Use of ground clay brick as a supplementary cementitious material in concrete hydration characteristics, mechanical properties, and ASR durability

The work presented in this Dissertation involves an effort to broaden sustainable applications (e.g., recycling waste material in concrete, reducing CO2 emissions in cement production) in construction industry. Finely ground brick obtained from demolished masonry was evaluated as a pozzolanic cementitious material in concrete. The hydration characteristics of this material and its effects on cement paste, mortar, and concrete mechanical properties, particularly on alkali-silica reaction deterioration was studied. Ground clay brick (GCB) was produced in the laboratory employing a ball mill. Chemical and physical properties comply with the designated ASTM standard that defines pozzolanic materials. The results of the study on cementitious pastes where cement was replaced by GCB up to 25% showed that the effect on water demand for normal consistency and time of setting was insignificant; the temperature rise during hydration was reduced; and the calcium hydroxide production was decreased. The testing of mechanical properties of concrete containing up to 25% GCB demonstrated that the values were low at early age but higher or comparable at later ages when compared to the control and the resistance to chloride penetration was improved. These results suggested a pozzolanic activity provided by finely ground brick. The results from the accelerated ASR testing of mortar mixtures showed that the expansions were significantly reduced and associated deterioration on the compressive and flexural strengths was limited with the use of GCB. The concrete tests confirmed the mortar testing that the expansion was effectively suppressed and the mechanical properties of a highly alkali-silica reactive mixture could be conserved when cement was replaced by GCB at 15 and 25% loading. Subsequent microstructural study revealed out the quantitatively low gel formation in the presence of GCB and further suggested a modification in gel chemistry by GCB. The reported experimental study demonstarted that GCB shows pozzolanic behavior similar to other conventional materials (e.g., fly ash, calcined clay, or natural pozzolan), and it can be used as a supplementary cementitious material in concrete applications. Use of GCB in concrete can effectively reduce the alkali-silica reaction deterioration in concrete

The analysis of relationship between organizational power and organizational trust

Purpose of this study is to determine the relationship between organizational power and organizational trust according to the perception of the teachers. The research is designed as a relational model and the sample of the study consists of 266 teachers, who were determined using criterion sampling technique. Data were collected using two scales. One of the scales used in the research is “Organizational Power Sources” scale, developed by Zafer (2008), it contains five sub-dimensions, namely expert, referent, reward, legitimate and coercive whereas the other is “Organizational Trust” scale developed by Daboval, Comish and Swindle and Gaster (1994) and adapted to Turkish by Yılmaz (2005). Pearson Product-Moment Correlation Analysis and Multiple Linear Regression Analysis are the techniques used to analyze the data. The results revealed that sub-dimensions of organizational power significantly predicted organizational trust scores

The analysis of relationship between organizational power and organizational trust

Purpose of this study is to determine the relationship between organizational power and organizational trust according to the perception of the teachers. The research is designed as a relational model and the sample of the study consists of 266 teachers, who were determined using criterion sampling technique. Data were collected using two scales. One of the scales used in the research is “Organizational Power Sources” scale, developed by Zafer (2008), it contains five sub-dimensions, namely expert, referent, reward, legitimate and coercive whereas the other is “Organizational Trust” scale developed by Daboval, Comish and Swindle and Gaster (1994) and adapted to Turkish by Yılmaz (2005). Pearson Product-Moment Correlation Analysis and Multiple Linear Regression Analysis are the techniques used to analyze the data. The results revealed that sub-dimensions of organizational power significantly predicted organizational trust scores

Southeast Michigan Local Road Concrete Pavement Durability Study

Counties and cities in Southeast Michigan have used concrete pavements for nearly 100 years to provide long-lasting, durable streets and roads. Issues of concrete durability have arisen with some of the pavements built after 1990. In order to evaluate the causes of spalling and other deterioration methods, the National Concrete Pavement Technology Center (CP Tech Center) was asked to study the concrete from a number of the pavements, evaluate the causes of the distress, and offer recommendations for improvements. Of particular concern are the roles of coarse aggregate type (limestone or blast furnace slag), alkali-silica reactivity (ASR), and the air entrainment system in the hardened concrete on the joint deterioration distresses that are being observed

Extended Use of Limestone Fines in Various Concretes

Limestone fines are increasingly used in cement and concrete for improved material properties and sustainability. This paper presents recent research at Iowa State University on utilization of limestone fines in concrete. It includes the beneficial uses of limestone fines in: (1) limestone blended Portland cement; (2) SFSCC (semi-flowable self-consolidating concrete); and (3) HPC (high performance concrete). The research results show that using 5%~10% of limestone fines to replace for Type IP cement (with 25% fly ash) increased mortar strength. Well-designed SFSCC with 25% limestone fines (by mass of cementitious materials) displayed desirable rheological and mechanical properties required for slip-forming construction. The newly developed limestone fines-based HPC reached the one-day compressive strength of over 28 MPa

Pavement Management Performance Modeling: Evaluating the Existing PCI Equations,

The work described in this report documents the activities performed for the evaluation, development, and enhancement of the Iowa Department of Transportation (DOT) pavement condition information as part of their pavement management system operation. The study covers all of the Iowa DOT’s interstate and primary National Highway System (NHS) and non-NHS system. A new pavement condition rating system that provides a consistent, unified approach in rating pavements in Iowa is being proposed. The proposed 100-scale system is based on five individual indices derived from specific distress data and pavement properties, and an overall pavement condition index, PCI-2, that combines individual indices using weighting factors. The different indices cover cracking, ride, rutting, faulting, and friction. The Cracking Index is formed by combining cracking data (transverse, longitudinal, wheel-path, and alligator cracking indices). Ride, rutting, and faulting indices utilize the International Roughness Index (IRI), rut depth, and fault height, respectively

Women Administrators in Education: Leadership Behavior Assessment According to Teachers' Perceptions

The purpose of this study is to reveal leadership behaviors of women administrators in education. The research was designed using the survey model and it was conducted with 936 randomly selected teachers who work on the schools administered by women administrators, in Istanbul. The Leader Behavior Description Questionnaire (Hemphill & Coones, 1957) has been used for data collection. T-test and ANOVA techniques have been used for data analysis. As the result of the research, it has been found that women administrators usually show "initiation of structure" type leadership behaviors

Effect of water-to-binder ratio, air content, and type of cementitious materials on fresh and hardened properties of binary and ternary blended concrete

The purpose of this study is to investigate the effects of water-to-binder ratio (w/b), air content, and type of cementitious material on the fresh and hardened properties of binary and ternary blended concrete mixtures in pavements. This experimental program prepared a total matrix of 54 mixtures with w/b of 0.40 and 0.45; nominal air content of 2, 4, and 8%; and three types of supplementary cementitious materials and one ordinary portland cement in different combinations. Binder systems included ordinary portland cement, binary mixtures with slag cement, Classes F and C fly ash, and ternary mixtures containing a combination of slag cement and one type of fly ash.Workability, total air content, air void system parameters (i.e., spacing factor and specific surface) in fresh concrete, setting time, compressive strength, surface resistivity, and shrinkage were determined. Test results showed that ternary mixtures followed the trends of their constituent materials. Binary and ternary mixtures containing Class C fly ash and slag cement exhibited higher compressive strength than the control mixture. The surface resistivity and shrinkage results of binary and ternary mixtures were equal to or improved over the control mixture

Effect of paste-to-voids volume ratio on the performance of concrete mixtures

The purpose of this study is to investigate the minimum paste volume required with an appropriate water-to-cementitious ratio (w/cm) to achieve required workability, strength, and durability requirements of concrete mixtures for pavements. In this experimental program, 64 concrete mixtures with varying w/cm, cementitious content, and binder type were prepared and tested. The fine aggregateto-total aggregate ratio was held constant for all the mixtures. Fresh and hardened concrete properties of the mixtures were determined at various ages. Test results have shown that approximately 1.5 times more paste by volume is required than voids between the aggregates to achieve a minimum performance in concrete for pavements. For a given w/cm, strength is independent of cementitious content after a critical value is provided. When w/cm is constant, increasing paste content increased chloride penetrability and air permeability

Preliminary Investigation on Determining the Minimum Cement Content in Rigid Pavements

This paper presents the preliminary results of an experimental program that consists of testing of concrete mixtures with varying water-to-binder ratios (w/b) and cementitious contents. The purpose of this laboratory study is to investigate the minimum cement content that can be used in rigid pavements without sacrificing the performance (i.e., strength and durability). Initially, 16 mixes using only portland cement and 48 mixes incorporating supplementary cementitious materials, namely class F fly ash, class C fly ash and slag as portland cement replacement at levels of 20%, 20% and 40%, respectively, were planned. This paper reports the results of a subset of this study. Concrete mixtures with w/b ranging from 0.43 to 0.65 and cementitious content ranging from 400 lb/yd3 to 700 lb/yd3 were designed. Compressive strength, chloride penetration and air permeability were determined. The findings of the study with the available data are as follows: strength is a function of w/b and independent of the binder content; air permeability increases as w/b and binder content increase; among all the mixtures containing different type and amount of cementitious materials, slag cement provides the lowest 28 day chloride penetration whereas class C fly ash results in the highest chloride penetration