Influence of early-age concrete behaviour on concrete pavements performance

Pukotine u razdjelnicama posljedica su ponašanja betona u početku uporabe konstrukcije što može utjecati na konstrukcijska svojstva betonskih kolnika. U radu se analiziraju dosadašnja znanja za procjenu utjecaja betona u početnom periodu uporabe betonske kolničke konstrukcije. Ispitivanje je pokazalo da je pri modeliranju ponašanja pukotina potrebno uzeti u obzir međudjelovanje (u vremenu i prostoru) grupe razdjelnica. Kao rezultat takvog pristupa može se predvidjeti odnos razdjelnica i širina pukotina kako bi se procijenili njihovi učinci na svojstva betonskih kolnika.Cracks in joints are the consequence of concrete behaviour in the initial period of use of pavement structures, which can affect structural properties of concrete pavements. Current knowledge on the influence of concrete in the initial period of use of concrete pavement structures is analysed in the paper. The analysis has shown that interaction (in space and time) of the group of joints must be taken into account in the scope of crack behaviour modelling. As a result of this approach, the relationship between joints and crack width can be predicted in order to evaluate their effects on properties of concrete pavements

Influence of early-age behaviour on structural design of sustainable thinner concrete slabs

Učinkovitost prijenosa opterećenja (load transfer efficiency - LTE) na dilatiranim betonskim kolnicima bez moždanika (jointed plain concrete pavements - JPCP), kao što su inovativne kratke ploče, određena je prema pukotinama koje se stvaraju ispod razdjelnica dok je beton svjež. Autori su prethodno razvili i kalibrirali model za predviđanje širine pukotina u tradicionalnim JPCP-ovima. Cilj prikazanog istraživanja je potvrditi ovaj model korištenjem kratkih ploča kako bi se utvrdila veza između širine pukotina i LTE-a. Nakon usporedbe predviđene širine pukotina s onima uočenim u urbanim, industrijskim i međugradskim JPCP-ovima s kratkim pločama, zaključuje se da je model koristan za uključivanje ponašanja svježeg betona pri projektiranju održivih tanjih ploča.The load transfer efficiency (LTE) of non-dowelled jointed plain concrete pavements (JPCPs), such as the innovative short slabs, is defined in terms of the cracks that form under the joints at an early age. The authors had previously developed and calibrated a model to predict crack widths in traditional JPCPs. The aim of this study is to validate this model using short slabs to relate crack width and LTE. After comparing the predicted crack width with actual ones observed in urban, industrial, and interurban short slab JPCPs, it is concluded that the model is useful for incorporating the early-age concrete behaviour into the structural design of these sustainable thinner slabs

Safety-centric and Smart Outdoor Workplace: A New Research Direction and Its Technical Challenges

Despite the fact that outside is becoming the frontier of indoor workplaces, a large amount of real-world work like road construction has to be done by outdoor human activities in open areas. Given the promise of the smart workplace in various aspects including productivity and safety, we decided to employ smart workplace technologies for a collaborative outdoor project both to improve the work efficiency and to reduce the worker injuries. Nevertheless, our trials on smart workplace implementation have encountered a few problems ranging from the theoretical confusion among different stakeholders, to the technical difficulties in extending underground devices' lifespan. This triggers our rethinking of and discussions about "smart workplace". Eventually, considering the unique characteristics of outdoor work (e.g., more sophisticated workflows and more safety-related situations than office work), we argue that "safety-centric and smart outdoor workplace" deserves dedicated research attentions and efforts under the umbrella discipline of smart environment. In addition, the identified technical challenges can in turn drive different research dimensions of such a distinguishing topic.Comment: 14 page

Different Approaches to Develop More Sustainable Concrete Alternatives

As important as it is, sustainability related with the concrete material is more than reducing the amount of cement in concrete mixes. In effect, there can be other types of contributions to a sustainable development using this fundamental material. The purpose of this book chapter is to analyse some of these approaches, in particular, concrete durability, reducing the amount of required concrete (and then cement) through innovative structural design, and reducing the amount of aggregates used in the concrete material. More specifically, examples and results obtained in Chile with biological self-healing concrete, thinner concrete pavements and concrete with industrial and domestic waste as partial aggregate replacement are included in the chapter. Due to its importance, the geo-dependency of the concrete material is addressed as well

Prediction of concrete compressive strength through artificial neural networks

Svojstva betona, uključujući i tlačnu čvrstoću, uglavnom se mogu smatrati vrlo nelinearnim funkcijama njegovih komponenata. Metode koje se koriste za projektiranje betonskih mješavina u svojoj su osnovi simulacije koje zahtijevaju skupe i vremenski zahtjevne korekcije u laboratoriju. U ovom se radu predlaže korisna podrška utemeljena na umjetnoj neuronskoj mreži, točnije primjeni višeslojne perceptronske mreže, a može se primijeniti za predviđanje tlačne čvrstoće betonskih mješavina. Razvijeni modeli omogućuju smanjenje broja laboratorijskih ispitivanja koja se provode u svrhu korekcije betonske mješavine.Concrete properties, including its compressive strength, are in general highly nonlinear functions of its components. Concrete mix design methods are basically simulations that require costly and time consuming adjustments in laboratory. A useful support tool based on artificial neural networks, using a multilayer perceptron network, is proposed in this paper as a means to predict compressive strength of concrete mixes. The developed models are useful for reducing the quantity of laboratory tests required for concrete mix design adjustments

Making the asphalt paving process explicit - A fundamental step for quality improvement

Cilj ovog rada je jasno definiranje postupka asfaltiranja kolnika i uz njega vezane podatke o temperaturi i zbijenosti asfalta te logističkog procesa, budući da je to temeljni preduvjet za postizanje poboljšanja. U tu svrhu, prikupljeni su podatci o temperaturi asfalta, putanjama kretanja valjaka, zbijenosti asfalta, brzini kretanja finišera te o logističkoj podršci kamionima koji dopremaju asfalt. Rezultati, analize i dobivene povratne informacije upućuju na postojanje konkretnih mogućnosti za poboljšanje, koje uključuju izbjegavanje zaustavljanja finišera tijekom asfaltiranja, ujednačeno zbijanje cijele površine kolnika te izrada strategije za kretanja valjaka.The objective of the paper is to make explicit the paving operations, the related asphalt temperature and density data, and the logistic process, as a fundamental step to identify improvement opportunities. For that, temperature data, roller compactor trajectories, asphalt density, paver speed, and trucks logistics, were collected. The results, analysis, and feedback received, point to specific opportunities for improvement, including avoiding the paver start-stop cycles, uniform compaction of the entire pavement surface, and definition of roller compaction strategy

Functional criteria for sustainable design of urban pavements

Functional criteria have been mostly defined in urban pavements using subjective methods, rather than by means of objective and repeatable procedures. The Whole Body Vibration, the Heart Rate Variability, and new technologies to determine the IRI (International Roughness Index), are nowadays available. For that, an analysis of available technologies is made under a PC-O (Pavements Clients-Oriented) integral perspective, including simulations with the HDM-4 computer program. The IRI criteria for speeds allowed on urban roadways, i.e. the so-called IRIcity criteria, are proposed in the paper

Joint faulting behaviour of innovative short concrete slabs

Pavements are one of the largest assets of a city and their functional condition (ride quality) is priority for their clients. In jointed plain concrete pavements (JPCPs), the presence of joint faulting (JF) reduces the ride quality. Today, short slabs are available as a cost-effective JPCP innovation. The objective of this paper is to analyse the JF behaviour of JPCPs with short slabs. For this, a deterioration model to predict it and trends of JF observed in short slabs of Chile and the United States are considered. The HDM-4 model always yields lower JF per joint in short slabs than in traditional ones. However, real-world short slabs show not only lower JF per joint (that the modelled JF), but also that more joints do not necessarily mean more JF per length of pavement that affect the ride quality. One of the relevant explanatory factors for it is the radical reduction of crack width at joints, which produces a fundamental increase of the load transfer efficiency. To maintain favourable behaviour observed in the field it is recommended to assure joint activation and to provide adequate stiffness of the layers below the short slabs

Analysis of Stress Relaxation in Jointed Plain Concrete Pavements

The cracks in concrete pavements are formed at early-age as consequence of internal stresses in the concrete. Therefore, the stress relaxation has an essential influence on the cracking process. To model this process allows to identify, for instance, the time for saw-cutting the joints or the cracks width that affects load transfer. Previously, the authors proposed a new equation of the relaxation factor, based on a theoretical and practical analysis of the transversal cracking in jointed plain concrete pavements. The objective of the present paper is to analyze the utility of this new equation of relaxation in the design and construction of jointed plain concrete pavements. For that, other cracking processes in plain concrete pavements (jointed and non-jointed) were modelled with the proposed equation. Wherever is possible the modelling results were compared with observations of the real behaviour of pavements. From the design point of view, with the modelling results of transverse crack width (>1.0 mm) is possible to considerate in the design, optimal slabs length with thinner cracks for better aggregate interlock. And for the longitudinal cracking in jointed plain concrete pavements, the modelling and the field observations, yield cracks width that provide load transfer (<0.1 mm). From the construction point of view, the cracking process in non-jointed plain concrete pavements, shows is possible to construct pavements of 7 m width in one gang without cracks risk, and adjustments can be made to a better prediction of the time of occurrence of the 1st transverse cracks