The slenderness ratio, in turn, depends upon the effective height (or length) and the effective thickness of the wall or column.
This video talks about the constituents of the concrete,. It explains the meaning of characteristic strength and target mean strength…Verifying Compressive Strength of Masonry – Characteristic Compressive Strength Of Masonry
As shown, the prism/block strength ratio decreases with increasing block strengths. Brazil, the characteristics and some aspects of their behavior are not fully known. Results of tests that allow to correlate the strength of concrete block, prism and wall for the high strength values reported herein are, as far as we know, unique.
Table 4 summarizes the characteristics and number of wall tests performed. Fortes , was used in the grout mix to reduce grout shrinkage and minimize the separation at the block and grout interface. It is a heat-treated calcium oxide admixture with a selected specific granulometry and with expansive property. Figure 4 shows the grout specimens and walls grouting procedure. Figure 5 shows the whole block, the block cut in half, and the bond-beam block. Each prism was built with two stacked blocks and one mortar joint. Figure 13 show the construction procedure sequence. The walls were unreinforced except that a horizontal steel 10-mm rebar was used in the mid-height bond beams. Regular cement-lime-sand mortar was used in the walls and prisms construction. For each wall group, twelve concrete blocks, six hollow prisms, and six grouted prisms were tested at the same time of the walls testing.
Figure 14 shows some walls ready to be tested. The wall was then loaded and unloaded twice up to 5% of the maximum expected load to lock the wall in place and check the instrumentation readings.
A wall was considered to fail when vertical cracks appeared and the applied load started to decrease or when the wall exhibited large lateral deformation with a vertical load drop.
The difference in the average wall strength is only 3.3%. The geometry of the blocks may explain the similar results obtained herein. Therefore, laying blocks with full bed mortar joints may have been inefficient because there is no vertical alignment of the webs. The t-test indicates a p-value of 2.7%. The existence of the mid-height bond beam may have contributed to better stress distribution the wall critical region and contributed to the strength increase for the full bed mortar joint walls.
Group 3 did not experienced the same kind of results, which invalidates this assumption. There is therefore a variability in the walls shortening. Group 2, some difference in the vertical shortening of walls is observed. Figure 24 remained approximately linear up to 70% of failure load. Figure 25 remained approximately linear up to 60% of failure load. Table 16 shows the average results of the modulus of elasticity obtained for the walls using the linear part of the stress-strain curves. The tensile stresses that induce the cracks are developed in the mortar-block interfaces due to restricted deformation of the mortar.
What is the difference between minimum compressive strength and specified
The apparent increase in the mortar strength is due to the biaxial or tri-axial stress state imposed to the mortar when it is loaded in conjunction with the blocks.
Groups 1 and 2 walls, the first crack was observed at about 60% of the ultimate load. Group 3 walls, cracking started at approximately 75% of the failure load. However, was similar to that of walls without the mid height bond beam. In the case of the grouted wall built with the mid height bond beam, the strength ratio to the grouted prism is only 0.5. Rules for reinforced and unreinforced masonry.
Compressive Strength Of Cement Concrete Cubes