Performance Assessment of Natural Pozzolan Roller Compacted Concrete Pavements

Concrete pavement is cost effective and beneficial because of its sustainability and durability. The maintenance and renovation periods for such pavement compared to other pavements are relatively long; however, a significant issue with pavements, especially roller compacted concrete pavements (RCCP), is salt scaling which occurs due to saline solutions such as deicer salts. In the present work, the performance of RCC containing a natural pozzolan called Trass, as a supple- mentary cementitious material, and an air-entraining agent for salt scaling was investigated. Mechanical and durability tests were performed on specimens containing a water to binder ratio of 0.32, with and without Trass, and an air-entraining agent. It was concluded that, Trass could not improve the compressive and tensile strengths, however, the permeability was improved. Moreover, the amount of mass loss due to salt scaling was not decreased. In all concrete mixtures, using a suitable amount of an air-entraining agent to maintain a total air content of 4.5–5% was found to be necessary for producing RCC containing Trass

Modeling Abrasion Resistance of Concrete Floors

Abrasion of industrial concrete floors is a major problem resulting in their lower service lives. Attempt has been made to relate the abrasion resistance of concrete to its compressive strength. However there are other factors which influence the abrasion resistance of concrete. In this study, several concrete mixtures containing different types of cements, aggregates, admixtures and additives such as silica fume and styrene butadiene rubber (S.B.R) polymer were made to assess their abrasion resistances. All concrete specimens were tested for wear action in accordance with ASTM and EN standard test methods. Based on data obtained from the tests, an empirical model was proposed to evaluate the abrasion resistance of different concretes. Results of this investigation show that the incorporation of silica fume, S.B.R polymer and granite aggregates in concrete improve its abrasion resistance. The proposed mathematical model is capable to predict the abrasion resistance of concrete and provide a guide for selection of materials to produce more durable concrete when subjected to wear action

Bond characherization between concrete substrate and repairing materials

The purpose of this investigation was to study the effect of bonding behavior of concrete substrate and repair materials. Three different cementitious or modified-cementitious repair materials and three surface roughnesses were studied. Repair materials were ordinary mortar, modified cementitious mortar by silica fume and modified cementitious mortar by styrene butadiene rubber latex. Surface preparations were smooth surface, rough surface and epoxy resin adhesive as a bonding agent. The method used for evaluation of bond strength was pull-off test. the influence of the electrical conductivity of repairing materials was analyzed by rapid chloride permeability test. Finally, the performance of the adhesives was evaluated considering both the bond strength and electrical conductivity. Results obtained from these tests indicated that the roughness of substrate surface has a main effect on the performance of bond between adhesives and concrete. There are not great differences in bonding strength between various repairing materials but considering electrical conductivity, modified cementitious mortars are better materials for using in corrosive environments to increase service life of repaired structure

Effect of mixture proportions on the drying shrinkage and permeation properties of high strength concrete containing class F fly ash

Sustainability of concrete can be improved by using large volume of fly ash as a replacement of cement and by ensuring improved durability of concrete. Durability of concrete containing large volume of class F fly ash is dependent on the design of mixture proportions. This paper presents an experimental study on the effect of mixture proportions on the drying shrinkage and permeation properties of high strength concrete containing large volume local class F fly ash. Concrete mixtures were designed with and without adjustments in the water to binder ratio (w/b) and the total binder content to take into account the incorporation of fly ash up to 40% of total binder. Concretes, in which the mixture proportions were adjusted for fly ash inclusion achieved equivalent strength of the control concrete and showed enhanced properties of drying shrinkage, sorptivity, water permeability and chloride penetration as compared to the control concrete. The improvement of durability properties was less significant when no adjustments were made to the w/b ratio and total binder content. The results show the necessity of the adjustments in mixture proportions of concrete to achieve improved durability properties when using class F fly ash as a cement replacement