I am down in Spain trying to lay a foundation for a house extension.
The building law in Spain requires that all structural concrete is sampled and tested. With this in mind we made a couple of test mixes which were sent away for testing. This mixes failed, with one coming in at C22 and the other at C24.
The first test used a C30 mix 1:2:3 (Cement:Sand:Stone) and the second mix was C25 1:2:4. All were mixed in a good small concrete mixer. The slump test showed a slump of 3.5 cm. Clean water was used for both mixes and the materials had been washed and were dust free.
The stone used in the mixes varied in size up to 15 mm (max size of stone for the concrete pump that we are going to use). I thought that the sand was too course and more like gravel (approx 2mm).
Where did we go wrong?
The building law in Spain requires that all structural concrete is sampled and tested. With this in mind we made a couple of test mixes which were sent away for testing. This mixes failed, with one coming in at C22 and the other at C24.
The first test used a C30 mix 1:2:3 (Cement:Sand:Stone) and the second mix was C25 1:2:4. All were mixed in a good small concrete mixer. The slump test showed a slump of 3.5 cm. Clean water was used for both mixes and the materials had been washed and were dust free.
The stone used in the mixes varied in size up to 15 mm (max size of stone for the concrete pump that we are going to use). I thought that the sand was too course and more like gravel (approx 2mm).
Where did we go wrong?