.2 mm surface crack width, and only a small number of undesirable cracks. Active crack control produced a higher number of transverse cracks near the terminal joint (last 150 ft) compared with the control section. Moisture and temperature management with active crack control during construction of the CRCP provided a desirable crack pattern and properties that should increase the overall service life of a pavement.

Structural behaviour of reinforced high performance concrete frames subjected to monotonic lateral loading.

This thesis describes the structural performance of reinforced one storey flexural and shear-critical frames made of high performance concretes (HPCs) such as: self-consolidating concrete (SCC), engineered cementitious composite (ECC) and ultra-high performance concrete (UHPC) subjected to monotonic lateral loading. The performance of SCC/ECC/UHPC frames are described based on load-deformation/moment-rotation responses, stiffness, strain developments, crack characterization, failure modes, ductility and energy absorbing capacity. The experimentally obtained moment and shear capacities of the frames are compared with those obtained from Codes and other existing design specifications. Overall, ECC frames showed better performance in terms of higher energy absorbing capacity and ductility compared to SCC/UHPC frames. ECC/UHPC frames showed higher load carrying capacity compared to SCC frames. ECC and UHPC shear-critical frames without shear reinforcement were able to prevent shear failure due to fiber bridging and crack control characteristics contributing to the enhanced shear resistance of the matrix.