The Prediction of Creep and Shrinkage Properties of Concrete, HR-136, 1970

This report is concerned with the prediction of the long-time creep and shrinkage behavior of concrete. It is divided into three main areas. l. The development of general prediction methods that can be used by a design engineer when specific experimental data are not available. 2. The development of prediction methods based on experimental data. These methods take advantage of equations developed in item l, and can be used to accurately predict creep and shrinkage after only 28 days of data collection. 3. Experimental verification of items l and 2, and the development of specific prediction equations for four sand-lightweight aggregate concretes tested in the experimental program. The general prediction equations and methods are developed in Chapter II. Standard Equations to estimate the creep of normal weight concrete (Eq. 9), sand-lightweight concrete (Eq. 12), and lightweight concrete (Eq. 15) are recommended. These equations are developed for standard conditions (see Sec. 2. 1) and correction factors required to convert creep coefficients obtained from equations 9, 12, and 15 to valid predictions for other conditions are given in Equations 17 through 23. The correction factors are shown graphically in Figs. 6 through 13. Similar equations and methods are developed for the prediction of the shrinkage of moist cured normal weight concrete (Eq. 30}, moist cured sand-lightweight concrete (Eq. 33}, and moist cured lightweight concrete (Eq. 36). For steam cured concrete the equations are Eq. 42 for normal weight concrete, and Eq. 45 for lightweight concrete. Correction factors are given in Equations 47 through 52 and Figs., 18 through 24. Chapter III summarizes and illustrates, by examples, the prediction methods developed in Chapter II. Chapters IV and V describe an experimental program in which specific prediction equations are developed for concretes made with Haydite manufactured by Hydraulic Press Brick Co. (Eqs. 53 and 54}, Haydite manufactured by Buildex Inc. (Eqs. 55 and 56), Haydite manufactured by The Cater-Waters Corp. (Eqs. 57 and 58}, and Idealite manufactured by Idealite Co. (Eqs. 59 and 60). General prediction equations are also developed from the data obtained in the experimental program (Eqs. 61 and 62) and are compared to similar equations developed in Chapter II. Creep and Shrinkage prediction methods based on 28 day experimental data are developed in Chapter VI. The methods are verified by comparing predicted and measured values of the long-time creep and shrinkage of specimens tested at the University of Iowa (see Chapters IV and V) and elsewhere. The accuracy obtained is shown to be superior to other similar methods available to the design engineer.

Loss of Prestress, Camber, and Deflection of Non-Composite and Composite Structures Using Different Weight Concretes, HR-137, 1970

General equations are presented for predicting loss of prestress and camber of both composite and non- composite prestressed concrete structures. Continuous time functins of all parameters needed to solve the equations are given, and sample results included. Computed prestress loss and camber are compared with experimental data for normal weight and lightweight concrete. Methods are also presented for predicting the effect of non-prestressed tension steel in reducing time-dependent loss of prestress and camber, and for the determination of short-time deflections of uncracked and cracked prestressed members. Comparisons with experimental results are indicated for these partially prestressed methods.

Abrasion of Aggregates as Affected by Grading, 1970

Many specifications for coarse aggregates, that are to be used in highway construction, limit the percentage of wear when tested by AASHO T-96 "Resistance to Abrasion of Coarse Aggregate by use of the Los Angeles Machine". This test consists of placing a 5000 gram sample of the aggregate in a "hollow steel cylinder, closed at both ends, having an inside diameter of 28 inches and an inside length of 20 inches. The cylinder - - - shall be mounted in such a manner that it may be rotated with the axis in a horizontal position. - A removable steel shelf, projecting radially 3-1/2 inches into the cylinder and extending its full length, shall be mounted along one element of the interior surface of the cylinder."

Iowa Roads and Streets Functional Classification Manual, 1970

This manual provides a set of procedural rules and regulations for use in functionally classifying all roads and streets in Iowa according to the character of service they are intended to provide. Functional classification is a requirement of House File 394 (Functional Highway Classification Bill) enacted by the 63rd General Assembly of the Iowa Legislature. Functional classification is defined in this Bill as: "The grouping of roads and streets into systems according to the character of service they will be expected to provide, and the assignment of jurisdiction over each class to the governmental unit having primary interest in each type of service."

Bituminous Mixes Prepared with Ungraded Local Aggregates, Iowa Highway Research Board Bulletin No. 19, 1960

Joint Publications from Iowa Engineering Experiment Station - Bulletin No. 190 and Iowa Highway Research Board - Bulletin No. 19. This bulletin is a report on the development of bituminous paving mixtures containing various local materials and asphaltic binders. The laboratory investigations described in this bulletin were performed as part of Iowa Highway Research Board project HR-20, "Treating Loess, Fine Sands, and Limestone Dusts With Liquid Binders." This project was awarded to the Iowa Engineering Experiment Station of Iowa State University in 1952, and continued to June, 1958.

Dynamics of Highway Bridges, Iowa Highway Research Board Bulletin 17, 1960

Joint Publications from Iowa Engineering Experiment Station - Bulletin No. 188 and Iowa Highway Research Board - Bulletin No. 17. In the design of highway bridges, the 'static live load is multiplied by a factor to compensate for the dynamic effect of moving vehicles. This factor, commonly referred to as an impact factor, is intended to provide for the dynamic response of the bridge to moving loads and suddenly applied forces. Many investigators have published research which contradicts the current impact formula 1,4,17. Some investigators feel that the problem of impact deals not only with the increase in over-all static live load but that it is an integral part of a dynamic load distribution problem. The current expanded highway program with the large number of bridge structures required emphasizes the need for investigating some of the dynamic behavior problems which have been generally ignored by highway engineers. These problems generally result from the inability of a designer to predict the dynamic response of a bridge structure. Many different investigations have been made of particular portions of the overall dynamic problem. The results of these varied investigations are inevitably followed by a number of unanswered questions. Ironically, many of the unanswered questions are those which are of immediate concern in the design of highway bridges, and this emphasizes the need for additional research on the problem of impact.

Guidelines for the Inclusion of Left-Turn Lanes at Rural Highway Intersections, HR-147, 1970

Provision of left turn lanes is a major problem which lacks an objective approach. Various techniques and procedures in use have been reviewed. Traffic characteristics at typical Iowa intersections have been measured. A rational approach for inclusion of a left turn lane has been developed, based on relating the benefits to the road user to the cost of providing the added turing lane. An analysis of field data gathered under this project indicates that the use of theoretical distribution to describe vehicle headways is not applicable to rural Iowa two lane roads. As an alternate approach the mass of field data gathered were examined using multiple regression techniques to yield equations for predicting stops and delays. The benefit-cost ratio technique is recommended as the criterion for decision making.

Bituminous Mixes Prepared with Foamed Asphalt, Iowa Highway Research Board Bulletin No. 18, 1960

A contract for Project HR-20 "Treating Loess, Fine Sands and Soft Limestones with Liquid Binders" of the Iowa Highway Research Board was awarded in December, 1951, to the Iowa Engineering Experiment Station of Iowa State University as its Project 295-S. By 1954 the studies of the fine materials and asphalts had progressed quite well, and a method of treating the fine materials, called the atomization process, had been applied. A study was begun in 1954 to see if some of the problems of the atomization process could be solved with the use of foamed asphalt. Foamed asphalt has several advantages. The foaming of asphalt increases its volume, reduces its viscosity, and alters its surface tension so that it will adhere tenaciously to solids. Foamed asphalt displaces moisture from the surface of a solid and coats it with a thin film. Foamed asphalt can permeate deeply into damp soils. In the past these unusual characteristics were considered nuisances to be avoided if possible.

Granular Base Materials for Flexible Pavements, HR-131, 1970

The coefficients of relative strength (CORS) of base courses for use in the American association state highway officials (AASHO) interim guide for the design of flexible pavements are determined here. Based on (1) volumetric strain--axial strain relationships at minimum volume, and (2) effective stress ratio-cohesion relationships at maximum effective stress ratio, CORS were determined from the results of laboratory triaxial tests on both asphalt-treated and untreated aggregate base course materials. The researchers conclude that volumetric strain-axial strain at minimum volume appear to be appropriate parameters for determining CORS.

Preliminary Studies of Remedial Measures for the Prevention of Bridge Deck Deterioration, HR-146, 1970

Four series of five specimens each were investigated for static and fatigue strength. These four series differed in that there were two variables, the first being the subsidence of concrete around reinforcing bars and the second being shrinkage due to two different curing conditions. The combinations of these variables were then compared to each other by use of, load-deflection curves and S-H fatigue curves.

Soil Stabilization With Chemicals, Iowa Highway Research Board Bulletin No. 22, 1960

In the search for new soil stabilizing agents the effects of six organic cations on plastic limit, liquid limit, shrinkage limit, air-dry strength and rate of slaking of a highly plastic clay subsoil were studied. In all cases the plasticity index and shrinkage were reduced by the treatments. The air-dry strength was lowered in varying degree, which was the only undesirable effect noted. With one exception resistance to slaking was improved. It is concluded that large organic cations show promise as possible stabilizing agents for highly plastic fine-grained soils.

Geologic and Engineering Properties of Pleistocene Materials in Iowa, Iowa Highway Research Board Bulletin No. 20, 1960

This bulletin is a compilation of the reports on completed research done for the Iowa State Highway Research Board Project HR-1, "The Loess and Glacial Till Materials of Iowa; an Investigation of Their Physical and Chemical Properties and Techniques for Processing Them to Increase Their All-Weather Stability for Road Construction.” The research, started in 1950, was done by the Iowa Engineering Experiment Station under its project 283-S. The project was supported by funds from the Iowa State Highway Commission.