Investigation of Rapid Thermal Analysis Procedures for Prediction of the Service Life of PCCP Carbonate Coarse Aggregate: Phase I, Progress Report, HR-337, 1992

The major objective of this research project is to utilize thermal analysis techniques in conjunction with x-ray analysis methods to identify and explain chemical reactions that promote aggregate related deterioration in Portland cement concrete. The first year of this project has been spent obtaining and analyzing limestone and dolomite samples that exhibit a wide range of field service performance. Most of the samples chosen for the study also had laboratory durability test information (ASTM C 666, method B) that was readily available. Preliminary test results indicate that a strong relationship exists between the average crystallite size of the limestone (calcite) specimens and their apparent decomposition temperatures as measured by thermogravimetric analysis. Also, premature weight loss in the thermogravimetric analysis tests appeared to be related to the apparent decomposition temperature of the various calcite test specimens.

Field Evaluation of Cold In-Place Recycling of Asphalt Concrete, HR-303, Construction Report, 1990

There are still many vintage portland cement concrete (PCC) pavements, 18 ft wide (5.4 m), dating back to pre-World War II era in use today. Successive overlays have been placed to cover joints and to improve rideability. The average thickness of the existing asphalt cement concrete (ACC) along route E66 in Tama County, Iowa, was 6.13 in. (15.6 cm). The rehabilitation strategy called for widening the base using the top 3 in. (7.6 cm) of the existing ACC by a recycling process involving cold milling and mixing with additional emulsion/rejuvenator. The material was then placed into a widening trench and compacted to match the level of the milled surface. This project was undertaken to develop a rehabilitation methodology to widen these older pavements economically and to have a finished surface capable of carrying traffic with little or no additional work.

A Different Perspective for Investigation of PCC Pavement Deterioration, HR-2074, Interim Report, 1996

Many early Iowa Portland Cement Concrete (PCC) pavements provided good performance without deterioration for more than 50 years. In the late 1950's, Iowa was faced with severe PCC pavement deterioration called D cracking due to crushed limestone containing a bad pore system. Selective quarrying solved the problem. In 1990, cracking deterioration was identified on a three year old US 20 pavement in central Iowa. The coarse aggregate was a crushed limestone with an excellent history of performance in PCC pavement. Examination of cores showed very few cracks through the coarse aggregate particles. The cracks were predominately confined to the matrix. A high resolution, low vacuum Hitachi Scanning Electron Microscope (SEM) with an energy dispersion detector was used to investigate the deterioration. Subsequent evaluation identified very little concentration of silica gel (silicon-Si), but did identify substantial amounts of sulfur-s and aluminum-Al (assumed to be ettringite) in the air voids. Some of these voids have cracks radiating from them leading us to conclude that the ettringite filled voids were a center of pressure causing the crack. The ettringite in the voids, after being subjected to sodium chloride (NaCl) brine, initially swells and then dissolves. The research has led to the conclusion that the premature deterioration may be due to ettringite and may have been mistakenly identified as Alkali-Silica reactivity (ASR).

Evaluation of Unbonded Ultrathin Whitetopping of Brick Streets, TR-466, Construction Report, 2002

Many cities in Iowa have retained the original brick street surfaces in downtown areas and in older residential areas as the base for modern driving surfaces. The original brick surfaces were not built to handle current and future traffic loadings. In recent years, these surfaces have tended to shift and become uneven, creating problems with safety. Asphaltic concrete overlays have been the typical rehabilitation technique in these situations. This has proven to be a successful rehabilitation technique in some cases; in other cases, the combination of movement of the brick and flexibility of the asphalt has proven to accentuate the original problems. Most of the existing literature on rehabilitation of brick streets shows the use of asphaltic concrete. Other rehabilitation methods include reconstruction of the brick surface and strengthening of the surface by placing asphaltic concrete or portland cement concrete, along with sand, underneath the brick layers. To date, little if anything has been done in the area of using portland cement concrete as an overlay of the brick surfaces. This final report documents the planning, construction, and performance of unbonded ultrathin whitetopping rehabilitation of a brick street in Oskaloosa, Iowa, in 2001. It also reports on a similar project in Des Moines that was constructed two years later in 2003.

The Use of Fly Ash in Highway Construction, HR-1031, Progress Report, 1986

In 1982 the Iowa DOT allowed a successful bidder the option of submitting materials and proportions using fly ash to produce a portland cement concrete (PCC) paving mixture to meet a specified compressive strength. The contractor, Irving F. Jensen, received approval for the use of a concrete mixture utilizing 500 lbs. of portland cement and 88 lbs. of fly ash as a replacement of 88 lbs. of portland cement. The PCC mixture was utilized on the Muscatine County US 61 relocation bypass paved as project F-61-4(32)--20-70. A Class "C" fly ash obtained from the Chillicothe electric generating plant approximately 100 miles away was used in the project. This use of fly ash in lieu of portland cement resulted in a cost savings of $64,500 and an energy savings of approximately 16 billion BTU. The compressive strength of this PCC mixture option was very comparable to concrete mixtures produced without the use of fly ash. The pavement has been performing very well. The substitution of fly ash for 15% of the cement has been allowed as a contractor's option since 1984. Due to the cost savings, it has been used in almost all Iowa PCC paving since that time.

The Relationship of Aggregate Durability to Trace Element Content, Interim Report, HR-266, 1984

This report is a brief overview of the recent Iowa Department of Transportation research in the area of durability of Portland cement, concrete under the direction of Wendeli Dubberke. Present plans are to publish a more detailed report on low Portland cement concrete- durability research in January, 1985.

Performance of Nongrouted Thin Bonded PCC Overlays, Construction Report, HR-291, 1986

The Iowa road system has approximately 13,000 miles of Portland Cement Concrete Pavements, many of which are reaching the stage where major rehabilitation is required. Age, greater than anticipated traffic, heavier loads and deterioration related to coarse aggregate in the original pavement are some of the reasons that these pavements have reached this level of distress. One method utilized to rehabilitate distressed or underdesigned PCC pavements is the thin bonded Portland Cement Concrete overlay. Since the introduction of thin bonded overlays on highway pavements in 1973, the concrete paving industry has made progress in reducing the construction costs of this rehabilitation technique. With the advent of the shotblast machine, surface preparation costs have decreased from over $4.00 per square yard to most recently $1.42 per square yard. Other construction costs, including placement, grouting and sawing, have also declined. With each project, knowledge and efficiency have improved.

Iowa Development of Rubblized Concrete Pavement Base Mills County, Construction Report, HR-315, 1990

The concept of rubblizing existing concrete pavement prior to the placement of an asphaltic cement concrete overlay has been around for several years and, in fact, has been tried successfully in the states of New York, Michigan, and Ohio. With available construction and maintenance dollars usually not meeting the demands of the needed work, much of the necessary rehabilitation of existing Portland cement concrete pavements is not being completed when it would be most beneficial. Research project HR-315, "Iowa Development of Rubblized Concrete", has been undertaken to determine the effects of rubblized concrete pavement base as it affects the cracking pattern and longevity of the ACC overlay.

Investigation of PCC Pavement Deterioration: A Few Facts are Worth More than 100 Opinions, Interim Report, HR-2074, 1995

Portland Cement Concrete (PCC) pavement has served the State of Iowa well for many years. The oldest Iowa pavement was placed in LeMars in 1904. Beginning in 1931, many miles of PCC pavement were built to "get out of the mud.” Many of these early pavements provided good performance without deterioration for more than 50 years. In the late 1950's, Iowa was faced with severe PCC pavement deterioration referred to as D cracking. Research identified the cause of this deterioration as crushed limestone containing a bad pore system. Selective quarrying and ledge control has alleviated this problem. In 1990, cracking deterioration was identified on a three year old pavement on us 20 in central Iowa. The coarse aggregate was a crushed limestone with an excellent history of performance in PCC pavement. Examination of cores showed very few cracks through the coarse aggregate particles. The cracks were predominately confined to the matrix. The deterioration was identified as alkali-silica reactivity (ASR) by a consultant.

Characterization and use of swine deep bedding ashes in cementitious composites

The deep bedding is a swine alternative production, especially in the finishing phase, whose byproduct can be recycled, reducing the environmental impact. The objectives of this study were to characterize the ash coming from the controlled burning of the swine deep bedding (SDBA) based on rice husk, and to evaluate their performance in composites as a partial substitute for Portland cement (PC). To measure the differences between SDBA and rice husk ash (RHA) as a reference, we have characterized: particle size distribution, real specific density, x-ray diffraction, electrical conductivity, scanning electron microscopy, chemical analysis and loss on ignition. Samples were prepared for two experimental series: control, and another one with the partial replacement of 30% of SDBA in relation to the mass of the Portland cement. According to the results obtained for physical and mechanical characterization, the composites with SDBA can be used as a constructive element in the rural construction.

Teollisuusjätteen käyttö kiinteytys-stabiloinnin sideaineena ja haitta-aineiden stabiloinnin tehostamisessa

Tässä kanditaatintyössä selvitettiin kuinka erilaiset sideaineseokset soveltuvat raskas-metallien sitomiseen 28 vuorokautta stabiloiduissa näytteistä. Työssä oletettiin teollisten jätefraktioiden käytön tehostavan eräiden metallien, kuten kupari ja sinkki, immobilisointia lievästi pilaantuneista maa-aineksista. Kokeellisessa osassa stabiloitiin Kokkolan satamasta ruopattua sedimenttiä, jonka sinkkipitoisuudet olivat ylittäneet saastuneen sedimentin ohjearvon (≥400 mg/kg). Sedimenttiin lisättiin eri sideaineseoksia ja näytteiden annettiin stabiloitua 28 vuorokautta, minkä jälkeen niistä testattiin liukenevat raskasmetallit muokatulla ravistelutestillä. Eri sideaineseoksilla saatuja tuloksia verrattiin pelkän yleissementin käyttöön. Lisäksi erillisistä näytteistä otettiin pyyhkäisyelektronimikros-koopilla (SEM) kuvia havainnollistamaan stabiloitumista. Näissä näytteissä käytettiin samoja sideaineita kuin tehdyissä kokeissa. Liukoisuustestien tuloksista voidaan huomata näytteissä ongelmalliseksi raskasmetalliksi identifioidun sinkin sitoutuvan parhaiten sementin ja kipsin sekoituksella. Myös tuhkaa sisältävät sideainesekoitukset pienensivät sinkin liukoisuutta verrattuna pelkkään yleis-sementtiin. Jatkotutkimuksissa voitaisiin testata erilaisia sideainesekoituksia betonira-kentamisessa, joilla saadaan ainakin 25 MPa lujuusarvo, pilaantunutta sedimenttiä tai maa-ainesta käyttäen.

Studies on the Quality of Rainwater at Various Land Use Locations and Variations by Interaction with Domestic Rainwater Harvesting Systems

The present study focused on the quality of rainwater at various land use locations and its variations on interaction with various domestic rainwater harvesting systems.Sampling sites were selected based upon the land use pattern of the locations and were classified as rural, urban, industrial and sub urban. Rainwater samples were collected from the south west monsoon of May 2007 to north east monsoon of October 2008, from four sampling sites namely Kothamangalam, Emakulam, Eloor and Kalamassery, in Ernakulam district of the State of Kerala, which characterized typical rural, urban, industrial and suburban locations respectively. Rain water samples at various stages of harvesting were also collected. The samples were analyzed according to standard procedures and their physico-chemical and microbiological parameters were determined. The variations of the chemical composition of the rainwater collected were studied using statistical methods. It was observed that 17.5%, 30%, 45.8% and 12.1% of rainwater samples collected at rural, urban, industrial and suburban locations respectively had pH less than 5.6, which is considered as the pH of cloud water at equilibrium with atmospheric CO,.Nearly 46% of the rainwater samples were in acidic range in the industrial location while it was only 17% in the rural location. Multivariate statistical analysls was done using Principal Component Analysis, and the sources that inf1uence the composition of rainwater at each locations were identified .which clearly indicated that the quality of rain water is site specific and represents the atmospheric characteristics of the free fall The quality of harvested rainwater showed significant variations at different stages of harvesting due to deposition of dust from the roof catchment surface, leaching of cement constituents etc. Except the micro biological quality, the harvested rainwater satisfied the Indian Standard guide lines for drinking water. Studies conducted on the leaching of cement constituents in water concluded that tanks made with ordinary portland cement and portland pozzolana cement could be safely used for storage of rain water.

Behaviour of laterised normal and self compacting concrete subjected to elevated temperatures

Concrete is a universal material in the construction industry. With natural resources like sand and aggregate, fast depleting, it is time to look for alternate materials to substitute these in the process of making concrete. There are instances like exposure to solar radiation, fire, furnaces, and nuclear reactor vessels, special applications like missile launching pads etc., where concrete is exposed to temperature variations In this research work, an attempt has been made to understand the behaviour of concrete when weathered laterite aggregate is used in both conventional and self compacting normal strength concrete. The study has been extended to understand the thermal behaviour of both types of laterised concretes and to check suitability as a fire protection material. A systematic study of laterised concrete considering parameters like source of laterite aggregate, grades of Ordinary Portland Cement (OPC) and types of supplementary cementitious materials (fly ash and GGBFS) has been carried out to arrive at a feasible combination of various ingredients in laterised concrete. A mix design methodology has been proposed for making normal strength laterised self compacting concrete based on trial mixes and the same has also been validated. The physical and mechanical properties of laterised concretes have been studied with respect to different variables like exposure temperature (200°C, 400°C and 600°C) and cooling environment (air cooled and water cooled). The behaviour of ferrocement elements with laterised self compacting concrete has also been studied by varying the cover to mesh reinforcement (10mm to 50mm at an interval of 10mm), exposure temperature and cooling environment.

Behavior of geopolymer concrete exposed to elevated temperatures

The research in the area of geopolymer is gaining momentum during the past 20 years. Studies confirm that geopolymer concrete has good compressive strength, tensile strength, flexural strength, modulus of elasticity and durability. These properties are comparable with OPC concrete.There are many occasions where concrete is exposed to elevated temperatures like fire exposure from thermal processor, exposure from furnaces, nuclear exposure, etc.. In such cases, understanding of the behaviour of concrete and structural members exposed to elevated temperatures is vital. Even though many research reports are available about the behaviour of OPC concrete at elevated temperatures, there is limited information available about the behaviour of geopolymer concrete after exposure to elevated temperatures. A preliminary study was carried out for the selection of a mix proportion. The important variable considered in the present study include alkali/fly ash ratio, percentage of total aggregate content, fine aggregate to total aggregate ratio, molarity of sodium hydroxide, sodium silicate to sodium hydroxide ratio, curing temperature and curing period. Influence of different variables on engineering properties of geopolymer concrete was investigated. The study on interface shear strength of reinforced and unreinforced geopolymer concrete as well as OPC concrete was also carried out. Engineering properties of fly ash based geopolymer concrete after exposure to elevated temperatures (ambient to 800 °C) were studied and the corresponding results were compared with those of conventional concrete. Scanning Electron Microscope analysis, Fourier Transform Infrared analysis, X-ray powder Diffractometer analysis and Thermogravimetric analysis of geopolymer mortar or paste at ambient temperature and after exposure to elevated temperature were also carried out in the present research work. Experimental study was conducted on geopolymer concrete beams after exposure to elevated temperatures (ambient to 800 °C). Load deflection characteristics, ductility and moment-curvature behaviour of the geopolymer concrete beams after exposure to elevated temperatures were investigated. Based on the present study, major conclusions derived could be summarized as follows. There is a definite proportion for various ingredients to achieve maximum strength properties. Geopolymer concrete with total aggregate content of 70% by volume, ratio of fine aggregate to total aggregate of 0.35, NaOH molarity 10, Na2SiO3/NaOH ratio of 2.5 and alkali to fly ash ratio of 0.55 gave maximum compressive strength in the present study. An early strength development in geopolymer concrete could be achieved by the proper selection of curing temperature and the period of curing. With 24 hours of curing at 100 °C, 96.4% of the 28th day cube compressive strength could be achieved in 7 days in the present study. The interface shear strength of geopolymer concrete is lower to that of OPC concrete. Compared to OPC concrete, a reduction in the interface shear strength by 33% and 29% was observed for unreinforced and reinforced geopolymer specimens respectively. The interface shear strength of geopolymer concrete is lower than ordinary Portland cement concrete. The interface shear strength of geopolymer concrete can be approximately estimated as 50% of the value obtained based on the available equations for the calculation of interface shear strength of ordinary portland cement concrete (method used in Mattock and ACI). Fly ash based geopolymer concrete undergoes a high rate of strength loss (compressive strength, tensile strength and modulus of elasticity) during its early heating period (up to 200 °C) compared to OPC concrete. At a temperature exposure beyond 600 °C, the unreacted crystalline materials in geopolymer concrete get transformed into amorphous state and undergo polymerization. As a result, there is no further strength loss (compressive strength, tensile strength and modulus of elasticity) in geopolymer concrete, whereas, OPC concrete continues to lose its strength properties at a faster rate beyond a temperature exposure of 600 °C. At present no equation is available to predict the strength properties of geopolymer concrete after exposure to elevated temperatures. Based on the study carried out, new equations have been proposed to predict the residual strengths (cube compressive strength, split tensile strength and modulus of elasticity) of geopolymer concrete after exposure to elevated temperatures (upto 800 °C). These equations could be used for material modelling until better refined equations are available. Compared to OPC concrete, geopolymer concrete shows better resistance against surface cracking when exposed to elevated temperatures. In the present study, while OPC concrete started developing cracks at 400 °C, geopolymer concrete did not show any visible cracks up to 600 °C and developed only minor cracks at an exposure temperatureof 800 °C. Geopolymer concrete beams develop crack at an early load stages if they are exposed to elevated temperatures. Even though the material strength of the geopolymer concrete does not decrease beyond 600 °C, the flexural strength of corresponding beam reduces rapidly after 600 °C temperature exposure, primarily due to the rapid loss of the strength of steel. With increase in temperature, the curvature at yield point of geopolymer concrete beam increases and thereby the ductility reduces. In the present study, compared to the ductility at ambient temperature, the ductility of geopolymer concrete beams reduces by 63.8% at 800 °C temperature exposure. Appropriate equations have been proposed to predict the service load crack width of geopolymer concrete beam exposed to elevated temperatures. These equations could be used to limit the service load on geopolymer concrete beams exposed to elevated temperatures (up to 800 °C) for a predefined crack width (between 0.1mm and 0.3 mm) or vice versa. The moment-curvature relationship of geopolymer concrete beams at ambient temperature is similar to that of RCC beams and this could be predicted using strain compatibility approach Once exposed to an elevated temperature, the strain compatibility approach underestimates the curvature of geopolymer concrete beams between the first cracking and yielding point.

Effect of accelerated carbonation on cementitious roofing tiles reinforced with lignocellulosic fibre

The present work evaluated the effects of accelerated carbonation on mechanical and physical characteristics of cementitious roofing tiles reinforced with vegetable fibre. The maximum load and toughness of the tiles have increased approximately 25% and 80% respectively as a consequence of the accelerated carbonation. Water absorption and apparent porosity decreased with carbonation while bulk density increased as a clear indication of the densification of the composite. The improvement on the mechanical performance suggests that the fibres retained their tensile strength in the inorganic matrix. Results of specimens extracted from the tested tiles after approximately 480 days in laboratory environment and further aged indicate that soak and dry cycles promoted some leaching of hydration products and more voids and lower density when performed before carbonation. The results indicate the utilization of accelerated carbonation as an effective procedure to mitigate the degradation suffered by the cellulose fibres in the less aggressive medium. (C) 2009 Elsevier Ltd. All rights reserved.