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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>SURFACE POPOUTS CAUSED BY ALKALI-AGGREGATE REACTION</title>
      <link>https://trid.trb.org/View/660043</link>
      <description><![CDATA[Small popouts often appear in the surfaces of hard-troweled concrete flatwork in some parts of the Midwest. This study seeks to determine the mechanism of popout formation, evaluate the factors believed to influence the formation of popouts, and develop remedial techniques. These popouts are caused by the shale particles in the local sand and are the result of alkali-silica reactions involving opaline materials in shale and alkali contributed by the cement. The popouts are a surface phenomenon and their severity appears to be a function of the alkali content at the slab surface. Alkali content at the surface depends on the portion of the cement alkali that is readily soluble, and the amount of alkali that is brought to the surface during drying of the concrete. Migration of alkali during drying can significantly increase the alkali concentration of the surface layer. High temperature, high wind velocity and low humidity can increase alkali migration towards the surface of a concrete slab during placing and curing. Alkali migration is also be increased by long periods of drying during finishing and the first stages of curing. Inappropriate curing procedures aggravate popouts.  If high-alkali cement is used in hot weather, wet curing is essential and should be initiated as early as possible. Fresh concrete should be protected from drying prior to the final finishing operations. Findings show ponding of slabs or the use of continually moist burlap, soil, or sand can eliminate popout formation.  It is also recommended that hard troweling be avoided whenever possible.]]></description>
      <pubDate>Tue, 01 Jul 2003 00:00:00 GMT</pubDate>
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      <title>DISCOLORED CONCRETE FLATWORK ... THE CAUSES AND HOW TO MINIMIZE THEM</title>
      <link>https://trid.trb.org/View/102576</link>
      <description><![CDATA[DISCOLORATION OF CONCRETE CAUSED BY CONCRETE MIX DESIGN & INGREDIENTS, AND CONCRETING PRACTICES BEFORE THE CONCRETE HAS HARDENED ARE REVIEWED. DISCOLORATION ARISING FROM THESE CAUSES ORDINARILY TAKE ONE OF THREE FORMS: (1) LARGE AREAS OF CONTRASTING COLOR, (2) BLACK SPOT OR DARK LEOPARD SPOTS AND (3) WHITE PATCHES CAUSED BY EFFLORESCENCE. FACTORS WHICH CAN RESULT IN SURFACE DISCOLORATION INCLUDE COLOR AND COMPOSITION OF THE CEMENT, WATER/CEMENT RATIO, CURING, ADMIXTURES, AND FINISHING PRACTICES. CAREFUL PREPARATION IS SUGGESTED TO AVOID DISCOLORATION BY: (1) DEVELOPING A UNIFORM NONADSORPTIVE SUBGRADE AND SCHEDULING CONCRETE DELIVERIES AND WORK CREW TO AVOID VARIATIONS IN PLACING AND FINISHING PROCEDURES, (2) AVOID ORDERING CONCRETE FROM MORE THAN ONE SOURCE AND AVOID THE USE OF CALCIUM CHLORIDE, ESPECIALLY IN CONCRETES WITH A LOW ALKALI CONTENT, (3) STANDARIZED CONCRETING AND FINISHING PRACTICES AND PROTECT THE CONCRETE BETWEEN FINISHING OPERATIONS, (4) TIME TROWELING TO PREVENT BURNING OF THE SURFACE AND (5) CURE THE CONCRETE THOROUGHLY AND UNIFORMLY, USING A WET-CURING TECHNIQUE, IF POSSIBLE. CORRECTIVE MEASURES ARE DESCRIBED FOR AREAS OF CONTRASTING COLOR, DARK SPOTS, LIGHT SPOTS, AND EFFLORESCENCE.]]></description>
      <pubDate>Fri, 06 May 1994 00:00:00 GMT</pubDate>
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      <title>REMEDIAL UNDERPINNING OF STEEL TANK FOUNDATION</title>
      <link>https://trid.trb.org/View/73894</link>
      <description><![CDATA[An ammonia storage circular steel tank, resting on a flexible reinforced concrete raft supported by a group of driven cast-in-situ piles, suffered considerable foundation distress when loaded to about 60% of its proposed test load. The paper analyzes the causes of foundation failure and presents all aspects of remedial underpinning, from concept to completion.  The tank has been put back to normal use by constructing under it a water tight basement designed on the concept of compensated foundation in addition to repairing the defective piles and lifting the deformed tank bottom slab back to its original configuration.  /Author/]]></description>
      <pubDate>Thu, 14 Sep 1978 00:00:00 GMT</pubDate>
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      <title>SURFACE DISCOLORATION OF CONCRETE FLATWORK</title>
      <link>https://trid.trb.org/View/102151</link>
      <description><![CDATA[LABORATORY STUDIES OF MOTTLING DISCOLORATION OF HORIZONTAL CONCRETE SLABS ARE DESCRIBED, SHOWING THAT DISCOLORATION IS INCREASED BY HARD TROWLING, BY USE OF CALCIUM CHLORIDE ADMIXTURES, OR BY POOR CURING OF THE SLABS. LOCAL DISCOLORATION CAN ALSO BE CAUSED BY NON-UNIFORM CURING CONDITIONS. AVOIDING THE USE OF CALCIUM CHLORIDE IN HARD- TROWELED FLATWORK WOULD ELIMINATE MUCH FLATWORK DISCOLORATION. IF CALCIUM CHLORIDE IS NECESSARY, CURING PROCEDURES RECOMMENDED TO MINIMIZE LOCAL DISCOLORATION ARE WATER PONDING OR USE OF SPRAYED MEMBRANE CURING COMPOUNDS. THE EFFECT OF CALCIUM CHLORIDE IS DEPENDENT ON THE ALKALI CONTENT OF THE CEMENT. IMMEDIATE AND THOROUGH WASHING OF THE CONCRETE SURFACE WITH WATER SEEMS THE EASIEST WAY OF "ERASING" DISCOLORATION. SPECIAL CHEMICAL TREATMENTS TO ERASE DISCOLORATION ARE OF ADDITIONAL BENEFIT. /PCA/]]></description>
      <pubDate>Mon, 01 Jun 1970 00:00:00 GMT</pubDate>
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