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  1. JohnGn

    Swiss Hammer in Iraq

    BigH: There have been quite a few articles on maturity testing in some of the trade journals very recently. One, in Concrete International, was entitled "Maturity Testing is the Future". Couldn't agree more. My reply to Wayne's post was in the hopes of helping him prevent the need for...
  2. JohnGn

    Swiss Hammer in Iraq

    Wayne Have you considered using maturity testing as an additional means of estimating in-place strength? It, too, is an ASTM standard (C1074) and has been around for 15-20 years. Not many people know about it yet, but it works well. We've done more than 5000 in-place tests with very good...
  3. JohnGn

    Winter Concrete

    To Concrete2: You should be safe with a 9-sack mix in a 20" thick wall covered with an insulating blanket and a good w/c. Air temp will mean very little in this case. In fact I'd say that your concrete will likely cure better in a cooler environment than a hot one. Four thoughts: 1. you...
  4. JohnGn

    Maturity Testing

    Maturity testing, done properly, is an excellent method of determining the in-place strength. My company has done thousands of maturity tests, and we even developed our own system to meet our stringent demands. We typically find that the in-place strength is so much higher than the strength of...
  5. JohnGn

    Un-bonded P-T in bridges

    Correction to info previously posted: I was wrong. It is NOT unbonded but bonded grouted PT that is being used on the Creve Coeur Lake Bridge in Missouri. The web walls are not PT--just the deck. The design actually did call for PT in the web walls but the contractor convinced everyone that...
  6. JohnGn

    Un-bonded P-T in bridges

    Glad to answer what I can! It is my understanding that the PT runs only across the top of the box, not in the web walls. They stress within the first 24 hours or so. They need 3500# in-place to stress. Once the concrete reaches that they stress and move the travellers. The concrete must...
  7. JohnGn

    Un-bonded P-T in bridges

    The bridge is cast in segments, and about every 5 segments there is a wall between the cells. The PT is totally internal. The segments have transverse cables and longitudinal cables, and the entire structure has cables that run the length of the bridge. The contractor is Walter Construction...
  8. JohnGn

    Un-bonded P-T in bridges

    It is a segmental cast-in-place structure with unbonded PT sheathed in green plastic and well greased. It's not precast. The anchorages are all sealed off but the strands are not grouted, at least I don't think they are. Is this the info you seek? --John
  9. JohnGn

    Un-bonded P-T in bridges

    I am involved in a project in Missouri where the entire 1.2 mile bridge is unbonded PT. In fact I was not aware that there were any restrictions on its use. But they don't tell me much... The whole bridge is made up of hundreds of individual sections, each one unbonded PT, and once the...
  10. JohnGn

    Winter Concrete

    It all depends on the mix you are using, on the temperature of the concrete on delivery, and on the efficiency of your insulating blankets. I've done jobs where the concrete itself generated enough heat to cure itself even in very cold (below freezing) temps were experienced. On the other...
  11. JohnGn

    Cold weather Concrete protection after curing

    In-place temperature monitoring is being used increasingly to track actual temperatures of the curing concrete. In addition to learning temperatures, one can couple the thermal data to known strength-gain data to arrive at an accurate estimate of the in-place maturity, which can then be...
  12. JohnGn

    ACI Standard for Maturity Testing Method

    My firm performs maturity testing based on the ASTM C1074 standard, and I have been asked before by clients if there is an applicable ACI standard. I feel that the ASTM standard is adequate, but I'm just trying to make all of my clients comfortable with the procedure. Thanks for the reply.
  13. JohnGn

    ACI Standard for Maturity Testing Method

    Is there an ACI Standard Practice for on-site Maturity Testing of concrete using thermal data, similar to the ASTM C-1074 standard?

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