A Study of Curing Methods and Type II Cements on the Durability of Concrete, R-11-Z(1), 1969

A program of A (90 day moist room), B (14 day moist room) and C (7 day moist room and 7 day 50%_humidity) type curing for the R-11-Z program of durability of concrete using the automatic freeze and thaw machine (ASTM C-291) has been used in the Materials Department of the Iowa State Highway Commission since December 6, 1966. A summary of the results obtained from then until March 25, 1968, indicates that the B and C type curing are yielding very little valuable information. However, the A cure exhibits a wide range of durability factors and also groups the aggregates in an order which is related to the service record (there are definite exceptions. The biggest disadvantage to the A cure is the length of time that it takes to complete the test (90 day cure and 38 day test). The Kansas Highway Department has experimented with different cements and aggregates in order to determine which combination offers a concrete with the best durability factor possible. In an experimental test section of highway, concrete made with a Type II cement appeared to have better durability than others made with Type I cements. Because of this, a question has been raised at the Iowa State Highway Commission - Can concrete made with Type II cements, because of a lesser amount of tricalcium aluminate, yield better durability than concrete made with Type I cements?

Concrete Pavement Mixture Design and Analysis (MDA): Evaluation of the Fresh and Hardened Properties of Concrete Mixtures Containing Permeability-Reducing Admixtures to Develop Standard Test Protocol, 2014

Concrete durability may be considered as the ability to maintain serviceability over the design life without significant deterioration, and is generally a direct function of the mixture permeability. Therefore, reducing permeability will improve the potential durability of a given mixture and, in turn, improve the serviceability and longevity of the structure. Given the importance of this property, engineers often look for methods that can decrease permeability. One approach is to add chemical compounds known as integral waterproofing admixtures or permeability-reducing admixtures, which help fill and block capillary pores in the paste. Currently, there are no standard approaches to evaluate the effectiveness of permeability-reducing admixtures or to compare different products in the US. A review of manufacturers’ data sheets shows that a wide range of test methods have been used, and rarely are the same tests used on more than one product. This study investigated the fresh and hardened properties of mixtures containing commercially available hydrophilic and hydrophobic types of permeability-reducing admixtures. The aim was to develop a standard test protocol that would help owners, engineers, and specifiers compare different products and to evaluate their effects on concrete mixtures that may be exposed to hydrostatic or non-hydrostatic pressure. In this experimental program, 11 concrete mixtures were prepared with a fixed water-to-cement ratio and cement content. One plain mixture was prepared as a reference, 5 mixtures were prepared using the recommended dosage of the different permeability-reducing admixtures, and 5 mixtures were prepared using double the recommended dosage. Slump, air content, setting time, compressive and flexural strength, shrinkage, and durability indicating tests including electrical resistivity, rapid chloride penetration, air permeability, permeable voids, and sorptivity tests were conducted at various ages. The data are presented and recommendations for a testing protocol are provided.

Soil-Cement Stabilization, Part 1, Materials and Construction, HR-75, 1962

This report covers the construction in 1961 of the soil-cement base and related pavement structure on Iowa 37 from Soldier to Dunlap, (F-861(6), Crawford, Harrison, Monona). The report also contains an account of the experimental work performed on the same road under research project HR-75.

Investigation of Video Crack and Patch Surveying for Pavement Management, MLR-92-01, 1992

The Iowa DOT has been using the AASHTO Present Serviceability Index (PSI) rating procedure since 1968 to rate the condition of pavement sections. A ride factor and a cracking and patching factor make up the PSI value. Crack and patch surveys have been done by sending crews out to measure and record the distress. Advances in video equipment and computers make it practical to videotape roads and do the crack and patch measurements in the office. The objective of the study was to determine the feasibility of converting the crack and patch survey operation to a video recording system with manual post processing. The summary and conclusions are as follows: Video crack and patch surveying is a feasible alternative to the current crack and patch procedure. The cost per mile should be about 25 percent less than the current procedure. More importantly, the risk of accidents is reduced by getting the people and vehicles off the roadway and shoulder. Another benefit is the elimination of the negative public perceptions of the survey crew on the shoulder.

Laboratory Performance Evaluation of CIR-Emulsion and its Comparison Against CIR-Foam Test Results from Phase 2, TR-474, 2009

Currently, no standard mix design procedure is available for CIR-emulsion in Iowa. The CIR-foam mix design process developed during the previous phase is applied for CIR-emulsion mixtures with varying emulsified asphalt contents. Dynamic modulus test, dynamic creep test, static creep test and raveling test were conducted to evaluate the short- and long-term performance of CIR-emulsion mixtures at various testing temperatures and loading conditions. A potential benefit of this research is a better understanding of CIR-emulsion material properties in comparison with those of CIR-foam material that would allow for the selection of the most appropriate CIR technology and the type and amount of the optimum stabilization material. Dynamic modulus, flow number and flow time of CIR-emulsion mixtures using CSS- 1h were generally higher than those of HFMS-2p. Flow number and flow time of CIR-emulsion using RAP materials from Story County was higher than those from Clayton County. Flow number and flow time of CIR-emulsion with 0.5% emulsified asphalt was higher than CIR-emulsion with 1.0% or 1.5%. Raveling loss of CIR-emulsion with 1.5% emulsified was significantly less than those with 0.5% and 1.0%. Test results in terms of dynamic modulus, flow number, flow time and raveling loss of CIR-foam mixtures are generally better than those of CIR-emulsion mixtures. Given the limited RAP sources used for this study, it is recommended that the CIR-emulsion mix design procedure should be validated against several RAP sources and emulsion types.

Development of a Transportation and Land Use Public Policy Education Program for Iowa, 2000

This literature review serves as a foundation for a transportation and land use public policy education program for Iowa. The objective of the review is to summarize relevant research findings, to review the state of practice and policies of other state and local governments, and to explore land use trends both within the state of Iowa and the nation as a whole. Much of what we learned has been incorporated into the course materials. Because we expect to identify more useful sources throughout the project, this literature review should be considered a work in progress.

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.

Cement Stabilization of Embankment Materials, 2015

Embankment subgrade soils in Iowa are generally rated as fair to poor as construction materials. These soils can exhibit low bearing strength, high volumetric instability, and freeze/thaw or wet/dry durability problems. Cement stabilization offers opportunities to improve these soils conditions. The objective of this study was to develop relationships between soil index properties, unconfined compressive strength and cement content. To achieve this objective, a laboratory study was conducted on 28 granular and non-granular materials obtained from 9 active construction sites in Iowa. The materials consisted of glacial till, loess, and alluvium sand. Type I/II portland cement was used for stabilization. Stabilized and unstabilized specimens were prepared using Iowa State University 2 in. by 2 in. compaction apparatus. Specimens were prepared, cured, and tested for unconfined compressive strength (UCS) with and without vacuum saturation. Percent fines content (F200), AASHTO group index (GI), and Atterberg limits were tested before and after stabilization. The results were analyzed using multi-variate statistical analysis to assess influence of the various soil index properties on post-stabilization material properties. Results indicated that F200, liquid limit, plasticity index, and GI of the materials generally decreased with increasing cement content. The UCS of the stabilized specimens increased with increasing cement content, as expected. The average saturated UCS of the unstabilized materials varied between 0 and 57 psi. The average saturated UCS of stabilized materials varied between 44 and 287 psi at 4% cement content, 108 and 528 psi at t 8% cement content, and 162 and 709 psi at 12% cement content. The UCS of the vacuum saturated specimens was on average 1.5 times lower than that of the unsaturated specimens. Multi-variate statistical regression models are provided in this report to predict F200, plasticity index, GI, and UCS after treatment, as a function of cement content and soil index properties.