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57 Based on the testing conducted (Appendix E4), processing addition dosages of less than 1% by mass of cement were not observed to influence the performance of cementitious sys- tems to a significant extent in any test. This was true for all the types of processing additions tested. Specifications should therefore allow the use of up to 1% processing addition with- out additional testing required beyond that already required in the cement specification. The effects of PA dosages of 5 to 7.5% were largely insignif- icant, but there were some effects and trends observed, mean- ing that in order to be conservative, some testing is required if such PAs are to be used in a cement. A modified copy of AASHTO M 85 that reflects these changes is attached. Some materials (e.g., cement kiln dust) appeared to be more likely to result in significant change than others. Al- though the experimental work was conducted using a lim- ited range of materials most likely to be used, it is advisable that the protocol not be limited to a fixed list of materials that is clearly not exhaustive. All of the materials used as processing additions in this work were found to influence at least one performance criterion to a significant extent. Therefore, it is recommended that no distinction be made between the testing requirements for different processing additions. If a dosage of PA greater than 1% is to be used, then the cementitious system should be tested to ensure that the per- formance of the system is satisfactory. ASTM C 465 sets out a number of tests as shown in Table 26. As noted in Chapter 3, there was some concern that the range of tests in ASTM C 465 did not cover some durability-related concerns, and this is supported by the test data (highlighted cells in Table 26). It is therefore suggested that a new protocol be developed based on those used in ASTM C 465, but including the tests shown in the last column in Table 26. Unnecessary tests (e.g., concrete strength testing beyond 28 days) should also be re- moved. No effect of processing additions was observed be- yond 28 days in this work that was not already observed at younger ages. The primary reason for retaining strength test- ing in the protocol would be to ensure that mistakes in batching the test mixtures are detected. The quality of the air-void system, ASR resistance, and freeze-thaw resistance was not included in this protocol because the results of such testing are much more markedly affected by other parame- ters such as admixture type, amount of mixing, and aggre- gate grading. Any testing based on processing additions would largely be meaningless. Concrete specifications should require a given air-void system and durability, and concrete mixtures containing processing additions can be designed to achieve the required performanceâas were the mixtures in this work. A maximum amount of processing addition of 5.0% has been selected on the basis that this is consistent with global practice. Greater amounts may be considered as blended ce- ments and can be covered under AASHTO M 240. Pass-fail limits for the selected tests can be based on exist- ing limits used in current standards, as shown in Table 26. What should also be required is that the manufacturer should declare the amount and type of processing addition being used. Independent testing of this amount is desirable, and test methods will still have to be refined to accomplish this determination. The factors limiting precision of these techniques is that the elements and compounds in most processing additions are the same as those in the base ce- ment. In addition, the dosages of processing additions are normally small, making data from a given analysis of a given element close to the detection limits of the test methods. Ideally, if the composition of the raw materials (i.e., clinker, sulfate system, limestone and processing addition) is known (or samples are available for analysis) then a least squares approach can be used to determine PA dosage. Some unique flags (e.g., insoluble residue and carbon content) can also be used to assess PA dosage if the composition of the raw materials is unknown, but the precision of the findings can vary. C H A P T E R 5 Recommended Improvements to Specifications
58 Tests on ASTM C 465 Tests Conducted Recommended Protocol Tests Test Method Test Method Test Limit Chemistry XRF Chemistry XRF/XRD/ AA Chemistry As per C 465 Raw materials Specific gravity Helium pycnometer Fineness C204 Particle size distribution Laser Fineness or particle size distribution As per C 465 Specific gravity D891 Specific gravity As per C 465 Particle shape Optical microscopy Optimum SO 3 C 563 Cement LOI, Insoluble residue C 114 Autoclave C151 Autoclave T 107 Autoclave As per C 465 Wa ter requirement C187 Wa ter requirement. T 129 Water requirement. As per C 465 Paste Set time C191 Set time T 131 Set time As per C 465 Cube strength C109 Cube strength T 131 Cube strength As per C 465 Shrinkage C596 Shrinkage C 596 Shrinkage As per C 465 Air entraining admixture C185 Air entraining admixture T 137 Air entraining admixture As per C 465 Stiffening T 185 Mortar Alkali silica reactivity C 227 Compressive strength C39 Compressive strength T 22 Compressive strength As per C 465 up to 28 days Flexural strength C78 Flexural strength T 97 Flexural strength As per C 465 up to 28 days Slump loss T 119 Set time T 197 Concrete Air void system C 457 Rapid chloride penetration T 277 Freeze thaw T 161 Deicer scaling C 672 modified Highlighted cells indicate test parameters shown to be affected by inclusion of processing additions Table 26. Current tests in ASTM C 465 and recommended protocol.
The protocol should also require sufficient data be pro- vided such that modifications to the phase calculations can be made to accommodate the PA. Guidance on how to make that accommodation is also needed. A copy of the proposed protocol has been prepared in AASHTO format and is attached. No changes have been made to the documents regarding organic processing additions because these were not covered under the scope of this project. Although some data were gen- erated on the effects of limestone, changes to M 85 with re- spect to limestone have not been suggested. 59
