6−50 CAST-IN-PLACE STRUCTURE CONCRETE MASONRY and SECTION 601; PORTLAND CEMENT CONCRETE shall apply, with the following additions:
607.05 Temperature Control Requirements.
607.05.1 Temperature Control. Mass concrete temperature control shall be monitored by maturity
loggers cast into the concrete, as described in Subsection 607.03.1 . Use of low heat concrete mixtures, pre-cooling of the concrete, insulated curing blankets, insulated forms, cooling pipes, and other measures may be necessary to satisfy the temperature control requirements. The Contractor shall notify the Engineer immediately when temperature control limits are exceeded. Complete concrete temperature records for each placement including the secure files generated by the automated temperature sensors shall be provided to the Engineer. The Engineer shall be provided unobstructed access to temperature sensors at any time to verify compliance with temperature control criteria.
a.When forms are placed in water, the forms and insulation shall be waterproof or otherwise protected against water absorption. The required combined form and insulation R-Value shall be determined through thermal analysis prior to placement using forecasted temperatures to meet the requirements to maintain the maximum peak and differential temperatures within the limits defined in its specification.
b.The temperature of the concrete at placement must not exceed 65°F for cold weather placements, nor 85°F for hot weather placements, unless active temperature control precautions are employed. All active temperature control piping shall be non-metallic and shall be filled with a non-shrink grout on the RIDOT Approved Products List upon completion of cooling operations. The temperature of the concrete at placement sha ll be within the acceptable range of values shown in the temperature control plan for the structural element.
c.Temperature sensors shall be maturity loggers as described in Subsection 607.02.2 . The logger shall be programmed with the appropriate datum temperature.
d.Wiring for loggers that must be cast into the concrete shall be secured to reinforcing or otherwise protected to prevent damage during concrete placement. The method of protection of the wires cast into the concrete shall be approved by the Engineer and shall use methods satisfactory to the Engineer. Wiring for loggers shall be clearly labeled to identify the location within the form at both ends before being placed into the form. Ambient temperature sensors shall be located no closer than 10 feet from the Mass Concrete Placement and shall be placed as to provide an accurate measurement of the environmental condition. Wire runs outside of concrete shall be encased in conduit where necessary to prevent damage during subsequent construction operations.
e.The Contractor shall not perform installa tion and verification checks for operation of any loggers unless the Engineer is present. The Contractor shall provide as-built versions of the temperature control plans showing the location of the loggers as identified by the unique serial numbers. Upon completion of monitoring all visible wires shall be removed from the concrete and any conduit penetrations filled with a non-shrink grout on the RIDOT Approved Product List. 6−51
f.Each logger shall be programmed with notes identifying the placement and relative location within the placement. Loggers shall be secured into position and function shall be verified at least one day prior to concrete placement. Temperature recording for each placement shall start no less than 2 hours prior to the initial concrete placement. The Contractor shall provide the Engineer safe access to the locations where readings will be taken, to observe the initialization of the loggers and record relevant information. This information shall include each logger serial number, location in the placement and start time. Access shall also be provided as needed for subsequent readings, as required by the Engineer.
g.Each logger for each placement shall be connected to the Wireless Remote Boxes purchased by the Contractor. The Contractor sha ll provide as many Wireless Remote Boxes as necessary to monitor all loggers simultaneously. The Contractor shall be aware that a sufficient quantity of Wireless Remote Boxes must be on hand to monitor all of the loggers for all of the placements being actively monitored at any given ti me during the project. The Contractor shall also maintain two (2) spare Remote Boxes or 10% of the total on hand, whichever is larger, in operating condition at all times.
h.The Contractor shall maintain the wireless system in operating condition, including maintaining any batteries at sufficient charge and protecting the units from damage due to the environment and other factors. This shall be done to ensure that the Remote Boxes are capable of retrieving and transmitting data on a daily basis for the duration of the specified monitoring period for the concrete placement.
i.The Contractor shall have at the Contractor's field office a Wireless System Radio Base Station compatible with the Wireless Remote Boxes and the same model shall be provided to the Engineer, as described in Subsection 607.02.2 . Both Wireless System Radio Base Stations shall be configured to access all of the active Wireless Remote Boxes at any given time without reconfiguration of any component. Upon setup of each Wireless Remote Box and prior to placement of the concrete, the Contractor shall test the remote operation of the system to verify that it works properly and that all loggers that are to be connected to the Wireless Remote Box can be accessed. The Contractor may, at his discretion, have a handheld reader for the loggers. However, this shall not be used, except to configure the loggers initially or to collect data in the event of a problem with a Wireless Remote Box. Any such problem shall be corrected within 24 hours. Upon connection/reconnection of a Wireless Remote Box, the operation shall be tested as described above.
j.Automated temperature measurements shall be downloaded within one hour of the start of each calendar day during which any element of temperature control is in place. Secure data files from each logger shall be provided to the Engineer on a daily basis.
k.The peak concrete temperature at any location within the mass shall not exceed 155°F at any point in time. Failure to maintain a maximum peak concrete temperature less than or equal to 155°F will be cause for rejection of the concrete placement by the Engineer.
l.The temperature differential shall not exceed 35°F or the value of the variable limit (if approved) at any point in time. Failure to control the maximum concrete temperature differential less than or equal to the specified limit may be cause for rejection of the concrete placement by the Engineer. Malfunctioning sensors, as determined by the Engineer, shall be excluded from the differential calculation. 6−52
m.The placement shall be completely protected from exposure to precipitation to prevent cooling of the surface. Such protection shall be maintained until temperature control is no longer required.
n.Forms shall remain in place until the estima ted strength of the concrete surface exceeds 2500 psi based on the lowest indicated maturity from the data loggers and until the differential between the mean center temperature and ambient temperature is less t han 30°F and decreasing. Ambient temperatures must be rising at the time of form removal. Forms shall not be removed prior to meeting all other requirements listed elsewhere in the Contract Documents.
o.Tenting, erecting windbreaks, covering with plastic or curing blankets or other means may be necessary to protect the concrete surface from rapid cooling after form removal. Any and all such measures shall be at no additional cost to the State.
p.Concrete surfaces shall be protected when the temperature differential between the peak temperature and ambient temperature is greater than 30°F.
q.Mass concrete temperature control procedures shall remain in effect until the temperature differential between the average peak temperature and the 3-day mean ambient low temperature is less than 35°F.
r.Mass concrete elements exposed to water shall have reached at least 28 days compressive strength as indicated by the approved Maturity Curve and shall have a peak temperature-to-water temperature differential less than 35°F prior to exposure.
s.Written approval shall be obtained from the Engineer before removing temperature control.
607.05.2 Curing. Curing requirements of Subsection 601.03.8 and Subsection 808.03.09 shall
apply, except as follows: Mass concrete placements shall be continuously moist cured for at least 14 days and until the 28-day compressive strength as indicated by the approved Maturity Curve is achieved. Maintaining moisture on the top surface with forms in place shall be considered adequate moist curing. If strength and thermal control are achieved prior to 14 days, forms may be removed but moist curing must be continued. Water used for curing shall be fresh water and shall not contain any salts or other components harmful to concrete. The temperature of any water used for moist curing of mass concrete shall be controlled to within 30°F of the peak concrete temperature.
607.05.3 Temperature Control Failure. Failure to meet the temperature control requirements of
this specification may be cause for rejection of the concrete. Subsequent mass concrete placements shall be immediately halted. The Contra ctor shall investigate the events that produced the failure, and shall submit a written report to the Engineer. The investigation shall include a thorough examination of the concrete placement, the reasons for non-compliance with these requirements and shall document the width and extent of all visible cracks (if any), after cleaning the surface to fully expose them. Surface crack intensity shall be measured after monitoring shows the temperature as measured by all sensors near the concrete surface has dropped to within 10°F of the concrete temperature, as measured by the sensors at the center of thermal mass. The 6−53investigation shall be conducted by a licensed Rhode Island Professional Engineer, and shall present crack repair options for approval by the Engineer in accordance with Subsection 607.05.4 . The Contractor shall remove all equipment and materials from the mass concrete element and clean the surface for the Engineer to verify the Contractor’s measurements of the crack intensity. The Contractor shall provide safe access for the Engineer’s inspection, at no additional cost to the State. At the discretion of the Engineer, repair or removal and replacement of the rejected placement may be required of the Contractor. If requi red, repair, or removal and replacement of the rejected placement shall be performed at no additional cost to the State. At the discretion of the Engineer, the Contractor shall be required to submit a revised Mass Concrete General Temperature Control Plan to address any deficiencies identified by the investigation, at no additional cost to the State. Subsequent mass concrete placements shall not resume without written approval by the Engineer. There shall be no claims for additional payment by the Contractor, nor will there be an extension of the project Completion Dates for any corrective actions required as a result of the rejected concrete and subsequent corrective measures to address any deficiencies identified by the investigation.
607.05.4 Crack Repairs. Cracking determined to be due to thermal issues shall be repaired by
approved methods. Determination of when cracking is caused by thermal issues will be solely by the Engineer. No repairs shall begin until the Engineer has approved the repair plan. In case of thermal cracking, the Contractor shall suspend further work on members of similar size and configuration, submit a written explanation of the thermal cracking and additional steps to be taken to eliminate future thermal cracking, and submit proposed modifications in writing to the Engineer for review. Concrete placement may not resume until the Engineer approves the proposed modifications.
607.06 METHOD OF MEASUREMENT. "Mass Concrete" will not be measured for payment.
607.07 BASIS OF PAYMENT. No separate payment will be made for this item. Compliance with the
above requirements shall be considered incidental to placement of mass concrete. Costs for this item shall be included in the bid prices of the appropriate items as listed in the Proposal.
Source: Rhode Island Standard Specifications (Bluebook), 2024 Edition. Pages 302–305 of 826.