Lightweight Concrete for High Strength - Expanded Shale & Clay

strength (10L made in the laboratory and 10F made in the field). The mix proportions are
presented in Table 4.1.
Table 4.1. Actual mixes used in the laboratory specimens (8L and 10L) and used to cast the
girders tested in Task 5 (8F and 10F)
Component Type 8L 8F 10L 10F
cement, Type III (lb/yd 3 ) 783 780 740 737
Fly ash, class F (lb/yd 3 ) 142 141 150 149
Silica Fume, (lb/yd 3 ) 19 19 100 100
Natural sand (lb/yd 3 ) 1022 1018 1030 1025
3/8" Lightweight aggregate (lb/yd 3 ) 947 944 955 956
Water (lb/yd 3 ) 268 284 227 260
AEA, Daravair 1000 (fl oz/yd 3 ) 7.8 7.8 7.4 5.5
Water reducer, WRDA 35 (fl oz/yd 3 ) 47 46.8 44.4 44.2
HRWR, Adva 100 (fl oz/yd 3 ) 47.5 53.4 102 95.8
Specimens used for testing mechanical properties were cured in two different ways:
ASTM C-39 (fog room and 73 o F) and accelerated curing that simulates the condition within a
precast prestressed member. Compressive strength for laboratory mixes was measured using 4 x
8-in. cylinders at 16, 20 and 24 hours, and then at, 7, 28, and 56 days. For field mixes strength
was measured at 1, 7, 28, 56, and more than 100 days after casting. The average compressive
strength of 8,000-psi and 10,000-psi HPLC (including laboratory and field mixes) is presented in
Figure 4.1. All creep and shrinkage specimens were accelerated cured.
Eight creep specimens were cast from each laboratory mix (8L and 10L) and four
specimens from each field mix. They were loaded at different ages (16 and 24 hours) and at
different stress-to-initial strength ratios (0.4 to 0.6). All creep and shrinkage cylinders were 4x15
inches. Specimens were kept at a constant 50% relative humidity and at 70 o F. There was no
statistical difference in creep results between field and laboratory mixes for both the 8,000 psi
and 10,000 psi mixes. Specific creep is the creep strain divided by the applied stress, while creep
coefficient is the creep strain divided by the initial elastic strain which is proportional to applied
stress.
It was also found that there was no significant difference between the creep coefficient
and specific creep for specimens loaded at 16 hours and at 24 hours and that the stress level
made no significant difference. Therefore, all results are combined in Figure 4.2.
4-2