Problem Clinic

  • Updates on High-Performance Concrete

     
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    Pre-Tensioning Steel Forms

     
  • Recycled Aggregate for Structural Concrete

    Q. We are in the early planning stage of a major commercial project. During site preparation, the general contractor will require us to demolish and crush a large quantity of existing concrete used in the structure and pavement. In fact, looking through our records, it appears we supplied the...

     
  • Reporting Tempering Water

    Q. We have just equipped several of our mixers with an on-board slump monitoring system. As the truck travels to or waits at the jobsite, the system monitors the mix's slump. When the system's controller senses a significant stiffening of the mix, it will maintain the load's targeted slump by...

     
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    Surface Crazing

     
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    Impossible Color Requirements

     
  • Testing for Bridge Deck Shrinkage

    Q: We plan to bid on some state bridge deck work planned in our area. Our district engineer is open to allowing a high-performance mix that will help mitigate the possibility of undue cracking. Our lab is analyzing several mixes with standard features such as strength, set time, and chloride...

     
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    Decorative Slab Core Samples

    We are involved in a dispute on the quality of a decorative slab for which we supplied concrete last fall. The project appears to be fine, but one set of test cylinders failed to meet compressive strength requirements.

     
  • Pervious Concrete Method Test Procedures

    Members of ASTM Subcommittee C9.49 are attempting to standardize the testing methods for pervious concrete. There is much interest in this topic, as committee secretary Jenny Hitch reports more than 120 people are members of this committee, making this one of the largest groups in C-9.

     
  • Testing for Quality Block

    We recently supplied several split-face blocks for a large commercial project. The work continued for several months, and with about two weeks left, we started receiving complaints about the quality of the units from the mason contractor.

     
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    Correcting for Aggregate Moisture

    Q: I'm fairly new in the concrete business and I know that a mix's water-cement ratio affects how well the concrete turns out. But why should I also care about something called "aggregate moisture," and what is it?

     
  • Standard Test Method for Density, Yield and Air Content

     
  • New Concrete Wall Standards

    The Portland Cement Association's (PCA) National Standards Development Committee has approved the first PCA standard utilizing the American National Standards Institute (ANSI) accredited voluntary consensus process.

     
  • Preparing for an SCC Job

    Q: Our lab has developed a self-consolidating concrete (SCC) mix design that we plan to use on a recently awarded project. It will be our first large SCC project. While we have provided the SCC recipe on several small jobs and for this project's test pours, this will be our first attempt to...

     
  • Reducing Formwork Pressure for SCC

    We are urging an engineer to specify self-consolidating concrete (SCC) on a project that includes several tall, vertical forms. The engineer recognizes the benefits of SCC regarding consolidation and final surface appearance. The contractor also wants to use SCC because it can speed up the pouring...

     
  • SCC Concrete Formwork Pressure Study; New Approved ASTM Standards

    A Progress Report and Task 1 Report for the Self-Consolidating Concrete Formwork Pressure Study are now available, and the latest on recently revised ASTM standards.

     
  • Retaining Wall Block Durability

    We have been trying to convince our local public works officials to specify segmental retaining wall (SRW) blocks on an upcoming project. We are located in the northern part of the United States. And the county's engineering staff is concerned that the SRW blocks will not be durable given our...

     
  • ASTM to Develop Green Roof Guide

    A proposed new ASTM International standard, WK14283, "Guide for Green Roof Systems," will identify terminology, principles, and concepts for building vegetated green roof systems.

     
  • Does Well-graded Aggregate Stand Up?

    Q: We are beginning to work on a new set of mix designs for a large commercial project. We are experimenting with some potential changes in the aggregate gradations of our commonly used products.

     
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    Hot Weather Concrete Practices

     
 
 
 
 

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