Reinforced concrete structures in service may be affected by aging, which may include changes in strength and stiffness beyond the baseline conditions which are assumed in structural design, in particular when the concrete is exposed to an aggressive environment. For reinforced concrete structures, due to the uncertainties in material and geometrical properties, in the magnitude and distribution of the loads, in the physical parameters which define the deterioration process, the structural safety should realistically be considered time-variant. This paper provides a computational probabilistic approach to predict the time-evolution of the mechanical and geometrical properties of a reinforced concrete structural element (i.e., bridge pile) subjected to corrosion-induced deterioration, due to diffusive attack of chlorides, in order to evaluate its service life or, complementarily, residual service life. Adopting appropriate degradation models of the material properties, concrete and reinforcing steel, as well as assuming appropriate probability density functions related to mechanical and deterioration parameters, the proposed model is based on Monte Carlo simulations in order to evaluate time-variant axial force-bending moment resistance domains, with the aim to estimate the time-variant reliability index. Finally, an application to estimate the expected lifetime of a deteriorating reinforced concrete bridge pile is described.

Estimation of energy and material input-output during the production and other lifecycle stages is the most basic and repeated procedure to evaluate the environmental impact. Therefore, it is important to develop an accurate, convincing and field-verified model for estimating the material and energy input-output at each lifecycle stages and at each plant or site. With this background, we have been developing energy-use estimation model at concrete production stage. In this paper, we firstly present the unique characteristics of concrete production process in Japan based on our previously proposed model. With this model, we statistically estimate three factors through the field questionnaire survey on ready-mixed concrete plants. The estimation has shown the following characteristics in electric consumption; 1) major manufacturing machineries such as mixer, belt conveyer and blowers are less electric consuming than facilities in constant operation (ex. air compressor), 2) around half of the constant electric consuming facilities can be stopped (at least in some conditions) when concrete shipping is not in queue, which may imply possible options for the reduction of electric energy-use.

The paper deals with the study of rheological and mechanical properties of concretes manufactured by using wash waters as partial replacement of drinking water. Concretes were manufactured by using only water utilized to wash concrete mixing transport trucks. Three different wash waters, with solid residue amount in the range 0.13% - 5.5% by mass were used. The waters were directly sampled in an innovative beton wash system. 30 and 35 concrete grades were manufactured. The superplasticizer dosage was adjusted in order to attain a slump value of 210 mm (8.3 in.) at the end of the mixing procedure. The workability and workability loss up to 60 minutes were also evaluated. The compressive strength at 1, 7 and 28 days was measured on cubic specimens. At 60 minutes, fresh water was added to compensate slump loss (retempering procedure) and a second series of cubic specimens was taken to evaluate compressive strength penalization. Suspended solids in wash water strongly influences the workability retention: the higher the solid content, the lower the workability loss over time and, hence, the water demand to compensate the slump decrease. At the same w/c ratio, the presence of solid particles in wash water causes an increase in the early compressive strength. A modification of the aggregate grading curve, consisting in reducing the sand fine fractions, should be considered, to manufacture concretes comparable to traditional ones.

The need to develop greener concrete is increasing day-by-day with the desire to develop sustainable infrastructures, resource conservation, and contribution to the reduction in the causes of global climate change by reducing carbon footprint of concrete and concrete-making materials, through environmentally-friendly techniques of concrete manufacturing by using recyclable materials, for example post-consumer products. This paper describes the possible roles of post-consumer products namely: used tires, plastics, and glass in the manufacture of greener concrete. Extensive research findings from the studies carried out at University of Wisconsin-Milwaukee Center for By-Products Utilization (UWM-CBU) and elsewhere describing the technology for beneficial use of recycled materials obtained from post-consumer materials in the manufacturing of greener concrete has been presented in this paper. The goal is to not waste such materials because waste is wasted if you waste it; otherwise, it is a resource for a society to be beneficially recycled.

Advances in concrete technology have led to a widespread use of High Performance Concretes (HPC) with a low water/binder ratio. Those concretes are prone to early age cracking because of the increased autogenous shrinkage, which is normally insignificant for w/b greater than 0.4 and appears mostly in the first days after setting, when the concrete has not reached its full tensile strength, and so it’s one of the principal causes of early age cracking impairing the structure durability. This study aims at quantifying the efficiency of Internal Curing with pre-saturated Light Weight Aggregates (LWA) on the reduction of autogenous shrinkage in HPC. A standard mixture (w/c = 0.3) was tested together with an Internal Cured one, in which a fraction of the normal weight aggregate was replaced by a pre-wetted LWA, to evaluate the differences in the mechanical properties (compressive and tensile strength, elastic modulus) and shrinkage behavior (plastic, autogenous, drying free and restrained shrinkage). In face of a slight decrease of the strength (about 9%) which did not compromise the structural use of the concrete, the pre-wetted LWA led to a 30% decrease of autogenous shrinkage, and a roughly 50% reduction in cracking potential.