Abstract

The Concrete Masonry Association of California and Nevada in conjunction with Brigham Young University devised a masonry prism testing scheme to aid in the determination of whether prisms constructed with grouts possessing high levels of supplemental cementitious materials could meet minimum masonry compressive strength requirements. ASTM standards, identical to that of concrete, place restrictions on quantities, by weight, of supplemental materials that can replace ordinary Portland cement. For an all fly ash replacement, up to 40% of Portland cement can be replaced while up to 70% can be replaced by a fly ash-slag combination. Research is focused on class F fly ash and ground granulated blast furnace slag replacing Portland cement in larger quantities. Manufacturing grouts with increasing incremental amounts help to establish higher use limitations associated specifically with masonry grout. Masonry prisms, concrete masonry units, type M mortar, and variations of grout were tested for their respective compressive strengths at age intervals of 14, 28, 42, 56, and 90 days. Grouts were designed to support the discussion of whether non-traditional grouts can achieve acceptable masonry compressive strength in prisms while not possessing adequate grout compressive strength. The control grout consisted of one mix design containing a cementitious materials content of 100% Portland cement. Three grouts replaced Portland cement with fly ash and three grouts replaced Portland cement with a fly ash-slag combination without modifying the cementitious material weight contribution. Class F fly ash replaced Portland cement at rates of 45%, 55%, and 65%. Class F fly ash-ground granulated blast furnace slag combinations replaced Portland cement at rates of 65%, 75%, and 85% where the combinations consisted of 25% fly ash and 40%, 50%, and 60% slag. Results indicate that all prisms exceeded the 10.3 MPa (1500 psi) minimum compressive strength requirements before the mandated 28-day age period. Neither 55% and 65% fly ash replacements nor the 85% fly ash-slag combination achieved grout strength minimums at the typical specified age. The grout mixtures manufactured with exceeding addition rates which attained greater than the minimum strength at the 28-day age were the 45% fly ash and 65% and 75% fly ash-slag combination. All grouts did, eventually, extend their strength gain beyond 13.8 MPa (2000 psi) through the course of testing and all but 65% fly ash achieved this strength within 42 days.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering

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