<?xml version="1.0" encoding="utf-8"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>TRB Publications Index</title><link>http://pubsindex.trb.org/</link><atom:link href="http://pubsindex.trb.org/common/TRIS Suite/feeds/rss.aspx?tc=NN%3ASccys%2A" rel="self" type="application/rss+xml" /><description></description><language>en-us</language><copyright>Copyright © 2015. National Academy of Sciences. All rights reserved.</copyright><docs>http://blogs.law.harvard.edu/tech/rss</docs><managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor><webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster><image><title>TRB Publications Index</title><url>http://pubsindex.trb.org/Images/PageHeader-wTitle.png</url><link>http://pubsindex.trb.org/</link></image><item><title>Early Age Monitoring of High Cement Replacement Mixtures for Pavement</title><link>http://pubsindex.trb.org/view/1996200</link><description><![CDATA[Decarbonization of concrete will require a combination of alternative binding materials and higher cement replacement rate with supplementary cementitious materials. Developing tools and methods that help engineers evaluate the properties of early age concrete pavement, such as setting time and strength gain, will be necessary to adopt new concrete mixes. Two concrete pavement test sections were constructed, a high early strength concrete mix with 25% (control) and 40% replacement of cement with fly ash (HVFAC), along with monitoring of the concrete’s setting time, saw-cut timing, and strength gain. A non-contact ultrasonic device was used to estimate setting time through measuring leaky Rayleigh wave energy transmission. The laboratory setting time of the control and HVFAC mix measured with the non-contact device was 5.5?h and 15?h, respectively, and agreed with measured isothermal calorimetry results. Further calorimeter tests showed that adding an accelerating admixture or replacing part of the cement with nano-limestone decreased the HVFAC setting time up to 4.4?h. The field setting time of the control mixture with the non-contact device measured 4.2?h, which was shorter than the laboratory estimate. Based only on the experience of construction personnel, saw-cutting for these mixtures was initiated too early and caused significant joint raveling, reinforcing the importance of in situ setting time measurement. The maturity method was successfully implemented with embedded wireless temperature sensors that rapidly and easily estimated the in-place compressive strength and improved opening time determination for concrete with high cement replacement levels, which are sensitive to the volume of supplementary cementitious materials, admixtures, and ambient conditions.]]></description><pubDate>Mon, 18 Jul 2022 16:06:53 GMT</pubDate><guid>http://pubsindex.trb.org/view/1996200</guid></item><item><title>Performance of Portland Cement-Based Rapid-Patching Materials with Different Cement and Accelerator Types, and Cement Contents</title><link>http://pubsindex.trb.org/view/1630109</link><description><![CDATA[Because of the requirements of opening pavement to traffic after placing repair concrete, it is essential for that concrete to achieve high early strength. To ensure this, a high cement content is generally used in Portland cement-based rapid-patching materials. Besides its associated high cost, high cement content tends to result in a less stable mix with high drying shrinkage, high autogenous shrinkage, high heat of hydration, and cracking potential. In addition, using chloride-based accelerators has adverse effects on concrete durability. Therefore, this paper presents an experimental assessment to improve rapid-patching concrete mixtures by reducing cement content through optimizing aggregate gradation. A non-chloride-based accelerator was also sought to replace the chloride-based accelerator when the accelerators are associated with two different series of patching materials using Type I and III cement, respectively. Fresh, early-age, mechanical, and permeability tests were conducted on each specific mixture design. As an important outcome, patching materials employing lower cement content together with an optimized aggregate gradation can meet the general requirements, which were found from the observation of several key parameters, including early-age strength, setting times, surface resistivity, and heat of hydration. Furthermore, the non-chloride-based accelerator showed promising behavior as an alternative accelerator when it is blended with the proper cement type and content.]]></description><pubDate>Wed, 12 Jun 2019 09:18:49 GMT</pubDate><guid>http://pubsindex.trb.org/view/1630109</guid></item><item><title>Assessment of Concrete Pavement Set Gradient Based on Analysis of Slab Behavior and Field Test Data</title><link>http://pubsindex.trb.org/view/1602158</link><description><![CDATA[This paper discusses how the set gradient in a jointed concrete slab is related to the cracking performance and its effects on fatigue crack model calibration. The role of curing quality on-set and how curing quality parameters are related to the set gradient is also discussed. To assess the impacts of curing practices on the set gradient of a newly constructed concrete slab, a field investigation was undertaken at the Florida Department of Transportation State Materials Office in Gainesville, Florida. This study investigated early age concrete pavement behavior with respect to the development of the set gradient. In this research, four test slabs were placed and cured under different conditions to create different states of stress and creep behavior during and after hardening of the concrete. Early age concrete temperature and moisture history are key factors that affect the slab curling and warping behavior as they pertain to the resulting set gradient. This paper elaborates on the details of the cracking performance data analysis of test data associated with the development of the set gradient.]]></description><pubDate>Mon, 20 May 2019 09:47:20 GMT</pubDate><guid>http://pubsindex.trb.org/view/1602158</guid></item><item><title>Effect of Climatic Factors on the Set Gradient of Newly Constructed Concrete Pavements</title><link>http://pubsindex.trb.org/view/1496439</link><description><![CDATA[In order to assess the effect of curing practices on the set of new constructed concrete pavement, a field investigation was undertaken at the Florida Department of Transportation (FDOT) State Materials Office (SMO) in Gainesville, Florida. This study investigated early age concrete pavement behavior with respect to the development of the set gradient. In this study, four test slabs were placed and cured under different conditions to create different states of stress and creep behavior during and after hardening of the concrete. Early age concrete temperature and moisture history are key factors affecting the slab curling and warping behavior as well as the set gradient that resulted in the test slabs. These factors are of course affected by variations of ambient weather, the curing compound type, and application rate which in turn were found to be important with respect to the induced temperature and moisture gradients inside the slab. The paper elaborates the details of the analysis of the test data associated with the development of the set gradient.]]></description><pubDate>Wed, 28 Feb 2018 13:25:58 GMT</pubDate><guid>http://pubsindex.trb.org/view/1496439</guid></item><item><title>Strength and Setting Time Enhancement in Alkali-Modified High-Volume Fly Ash Binders</title><link>http://pubsindex.trb.org/view/1339108</link><description><![CDATA[Portland cement concrete is the most widely used building material, but as CO2 emissions regulation become increasingly stringent, the concrete industry is becoming more and more interested in replacing a greater percentage of ordinary portland cement (OPC) with supplementary cementitious materials (SCMs). In this study, several sustainable binders were developed by replacing 70% of OPC with class F fly ash. Without enhancement, the binder exhibited prohibitively long setting time and inadequate early-age compressive strength. Low dosages of alkalis, including sodium hydroxide (0-1.5M) and sodium silicate hydrate (0-2%), were added to modify the early age hydration kinetics, microstructure, and strength development. The heat of hydration, microstructure, composition, and compressive strength of the modified binders were evaluated. The addition of alkalis significantly increased early- and later-age compressive strength, reduced setting time, and promoted more rapid hydration compared to control mixture. Additions of alkalis resulted in up to 55% increased strength. The increase in compressive strength decreased when the dosage of alkali exceeds an optimum level, especially at later ages. Mixtures with added sodium silicate resulted in a reduction in the peak heat of hydration compared to those with added sodium hydroxide.]]></description><pubDate>Fri, 20 Mar 2015 15:20:59 GMT</pubDate><guid>http://pubsindex.trb.org/view/1339108</guid></item><item><title>Recent Virginia Department of Transportation Applications with Self-Consolidating Concrete</title><link>http://pubsindex.trb.org/view/1338400</link><description><![CDATA[Self-consolidating concrete (SCC) exhibits very high workability; it easily fills the congested spaces between the reinforcement (both mild steel and prestressing steel) and formwork under the influence of its own mass without the use of any additional consolidation energy. A review of the use of SCC was conducted by the Virginia Department of Transportation in both cast-in-place and precast applications, such as repairs, pier cap placements, and beams with both normal weight and lightweight concretes. Both completed and ongoing studies indicate that SCC, whether in cast-in-place or precast applications, can be successfully used in bridge structures. The following practices should be followed. Care should be exercised with workability retention during the project to avoid consolidation issues; forms should be secured; concrete should be placed in forms in incremental heights to prevent bulging and failure; proper mix designs with fines should be ensured for flowability and stability; viscosity-modifying admixtures should be added for stability; and proper setting times for timely finishing operations should be established.]]></description><pubDate>Thu, 26 Feb 2015 10:03:55 GMT</pubDate><guid>http://pubsindex.trb.org/view/1338400</guid></item><item><title>Benefits of Portland-Limestone Cement for Concrete with Rounded Gravel Aggregates and Higher Fly Ash Replacement Rates</title><link>http://pubsindex.trb.org/view/1338395</link><description><![CDATA[Recently, portland-limestone cement (PLC) has garnered increased interest in the US due to potentially greater environmental sustainability and enhancement of certain concrete properties and/or performance. Combined with supplementary cementitious materials (SCMs), these benefits can be further extended. This paper builds on past works of the authors, tailored to Mississippi’s current concrete practices, by evaluating concrete mixtures with rounded gravel aggregates and greater replacement of cement with SCMs (primarily fly ash). In total, 15 different cementitious combinations were used in concrete and cement paste mixtures. Concrete specimens from 30 mixtures (360 specimens) were tested, featuring various combinations of cements, SCMs, and admixtures. Replicates of these 30 mixtures were created in cement paste mixtures (540 specimens). Major variables included SCM type, replacement rate, and cement source. Mixtures were tested for compressive strength, time of setting or thermal setting indication, and slump and air content, in the case of concrete mixtures. A small subsection of concrete mixtures was also examined using petrography. Results indicated that use of PLC vs. ordinary portland cement (OPC) resulted in notable compressive strength improvements in mixtures with high Class C fly ash replacement (especially 40%). Slump and air content were not statistically different in PLC vs. OPC mixtures; however time of setting was lower in mixtures with PLC. Hydration-related distinctions (PLC vs. OPC mixtures) were evident in petrographic images, with some observed differences in cement paste character and the paste-to-aggregate interfacial transition zone (ITZ).]]></description><pubDate>Thu, 26 Feb 2015 10:03:51 GMT</pubDate><guid>http://pubsindex.trb.org/view/1338395</guid></item><item><title>Concepts to Enhance Specification and Inspection of Curing Effectiveness in Concrete Pavement Design and Construction</title><link>http://pubsindex.trb.org/view/1339233</link><description><![CDATA[This paper presents an approach that can be used to consider the effect of the quality of curing and the time of placement (collectively referred to as "curing effectiveness" ) on the development of the set gradient and its importance to long-term performance of jointed concrete pavement structures. The approach involves the definition of a curing quality index, referred to as the "effectiveness index,"  that is reconfigured to function as a boundary interface to account for the effect of ambient conditions and represent the method of curing on potential moisture evaporation during hardening shortly after construction. Moisture and temperature boundary conditions are incorporated into a simple spreadsheet tool to evaluate heat and moisture transfer mechanisms at the cured surface of a concrete pavement during placement operations. Key parameters for development of set gradients in a concrete slab are identified, and a discussion is presented about how these parameters can be included in construction specifications and monitored as part of routine inspections. This paper also explains a laboratory and field protocol to monitor curing quality and facilitate an inspection program for concrete pavement construction and satisfy specification requirements to meet an expected design life.]]></description><pubDate>Mon, 16 Feb 2015 16:55:43 GMT</pubDate><guid>http://pubsindex.trb.org/view/1339233</guid></item><item><title>The Effect of Delayed Compaction of Stabilized Soil-Cement</title><link>http://pubsindex.trb.org/view/1308655</link><description><![CDATA[No abstract available.]]></description><pubDate>Fri, 30 May 2014 11:46:32 GMT</pubDate><guid>http://pubsindex.trb.org/view/1308655</guid></item><item><title>Investigation of Fresh State Properties of Ternary Based HPC Mixtures</title><link>http://pubsindex.trb.org/view/1287768</link><description><![CDATA[The properties of ternary based High Performance Concrete (HPC) mixtures in their fresh state are very important for the contractor side of the cement industry as they could not plan their operations ahead of time. This research identified the fresh properties of ternary mixtures that need to be considered on field projects to use for both the construction industry and as a stepping stone for further research regarding this topic. Total 39 mixture designs were prepared in this study to cover a breadth of material combinations. The results show that the setting time of concrete is modified by pozzolans. It is interesting to note that the portland-pozzolan blended cements that have been optimized for sulfur content were affected in a similar manner like ordinary portland cement. It is recommended that more research needs to be conducted to investigate the possibility of optimization of the sulfur content in the ternary mixtures to obtain the desired setting time characteristics for construction. The bleeding potential was improved with the addition of mineral admixtures to reduce it. Silica fume and metakaolin were very efficient in lowering bleeding potential. On the other hand, a pessimum phenomenon was observed when the amount of Class C fly ash was increased in the mixture. These results can help the construction industry to understand the interaction between the different supplementary cementitious materials (SCMs) in a concrete mixture and indicate that a superposition of characteristics is not adequate for using a ternary mixture of concrete.]]></description><pubDate>Fri, 21 Feb 2014 15:16:22 GMT</pubDate><guid>http://pubsindex.trb.org/view/1287768</guid></item><item><title>Working Time, Setting Behavior, and Maturity of Concrete Mixtures and their Relationships</title><link>http://pubsindex.trb.org/view/1241432</link><description><![CDATA[Concrete has to be workable for a certain period of time for quality construction, from placing to finishing. The working time limit, as defined by Iowa DOT, is the elapsed time from the time when cementitious materials of a concrete mixture are mixed with water to the time when the concrete has a penetration resistance of 200 psi. In the present study, working time limits of pavement concrete mixtures made with two selected retarders, with and without fly ash replacement, were measured under three different temperatures (65, 75, and 85°F), and the results are compared with those measured in 1980s. A new approach to predicting concrete penetration resistance is developed based on the concrete maturity, or time-temperature factor (TTF). The results indicate that probably due to the changes in modern concrete materials (such as cement and admixture properties), some newly measured working time limits are up to 22% higher than those measured in 1980s. Concrete penetration resistance correlates well with the concrete maturity, or TTF. This relationship enables engineers to assess penetration resistance of field concrete any time, with no special consideration for the concrete curing condition.]]></description><pubDate>Fri, 19 Apr 2013 16:54:56 GMT</pubDate><guid>http://pubsindex.trb.org/view/1241432</guid></item><item><title>Improving Concrete Sustainability and Performance with Use of Portland–Limestone Cement Synergies</title><link>http://pubsindex.trb.org/view/1242595</link><description><![CDATA[The increased use of portland–limestone cements (PLCs) in the United States is anticipated in response to a new provision that has been added to blended cement specifications for PLCs containing up to 15% limestone. Published research has documented the performance synergies of cementitious mixtures with finely ground limestone (which has particle sizes generally smaller than cement particle sizes), especially in combination with certain supplementary cementitious materials (SCMs). Time of setting and strength development benefits are reported, generally in proportion to limestone fineness. It appears possible to fully develop the potential for these performance synergies in mill-ground PLCs, in which limestone comprises the majority of the finest particles. This study further investigated performance trends observed in concrete with PLC using separately proportioned, commercially ground limestone and ordinary portland cement, as well as cement mill–ground PLC samples. The influences of variables such as SCM type and limestone fineness were evaluated with laboratory paste mixtures. Set acceleration increased with limestone fineness for all combinations, including mixtures without SCMs. Strength improvements were clearly evident with all SCMs, more significantly with Class C ash and slag cement than with Class F ash. All strength trends improved as limestone fineness was increased. Consistently enhanced setting and strength performance appear achievable with PLCs. Optimizing particle fineness will be a key factor in achieving these benefits. As performance contributions of SCMs in combination with PLCs may exceed those of similar mixtures with traditional ordinary portland cements, SCM use can be maximized and related sustainability impacts further extended.]]></description><pubDate>Thu, 18 Apr 2013 08:51:08 GMT</pubDate><guid>http://pubsindex.trb.org/view/1242595</guid></item><item><title>International symposium on mechanical properties of special concrete</title><link>http://pubsindex.trb.org/view/1187680</link><description></description><pubDate>Fri, 24 Aug 2012 07:30:20 GMT</pubDate><guid>http://pubsindex.trb.org/view/1187680</guid></item><item><title>Factors influencing setting and hardening of asphalt in bituminous pavements</title><link>http://pubsindex.trb.org/view/1178511</link><description></description><pubDate>Fri, 24 Aug 2012 01:50:56 GMT</pubDate><guid>http://pubsindex.trb.org/view/1178511</guid></item><item><title>Reducing Set Retardation in High-Volume Fly Ash Mixtures with the Use of Limestone: Improving Constructability for Sustainability</title><link>http://pubsindex.trb.org/view/1128807</link><description><![CDATA[High-volume fly ash (HVFA) concretes are attractive not only because they reduce cement content and the associated greenhouse gases, but also because they avoid landfilling excessive quantities of fly ash. These sustainability benefits are often tempered by practical constructability limitations that may exist for HVFA concretes: retardation and diminution of the early-age reaction, delay in setting (and finishing operations), and lower early-age strength. This paper explores the alleviation of these deficiencies in HVFA mixtures by the incorporation of fine limestone powders into ternary blends. Isothermal calorimetry and Vicat needle penetration measurements are employed to assess reaction rates and setting times, respectively. A systematic variation of the content and fineness of the limestone powder in mixtures containing either a Class C or a Class F fly ash indicates that setting times are linearly correlated with the surface area supplied by the limestone. Comparison of a limestone system to a system containing an inert titanium dioxide of similar particle size indicates that the acceleration and amplification effects of the limestone can be attributed to both physical (nucleation) and chemical (additional calcium ions) processes. The results indicate that ternary blends with 40% of the cement by volume replaced by 30% to 35% fly ash and 5% to 10% limestone at a constant water volume fraction can be achieved without significant delay in setting.]]></description><pubDate>Mon, 25 Jun 2012 14:33:51 GMT</pubDate><guid>http://pubsindex.trb.org/view/1128807</guid></item></channel></rss>