INFLUNCE OF INCREASING WATER:CEMENT RATIO ON THE SOME PROPERTIES OF CONCRETE CONTAINS LOW CONTENT OF POLYMER

Introduction:
This research includes the variation effect of (W/C) water: cement ratio on the properties as compressive strength, flexural strength , density and workability of concrete contains low Polymer SBR ratio. 1:2:4 (cement: sand:gravel) by weight mixes were used . The polymer was added as percentages of cement weight and it was 2%. Reference mix was made. Water cement ratio (w/c) were used are 0.2 , 0.3 , 0.4 , 0.5 and 0.6 respectively and 0.35 (w/c) was used for reference mix . The density of concrete varied between 2030 kg/m3 and 2360 kg/m3.

TESTS

Density:
The weight of every specimen was recorded air-dry and dimension prior to test.

Slump Test:

This test were done according to ASTM C 143-90a.

Compression Strength Test:

The compression strength tests were performed according to B.S.1881:Part 116:1983(7). A100X100X100mm cube steel moulds were used. The moulds were lightely oiled before filling with concrete. ELE machine with a 1000kN load capacity were used for that test.

Flexural Strength Test:

Flexural strength tests were carried out according to B.S.1881:Part 118:1983. For this test a 50kN ELE testing machine were used.

RESULTS AND DISCUSSION:

The results of polymer modified concrete revealed that the lowest 28-day density (air-dry) reached 2030 kg/m3 for mix2 which it had a w/c=0.2 . The highest was 2360 kg/m3 for mix4 of w/c=0.3 . The density of reference mix (mix1) (without polymer) is 2360 kg/m3 . The water:cement ratio effect is clear in increasing density (see Fig(4)). This can be attributed to the effect of water in decreasing friction between the agg. Particals.

Slump (workability)-water :

cement ratio relationship: As we see in table(4) and Fig:(6) , the effect of (w/c) is more than 0.3 . The effect of low content of polymer SBR was not appear clearly in the mixes of low water : cement ratio .

Compressive Strength:

In all mixes compressive strength increased with age. Max compressive strength at age of 180 day was 28.4 Mpa. for mix3 (w/c=0.3) whereas the lowest compressive strength was 13.32 Mpa. For mix6 (w/c=0.6). Compressive strength at 180 day age of reference mix (mix1 , w/c=0.35) was equal to 24.7 Mpa. That means low content of SBR polymer which equal to 2% developed the compressive strength only when the w/c is low value , so that at very low water : cement ratio and high water cement ratio the effect of low content of SBR polymer was not appear clearly in developing of compressive strength.